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Saturday, November 17, 2018

Phineas Gage

From Wikipedia, the free encyclopedia

Phineas P. Gage
Phineas Gage Cased Daguerreotype WilgusPhoto2008-12-19 EnhancedRetouched Color.jpg
Gage and his "constant companion"‍—‌his inscribed tamping iron‍—‌sometime after 1849, seen in the portrait (identified 2009) which "exploded the common image of Gage as a dirty, disheveled misfit". 
BornJuly 9, 1823 (date uncertain)
Grafton County, New Hampshire
DiedMay 21, 1860 (aged 36)
In or near San Francisco
Cause of deathStatus epilepticus
Burial placeCypress Lawn Memorial Park, California (skull in Warren Anatomical Museum, Boston)
Residence
Occupation
Known forPersonality change after brain injury
Home townLebanon, New Hampshire
Spouse(s)None
ChildrenNone

Phineas P. Gage (1823–1860) was an American railroad construction foreman remembered for his improbable survival of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and for that injury's reported effects on his personality and behavior over the remaining 12 years of his life‍—‌effects sufficiently profound (for a time at least) that friends saw him as "no longer Gage". 


The iron's path, per Harlow
Long known as the "American Crowbar Case"‍—‌once termed "the case which more than all others is cal­cu­lated to excite our wonder, impair the value of prognosis, and even to subvert our phys­i­o­log­i­cal doctrines" ‍—‌Phineas Gage influenced 19th-century discussion about the mind and brain, par­tic­u­larly debate on cerebral local­i­za­tion, and was perhaps the first case to suggest the brain's role in deter­min­ing per­son­al­ity, and that damage to specific parts of the brain might induce specific per­son­al­ity changes.

Gage is a fixture in the curricula of neurology, psychology, and neuroscience, one of "the great medical curiosities of all time" and "a living part of the medical folklore"  frequently mentioned in books and scientific papers; he even has a minor place in popular culture. Despite this celebrity, the body of established fact about Gage and what he was like (whether before or after his injury) is small, which has allowed "the fitting of almost any theory [desired] to the small number of facts we have" ‍—‌Gage acting as a "Rorschach inkblot"  in which proponents of various conflicting theories of the brain all saw support for their views. Historically, published accounts of Gage (including scientific ones) have almost always severely exaggerated and distorted his behavioral changes, frequently contradicting the known facts.

A report of Gage's physical and mental condition shortly before his death implies that his most serious mental changes were temporary, so that in later life he was far more functional, and socially far better adapted, than in the years immediately following his accident. A social recovery hypothesis suggests that Gage's work as a stagecoach driver in Chile fostered this recovery by providing daily structure which allowed him to regain lost social and personal skills.

Life

Background

Cavendish, Vermont, 20 years after Gage's accident: (a) Region of the accident site; (t) Gage's lodgings, to which he was taken after his injury; (h) Harlow's home and surgery.

Gage was the first of five children born to Jesse Eaton Gage and Hannah Trussell (Swetland) Gage of Grafton County, New Hampshire. Little is known about his upbringing and education beyond that he was literate.

Town doctor John Martyn Harlow described Gage as "a perfectly healthy, strong and active young man, twenty-five years of age, nervo-bilious temperament, five feet six inches [168 cm] in height, average weight one hundred and fifty pounds [68 kg], possessing an iron will as well as an iron frame; muscular system unusually well developed‍—‌having had scarcely a day's illness from his childhood to the date of [his] injury". (In the pseudoscience of phrenology, which was then just ending its vogue, nervo-bilious denoted an unusual combination of "excitable and active mental powers" with "energy and strength [of] mind and body [making] possible the endurance of great mental and physical labor".)

Gage may have first worked with explosives on farms as a youth, or in nearby mines and quarries. He is known to have worked on construction of the Hudson River Railroad near Cortlandt Town, New York, and by the time of his accident he was a blasting foreman (possibly an independent contractor) on railway construction projects. His employers' "most efficient and capable foreman ... a shrewd, smart business man, very energetic and persistent in executing all his plans of operation", he had even commissioned a custom-made tamping iron‍—‌a large iron rod‍—‌for use in setting explosive charges.​​

Accident

Line of the Rutland & Burlington Railroad passing through "cut" in rock south of Cavendish. Gage met with his accident while setting ex­plo­sives to create either this cut or a similar one nearby.
 
Explosive charge ready for fuse to be lit. tamping (sand) directs blast into surrounding rock.
 
Gage's mouth was open at the moment of the ex­plo­sion, and his skull tem­po­rarily "hinged" open as the iron passed through, then was pulled closed by the resilience of soft tissues once the iron had exited through the top of 
Gage's head.
 
Panel from Bring Me the Head of Phineas Gage, a portrayal of Gage in popular culture
 
On September 13, 1848, Gage was directing a work gang blasting rock while preparing the roadbed for the Rutland & Burlington Railroad south of the town of Cavendish, Vermont. Setting a blast entailed boring a hole deep into an out­crop of rock; adding blasting powder and a fuse; then using the tamping iron to pack ("tamp") sand, clay, or other inert material into the hole above the powder, in order to contain the blast's energy and direct it into surrounding rock.

As Gage was doing this around 4:30 p.m., his attention was attracted by his men working behind him. Looking over his right shoulder, and inad­vert­ent­ly bringing his head into line with the blast hole, Gage opened his mouth to speak; in that same instant the tamping iron sparked against the rock and (possibly because the sand had been omitted) the powder exploded. Rocketed from the hole, the tamping iron‍—‌1 14 inches (3.2 cm) in diameter, three feet seven inches (1.1 m) long, and weighing 13 14 pounds (6.0 kg)‍—‌entered the left side of Gage's face in an upward direction, just forward of the angle of the lower jaw. Continuing upward outside the upper jaw and possibly fracturing the cheekbone, it passed behind the left eye, through the left side of the brain, then completely out the top of the skull through the frontal bone.

Despite 19th-century references to Gage as the "American Crowbar Case", his tamping iron did not have the bend or claw some­times asso­ci­at­ed with the term crowbar; rather, it was simply a pointed cylinder something like a javelin, round and fairly smooth:
The end which entered first is pointed; the taper being [eleven inches (27 cm) long, ending in a ​14-inch (7 mm) point] ... cir­cum­stances to which the patient perhaps owes his life. The iron is unlike any other, and was made by a neigh­bour­ing blacksmith to please the fancy of the owner.
The tamping iron landed point-first some 80 feet (25 m) away, "smeared with blood and brain".

Gage was thrown onto his back and gave some brief convulsions of the arms and legs, but spoke within a few minutes, walked with little assistance, and sat upright in an oxcart for the 34-mile (1.2 km) ride to his lodgings in town. About 30 minutes after the accident physician Edward H. Williams, finding Gage sitting in a chair outside the hotel, was greeted with "one of the great understatements of medical history":
When I drove up he said, "Doctor, here is business enough for you." I first noticed the wound upon the head before I alighted from my carriage, the pulsations of the brain being very distinct. The top of the head appeared somewhat like an inverted funnel, as if some wedge-shaped body had passed from below upward. Mr. Gage, during the time I was examining this wound, was relating the manner in which he was injured to the bystanders. I did not believe Mr. Gage's statement at that time, but thought he was deceived. Mr. Gage persisted in saying that the bar went through his head. Mr. G. got up and vomited; the effort of vomiting pressed out about half a teacupful of the brain [through the exit hole at the top of the skull], which fell upon the floor.
Harlow took charge of the case around 6 p.m.:
You will excuse me for remarking here, that the picture presented was, to one unaccustomed to military surgery, truly terrific; but the patient bore his sufferings with the most heroic firmness. He recognized me at once, and said he hoped he was not much hurt. He seemed to be perfectly conscious, but was getting exhausted from the hemorrhage. His person, and the bed on which he was laid, were literally one gore of blood.

Initial treatment

A nightcap of the period

With Williams' assistance Harlow shaved the scalp around the region of the tamping iron's exit, then removed coagulated blood, small bone fragments, and "an ounce or more" of protruding brain. After probing for foreign bodies and replacing two large detached pieces of bone, Harlow closed the wound with adhesive straps, leaving it partially open for drainage; the entrance wound in the cheek was bandaged only loosely, for the same reason. A wet compress was applied, then a nightcap, then further bandaging to secure these dressings. Harlow also dressed Gage's hands and forearms (which along with his face had been "deeply burned") and ordered that Gage's head be kept elevated.
Late that evening Harlow noted: "Mind clear. Constant agitation of his legs, being alternately retracted and extended like the shafts of a fulling mill. Says he 'does not care to see his friends, as he shall be at work in a few days.'" 

Convalescence

The first known report of Gage's ac­ci­dent, under­stat­ing the size of his tamp­ing iron (by confusing its diam­e­ter with its cir­cum­fer­ence) and over­stat­ing damage to his jaw. "His fame is of the kind that is, and in his case literally so, thrust upon other­wise ordinary people", writes Malcolm Macmillan.

Despite his own optimism, Gage's convalescence was long, difficult, and uneven. Though recognizing his mother and uncle—summoned from Lebanon, New Hampshire, 30 miles (50 km) away‍—‌on the morning after the accident, on the second day he "lost control of his mind, and became decidedly delirious". By the fourth day, he was again "rational ... knows his friends", and after a week's further improvement Harlow entertained, for the first time, the thought "that it was possible for Gage to recover ... This improvement, however, was of short duration." 

Beginning 12 days after the accident, Gage was semi-comatose, "seldom speaking unless spoken to, and then answering only in monosyllables", and on the 13th day Harlow noted, "Failing strength ... coma deepened; the globe of the left eye became more protuberant, with ["fungus"‍—‌deteriorated, infected tissue] pushing out rapidly from the internal canthus [as well as] from the wounded brain, and coming out at the top of the head." By the 14th day, "The exhalations from the mouth and head [are] horribly fetid. Comatose, but will answer in monosyllables if aroused. Will not take nourishment unless strongly urged. The friends and attendants are in hourly expectancy of his death, and have his coffin and clothes in readiness."

