SETI@home

From Wikipedia, the free encyclopedia

SETI@home

Developer(s)	University Of California, Berkeley
Initial release	May 17, 1999
Stable release	SETI@home v8：8.00 / December 30, 2015; 3 years ago SETI@home v8 for nVidia and AMD/ATi GPU Card：8.12/ May 19, 2016; 3 years ago AstroPulse v7：7.00/ October 7, 2014; 4 years ago AstroPulse v7 for nVidia and AMD/ATi GPU Card：7.10/ April 23, 2015; 4 years ago
Development status	Online
Project goal(s)	Discovery of radio evidence of extraterrestrial life
Funding	Public funding and private donations
Operating system	Microsoft Windows, Linux, Android, macOS, Solaris, IBM AIX, FreeBSD, DragonflyBSD, OpenBSD, NetBSD, HP-UX, IRIX, Tru64 Unix, OS/2 Warp, eComStation
Platform	Cross-platform
Available in	English
Type	Volunteer computing
License	GPL
Active users	103,480 (January 2018)
Total users	1,716,012 (January 2018)
Website	SETI@home

SETI@home ("SETI at home") is an Internet-based public volunteer computing project employing the BOINC software platform created by the Berkeley SETI Research Center and is hosted by the Space Sciences Laboratory, at the University of California, Berkeley. Its purpose is to analyze radio signals, searching for signs of extraterrestrial intelligence, and as such is one of many activities undertaken as part of the worldwide SETI effort.

SETI@home was released to the public on May 17, 1999, making it the third large-scale use of distributed computing over the Internet for research purposes, after Great Internet Mersenne Prime Search (GIMPS) was launched in 1996 and distributed.net in 1997. Along with MilkyWay@home and Einstein@home, it is the third major computing project of this type that has the investigation of phenomena in interstellar space as its primary purpose.

Scientific research

The two original goals of SETI@home were:

• to do useful scientific work by supporting an observational analysis to detect intelligent life outside Earth
• to prove the viability and practicality of the "volunteer computing" concept

The second of these goals is considered to have succeeded completely. The current BOINC environment, a development of the original SETI@home, is providing support for many computationally intensive projects in a wide range of disciplines.

The first of these goals has to date yielded no conclusive results: no evidence for ETI signals has been shown via SETI@home. However, the ongoing continuation is predicated on the assumption that the observational analysis is not an "ill-posed" one. The remainder of this article deals specifically with the original SETI@home observations/analysis. The vast majority of the sky (over 98%) has yet to be surveyed, and each point in the sky must be surveyed many times to exclude even a subset of possibilities.

Procedure details

SETI@home searches for possible evidence of radio transmissions from extraterrestrial intelligence using observational data from the Arecibo radio telescope and the Green Bank Telescope. The data is taken "piggyback" or "passively" while the telescope is used for other scientific programs. The data is digitized, stored, and sent to the SETI@home facility. The data are then parsed into small chunks in frequency and time, and analyzed, using software, to search for any signals—that is, variations which cannot be ascribed to noise, and hence contain information. Using distributed computing, SETI@home sends the millions of chunks of data to be analyzed off-site by home computers, and then have those computers report the results. Thus what appears a difficult problem in data analysis is reduced to a reasonable one by aid from a large, Internet-based community of borrowed computer resources. 

The software searches for five types of signals that distinguish them from noise:

• Spikes in power spectra
• Gaussian rises and falls in transmission power, possibly representing the telescope beam's main lobe passing over a radio source
• Triplets — three power spikes in a row
• Pulsing signals that possibly represent a narrowband digital-style transmission
• Autocorrelation detects signal waveforms.

There are many variations on how an ETI signal may be affected by the interstellar medium, and by the relative motion of its origin compared to Earth. The potential "signal" is thus processed in many ways (although not testing all detection methods nor scenarios) to ensure the highest likelihood of distinguishing it from the scintillating noise already present in all directions of outer space. For instance, another planet is very likely to be moving at a speed and acceleration with respect to Earth, and that will shift the frequency, over time, of the potential "signal." Checking for this through processing is done, to an extent, in the SETI@home software. 

