Neuropsychology is the study and characterization of the behavioral modifications that follow a neurological trauma or condition. It is both an experimental and clinical field of psychology that aims to understand how behavior and cognition are influenced by brain functioning and is concerned with the diagnosis and treatment of behavioral and cognitive effects of neurological disorders. Whereas classical neurology focuses on the pathology of the nervous system and classical psychology is largely divorced from it, neuropsychology seeks to discover how the brain correlates with the mind through the study of neurological patients. It thus shares concepts and concerns with neuropsychiatry and with behavioral neurology in general. The term neuropsychology has been applied to lesion studies in humans and animals. It has also been applied in efforts to record electrical activity from individual cells (or groups of cells) in higher primates (including some studies of human patients).
In practice, neuropsychologists tend to work in research settings (universities, laboratories or research institutions), clinical settings (medical hospitals or rehabilitation settings, often involved in assessing or treating patients with neuropsychological problems), or forensic settings or industry (often as clinical-trial consultants where CNS function is a concern).
History
Neuropsychology is a relatively new discipline within the field of psychology. The first textbook defining the field, Fundamentals of Human Neuropsychology, was initially published by Kolb and Whishaw in 1980. However, the history of its development can be traced back to the Third Dynasty in ancient Egypt, perhaps even earlier. There is much debate as to when societies started considering the functions of different organs. For many centuries, the brain
was thought useless and was often discarded during burial processes and
autopsies. As the field of medicine developed its understanding of
human anatomy and physiology,
different theories were developed as to why the body functioned the way
it did. Many times, bodily functions were approached from a religious
point of view and abnormalities were blamed on bad spirits and the gods.
The brain has not always been considered the center of the functioning
body. It has taken hundreds of years to develop our understanding of the
brain and how it affects our behaviors.
Ancient Egypt
In ancient Egypt, writings on medicine date from the time of the priest Imhotep.
They took a more scientific approach to medicine and disease,
describing the brain, trauma, abnormalities, and remedies for reference
for future physicians. Despite this, Egyptians saw the heart not the
brain as the seat of the soul.
Aristotle
Senses, perception, memory, dreams, action in Aristotle's biology. Impressions are stored in the seat of perception, linked by his Laws of Association (similarity, contrast, and contiguity).
Aristotle
reinforced this focus on the heart which originated in Egypt. He
believed the heart to be in control of mental processes, and looked on
the brain, due to its inert nature, as a mechanism for cooling the heat
generated by the heart.
He drew his conclusions based on the empirical study of animals. He
found that while their brains were cold to the touch and that such
contact did not trigger any movements, the heart was warm and active,
accelerating and slowing dependent on mood.
Such beliefs were upheld by many for years to come, persisting through
the Middle Ages and the Renaissance period until they began to falter in
the 17th century due to further research.
The influence of Aristotle in the development of neuropsychology is
evident within language used in modern day, since we "follow our hearts"
and "learn by the heart."
Hippocrates
Hippocrates
viewed the brain as the seat of the soul. He drew a connection between
the brain and behaviors of the body, writing: "The brain exercises the
greatest power in the man."
Apart from moving the focus from the heart as the "seat of the soul" to
the brain, Hippocrates did not go into much detail about its actual
functioning. However, by switching the attention of the medical
community to the brain, his theory led to more scientific discovery of
the organ responsible for our behaviors. For years to come, scientists
were inspired to explore the functions of the body and to find concrete
explanations for both normal and abnormal behaviors. Scientific
discovery led them to believe that there were natural and organically
occurring reasons to explain various functions of the body, and it could
all be traced back to the brain. Hippocrates introduced the concept of
the mind – which was widely seen as a separate function apart from the
actual brain organ.
René Descartes
Philosopher René Descartes expanded upon this idea and is most widely known for his work on the mind-body problem.
Often Descartes's ideas were looked upon as overly philosophical and
lacking in sufficient scientific foundation. Descartes focused much of
his anatomical experimentation on the brain, paying special attention to
the pineal gland – which he argued was the actual "seat of the soul."