The entry damage to Gage's left cheek, and the raised bone fragment in the exit area above his forehead, are visible in this plaster cast taken in late 1849.
 
Galvanized, Harlow "cut off the fungi which were sprouting out from the top of the brain and filling the opening, and made free application of caustic [i.e. crystalline silver nitrate] to them. With a scalpel I laid open the [frontalis muscle, from the exit wound to the top of the nose] and immediately there were discharged eight ounces [250 ml] of ill-conditioned pus, with blood, and excessively fetid."  ("Gage was lucky to encounter Dr. Harlow when he did", wrote Barker. "Few doctors in 1848 would have had the experience with cerebral abscess with which Harlow left [Jefferson Medical College] and which probably saved Gage's life."

On the 24th day, Gage "succeeded in raising himself up, and took one step to his chair". One month later, he was walking "up and down stairs, and about the house, into the piazza", and while Harlow was absent for a week Gage was "in the street every day except Sunday", his desire to return to his family in New Hampshire being "uncontrollable by his friends ... he went without an overcoat and with thin boots; got wet feet and a chill". He soon developed a fever, but by mid-November he was "feeling better in every respect ... walking about the house again". Harlow's prognosis at this point: Gage "appears to be in a way of recovering, if he can be controlled".

Subsequent life and travels

"Disfigured yet still hand­some". Note ptosis of the left eye and scar on forehead.
 
By November 25 (10 weeks after his injury), Gage was strong enough to return to his parents' home in Lebanon, New Hampshire, traveling there in a "close carriage" (an enclosed conveyance of the kind used for transporting the insane). Though "quite feeble and thin ... weak and childish" on arriving, by late December he was "riding out, improving both mentally and physically", and by February 1849 he was "able to do a little work about the horses and barn, feeding the cattle etc. [and] as the time for ploughing came [i.e. about May or June] he was able to do half a day's work after that and bore it well". In August his mother told an inquiring physician that his memory seemed somewhat impaired, though slightly enough that a stranger would not notice.

Injuries

In April 1849, Gage returned to Cavendish and visited Harlow, who noted at that time loss of vision (and ptosis) of the left eye, a large scar on the forehead (from Harlow's draining of the abscess) and
upon the top of the head ... a quadrangular fragment of bone ... raised and quite prominent. Behind this is a deep depression, [2 in by 1 1/2 in wide, 5 cm by 4 cm], beneath which the pulsations of the brain can be perceived. Partial paralysis of the left side of the face. His physical health is good, and I am inclined to say he has recovered. Has no pain in head, but says it has a queer feeling which he is not able to describe.
Gage's rearmost left upper molar, immediately adjacent to the point of entry through the cheek, was also lost. Though a year later some weakness remained, Harlow wrote that "physically, the recovery was quite complete during the four years immediately succeeding the injury".

New England and New York (1849–1852)

Phineas was accustomed to entertain his little nephews and nieces with the most fabulous recit­als of his wonder­ful feats and hair-breadth escapes, without any found­at­ion except in his fancy. He con­ceived a great fondness for pets and souve­nirs, espe­cial­ly for children, horses and dogs‍—‌only exceeded by his attach­ment for his tamping iron, which was his constant com­pan­ion during the remainder of his life.
J. M. Harlow (1868)

In November 1849, Henry Jacob Bigelow, the Professor of Surgery at Harvard Medical School, brought Gage to Boston for several weeks and, after satisfying himself that the tamping iron had actually passed through Gage's head, presented him to a meeting of the Boston Society for Medical Improvement and (possibly) to the medical school class.

Gage appeared for a time at Barnum's American Museum in New York City.
 
"Admittance 12 1/2 cents" (equiv­a­lent to about $4 in 2017). Gage briefly resumed exhib­it­ing just before going to Chile, possibly to help finance that move. This adver­tise­ment appeared August 1852 in Montpelier, Vermont.​​
 
Unable to reclaim his railroad job (see § Early observations, below) Gage was for a time "a kind of living museum exhibit"  at Barnum's American Museum in New York City. (This was not the later Barnum's circus; there is no evidence Gage ever exhibited with a troupe or circus, or on a fairground.) Advertisements have also been found for public appearances by Gage‍—‌which he may have arranged and promoted himself‍—‌in New Hampshire and Vermont, supporting Harlow's statement that Gage made public appearances in "most of the larger New England towns". (Years later Bigelow wrote that Gage had been "a shrewd and intelligent man and quite disposed to do anything of that sort to turn an honest penny", but gave up such efforts because "[that] sort of thing has not much interest for the general public".)​​

For about 18 months, he worked for the owner of a stable and coach service in Hanover, New Hampshire.

Chile and California (1852–1860)

In August 1852, Gage was invited to Chile to work as a long-distance stagecoach driver there, "caring for horses, and often driving a coach heavily laden and drawn by six horses" on the ValparaísoSantiago route. After his health began to fail in mid-1859, he left Chile for San Francisco, arriving (in his mother's words) "in a feeble condition, having failed very much since he left New Hampshire ... Had many ill turns while in Valparaiso, especially during the last year, and suffered much from hardship and exposure." In San Francisco he recovered under the care of his mother and sister, who had relocated there from New Hampshire around the time he went to Chile. Then, "anxious to work", he found employment with a farmer in Santa Clara.

In February 1860, Gage began to have epileptic seizures. He lost his job, and (wrote Harlow) as the seizures increased in frequency and severity he "continued to work in various places [though he] could not do much".

Death and exhumation

New Hampshire Statesman, July 21, 1860​​
 
Gage's brother-in-law (a San Fran­cis­co city offi­cial) and his fam­i­ly per­son­al­ly de­liv­ered Gage's skull and iron to Harlow.​​ 
 
"[T]he mother and friends, waiving the claims of personal and private affec­tion, with a mag­na­nim­ity more than praise­worthy, at my request have cheer­fully placed this skull in my hands, for the benefit of science." Gage's skull (sawn to show inte­rior) and iron, photo­graphed for Harlow in 1868.​​
 
On May 18 Gage "left Santa Clara and went home to his mother. At 5 o'clock, A.M., on the 20th, he had a severe con­vul­sion. The family physician was called in, and bled him. The con­vul­sions were repeated frequently during the suc­ceed­ing day and night," and he died in status epi­lep­ti­cus, in or near San Francisco, late on May 21, 1860. He was buried in San Francisco's Lone Mountain Cemetery.​​

In 1866, Harlow (who had "lost all trace of [Gage], and had well nigh abandoned all ex­pec­ta­tion of ever hearing from him again") somehow learned that Gage had died in California, and made contact with his family there. At Harlow's request the family had Gage's skull exhumed, then personally delivered it to Harlow, who was by then a prominent physician, busi­ness­man, and civic leader in Woburn, Massachusetts.​​

About a year after the accident, Gage had given his tamping iron to Harvard Medical School's Warren Anatomical Museum, but he later reclaimed it​​ and made what he called "my iron bar" his "constant companion during the remainder of his life"; now it too was delivered by Gage's family to Harlow. (Though some accounts assert that Gage's iron had been buried with him, there is no evidence for this.) After studying them for a triumphal 1868 retrospective paper on Gage Harlow redeposited the iron‍—‌this time with the skull‍—‌in the Warren Museum, where they remain on display today.

The tamping iron bears the following inscription, commissioned by Bigelow in conjunction with the iron's original deposit in the Museum (though the date given for the accident is one day off):
This is the bar that was shot through the head of Mr Phinehas[sic] P. Gage at Cavendish Vermont Sept 14,[sic] 1848. He fully recovered from the injury & deposited this bar in the Museum of the Medical College of Harvard University.  • Phinehas P. Gage  • Lebanon Grafton Cy N–H  • Jan 6 1850
The date Jan 6 1850 falls within the period during which Gage was in Boston under Bigelow's observation.

In 1940 Gage's headless remains were moved to Cypress Lawn Cemetery as part of a mandated relocation of San Francisco's dead to new resting places outside city limits (see San Francisco cemetery relocations).


Excerpt from record book, Lone Mountain Cemetery, San Francisco, reflecting the May 23, 1860 interment of Phineas B.[sic] Gage by undertakers N. Gray & Co. (Position pointer over writing for transcription.)

Mental changes and brain damage

Mental changes

"I dressed him, God healed him." Dr. J. M. Harlow, who attended Gage after the "rude missile had been shot through his brain" and obtained his skull for study after his death. Shown here in later life, Harlow's interest in phre­nol­o­gy prepared him to accept that Gage's injury had changed his behavior.
 
"The leading feature of this case is its improbability." Harvard's Prof. H. J. Big­e­low in 1854. His anti-localiz­a­tion­ist training pre­dis­posed him to minimize Gage's behavioral changes.

Gage may have been the first case to suggest the brain's role in determining personality and that damage to specific parts of the brain might induce specific personality changes, but the nature, extent, and duration of these changes have been difficult to establish. Only a handful of sources give direct information on what Gage was like (either before or after the accident), the mental changes published after his death were much more dramatic than anything reported while he was alive, and few sources are explicit about the period of Gage's life to which each of their various descriptions of him (which vary widely in their implied level of functional impairment) is meant to apply.

Early observations (1849–1852)

Harlow ("virtually our only source of information" on Gage, according to psychologist Malcolm Macmillan) described the pre-accident Gage as hard-working, responsible, and "a great favorite" with the men in his charge, his employers having regarded him as "the most efficient and capable foreman in their employ"; he also took pains to note that Gage's memory and general intelligence seemed unimpaired after the accident, outside the periods of delirium. Nonetheless these same employers, after Gage's accident, "considered the change in his mind so marked that they could not give him his place again":
The equilibrium or balance, so to speak, between his intel­lec­tu­al faculties and animal pro­pen­si­ties, seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity (which was not pre­vi­ous­ly his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times per­ti­na­cious­ly obstinate, yet capricious and vac­il­lat­ing, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intel­lec­tu­al capacity and man­i­fes­ta­tions, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart business man, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaint­ances said he was "no longer Gage".
This description ("now routinely quoted", says Kotowicz) is from Harlow's observations set down soon after the accident, but Harlow‍—‌perhaps hesitant to describe his patient negatively while he was still alive—‌delayed publishing it until 1868, after Gage had died and his family had supplied "what we so much desired to see" (as Harlow termed Gage's skull).