The process is somewhat like tuning a radio to various channels, and looking at the signal strength meter. If the strength of the signal goes up, that gets attention. More technically, it involves a lot of digital signal processing, mostly discrete Fourier transforms at various chirp rates and durations.

Results

To date, the project has not confirmed the detection of any ETI signals. However, it has identified several candidate targets (sky positions), where the spike in intensity is not easily explained as noisespots, for further analysis. The most significant candidate signal to date was announced on September 1, 2004, named Radio source SHGb02+14a. 

While the project has not reached the stated primary goal of finding extraterrestrial intelligence, it has proved to the scientific community that distributed computing projects using Internet-connected computers can succeed as a viable analysis tool, and even beat the largest supercomputers. However, it has not been demonstrated that the order of magnitude excess in computers used, many outside the home (the original intent was to use 50,000-100,000 "home" computers), has benefited the project scientifically. (For more on this, see § Challenges to the project below.)

Astronomer Seth Shostak stated in 2004 that he expects to get a conclusive signal and proof of alien contact between 2020 and 2025, based on the Drake equation. This implies that a prolonged effort may benefit SETI@home, despite its (present) twenty-year run without success in ETI detection.

Technology

Anybody with an at least intermittently Internet-connected computer can participate in SETI@home by running a free program that downloads and analyzes radio telescope data.

Observational data are recorded on 2-terabyte SATA hard disk drives at the Arecibo Observatory in Puerto Rico, each holding about 2.5 days of observations, which are then sent to Berkeley. Arecibo does not have a broadband Internet connection, so data must go by postal mail to Berkeley. Once there, it is divided in both time and frequency domains work units of 107 seconds of data, or approximately 0.35 megabytes (350 kilobytes or 350,000 bytes), which overlap in time but not in frequency. These work units are then sent from the SETI@home server over the Internet to personal computers around the world to analyze.

The analysis software can search for signals with about one-tenth the strength of those sought in previous surveys, because it makes use of a computationally-intensive algorithm called coherent integration that no one else has had the computing power to implement.

Data is merged into a database using SETI@home computers in Berkeley. Interference is rejected, and various pattern-detection algorithms are applied to search for the most interesting signals. 

The project uses CUDA for GPU processing since 2015.

Since 2016, the project has also been helping to process data from the Breakthrough Listen project which has been recorded at Green Bank Telescope.

Software

The BOINC Manager working on the SETI@home project (v 7.6.22).

 

Screenshot of SETI@home Enhanced BOINC Screensaver (v6.03)

 

Screenshot of SETI@home Classic Screensaver (v3.07)

 

The SETI@home distributed computing software runs either as a screensaver or continuously while a user works, making use of processor time that would otherwise be unused. 

The initial software platform, now referred to as "SETI@home Classic," ran from May 17, 1999, to December 15, 2005. This program was only capable of running SETI@home; it was replaced by Berkeley Open Infrastructure for Network Computing (BOINC), which also allows users to contribute to other distributed computing projects at the same time as running SETI@home. The BOINC platform will also allow testing for more types of signals.

The discontinuation of the SETI@home Classic platform has rendered older Macintosh computers running the classic Mac OS unsuitable for participating in the project.

SETI@home is available for the Sony PlayStation 3 console.

On May 3, 2006, new work units for a new version of SETI@home called "SETI@home Enhanced" started distribution. Since computers now have the power for more computationally intensive work than when the project began, this new version is more sensitive by a factor of two concerning Gaussian signals and to some kinds of pulsed signals than the original SETI@home (BOINC) software. This new application has been optimized to the point where it will run faster on some work units than earlier versions. However, some work units (the best work units, scientifically speaking) will take significantly longer. 

In addition, some distributions of the SETI@home applications have been optimized for a particular type of CPU. They are referred to as "optimized executables" and have been found to run faster on systems specific for that CPU. As of 2007, most of these applications are optimized for Intel processors and their corresponding instruction sets.