Still deeply rooted in a spiritual outlook towards the scientific world,
the body was said to be mortal, and the soul immortal. The pineal gland
was then thought to be the very place at which the mind would interact
with the mortal and machine-like body. At the time, Descartes was
convinced the mind had control over the behaviors of the body
(controlling the person) – but also that the body could have influence
over the mind, which is referred to as dualism.
This idea that the mind essentially had control over the body, but the
body could resist or even influence other behaviors, was a major turning
point in the way many physiologists would look at the brain. The
capabilities of the mind were observed to do much more than simply
react, but also to be rational and function in organized, thoughtful
ways – much more complex than he thought the animal world to be. These
ideas, although disregarded by many and cast aside for years led the
medical community to expand their own ideas of the brain and begin to
understand in new ways just how intricate the workings of the brain
really were, and the complete effects it had on daily life, as well,
which treatments would be the most beneficial to helping those people
living with a dysfunctional mind. The mind-body problem, spurred by René
Descartes, continues to this day with many philosophical arguments both
for and against his ideas. However controversial they were and remain
today, the fresh and well-thought-out perspective Descartes presented
has had long-lasting effects on the various disciplines of medicine,
psychology and much more, especially in putting an emphasis on
separating the mind from the body in order to explain observable
behaviors.
Thomas Willis
It was in the mid-17th century that another major contributor to the field of neuropsychology emerged. Thomas Willis
studied at Oxford University and took a physiological approach to the
brain and behavior. It was Willis who coined the words 'hemisphere' and
'lobe' when referring to the brain.
He was one of the earliest to use the words 'neurology' and
'psychology'. Rejecting the idea that humans were the only beings
capable of rational thought, Willis looked at specialized structures of
the brain.
He theorized that higher structures accounted for complex functions,
whereas lower structures were responsible for functions similar to those
seen in other animals, consisting mostly of reactions and automatic
responses. He was particularly interested in people who suffered from manic disorders and hysteria.
His research constituted some of the first times that psychiatry and
neurology came together to study individuals. Through his in-depth study
of the brain and behavior, Willis concluded that automated responses
such as breathing, heartbeats and other various motor activities were
carried out within the lower region of the brain. Although much of his
work has been made obsolete, his ideas presented the brain as more
complex than previously imagined, and led the way for future pioneers to
understand and build upon his theories, especially when it came to
looking at disorders and dysfunctions in the brain.
Franz Joseph Gall
Neuroanatomist and physiologist Franz Joseph Gall
made major progress in understanding the brain. He theorized that
personality was directly related to features and structures within the
brain. However, Gall's major contribution within the field of
neuroscience is his invention of phrenology.
This new discipline looked at the brain as an organ of the mind, where
the shape of the skull could ultimately determine one's intelligence and
personality.
This theory was like many circulating at the time, as many scientists
were taking into account physical features of the face and body, head
size, anatomical structure, and levels of intelligence; only Gall looked
primarily at the brain. There was much debate over the validity of
Gall's claims however, because he was often found to be wrong in his
predictions. He was once sent a cast of René Descartes' skull, and
through his method of phrenology claimed the subject must have had a
limited capacity for reasoning and higher cognition.
As controversial and false as many of Gall's claims were, his
contributions to understanding cortical regions of the brain and
localized activity continued to advance understanding of the brain,
personality, and behavior. His work is considered crucial to having laid
a firm foundation in the field of neuropsychology, which would flourish
over the next few decades.