In the interim, Harlow's 1848 report, published just as Gage was emerging from his convalescence, merely hinted at psychological symptoms:
The mental manifestations of the patient, I reserve to a future communication. I think the case ... is exceedingly interesting to the enlightened physiologist and intellectual philosopher.
"Before the in­jury he was quiet and re­spect­ful." 1851 report ap­par­ently based on infor­ma­tion from Harlow, coun­ter­ing Bigelow's claim that Gage was mentally unchanged.

But after Bigelow termed Gage "quite recovered in faculties of body and mind" with only "inconsiderable disturbance of function", a rejoinder in the American Phrenological Journal‍—‌
That there was no difference in his mental manifestations after the recovery [is] not true ... he was gross, profane, coarse, and vulgar, to such a degree that his society was intolerable to decent people.
‍—‌was apparently based on information anonymously supplied by Harlow. Pointing out that Bigelow's extensive verbatim quotations from Harlow's 1848 papers omitted Harlow's promise to follow up with details of Gage's "mental manifestations", Barker explains Bigelow's and Harlow's contradictory evaluations (less than a year apart) by differences in their educational backgrounds, in particular their attitudes toward cerebral localization (the idea that different regions of the brain are specialized for different functions) and phrenology (the nineteenth-century pseudoscience that held that talents and personality can be inferred from the shape of a person's skull):
Harlow's interest in phrenology prepared him to accept the change in [Gage's] character as a significant clue to cerebral function which merited publication. Bigelow had [been taught] that damage to the cerebral hemispheres had no intellectual effect, and he was unwilling to consider Gage's deficit significant ... The use of a single case [including Gage's] to prove opposing views on phrenology was not uncommon.
A reluctance to ascribe a biological basis to "higher mental functions" (functions‍—‌such as language, personality, and moral judgment‍—‌beyond the merely sensory and motor) may have been a further reason Bigelow discounted the behavioral changes in Gage which Harlow had noted.

Later observations (1852–1858)

"Please deliver my iron bar to the bearer". While in Chile, Gage had his relative B. R. Sweetland retrieve the tamping iron from Harvard's Warren Anatomical Museum.

In 1860, an American physician who had known Gage in Chile described him as still "engaged in stage driving [and] in the enjoyment of good health, with no impairment whatever of his mental faculties". Together with the fact that Gage was hired by his employer in advance, in New England, to become part of the new coaching enterprise in Chile, this implies that Gage's most serious mental changes had been temporary, so that the "fitful, irreverent ... capricious and vacillating" Gage described by Harlow immediately post-accident became, over time, far more functional and socially far better adapted.

Macmillan writes that this conclusion is reinforced by the responsibilities and challenges associated with stagecoach work such as that done by Gage in Chile, including the requirement that drivers "be reliable, resourceful, and possess great endurance. But above all, they had to have the kind of personality that enabled them to get on well with their passengers." ​​ A day's work for Gage meant "a 13-hour journey over 100 miles [160 km] of poor roads, often in times of political instability or frank revolution. All this‍—‌in a land to whose language and customs Phineas arrived an utter stranger‍—‌militates as much against permanent disinhibition [i.e. an inability to plan and self-regulate] as do the extremely complex sensory-motor and cognitive skills required of a coach driver." ​​ (An American visitor wrote: "The departure of the coach was always a great event at Valparaiso‍—‌a crowd of ever-astonished Chilenos assembling every day to witness the phenomenon of one man driving six horses.")

Social recovery

A Concord stagecoach, likely the type driven by Gage in Chile

Macmillan writes that this contrast‍—‌between Gage's early, versus later, post-accident behavior‍—‌reflects his "[gradual change] from the commonly portrayed impulsive and uninhibited person into one who made a reasonable 'social recovery'", citing persons with similar injuries for whom "someone or something gave enough structure to their lives for them to relearn lost social and personal skills":
Phineas' survival and rehabilitation demonstrated a theory of recovery which has influenced the treatment of frontal lobe damage today. In modern treatment, adding structure to tasks by, for example, mentally visualising a written list, is considered a key method in coping with frontal lobe damage.
According to contemporary accounts by visitors to Chile, Gage would have had to
rise early in the morning, prepare himself, and groom, feed, and harness the horses; he had to be at the departure point at a specified time, load the luggage, charge the fares and get the passengers settled; and then had to care for the passengers on the journey, unload their luggage at the destination, and look after the horses. The tasks formed a structure that required control of any impulsiveness he may have had.
En route (Macmillan continues):
much foresight was required. Drivers had to plan for turns well in advance, and sometimes react quickly to manoeuvre around other coaches, wagons, and birlochos travelling at various speeds ... Adaptation had also to be made to the physical condition of the route: although some sections were well-made, others were dangerously steep and very rough.
Thus Gage's stagecoach work‍—‌"a highly structured environment in which clear sequences of tasks were required [but within which] contingencies requiring foresight and planning arose daily"‍—‌resembles rehabilitation regimens first developed by Soviet neuropsychologist Alexander Luria for the reestablishment of self-regulation in World War II soldiers suffering frontal lobe injuries.

A neurological basis for such recoveries may be found in emerging evidence "that damaged [neural] tracts may re-establish their original connections or build alternative pathways as the brain recovers" from injury. Macmillan adds that if Gage made such a recovery‍—‌if he eventually "figured out how to live" (as Fleischman put it) despite his injury‍—‌then it "would add to current evidence that rehabilitation can be effective even in difficult and long-standing cases"; and if Gage could achieve such improvement without medical supervision, "what are the limits for those in formal rehabilitation programs?"  As author Sam Kean put it, "If even Phineas Gage bounced back‍—‌that's a powerful message of hope." 

Exaggeration and distortion of mental changes

A moral man, Phineas Gage
Tamping powder down holes for his wage
       Blew his special-made probe
       Through his left frontal lobe
Now he drinks, swears, and flies in a rage.
Anonymous

Macmillan's analysis of scientific and popular accounts of Gage found that they almost always distort and exaggerate his behavioral changes well beyond anything described by anyone who had direct contact with him, concluding that the known facts are "inconsistent with the common view of Gage as a boastful, brawling, foul-mouthed, dishonest useless drifter, unable to hold down a job, who died penniless in an institution".  In the words of Barker, "As years passed, the case took on a life of its own, accruing novel additions to Gage's story without any factual basis". Even today (writes Zbigniew Kotowicz) "Most commentators still rely on hearsay and accept what others have said about Gage, namely, that after the accident he became a psychopath"; Grafman has written that "the details of [Gage's] social cognitive impairment have occasionally been inferred or even embellished to suit the enthusiasm of the story teller"; and Goldenberg calls Gage "a (nearly) blank sheet upon which authors can write stories which illustrate their theories and entertain the public". 

For example, Harlow's statement that Gage "continued to work in various places; could not do much, changing often, and always finding something that did not suit him in every place he tried" refers only to Gage's final months, after convulsions had set in. But it has been misinterpreted as meaning that Gage never held a regular job after his accident, "was prone to quit in a capricious fit or be let go because of poor discipline", "never returned to a fully independent existence", "spent the rest of his life living miserably off the charity of others and traveling around the country as a sideshow freak", and ("dependent on his family"  or "in the custody of his parents") died "in careless dissipation". In fact, after his initial post-recovery months spent traveling and exhibiting, Gage supported himself‍—‌at a total of two jobs‍—‌from early 1851 until just before his death in 1860.​​

Other behaviors ascribed to the post-accident Gage that are either unsupported by, or in contradiction to, the known facts include the following:
  • mistreatment of wife and children (though Gage actually had neither);
  • inappropriate sexual behavior, promiscuity, or impaired sexuality;
  • lack of forethought, concern for the future, or capacity for embarrassment;
  • parading his self-misery, and vainglory in showing his wounds;
  • "gambling" himself into "emotional and reputational ... bankruptcy";
  • irresponsibility, untrustworthiness, aggressiveness, violence;
  • vagrancy, begging, drifting, drinking;
  • lying, brawling, bullying;
  • psychopathy, inability to make ethical decisions;
  • loss of all respect for social conventions;
  • acting like an "idiot"  or a "lout";
  • living as a "layabout"  or a "boorish mess";
  • "[alienating] almost everyone who had ever cared about him";
  • dying "due to a debauch".
None of these behaviors is mentioned by anyone who had met Gage or even his family, and as Kotowicz put it, "Harlow does not report a single act that Gage should have been ashamed of."  Gage is "a great story for illustrating the need to go back to original sources", writes Macmillan, most authors having been "content to summarize or paraphrase accounts that are already seriously in error". 

Nonetheless (write Daffner and Searl) "the telling of [Gage's] story has increased interest in understanding the enigmatic role that the frontal lobes play in behavior and personality", and Ratiu has said that in teaching about the frontal lobes, an anecdote about Gage is like an "ace [up] your sleeve. It's just like whenever you talk about the French Revolution you talk about the guillotine, because it's so cool."  Benderly suggests that instructors use the Gage case to illustrate the importance of critical thinking.

Extent of brain damage

The left frontal lobe (red), with Ratiu et al.'s estimate of the tamping iron's path.
It is regretted that an autopsy could not have been had, so that the pre­cise condi­tion of the en­ceph­a­lon at the time of his death might have been known.
J. M. Harlow (1868)
 
False-color representations of cerebral fiber pathways affected, per Van Horn et al.
 
Debate about whether the trauma and subse­quent infection had damaged both of Gage's frontal lobes (left and right), or only the left, began almost immedi­ate­ly after his accident. The 1994 conclu­sion of Hanna Damasio et al., that the tamping iron did physical damage to both lobes, was drawn not from Gage's skull but from a cadaver skull digitally deformed to match the dimen­sions of Gage's​​‍—‌and made a priori assumptions about the location of Gage's internal injuries and the exit wound, some of which contradict Harlow's observations. Using CT scans of Gage's actual skull, Ratiu et al. and Van Horn et al. both rejected that conclusion, agreeing with Harlow's belief‍—‌based on probing Gage's wounds with his fingers‍—‌that only the left frontal lobe had been damaged.