The results of the data processing are normally automatically transmitted when the computer is next connected to the Internet; it can also be instructed to connect to the Internet as needed.

Statistics

With over 5.2 million participants worldwide, the project is the distributed computing project with the most participants to date. The original intent of SETI@home was to utilize 50,000-100,000 home computers. Since its launch on May 17, 1999, the project has logged over two million years of aggregate computing time. On September 26, 2001, SETI@home had performed a total of 10²¹ floating point operations. It was acknowledged by the 2008 edition of the Guinness World Records as the largest computation in history. With over 145,000 active computers in the system (1.4 million total) in 233 countries, as of 23 June 2013, SETI@home had the ability to compute over 668 teraFLOPS. For comparison, the Tianhe-2 computer, which as of 23 June 2013 was the world's fastest supercomputer, was able to compute 33.86 petaFLOPS (approximately 50 times greater).

Project future

There were plans to get data from the Parkes Observatory in Australia to analyze the southern hemisphere. However, as of 3 June 2018, these plans were not mentioned in the project's website. Other plans include a Multi-Beam Data Recorder, a Near Time Persistency Checker and Astropulse (an application that uses coherent dedispersion to search for pulsed signals). Astropulse will team with the original SETI@home to detect other sources, such as rapidly rotating pulsars, exploding primordial black holes, or as-yet unknown astrophysical phenomena. Beta testing of the final public release version of Astropulse was completed in July 2008, and the distribution of work units to higher spec machines capable of processing the more CPU intensive work units started in mid-July 2008.

Competitive aspect

SETI@home users quickly started to compete with one another to process the maximum number of work units. Teams were formed to combine the efforts of individual users. The competition continued and grew larger with the introduction of BOINC. 

As with any competition, attempts have been made to "cheat" the system and claim credit for work that has not been performed. To combat cheats, the SETI@home system sends every work unit to multiple computers, a value known as "initial replication" (currently 2). Credit is only granted for each returned work unit once a minimum number of results have been returned and the results agree, a value known as "minimum quorum" (currently 2). If, due to computation errors or cheating by submitting false data, not enough results agree, more identical work units are sent out until the minimum quorum can be reached. The final credit granted to all machines which returned the correct result is the same and is the lowest of the values claimed by each machine. The claimed credit by each machine for an identical work unit often varies due to minor differences in floating point arithmetic on different processors.

Some users have installed and run SETI@home on computers at their workplaces — an act known as "Borging", after the assimilation-driven Borg of Star Trek. In some cases, SETI@home users have misused company resources to gain work-unit results — with at least two individuals getting fired for running SETI@home on an enterprise production system. There is a thread in the newsgroup alt.sci.seti which bears the title "Anyone fired for SETI screensaver" and ran starting as early as September 14, 1999. 

Other users collect large quantities of equipment together at home to create "SETI farms", which typically consist of a number of computers consisting of only a motherboard, CPU, RAM and power supply that are arranged on shelves as diskless workstations running either Linux or old versions of Microsoft Windows "headless" (without a monitor).

Challenges to the project

There are other challenges to the project's future viability. 

Like any project of prolonged duration, there are factors that may result in its termination. Some of these are detailed below:

Potential closure of Arecibo Observatory

At present, SETI@home procures its data from the Arecibo Observatory facility operated by the National Astronomy and Ionosphere Center and administered by SRI International. 

The decreasing operating budget for the observatory has created a shortfall of funds which has not been made up from other sources such as private donors, NASA, other foreign research institutions, nor private non-profit organizations such as SETI@home. 

However, in the overall longterm views held by many involved with the SETI project, any usable radio telescope could take over from Arecibo, as all the SETI systems are portable and relocatable.

Alternative distributed computing projects

When the project launched, there were few alternative ways of donating computer time to research projects. However, there are now many other projects that are competing for such time.

More restrictive computer use policies in businesses

In one documented case, an individual was fired for explicitly importing and using the SETI@home software on computers used for the U.S. state of Ohio. In another incident a school IT director resigned after his installation allegedly cost his school district $1 million in removal costs; however, other reasons for this firing included lack of communication with his superiors, not installing firewall software and alleged theft of computer equipment, leading a ZDNet editor to comment that "the distributed computing nonsense was simply the best and most obvious excuse the district had to terminate his contract with cause".