Jean-Baptiste Bouillaud
Jean-Baptiste Bouillaud
Towards the late 19th century, the belief that the size of ones skull
could determine their level of intelligence was discarded as science
and medicine moved forward. A physician by the name of Jean-Baptiste Bouillaud
expanded upon the ideas of Gall and took a closer look at the idea of
distinct cortical regions of the brain each having their own independent
function. Bouillaud was specifically interested in speech and wrote
many publications on the anterior region of the brain being responsible
for carrying out the act of ones speech, a discovery that had stemmed
from the research of Gall. He was also one of the first to use larger
samples for research although it took many years for that method to be
accepted. By looking at over a hundred different case studies, Bouillaud
came to discover that it was through different areas of the brain that
speech is completed and understood. By observing people with brain
damage, his theory was made more concrete. Bouillaud, along with many
other pioneers of the time made great advances within the field of
neurology, especially when it came to localization of function. There
are many arguable debates as to who deserves the most credit for such
discoveries, and often, people remain unmentioned, but Paul Broca
is perhaps one of the most famous and well known contributors to
neuropsychology – often referred to as "the father" of the discipline.
Paul Broca
Inspired by the advances being made in the area of localized function within the brain, Paul Broca
committed much of his study to the phenomena of how speech is
understood and produced. Through his study, it was discovered and
expanded upon that we articulate via the left hemisphere. Broca's
observations and methods are widely considered to be where
neuropsychology really takes form as a recognizable and respected
discipline. Armed with the understanding that specific, independent
areas of the brain are responsible for articulation and understanding of
speech, the brains abilities were finally being acknowledged as the
complex and highly intricate organ that it is. Broca was essentially the
first to fully break away from the ideas of phrenology and delve deeper
into a more scientific and psychological view of the brain.
Karl Spencer Lashley
Lashley's works and theories that follow are summarized in his book Brain Mechanisms and Intelligence.
Lashley's theory of the Engram was the driving force for much of his
research. An engram was believed to be a part of the brain where a
specific memory was stored. He continued to use the training/ablation
method that Franz had taught him. He would train a rat to learn a maze
and then use systematic lesions and removed sections of cortical tissue
to see if the rat forgot what it had learned.
Through his research with the rats, he learned that forgetting
was dependent on the amount of tissue removed and not where it was
removed from. He called this mass action and he believed that it
was a general rule that governed how brain tissue would respond,
independent of the type of learning. But we know now that mass action
was a misinterpretation of his empirical results, because in order to
run a maze the rats required multiple cortical areas, so cutting into
small individual parts alone will not impair the rats' brains much, but
taking large sections removes multiple cortical areas at one time,
affecting various functions such as sight, motor coordination and
memory, making the animal unable to run a maze properly.
Lashley also proposed that a portion of a functional area could
carry out the role of the entire area, even when the rest of the area
has been removed. He called this phenomenon equipotentiality. We know
now that he was seeing evidence of plasticity in the brain. The brain
has the spectacular ability for certain areas to take over the functions
of other areas if those areas should fail or be removed, although not
to the extent initially argued by Lashley.
Approaches
Experimental neuropsychology is an approach that uses methods from experimental psychology
to uncover the relationship between the nervous system and cognitive
function. The majority of work involves studying healthy humans in a
laboratory setting, although a minority of researchers may conduct
animal experiments. Human work in this area often takes advantage of
specific features of our nervous system (for example that visual
information presented to a specific visual field is preferentially processed by the cortical hemisphere on the opposite side) to make links between neuroanatomy and psychological function.
Clinical neuropsychology is the application of neuropsychological knowledge to the assessment (see neuropsychological test and neuropsychological assessment), management, and rehabilitation of people who have suffered illness or injury (particularly to the brain) which has caused neurocognitive
problems. In particular they bring a psychological viewpoint to
treatment, to understand how such illness and injury may affect and be
affected by psychological factors.
They also can offer an opinion as to whether a person is demonstrating
difficulties due to brain pathology or as a consequence of an emotional
or another (potentially) reversible cause or both. For example, a test
might show that both patients X and Y are unable to name items that they
have been previously exposed to within the past 20 minutes (indicating
possible dementia). If patient Y can name some of them with further
prompting (e.g. given a categorical clue such as being told that the
item they could not name is a fruit), this allows a more specific
diagnosis than simply dementia (Y appears to have the vascular type
which is due to brain pathology but is usually at least somewhat
reversible). Clinical neuropsychologists often work in hospital
settings in an interdisciplinary medical team; others work in private
practice and may provide expert input into medico-legal proceedings.