In addition, Ratiu et al. noted that the hole in the base of the cranium (created as the tamping iron passed through the sphenoidal sinus into the brain) has a diameter about half that of the iron itself; combining this with the hairline fracture beginning behind the exit region and running down the front of the skull, they concluded that the skull "hinged" open as the iron entered from below, then was pulled closed by the resilience of soft tissues once the iron had exited through the top of the head.

Van Horn et al. concluded that damage to Gage's white matter (of which they made detailed estimates) was as or more significant to Gage's mental changes than cerebral cortex (gray matter) damage. Thiebaut de Schotten et al. estimated white-matter damage in Gage and two other famous patients ("Tan" and "H.M."), concluding that these three cases "suggest that social behavior, language, and memory depend on the coordinated activity of different [brain] regions rather than single areas in the frontal or temporal lobes."

Factors favoring Gage's survival

"I have the pleasure of being able to present to you [a case] without parallel in the annals of surgery."  Harlow's 1868 presentation to the Mas­sa­chu­setts Medical Society of Gage's skull, tamping iron, and post-accident history.

Harlow saw Gage's survival as demonstrating "the wonderful resources of the system in enduring the shock and in overcoming the effects of so frightful a lesion, and as a beautiful display of the recuperative powers of nature", and listed what he saw as the circumstances favoring it:
1st. The subject was the man for the case. His physique, will, and capacity of endurance, could scarcely be excelled.
For Harlow's description of the pre-accident Gage, see § Background, above.
2d. The shape of the missile‍—‌being pointed, round and comparatively smooth, not leaving behind it prolonged concussion or compression.
Despite its very large diameter and mass (compared to a weapon-fired projectile) the tamping iron's relatively low velocity drastically reduced the energy available to compressive and concussive "shock waves".​​

Harlow continued:
3d. The point of entrance ... [The tamping iron] did little injury until it reached the floor of the cranium, when, at the same time that it did irreparable damage, it [created the] opening in the base of the skull, for drainage, [without which] recovery would have been impossible.
Barker writes that "[Head injuries] from falls, horse kicks, and gunfire, were well known in pre–Civil War America [and] every contemporary course of lectures on surgery described the diagnosis and treatment" of such injuries. But to Gage's benefit, surgeon Joseph Pancoast had performed "his most celebrated operation for head injury before Harlow's medical class, [trepanning] to drain the pus, resulting in temporary recovery. Unfortunately, symptoms recurred and the patient died. At autopsy, reaccumulated pus was found: granulation tissue had blocked the opening in the dura." By keeping the exit wound open, and elevating Gage's head to encourage drainage from the cranium into the sinuses (through the hole made by the tamping iron), Harlow "had not repeated Professor Pancoast's mistake".​​
No attempt will be made by me to cite analo­gous cases, as after ran­sack­ing the lit­er­a­ture of sur­gery in quest of such, I learn that all, or nearly all, soon came to a fatal result.
J. M. Harlow (1868)

Finally,
4th. The portion of the brain traversed was, for several reasons, the best fitted of any part of the cerebral substance to sustain the injury.
Precisely what Harlow's "several reasons" were is unclear, but he was likely referring, at least in part, to the understanding (slowly developing since ancient times) that injuries to the front of the brain are less dangerous than those to the rear, because the latter frequently interrupt vital functions such as breathing and circulation. For example, surgeon James Earle wrote in 1790 that "a great part of the cerebrum may be taken away without destroying the animal, or even depriving it of its faculties, whereas the cerebellum will scarcely admit the smallest injury, without being followed by mortal symptoms."

Harlow's 1868 paper on Gage was widely reported. This item appeared in Scientific American for July, 1868.

Ratiu et al. and Van Horn et al. both concluded that the superior sagittal sinus must have remained intact, both because Harlow does not mention loss of cerebrospinal fluid through the nose, and because otherwise Gage would almost certainly have suffered fatal blood loss or air embolism. Harlow's moderate (in the context of medical practice of the time) use of emetics, purgatives, and (in one instance) bleeding would have "produced dehydration with reduction of intracranial pressure [which] may have favorably influenced the outcome of the case", according to Steegmann.

As to his own role in Gage's survival, Harlow merely averred, "I can only say ... with good old Ambroise Paré, I dressed him, God healed him", but Macmillan calls this self-assessment far too modest. Noting that Harlow had been a "relatively inexperienced local physician ... graduated four and a half years earlier", Macmillan's discussion of Harlow's "skillful and imaginative adaptation [of] conservative and progressive elements from the available therapies to the particular needs posed by Gage's injuries" emphasizes that he "did not apply rigidly what he had learned", for example foregoing an exhaustive search for bone fragments (which risked hemorrhage and further brain injury) and applying caustic to the "fungi" instead of excising it (which risked hemorrhage) or forcing it into the wound (which risked compressing the brain).

Early medical attitudes

Skepticism

The very small amount of atten­tion that has been given to [this] case can only be ex­plained by the fact that it far tran­scends any case of recov­ery from inju­ry of the head that can be found in the rec­ords of sur­gery. It was too mon­strous for belief ...
J. B. S. Jackson (1870)


Barker notes that Harlow's original 1848 report of Gage's survival and recovery "was widely disbelieved, for obvious reasons"  and Harlow, in his 1868 retrospective, recalled this early skepticism:
The case occurred nearly twenty years ago, in an obscure country town ..., was attended and reported by an obscure country physician, and was received by the Metropolitan Doctors with several grains of caution, insomuch that many utterly refused to believe that the man had risen, until they had thrust their fingers into the hole [in] his head, and even then they required of the Country Doctor attested statements, from clergymen and lawyers, before they could or would believe‍—‌many eminent surgeons regarding such an occurrence as a physiological impossibility, the appearances presented by the subject being variously explained away.
"A distinguished Professor of Surgery in a distant city", Harlow continued, had even dismissed Gage as a "Yankee invention".

According to the Boston Medical and Surgical Journal (1869) it was the 1850 report on Gage by Bigelow‍—‌Harvard's Professor of Surgery and "a majestic and author­i­ta­tive figure on the medical scene of those times" ‍—‌that "finally succeeded in forcing [the case's] authenticity upon the credence of the pro­fes­sion ... as could hardly have been done by any one in whose sagacity and surgical knowledge his confrères had any less confidence". Noting that, "The leading feature of this case is its improb­a­bil­i­ty ... This is the sort of accident that happens in the pantomime at the theater, not elsewhere", Bigelow emphasized that though "at first wholly skeptical, I have been personally convinced".

Nonetheless (Bigelow wrote just before Harlow's 1868 presentation of Gage's skull) though "the nature of [Gage's] injury and its reality are now beyond doubt ... I have received a letter within a month [purporting] to prove that ... the accident could not have happened." 

Standard for other brain injuries

"[Few objects] have at­tract­ed more vis­i­tors and spread farther the fame of the Museum"​​ than its "most val­u­a­ble specimen"

As the reality of Gage's accident and survival gained credence, it became "the standard against which other injuries to the brain were judged", and it has retained that status despite competition from a growing list of other unlikely-sounding brain-injury accidents, including encounters with axes, bolts, low bridges, exploding firearms, a revolver shot to the nose, other tamping irons, and falling Eucalyptus branches. For example, after a miner survived traversal of his skull by a gas pipe 58 inch (1.6 cm) in diameter (extracted "not without considerable difficulty and force, owing to a bend in the portion of the rod in his skull") his physician invoked Gage as the "only case comparable with this, in the amount of brain injury, that I have seen reported".

Often these comparisons carried hints of humor, competitiveness, or both. The Boston Medical and Surgical Journal, for example, termed Gage "the patient whose cerebral organism had been comparatively so little disturbed by its abrupt and intrusive visitor"; and a Kentucky doctor, reporting a patient's survival of a gunshot through the nose, bragged, "If you Yankees can send a tamping bar through a fellow's brain and not kill him, I guess there are not many can shoot a bullet between a man's mouth and his brains, stopping just short of the medulla oblongata, and not touch either." Similarly, when a lumbermill foreman returned to work soon after a saw cut three inches (8 cm) into his skull from just between the eyes to behind the top of his head, his surgeon (who had removed from this wound "thirty-two pieces of bone, together with considerable sawdust") termed the case "second to none reported, save the famous tamping-iron case of Dr. Harlow", though apologizing that "I cannot well gratify the desire of my professional brethren to possess [the patient's] skull, until he has no further use for it himself."

As these and other remarkable brain-injury survivals accumulated, the Boston Medical and Surgical Journal pretended to wonder whether the brain has any function at all: "Since the antics of iron bars, gas pipes, and the like skepticism is discomfitted, and dares not utter itself. Brains do not seem to be of much account now-a-days." The Transactions of the Vermont Medical Society was similarly facetious: "'The times have been,' says Macbeth [Act III], 'that when the brains were out the man would die. But now they rise again.' Quite possibly we shall soon hear that some German professor is exsecting it." 

Theoretical misuse

The Gage who appears in contemporary psychology textbooks is simply a compound creature ... a stunning example of the ideological uses of case histories and their mythological reconstruction.
Rhodri Hayward

Though Gage is considered the "index case for personality change due to frontal lobe damage", ​​ the uncertain extent of his brain damage​​ and the limited understanding of his behavioral changes render him "of more historical then neurologic interest". Thus, Macmillan writes, "Phineas' story is [primarily] worth remembering because it illustrates how easily a small stock of facts becomes transformed into popular and scientific myth", the paucity of evidence having allowed "the fitting of almost any theory [desired] to the small number of facts we have". A similar concern was expressed as early as 1877, when British neurologist David Ferrier (writing to Harvard's Henry Pickering Bowditch in an attempt "to have this case definitely settled") complained that, "In investigating reports on diseases and injuries of the brain, I am constantly being amazed at the inexactitude and distortion to which they are subject by men who have some pet theory to support. The facts suffer so frightfully ..." More recently, neurologist Oliver Sacks refers to the "interpretations and misinterpretations [of Gage] from 1848 to the present", and Jarrett discusses the use of Gage to promote "the myth, found in hundreds of psychology and neuroscience textbooks, plays, films, poems, and YouTube skits[:] Personality is located in the frontal lobes ... and once those are damaged, a person is changed forever." 