As of 16 October 2005, approximately one-third of the processing for the non-BOINC version of the software was performed on work or school based machines. As many of these computers will give reduced privileges to ordinary users, it is possible that much of this has been done by network administrators. 

To some extent, this may be offset by better connectivity to home machines and increasing performance of home computers, especially those with GPUs, which have also benefited other distributed computing projects such as Folding@Home. The spread of mobile computing devices provides another large resource for distributed computing. For example, in 2012, Piotr Luszczek (a former doctoral student of Jack Dongarra), presented results showing that an iPad 2 matched the historical performance of a Cray-2 (the fastest computer in the world in 1985) on an embedded LINPACK benchmark.

Funding

There is currently no government funding for SETI research, and private funding is always limited. Berkeley Space Science Lab has found ways of working with small budgets, and the project has received donations allowing it to go well beyond its original planned duration, but it still has to compete for limited funds with other SETI projects and other space sciences projects. 

In a December 16, 2007 plea for donations, SETI@home stated its present modest state and urged donations of $476,000 needed for continuation into 2008.

Unofficial clients

A number of individuals and companies made unofficial changes to the distributed part of the software to try to produce faster results, but this compromised the integrity of all the results. As a result, the software had to be updated to make it easier to detect such changes, and discover unreliable clients. BOINC will run on unofficial clients; however, clients that return different and therefore incorrect data are not allowed, so corrupting the result database is avoided. BOINC relies on cross-checking to validate data but unreliable clients need to be identified, to avoid situations when two of these report the same invalid data and therefore corrupt the database. A very popular unofficial client (lunatic) allows users to take advantage of the special features provided by their processor(s) such as SSE, SSE2, SSE3, SSSE3, SSE4.1, and AVX to allow for faster processing. The only downside to this is that if the user selects features that their processor(s) do not support, the chances of bad results and crashes rise significantly. Tools (such as CPU-Z) are freely available to tell users what features are supported by their processor(s).

Hardware and database failures

SETI@home is a test bed for further development not only of BOINC but of other hardware and software (database) technology. Under SETI@home processing loads, these experimental technologies can be more challenging than expected, as SETI databases do not have typical accounting and business data or relational structures. The non-traditional database uses often do incur greater processing overheads and risk of database corruption and outright database failure. Hardware, software and database failures can (and do) cause dips in project participation.

The project has had to shut down several times to change over to new databases capable of handling more massive datasets. Hardware failure has proven to be a substantial source of project shutdowns—as hardware failure is often coupled with database corruption.

Andreas Vesalius

From Wikipedia, the free encyclopedia

Andreas Vesalius
A portrait of Vesalius from De humani corporis fabrica
Born	31 December 1514 Brussels, Habsburg Netherlands (modern-day Belgium)
Died	15 October 1564 (aged 49) Zakynthos, Venetian Ionian Islands (modern-day Greece)
Alma mater	University of Pavia University of Padua
Known for	De humani corporis fabrica (On the Fabric of the Human Body)
Scientific career
Fields	Anatomy
Thesis	Paraphrasis in nonum librum Rhazae medici Arabis clarissimi ad regem Almansorem, de affectuum singularum corporis partium curatione (1537)
Doctoral advisor	Johannes Winter von Andernach Gemma Frisius
Doctoral students	Matteo Realdo Colombo
Influences	Galen Jacques Dubois Jean Fernel
Influenced	Gabriele Falloppio

Andreas Vesalius was a 16th-century Flemish anatomist, physician, and author of one of the most influential books on human anatomy, De humani corporis fabrica (On the Fabric of the Human Body). Vesalius is often referred to as the founder of modern human anatomy. He was born in Brussels, which was then part of the Habsburg Netherlands. He was professor at the University of Padua and later became Imperial physician at the court of Emperor Charles V.