Cognitive neuropsychology
is a relatively new development and has emerged as a distillation of
the complementary approaches of both experimental and clinical
neuropsychology. It seeks to understand the mind and brain by studying
people who have suffered brain injury or neurological illness. One model
of neuropsychological functioning is known as functional localization.
This is based on the principle that if a specific cognitive problem can
be found after an injury to a specific area of the brain, it is
possible that this part of the brain is in some way involved. However,
there may be reason to believe that the link between mental functions
and neural regions is not so simple. An alternative model of the link
between mind and brain, such as parallel processing,
may have more explanatory power for the workings and dysfunction of the
human brain. Yet another approach investigates how the pattern of
errors produced by brain-damaged individuals can constrain our
understanding of mental representations and processes without reference
to the underlying neural structure. A more recent but related approach
is cognitive neuropsychiatry which seeks to understand the normal function of mind and brain by studying psychiatric or mental illness.
Connectionism is the use of artificial neural networks
to model specific cognitive processes using what are considered to be
simplified but plausible models of how neurons operate. Once trained to
perform a specific cognitive task these networks are often damaged or
'lesioned' to simulate brain injury or impairment in an attempt to
understand and compare the results to the effects of brain injury in
humans.
Functional neuroimaging uses specific neuroimaging
technologies to take readings from the brain, usually when a person is
doing a particular task, in an attempt to understand how the activation
of particular brain areas is related to the task. In particular, the
growth of methodologies to employ cognitive testing within established functional magnetic resonance imaging (fMRI) techniques to study brain-behavior relations is having a notable influence on neuropsychological research.
In practice these approaches are not mutually exclusive and most
neuropsychologists select the best approach or approaches for the task
to be completed.
Methods and tools
- Standardized neuropsychological tests
- These tasks have been designed so the performance on the task can be linked to specific neurocognitive processes. These tests are typically standardized, meaning that they have been administered to a specific group (or groups) of individuals before being used in individual clinical cases. The data resulting from standardization are known as normative data. After these data have been collected and analyzed, they are used as the comparative standard against which individual performances can be compared. Examples of neuropsychological tests include: the Wechsler Memory Scale (WMS), the Wechsler Adult Intelligence Scale (WAIS), Boston Naming Test, the Wisconsin Card Sorting Test, the Benton Visual Retention Test, and the Controlled Oral Word Association.
- Brain scans
- The use of brain scans to investigate the structure or function of the brain is common, either as simply a way of better assessing brain injury with high resolution pictures, or by examining the relative activations of different brain areas. Such technologies may include fMRI (functional magnetic resonance imaging) and positron emission tomography (PET), which yields data related to functioning, as well as MRI (magnetic resonance imaging) and computed axial tomography (CAT or CT), which yields structural data.
- Global Brain Project
- Brain models based on mouse and monkey have been developed based on theoretical neuroscience involving working memory and attention, while mapping brain activity based on time constants validated by measurements of neuronal activity in various layers of the brain. These methods also map to decision states of behavior in simple tasks that involve binary outcomes.
- Electrophysiology
- The use of electrophysiological measures designed to measure the activation of the brain by measuring the electrical or magnetic field produced by the nervous system. This may include electroencephalography (EEG) or magneto-encephalography (MEG).
- Experimental tasks
- The use of designed experimental tasks, often controlled by computer and typically measuring reaction time and accuracy on a particular tasks thought to be related to a specific neurocognitive process. An example of this is the Cambridge Neuropsychological Test Automated Battery (CANTAB) or CNS Vital Signs (CNSVS).
- Software products
- Researchers have mapped to neural activity in the brain through brain scan or MRI. Applications based on Neuropsychology are being used to influence behavior design and habit formation. An example of such a product is fooya, which is a mobile App for children that has been shown in randomized and controlled studies to influence dietary preferences among children.