Cerebral localization

In the nineteenth-century debate over whether the various mental functions are or are not localized in specific regions of the brain (see Cerebral localization), both sides managed to enlist Gage in support of their theories. For example, after Dupuy wrote that Gage proved that the brain is not localized (characterizing him as a "striking case of destruction of the so-called speech centre without consequent aphasia") Ferrier made a "devastating reply" in his 1878 Goulstonian Lectures, "On the Localisation of Cerebral Disease", of which Gage (along with the woodcuts of his skull and tamping iron from Harlow's 1868 paper) was "an absolutely dominating feature".

Phrenology

Phrenologists contended that destruction of the mental "organs" of Veneration and Benevolence caused Gage's behavioral changes. Harlow may have believed that the Organ of Comparison was damaged as well.

Throughout the nineteenth century, adherents of phrenology contended that Gage's mental changes (his profanity, for example) stemmed from destruction of his mental "organ of Benevolence"‍—‌as phrenologists saw it, the part of the brain responsible for "goodness, benevolence, the gentle character ... [and] to dispose man to conduct himself in a manner conformed to the maintenance of social order"‍—‌and/or the adjacent "organ of Veneration"‍—‌related to religion and God, and respect for peers and those in authority. (Phrenology held that the organs of the "grosser and more animal passions are near the base of the brain; literally the lowest and nearest the animal man [while] highest and farthest from the sensual are the moral and religions feelings, as if to be nearest heaven". Thus Veneration and Benevolence are at the apex of the skull‍—‌the region of exit of Gage's tamping iron.)

Harlow wrote that Gage, during his convalescence, did not "estimate size or money accurately[,] would not take $1000 for a few pebbles" and was not particular about prices when visiting a local store; by these examples Harlow may have been implying damage to phrenology's "Organ of Comparison".

Psychosurgery and lobotomy

It is frequently asserted that what happened to Gage played a role in the later development of various forms of psychosurgery‍—‌particularly lobotomy‍—‌or even that Gage's accident constituted "the first lobotomy". Aside from the question of why the unpleasant changes usually (if hyperbolically) attributed to Gage would inspire surgical imitation, there is no such link, according to Macmillan:
There is simply no evidence that any of these operations were deliberately designed to produce the kinds of changes in Gage that were caused by his accident, nor that knowledge of Gage's fate formed part of the rationale for them ‍... [W]hat his case did show came solely from his surviving his accident: major operations [such as for tumors] could be performed on the brain without the outcome necessarily being fatal.

Somatic marker hypothesis

Memorial plaque, Cavendish, Vermont

Antonio Damasio, in support of his somatic marker hypothesis (relating decision-making to emotions and their biological underpinnings), draws parallels between behaviors he ascribes to Gage and those of modern patients with damage to the orbitofrontal cortex and amygdala. But Damasio's depiction of Gage has been severely criticized, for example by Kotowicz:
Damasio is the principal perpetrator of the myth of Gage the psychopath ... Damasio changes [Harlow's] narrative, omits facts, and adds freely ... His account of Gage's last months [is] a grotesque fabrication [insinuating] that Gage was some riff-raff who in his final days headed for California to drink and brawl himself to death ... It seems that the growing commitment to the frontal lobe doctrine of emotions brought Gage to the limelight and shapes how he is described.
As Kihlstrom put it, "[M]any modern commentators exaggerate the extent of Gage's personality change, perhaps engaging in a kind of retrospective reconstruction based on what we now know, or think we do, about the role of the frontal cortex in self-regulation." Macmillan gives detailed criticism of Antonio Damasio's various presentations of Gage (some of which are joint work with Hannah Damasio and others).

Portraits

Inscription on iron as seen in portrait detail: ... [Phine]has P. Gage at Cavendish, Vermont, Sept. 14, 1848. He fully ...
 
The second portrait of Gage identified (2010)

Two daguerreotype portraits of Gage, identi­fied in 2009 and 2010, are the only like­nes­ses of him known other than a plaster head cast taken for Bigelow in late 1849 (and now in the Warren Museum along with Gage's skull and tamping iron). The first shows a "disfigured yet still-handsome" Gage with left eye closed and scars clearly visible, "well dressed and confident, even proud" and holding his iron, on which portions of its inscription can be made out. (For decades the portrait's owners had believed that it depicted an injured whaler with his harpoon.) The second, copies of which are in the possession of two branches of the Gage family, shows Gage in a somewhat different pose wearing the same waistcoat and possibly the same jacket, but with a different shirt and tie.

Authenticity was confirmed by photo-overlaying the inscription on the tamping iron, as seen in the portraits, against that on the actual tamping iron, and matching the subject's injuries to those preserved in the head cast. However, about when, where, and by whom the portraits were taken nothing is known, except that they were created no earlier than January 1850 (when the inscription was added to the tamping iron), on different occasions, and are likely by different photographers.

The portraits support other evidence that Gage's most serious mental changes were temporary (see § Social recovery, above). "That [Gage] was any form of vagrant following his injury is belied by these remarkable images", wrote Van Horn et al. "Although just one picture," Kean commented in reference to the first image discovered, "it exploded the common image of Gage as a dirty, disheveled misfit. This Phineas was proud, well-dressed, and disarmingly handsome." 

Executive dysfunction

From Wikipedia, the free encyclopedia

In psychology and neuroscience, executive dysfunction, or executive function deficit, is a disruption to the efficacy of the executive functions, which is a group of cognitive processes that regulate, control, and manage other cognitive processes. Executive dysfunction can refer to both neurocognitive deficits and behavioural symptoms. It is implicated in numerous psychopathologies and mental disorders, as well as short-term and long-term changes in non-clinical executive control.

Executive dysfunction is not the same as dysexecutive syndrome, a term coined by Alan Baddeley to describe a common pattern of dysfunction in executive functions, such as deficiencies in planning, abstract thinking, flexibility and behavioural control. This group of symptoms, usually resulting from brain damage, tend to occur together. However, the existence of dysexecutive syndrome is controversial.

Overview

Executive functioning is a theoretical construct representing a domain of cognitive processes that regulate, control, and manage other cognitive processes. Executive functioning is not a unitary concept; it is a broad description of the set of processes involved in certain areas of cognitive and behavioural control. Executive processes are integral to higher brain function, particularly in the areas of goal formation, planning, goal-directed action, self-monitoring, attention, response inhibition, and coordination of complex cognition and motor control for effective performance. Deficits of the executive functions are observed in all populations to varying degrees, but severe executive dysfunction can have devastating effects on cognition and behaviour in both individual and social contexts.

Executive dysfunction does occur to a minor degree in all individuals on both short-term and long-term scales. In non-clinical populations, the activation of executive processes appears to inhibit further activation of the same processes, suggesting a mechanism for normal fluctuations in executive control. Decline in executive functioning is also associated with both normal and clinical aging. In aging populations, the decline of memory processes appears to affect executive functions, which also points to the general role of memory in executive functioning.

Executive dysfunction appears to consistently involve disruptions in task-oriented behavior, which requires executive control in the inhibition of habitual responses and goal activation. Such executive control is responsible for adjusting behaviour to reconcile environmental changes with goals for effective behaviour. Impairments in set shifting ability are a notable feature of executive dysfunction; set shifting is the cognitive ability to dynamically change focus between points of fixation based on changing goals and environmental stimuli. This offers a parsimonious explanation for the common occurrence of impulsive, hyperactive, disorganized, and aggressive behaviour in clinical patients with executive dysfunction. Executive dysfunction, particularly in working memory capacity, may also lead to varying degrees of emotional dysregulation, which can manifest as chronic depression, anxiety, or hyperemotionality. Russell Barkley proposed a hybrid model of the role of behavioural disinhibition in the presentation of ADHD, which has served as the basis for much research of both ADHD and broader implications of the executive system.

Other common and distinctive symptoms of executive dysfunction include utilization behaviour, which is compulsive manipulation/use of nearby objects due simply to their presence and accessibility (rather than a functional reason); and imitation behaviour, a tendency to rely on imitation as a primary means of social interaction. Research also suggests that executive set shifting is a co-mediator with episodic memory of feeling-of-knowing (FOK) accuracy, such that executive dysfunction may reduce FOK accuracy.

There is some evidence suggesting that executive dysfunction may produce beneficial effects as well as maladaptive ones. Abraham et al. demonstrate that creative thinking in schizophrenia is mediated by executive dysfunction, and they establish a firm etiology for creativity in psychoticism, pinpointing a cognitive preference for broader top-down associative thinking versus goal-oriented thinking, which closely resembles aspects of ADHD. It is postulated that elements of psychosis are present in both ADHD and schizophrenia/schizotypy due to dopamine overlap.

Cause

The cause of executive dysfunction is heterogeneous, as many neurocognitive processes are involved in the executive system and each may be compromised by a range of genetic and environmental factors. Learning and development of long-term memory play a role in the severity of executive dysfunction through dynamic interaction with neurological characteristics. Studies in cognitive neuroscience suggest that executive functions are widely distributed throughout the brain, though a few areas have been isolated as primary contributors. Executive dysfunction is studied extensively in clinical neuropsychology as well, allowing correlations to be drawn between such dysexecutive symptoms and their neurological correlates.

Executive processes are closely integrated with memory retrieval capabilities for overall cognitive control; in particular, goal/task-information is stored in both short-term and long-term memory, and effective performance requires effective storage and retrieval of this information.

Executive dysfunction characterizes many of the symptoms observed in numerous clinical populations. In the case of acquired brain injury and neurodegenerative diseases there is a clear neurological etiology producing dysexecutive symptoms. Conversely, syndromes and disorders are defined and diagnosed based on their symptomatology rather than etiology. Thus, while Parkinson's disease, a neurodegenerative condition, causes executive dysfunction, a disorder such as attention-deficit/hyperactivity disorder is a classification given to a set of subjectively-determined symptoms implicating executive dysfunction – current models indicate that such clinical symptoms are caused by executive dysfunction.