Andreas Vesalius is the Latinized form of the Dutch Andries van Wesel. It was a common practice among European scholars in his time to Latinize their names. His name is also given as Andrea Vesalius, André Vésale, Andrea Vesalio, Andreas Vesal, André Vesalio and Andre Vesale.

Early life and education

Vesalius was born as Andries van Wesel to his father Andries van Wesel and mother Isabel Crabbe on 31 December 1514 in Brussels, which was then part of the Habsburg Netherlands. His great grandfather, Jan van Wesel, probably born in Wesel, received a medical degree from the University of Pavia and taught medicine in 1528 at the University of Leuven. His grandfather, Everard van Wesel, was the Royal Physician of Emperor Maximilian, while his father, Anders van Wesel, served as apothecary to Maximilian, and later valet de chambre to his successor Charles V. Anders encouraged his son to continue in the family tradition and enrolled him in the Brethren of the Common Life in Brussels to learn Greek and Latin prior to learning medicine, according to standards of the era.

In 1528 Vesalius entered the University of Leuven (Pedagogium Castrense) taking arts, but when his father was appointed as the Valet de Chambre in 1532, he decided instead to pursue a career in the military at the University of Paris, where he relocated in 1533. There he studied the theories of Galen under the auspices of Jacques Dubois (Jacobus Sylvius) and Jean Fernel. It was during this time that he developed an interest in anatomy, and he was often found examining excavated bones in the charnel houses at the Cemetery of the Innocents. 

Vesalius was forced to leave Paris in 1536 owing to the opening of hostilities between the Holy Roman Empire and France and returned to Leuven. He completed his studies there under Johann Winter von Andernach and graduated the following year. His thesis, Paraphrasis in nonum librum Rhazae medici arabis clariss. ad regem Almansorum de affectuum singularum corporis partium curatione, was a commentary on the ninth book of Rhazes. He remained at Leuven for a while, before leaving after a dispute with his professor. After settling briefly in Venice in 1536, he moved to the University of Padua (Universitas artistarum) to study for his medical doctorate, which he received in 1537.

Medical career and accomplishments

On the day of his graduation he was immediately offered the chair of surgery and anatomy (explicator chirurgiae) at Padua. He also guest-lectured at the Bologna and the Pisa. Prior to taking up his position in Padua, Vesalius traveled through Italy, and assisted the future Pope Paul IV and Ignatius of Loyola to heal those afflicted by Hansen’s disease (leprosy). In Venice, he met the illustrator Johan van Calcar, a student of Titian. It was with van Calcar that Vesalius published his first anatomical text, Tabulae Anatomicae Sex, in 1538. Previously these topics had been taught primarily from reading classical texts, mainly Galen, followed by an animal dissection by a barber–surgeon whose work was directed by the lecturer. No attempt was made to confirm Galen's claims, which were considered unassailable. Vesalius, in contrast, performed dissection as the primary teaching tool, handling the actual work himself and urging students to perform dissection themselves. He considered hands-on direct observation to be the only reliable resource. 

Vesalius created detailed illustrations of anatomy for students in the form of six large woodcut posters. When he found that some of them were being widely copied, he published them all in 1538 under the title Tabulae anatomicae sex. He followed this in 1539 with an updated version of Guinter's anatomical handbook, Institutiones anatomicae.

 

In 1539 he also published his Venesection letter on bloodletting. This was a popular treatment for almost any illness, but there was some debate about where to take the blood from. The classical Greek procedure, advocated by Galen, was to collect blood from a site near the location of the illness. However, the Muslim and medieval practice was to draw a smaller amount of blood from a distant location. Vesalius' pamphlet generally supported Galen's view, but with qualifications that rejected the infiltration of Galen. 

In 1541 while in Bologna, Vesalius discovered that all of Galen's research had to be restricted to animals; since dissection had been banned in ancient Rome. Galen had dissected Barbary macaques instead, which he considered structurally closest to man. Even though Galen produced many errors due to the anatomical material available to him, he was a qualified examiner, but his research was weakened by stating his findings philosophically, so his findings were based on religious precepts rather than science. Vesalius contributed to the new Giunta edition of Galen's collected works and began to write his own anatomical text based on his own research. Until Vesalius pointed out Galen's substitution of animal for human anatomy, it had gone unnoticed and had long been the basis of studying human anatomy. However, some people still chose to follow Galen and resented Vesalius for calling attention to the difference.