Neurophysiology

As previously mentioned, executive functioning is not a unitary concept. Many studies have been conducted in an attempt to pinpoint the exact regions of the brain that lead to executive dysfunction, producing a vast amount of often conflicting information indicating wide and inconsistent distribution of such functions. A common assumption is that disrupted executive control processes are associated with pathology in prefrontal brain regions. This is supported to some extent by the primary literature, which shows both pre-frontal activation and communication between the pre-frontal cortex and other areas associated with executive functions such as the basal ganglia and cerebellum.

In most cases of executive dysfunction, deficits are attributed to either frontal lobe damage or dysfunction, or to disruption in fronto-subcortical connectivity. Neuroimaging with PET and fMRI has confirmed the relationship between executive function and functional frontal pathology. Neuroimaging studies have also suggested that some constituent functions are not discretely localized in prefrontal regions. Functional imaging studies using different tests of executive function have implicated the dorsolateral prefrontal cortex to be the primary site of cortical activation during these tasks. In addition, PET studies of patients with Parkinson's disease have suggested that tests of executive function are associated with abnormal function in the globus pallidus and appear to be the genuine result of basal ganglia damage.

With substantial cognitive load, fMRI signals indicate a common network of frontal, parietal and occipital cortices, thalamus, and the cerebellum. This observation suggests that executive function is mediated by dynamic and flexible networks that are characterized using functional integration and effective connectivity analyses. The complete circuit underlying executive function includes both a direct and an indirect circuit. The neural circuit responsible for executive functioning is, in fact, located primarily in the frontal lobe. This main circuit originates in the dorsolateral prefrontal cortex/orbitofrontal cortex and then projects through the striatum and thalamus to return to the prefrontal cortex.

Not surprisingly, plaques and tangles in the frontal cortex can cause disruption in functions as well as damage to the connections between prefrontal cortex and the hippocampus. Another important point is in the finding that structural MRI images link the severity of white matter lesions to deficits in cognition.

The emerging view suggests that cognitive processes materialize from networks that span multiple cortical sites with closely collaborative and over-lapping functions. A challenge for future research will be to map the multiple brain regions that might combine with each other in a vast number of ways, depending on the task requirements.

Genetics

Certain genes have been identified with a clear correlation to executive dysfunction and related psychopathologies. According to Friedman et al. (2008), the heritability of executive functions is among the highest of any psychological trait. The dopamine receptor D4 gene (DRD4) with 7'-repeating polymorphism (7R) has been repeatedly shown to correlate strongly with impulsive response style on psychological tests of executive dysfunction, particularly in clinical ADHD. The catechol-o-methyl transferase gene (COMT) codes for an enzyme that degrades catecholamine neurotransmitters (DA and NE), and its Val158Met polymorphism is linked with the modulation of task-oriented cognition and behavior (including set shifting) and the experience of reward, which are major aspects of executive functioning. COMT is also linked to methylphenidate (stimulant medication) response in children with ADHD. Both the DRD4/7R and COMT/Val158Met polymorphisms are also correlated with executive dysfunction in schizophrenia and schizotypal behaviour.

Testing and measurement

There are several measures that can be employed to assess the executive functioning capabilities of an individual. Although a trained non-professional working outside of an institutionalized setting can legally and competently perform many of these measures, a trained professional administering the test in a standardized setting will yield the most accurate results.

Clock drawing test

The Clock drawing test (CDT) is a brief cognitive task that can be used by physicians who suspect neurological dysfunction based on history and physical examination. It is relatively easy to train non-professional staff to administer a CDT. Therefore, this is a test that can easily be administered in educational and geriatric settings and can be utilized as a precursory measure to indicate the likelihood of further/future deficits. Also, generational, educational and cultural differences are not perceived as impacting the utility of the CDT.

The procedure of the CDT begins with the instruction to the participant to draw a clock reading a specific time (generally 11:10). After the task is complete, the test administrator draws a clock with the hands set at the same specific time. Then the patient is asked to copy the image. Errors in clock drawing are classified according to the following categories: omissions, perseverations, rotations, misplacements, distortions, substitutions and additions. Memory, concentration, initiation, energy, mental clarity and indecision are all measures that are scored during this activity. Those with deficits in executive functioning will often make errors on the first clock but not the second. In other words, they will be unable to generate their own example, but will show proficiency in the copying task.

Stroop task

The cognitive mechanism involved in the Stroop task is referred to as directed attention. The Stroop task requires the participant to engage in and allows assessment of processes such as attention management, speed and accuracy of reading words and colours and of inhibition of competing stimuli. The stimulus is a colour word that is printed in a different colour than what the written word reads. For example, the word "red" is written in a blue font. One must verbally classify the colour that the word is displayed/printed in, while ignoring the information provided by the written word. In the aforementioned example, this would require the participant to say "blue" when presented with the stimulus. Although the majority of people will show some slowing when given incompatible text versus font colour, this is more severe in individuals with deficits in inhibition. The Stroop task takes advantage of the fact that most humans are so proficient at reading colour words that it is extremely difficult to ignore this information, and instead acknowledge, recognize and say the colour the word is printed in. The Stroop task is an assessment of attentional vitality and flexibility. More modern variations of the Stroop task tend to be more difficult and often try to limit the sensitivity of the test.

Wisconsin card sorting test

The Wisconsin Card Sorting Test (WCST) is used to determine an individual's competence in abstract reasoning, and the ability to change problem-solving strategies when needed. These abilities are primarily determined by the frontal lobes and basal ganglia, which are crucial components of executive functioning; making the WCST a good measure for this purpose.

The WCST utilizes a deck of 128 cards that contains four stimulus cards. The figures on the cards differ with respect to color, quantity, and shape. The participants are then given a pile of additional cards and are asked to match each one to one of the previous cards. Typically, children between ages 9 and 11 are able to show the cognitive flexibility that is needed for this test.

Trail-making test

Another prominent test of executive dysfunction is known as the Trail-making test. This test is composed of two main parts (Part A & Part B). Part B differs from Part A specifically in that it assesses more complex factors of motor control and perception. Part B of the Trail-making test consists of multiple circles containing letters (A-L) and numbers (1-12). The participant's objective for this test is to connect the circles in order, alternating between number and letter (e.g. 1-A-2-B) from start to finish. The participant is required not to lift their pencil from the page. The task is also timed as a means of assessing speed of processing. Set-switching tasks in Part B have low motor and perceptual selection demands, and therefore provide a clearer index of executive function. Throughout this task, some of the executive function skills that are being measured include impulsivity, visual attention and motor speed.

In clinical populations

The executive system's broad range of functions relies on, and is instrumental in, a broad range of neurocognitive processes. Clinical presentation of severe executive dysfunction that is unrelated to a specific disease or disorder is classified as a dysexecutive syndrome, and often appears following damage to the frontal lobes of the cerebral cortex. As a result, Executive dysfunction is implicated etiologically and/or co-morbidly in many psychiatric illnesses, which often show the same symptoms as the dysexecutive syndrome. It has been assessed and researched extensively in relation to cognitive developmental disorders, psychotic disorders, affective disorders, and conduct disorders, as well as neurodegenerative diseases and acquired brain injury (ABI).

Environmental dependency syndrome is a dysexecutive syndrome marked by significant behavioural dependence on environmental cues and is marked by excessive imitation and utilization behaviour. It has been observed in patients with a variety of etiologies including ABI, exposure to phendimetrazine tartrate, stroke, and various frontal lobe lesions.

Schizophrenia

Schizophrenia is commonly described as a mental disorder in which a person becomes detached from reality because of disruptions in the pattern of thinking and perception. Although the etiology is not completely understood, it is closely related to dopaminergic activity and is strongly associated with both neurocognitive and genetic elements of executive dysfunction. Individuals with schizophrenia may demonstrate amnesia for portions of their episodic memory. Observed damage to explicit, consciously accessed, memory is generally attributed to the fragmented thoughts that characterize the disorder. These fragmented thoughts are suggested to produce a similarly fragmented organization in memory during encoding and storage, making retrieval more difficult. However, implicit memory is generally preserved in patients with schizophrenia.

Patients with schizophrenia demonstrate spared performance on measures of visual and verbal attention and concentration, as well as on immediate digit span recall, suggesting that observed deficits cannot be attributed to deficits in attention or short-term memory. However, impaired performance was measured on psychometric measures assumed to assess higher order executive function. Working memory and multi-tasking impairments typically characterize the disorder. Persons with schizophrenia also tend to demonstrate deficits in response inhibition and cognitive flexibility.

Patients often demonstrate noticeable deficits in the central executive component of working memory as conceptualized by Baddeley and Hitch. However, performance on tasks associated with the phonological loop and visuospatial sketchpad are typically less affected. More specifically, patients with schizophrenia show impairment to the central executive component of working memory, specific to tasks in which the visuospatial system is required for central executive control. The phonological system appears to be more generally spared overall.

Attention deficit hyperactivity disorder

A triad of core symptoms, namely inattention, hyperactivity, and impulsivity characterize attention deficit/hyperactivity disorder. Individuals with ADHD often experience problems with organization, discipline, and setting priorities, and these difficulties often persist from childhood through adulthood. In both children and adults with ADHD, an underlying executive dysfunction involving the prefrontal regions and other interconnected subcortical structures has been found. As a result, people with ADHD commonly perform more poorly than matched controls on interference control, mental flexibility and verbal fluency. Also, a more central impairment in self-regulation is noted in cases of ADHD. However, some research has suggested the possibility that the severity of executive dysfunction in individuals with ADHD declines with age as they learn to compensate for the aforementioned deficits. Thus, a decrease in executive dysfunction in adults with ADHD as compared to children with ADHD is thought reflective of compensatory strategies employed on behalf of the adults (e.g. using schedules to organize tasks) rather than neurological differences.

Although ADHD has typically been conceptualized in a categorical diagnostic paradigm, it has also been proposed that this disorder should be considered within a more dimensional behavioural model that links executive functions to observed deficits. Proponents argue that classic conceptions of ADHD falsely localize the problem at perception (input) rather than focusing on the inner processes involved in producing appropriate behaviour (output). Moreover, others have theorized that the appropriate development of inhibition (something that is seen to be lacking in individuals with ADHD) is essential for the normal performance of other neuropsychological abilities such as working memory, and emotional self-regulation. Thus, within this model, deficits in inhibition are conceptualized to be developmental and the result of atypically operating executive systems.

Autism spectrum disorder

Autism is diagnosed based on the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activities and interests. It is a disorder that is defined according to behaviour as no specific biological markers are known. Due to the variability in severity and impairment in functioning exhibited by persons with autism, the disorder is typically conceptualized as existing along a continuum (or spectrum) of severity.
Individuals with autism commonly show impairment in three main areas of executive functioning:
  • Fluency. Fluency refers to the ability to generate novel ideas and responses. Although adult populations are largely underrepresented in this area of research, findings have suggested that children with autism generate fewer novel words and ideas and produce less complex responses than matched controls.
  • Planning. Planning refers to a complex, dynamic process, wherein a sequence of planned actions must be developed, monitored, re-evaluated and updated. Persons with autism demonstrate impairment on tasks requiring planning abilities relative to typically functioning controls, with this impairment maintained over time. As might be suspected, in the case of autism comorbid with learning disability, an additive deficit is observed in many cases.
  • Flexibility. Poor mental flexibility, as demonstrated in individuals with autism, is characterized by perseverative, stereotyped behaviour, and deficits in both the regulation and modulation of motor acts. Some research has suggested that individuals with autism experience a sort of 'stuck-in-set' perseveration that is specific to the disorder, rather than a more global perseveration tendency. These deficits have been exhibited in cross-cultural samples and have been shown to persist over time.
Although there has been some debate, inhibition is generally no longer considered to be an executive function deficit in people with autism. Individuals with autism have demonstrated differential performance on various tests of inhibition, with results being taken to indicate a general difficulty in the inhibition of a habitual response. However, performance on the Stroop task, for example, has been unimpaired relative to matched controls. An alternative explanation has suggested that executive function tests that demonstrate a clear rationale are passed by individuals with autism. In this light, it is the design of the measures of inhibition that have been implicated in the observation of impaired performance rather than inhibition being a core deficit.

In general, individuals with autism show relatively spared performance on tasks that do not require mentalization. These include: use of desire and emotion words, sequencing behavioural pictures, and the recognition of basic facial emotional expressions. In contrast, individuals with autism typically demonstrated impaired performance on tasks that do require mentalizing. These include: false beliefs, use of belief and idea words, sequencing mentalistic pictures, and recognizing complex emotions such as admiring or scheming.

Bipolar disorder

Bipolar disorder is a mood disorder that is characterized by both highs (mania) and lows (depression) in mood. These changes in mood sometimes alternate rapidly (changes within days or weeks) and sometimes not so rapidly (within weeks or months). Current research provides strong evidence of cognitive impairments in individuals with bipolar disorder, particularly in executive function and verbal learning. Moreover, these cognitive deficits appear to be consistent cross-culturally, indicating that these impairments are characteristic of the disorder and not attributable to differences in cultural values, norms, or practice. Functional neuroimaging studies have implicated abnormalities in the dorsolateral prefrontal cortex and the anterior cingulate cortex as being volumetrically different in individuals with bipolar disorder.

Individuals affected by bipolar disorder exhibit deficits in strategic thinking, inhibitory control, working memory, attention, and initiation that are independent of affective state. In contrast to the more generalized cognitive impairment demonstrated in persons with schizophrenia, for example, deficits in bipolar disorder are typically less severe and more restricted. It has been suggested that a "stable dys-regulation of prefrontal function or the subcortical-frontal circuitry [of the brain] may underlie the cognitive disturbances of bipolar disorder". Executive dysfunction in bipolar disorder is suggested to be associated particularly with the manic state, and is largely accounted for in terms of the formal thought disorder that is a feature of mania. It is important to note, however, that patients with bipolar disorder with a history of psychosis demonstrated greater impairment on measures of executive functioning and spatial working memory compared with bipolar patients without a history of psychosis suggesting that psychotic symptoms are correlated with executive dysfunction.

Parkinson's disease

Parkinson's disease (PD) primarily involves damage to subcortical brain structures and is usually associated with movement difficulties, in addition to problems with memory and thought processes. Persons affected by PD often demonstrate difficulties in working memory, a component of executive functioning. Cognitive deficits found in early PD process appear to involve primarily the fronto-executive functions. Moreover, studies of the role of dopamine in the cognition of PD patients have suggested that PD patients with inadequate dopamine supplementation are more impaired in their performance on measures of executive functioning. This suggests that dopamine may contribute to executive control processes. Increased distractibility, problems in set formation and maintaining and shifting attentional sets, deficits in executive functions such as self-directed planning, problems solving, and working memory have been reported in PD patients. In terms of working memory specifically, persons with PD show deficits in the areas of: a) spatial working memory; b) central executive aspects of working memory; c) loss of episodic memories; d) locating events in time.

Spatial working memory. PD patients often demonstrate difficulty in updating changes in spatial information and often become disoriented. They do not keep track of spatial contextual information in the same way that a typical person would do almost automatically. Similarly, they often have trouble remembering the locations of objects that they have recently seen, and thus also have trouble with encoding this information into long-term memory.

Central executive aspects. PD is often characterized by a difficulty in regulating and controlling one's stream of thought, and how memories are utilized in guiding future behaviour. Also, persons affected by PD often demonstrate perseverative behaviours such as continuing to pursue a goal after it is completed, or an inability to adopt a new strategy that may be more appropriate in achieving a goal. However, some recent research suggests that PD patients may actually be less persistent in pursuing goals than typical persons and may abandon tasks sooner when they encounter problems of a higher level of difficulty.

Loss of episodic memories. The loss of episodic memories in PD patients typically demonstrates a temporal gradient wherein older memories are generally more preserved than newer memories. Also, while forgetting event content is less compromised in Parkinson's than in Alzheimer's, the opposite is true for event data memories.

Locating events in time. PD patients often demonstrate deficits in their ability to sequence information, or date events. Part of the problems is hypothesized to be due to a more fundamental difficulty in coordinating or planning retrieval strategies, rather than failure at the level of encoding or storing information in memory. This deficit is also likely to be due to an underlying difficulty in properly retrieving script information. PD patients often exhibit signs of irrelevant intrusions, incorrect ordering of events, and omission of minor components in their script retrieval, leading to disorganized and inappropriate application of script information.

Treatment

Psychosocial treatment

Since 1997 there has been experimental and clinical practice of psychosocial treatment for adults with executive dysfunction, and particularly attention-deficit/hyperactivity disorder (ADHD). Psychosocial treatment addresses the many facets of executive difficulties, and as the name suggests, covers academic, occupational and social deficits. Psychosocial treatment facilitates marked improvements in major symptoms of executive dysfunction such as time management, organization and self-esteem.

Cognitive-behavioral therapy and group rehabilitation

Cognitive-behavioural therapy (CBT) is a frequently suggested treatment for executive dysfunction, but has shown limited effectiveness. However, a study of CBT in a group rehabilitation setting showed a significant increase in positive treatment outcome compared with individual therapy. Patients' self-reported symptoms on 16 different ADHD/executive-related items were reduced following the treatment period.

Treatment for patients with acquired brain injury

The use of auditory stimuli has been examined in the treatment of dysexecutive syndrome. The presentation of auditory stimuli causes an interruption in current activity, which appears to aid in preventing "goal neglect" by increasing the patients' ability to monitor time and focus on goals. Given such stimuli, subjects no longer performed below their age group average IQ.

Patients with acquired brain injury have also been exposed to goal management training (GMT). GMT skills are associated with paper-and-pencil tasks that are suitable for patients having difficulty setting goals. From these studies there has been support for the effectiveness of GMT and the treatment of executive dysfunction due to ABI.

Developmental context

An understanding of how executive dysfunction shapes development has implications how we conceptualize executive functions and their role in shaping the individual. Disorders affecting children such as ADHD, along with oppositional defiant disorder, conduct disorder, high functioning autism and Tourette's syndrome have all been suggested to involve executive functioning deficits. The main focus of current research has been on working memory, planning, set shifting, inhibition, and fluency. This research suggests that differences exist between typically functioning, matched controls and clinical groups, on measures of executive functioning.

Some research has suggested a link between a child's abilities to gain information about the world around them and having the ability to override emotions in order to behave appropriately. One study required children to perform a task from a series of psychological tests, with their performance used as a measure of executive function. The tests included assessments of: executive functions (self-regulation, monitoring, attention, flexibility in thinking), language, sensorimotor, visuospatial, and learning, in addition to social perception. The findings suggested that the development of theory of mind in younger children is linked to executive control abilities with development impaired in individuals who exhibit signs of executive dysfunction.

Both ADHD and obesity are complicated disorders and each produces a large impact on an individual's social well being. This being both a physical and psychological disorder has reinforced that obese individuals with ADHD need more treatment time (with associated costs), and are at a higher risk of developing physical and emotional complications. The cognitive ability to develop a comprehensive self-construct and the ability to demonstrate capable emotion regulation is a core deficit observed in people with ADHD and is linked to deficits in executive function. Overall, low executive functioning seen in individuals with ADHD has been correlated with tendencies to overeat, as well as with emotional eating. This particular interest in the relationship between ADHD and obesity is rarely clinically assessed and may deserve more attention in future research.

It has been made known that young children with behavioral problems show poor verbal ability and executive functions. The exact distinction between parenting style and the importance of family structure on child development is still somewhat unclear. However, in infancy and early childhood, parenting is among the most critical external influences on child reactivity. In Mahoney's study of maternal communication, results indicated that the way mothers interacted with their children accounted for almost 25% of variability in children's rate of development. Every child is unique, making parenting an emotional challenge that should be most closely related to the child's level of emotional self-regulation (persistence, frustration and compliance). A promising approach that is currently being investigated amid intellectually disabled children and their parents is responsive teaching. Responsive teaching is an early intervention curriculum designed to address the cognitive, language, and social needs of young children with developmental problems. Based on the principle of "active learning", responsive teaching is a method that is currently being applauded as adaptable for individual caregivers, children and their combined needs The effect of parenting styles on the development of children is an important area of research that seems to be forever ongoing and altering. There is no doubt that there is a prominent link between parental interaction and child development but the best child rearing technique continues to vary amongst experts.

Evolutionary perspective

The prefrontal lobe controls two related executive functioning domains. The first is mediation of abilities involved in planning, problem solving, and understanding information, as well as engaging in working memory processes and controlled attention. In this sense, the prefrontal lobe is involved with dealing with basic, everyday situations, especially those involving metacognitive functions. The second domain involves the ability to fulfill biological needs through the coordination of cognition and emotions which are both associated with the frontal and prefrontal areas.

From an evolutionary perspective, it has been hypothesized that the executive system may have evolved to serve several adaptive purposes. The prefrontal lobe in humans has been associated both with metacognitive executive functions and emotional executive functions. Theory and evidence suggest that the frontal lobes in other primates also mediate and regulate emotion, but do not demonstrate the metacognitive abilities that are demonstrated in humans. This uniqueness of the executive system to humans implies that there was also something unique about the environment of ancestral humans, which gave rise to the need for executive functions as adaptations to that environment. Some examples of possible adaptive problems that would have been solved by the evolution of an executive system are: social exchange, imitation and observational learning, enhanced pedagogical understanding, tool construction and use, and effective communication.

In a similar vein, some have argued that the unique metacognitive capabilities demonstrated by humans have arisen out of the development of a sophisticated language (symbolization) systems and culture. Moreover, in a developmental context, it has been proposed that each executive function capability originated as a form of public behaviour directed at the external environment, but then became self-directed, and then finally, became private to the individual, over the course of the development of self-regulation. These shifts in function illustrate the evolutionarily salient strategy of maximizing longer-term social consequences over near-term ones, through the development of an internal control of behaviour.

Comorbidity

Flexibility problems are more likely to be related to Anxiety, and Metacognition problems are more likely to be related to depression.

Socio-cultural implications

Education

In the classroom environment, children with executive dysfunction typically demonstrate skill deficits that can be categorized into two broad domains: a) self-regulatory skills; and b) goal-oriented skills. The table below is an adaptation of McDougall's summary and provides an overview of specific executive function deficits that are commonly observed in a classroom environment. It also offers examples of how these deficits are likely to manifest in behaviour.

Self-regulatory skills
Often exhibit deficits in... Manifestations in the classroom
Perception. Awareness of something happening in the environment Doesn't "see" what is happening; Doesn't "hear" instructions
Modulation. Awareness of the amount of effort needed to perform a task (successfully) Commission of errors at easy levels and success at harder levels; Indication that student thinks the task is "easy" then cannot do it correctly; Performance improves once the student realized that the task is more difficult than originally thought
Sustained attention. Ability to focus on a task or situation despite distractions, fatigue or boredom Initiates the task, but doesn't continue to work steadily; Easily distracted; Fatigues easily; Complains task is too long or too boring
Flexibility. Ability to change focus, adapt to changing conditions or revise plans in the face of obstacles, new information or mistakes (can also be considered as "adaptability") Slow to stop one activity and begin another after being instructed to do so; Tendency to stay with one plan or strategy even after it is shown to be ineffective; Rigid adherence to routines; Refusal to consider new information
Working memory. Ability to hold information in memory while performing complex tasks with information Forgets instructions (especially if multi-step); Frequently asks for information to be repeated; Forgets books at home or at school; Can't do mental arithmetic; Difficulty making connections with previously learned information; Difficulty with reading comprehension
Response inhibition. Capacity to think before acting (deficits are often observed as "impulsivity") Seems to act without thinking; Frequently interrupts; Talks out in class; Often out of seat/away from desk; Rough play gets out of control; Doesn't consider consequences of actions
Emotional regulation. Ability to modulate emotional responses Temper outbursts; Cries easily; Very easily frustrated; Very quick to anger; Acts silly

Goal-oriented skills
Often exhibit deficits in... Manifestations in the classroom
Planning. Ability to list steps needed to reach a goal or complete a task Doesn't know where to start when given large assignments; Easily overwhelmed by task demands; Difficulty developing a plan for long-term projects; Problem-solving strategies are very limited and haphazard; Starts working before adequately considering the demands of a task; Difficulty listing steps required to complete a task
Organization. Ability to arrange information or materials according to a system Disorganized desk, binder, notebooks, etc.; Loses books, papers, assignments, etc.; Doesn't write down important information; Difficulty retrieving information when needed
Time management. Ability to comprehend how much time is available, or to estimate how long it will take to complete a task, and keep track of how much time has passed relative to the amount of the task completed Very little work accomplished during a specified period of time; Wasting time, then rushing to complete a task at the last minute; Often late to class/assignments are often late; Difficulty estimating how long it takes to do a task; Limited awareness of the passage of time
Self-monitoring. Ability to stand back and evaluate how you are doing (can also be thought of as "metacognitive" abilities) Makes "careless" errors; Does not check work before handing it in; Does not stop to evaluate how things are going in the middle of a task or activity; Thinks a task was well done, when in fact it was done poorly; Thinks a task was poorly done, when in fact it was done well

Teachers play a crucial role in the implementation of strategies aimed at improving academic success and classroom functioning in individuals with executive dysfunction. In a classroom environment, the goal of intervention should ultimately be to apply external control, as needed (e.g. adapt the environment to suit the child, provide adult support) in an attempt to modify problem behaviours or supplement skill deficits. Ultimately, executive function difficulties should not be attributed to negative personality traits or characteristics (e.g. laziness, lack of motivation, apathy, and stubbornness) as these attributions are neither useful nor accurate.

Several factors should be considered in the development of intervention strategies. These include, but are not limited to: developmental level of the child, comorbid disabilities, environmental changes, motivating factors, and coaching strategies. It is also recommended that strategies should take a proactive approach in managing behaviour or skill deficits (when possible), rather than adopt a reactive approach. For example, an awareness of where a student may have difficulty throughout the course of the day can aid the teacher in planning to avoid these situations or in planning to accommodate the needs of the student.

People with executive dysfunction have a slower cognitive processing speed and thus often take longer to complete tasks than people who demonstrate typical executive function capabilities. This can be frustrating for the individual and can serve to impede academic progress. Disorders affecting children such as ADHD, along with oppositional defiant disorder, conduct disorder, high functioning autism and Tourette's syndrome have all been suggested to involve executive functioning deficits. The main focus of current research has been on working memory, planning, set shifting, inhibition, and fluency. This research suggests that differences exist between typically functioning, matched controls and clinical groups, on measures of executive functioning.

Moreover, some people with ADHD report experiencing frequent feelings of drowsiness. This can hinder their attention for lectures, readings, and completing assignments. Individuals with this disorder have also been found to require more stimuli for information processing in reading and writing. Slow processing may manifest in behavior as signaling a lack of motivation on behalf of the learner. However, slow processing is reflective of an impairment of the ability to coordinate and integrate multiple skills and information sources.

The main concern with individuals with autism regarding learning is in the imitation of skills. This can be a barrier in many aspects such as learning about others intentions, mental states, speech, language, and general social skills. Individuals with autism tend to be dependent on the routines that they have already mastered, and have difficulty with initiating new non-routine tasks. Although an estimated 25–40% of people with autism also have a learning disability, many will demonstrate an impressive rote memory and memory for factual knowledge. As such, repetition is the primary and most successful method for instruction when teaching people with autism.

Being attentive and focused for people with Tourette's syndrome is a difficult process. People affected by this disorder tend to be easily distracted and act very impulsively. That is why it is very important to have a quiet setting with few distractions for the ultimate learning environment. Focusing is particularly difficult for those who are affected by Tourette's syndrome comorbid with other disorders such as ADHD or obsessive-compulsive disorder, it makes focusing very difficult. Also, these individuals can be found to repeat words or phrases consistently either immediately after they are learned or after a delayed period of time.

Criminal behaviour

Prefrontal dysfunction has been found as a marker for persistent, criminal behavior. The prefrontal cortex is involved with mental functions including; affective range of emotions, forethought, and self-control. Moreover, there is a scarcity of mental control displayed by individuals with a dysfunction in this area over their behavior, reduced flexibility and self-control and their difficulty to conceive behavioral consequences, which may conclude in unstable (or criminal) behavior. In a recent study conducted by Barbosa & Monteiro, it was discovered that the recurrent criminals that were considered in this study suffered from executive dysfunction. In view of the fact that abnormalities in executive function can limit how people respond to rehabilitation and re-socialization programs these findings of the recurrent criminals are justified. Statistically significant relations have been discerned between anti-social behavior and executive function deficits. These findings relate to the emotional instability that is connected with executive function as a detrimental symptom that can also be linked towards criminal behavior. Conversely, it is unclear as to the specificity of anti-social behavior to executive function deficits as opposed to other generalized neuropsychological deficits. The uncontrollable deficiency of executive function has an increased expectancy for aggressive behavior that can result in a criminal deed. Orbitofrontal injury also hinders the ability to be risk avoidant, make social judgments, and may cause reflexive aggression. A common retort to these findings is that the higher incidence of cerebral lesions among the criminal population may be due to the peril associated with a life of crime. Along with this reasoning, it would be assumed that some other personality trait is responsible for the disregard of social acceptability and reduction in social aptitude.

Furthermore, some think the dysfunction cannot be entirely to blame. There are interacting environmental factors that also have an influence on the likelihood of criminal action. This theory proposes that individuals with this deficit are less able to control impulses or foresee the consequences of actions that seem attractive at the time (see above) and are also typically provoked by environmental factors. One must recognize that the frustrations of life, combined with a limited ability to control life events, can easily cause aggression and/or other criminal activities. Early brain Damage causes dopamine(epigentically) to select for "Seeking" behavior in the very short term...this is the window for existence for these individuals...the future has no meaning so consequences have no meaning

Entropy (information theory)

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Entropy_(information_theory) In info...