Galen had assumed that arteries carried the purest blood to higher organs such as the brain and lungs from the left ventricle of the heart, while veins carried blood to the lesser organs such as the stomach from the right ventricle. In order for this theory to be correct, some kind of opening was needed to interconnect the ventricles, and Galen claimed to have found them. So paramount was Galen's authority that for 1400 years a succession of anatomists had claimed to find these holes, until Vesalius admitted he could not find them. Nonetheless, he did not venture to dispute Galen on the distribution of blood, being unable to offer any other solution, and so supposed that it diffused through the unbroken partition between the ventricles.

Other famous examples of Vesalius disproving Galen's assertions were his discoveries that the lower jaw (mandible) was composed of only one bone, not two (which Galen had assumed based on animal dissection) and that humans lack the rete mirabile, a network of blood vessels at the base of the brain that is found in sheep and other ungulates. 

In 1543, Vesalius conducted a public dissection of the body of Jakob Karrer von Gebweiler, a notorious felon from the city of Basel, Switzerland. He assembled and articulated the bones, finally donating the skeleton to the University of Basel. This preparation ("The Basel Skeleton") is Vesalius' only well-preserved skeletal preparation, and also the world's oldest surviving anatomical preparation. It is still displayed at the Anatomical Museum of the University of Basel.

In the same year Vesalius took residence in Basel to help Johannes Oporinus publish the seven-volume De humani corporis fabrica (On the fabric of the human body), a groundbreaking work of human anatomy that he dedicated to Charles V. Many believe it was illustrated by Titian's pupil Jan Stephen van Calcar, but evidence is lacking, and it is unlikely that a single artist created all 273 illustrations in a period of time so short. At about the same time he published an abridged edition for students, Andrea Vesalii suorum de humani corporis fabrica librorum epitome, and dedicated it to Philip II of Spain, the son of the Emperor. That work, now collectively referred to as the Fabrica of Vesalius, was groundbreaking in the history of medical publishing and is considered to be a major step in the development of scientific medicine. Because of this, it marks the establishment of anatomy as a modern descriptive science.

Though Vesalius' work was not the first such work based on actual dissection, nor even the first work of this era, the production quality, highly detailed and intricate plates, and the likelihood that the artists who produced it were clearly present in person at the dissections made it an instant classic. Pirated editions were available almost immediately, an event Vesalius acknowledged in a printer's note would happen. Vesalius was 28 years old when the first edition of Fabrica was published.

Imperial physician and death

The Holy Roman Emperor, Charles V, who was an important patron of Vesalius

 

Soon after publication, Vesalius was invited to become imperial physician to the court of Emperor Charles V. He informed the Venetian Senate that he would leave his post in Padua, which prompted Duke Cosimo I de' Medici to invite him to move to the expanding university in Pisa, which he declined. Vesalius took up the offered position in the imperial court, where he had to deal with other physicians who mocked him for being a mere barber surgeon instead of an academic working on the respected basis of theory.

In the 1540s, shortly after entering in service of the emperor, Vesalius married Anne van Hamme, from Vilvorde, Belgium. They had one daughter, named Anne, who died in 1588.

Over the next eleven years Vesalius traveled with the court, treating injuries caused in battle or tournaments, performing postmortems, administering medication, and writing private letters addressing specific medical questions. During these years he also wrote the Epistle on the China root, a short text on the properties of a medical plant whose efficacy he doubted, as well as a defense of his anatomical findings. This elicited a new round of attacks on his work that called for him to be punished by the emperor. In 1551, Charles V commissioned an inquiry in Salamanca to investigate the religious implications of his methods. Although Vesalius' work was cleared by the board, the attacks continued. Four years later one of his main detractors and one-time professors, Jacobus Sylvius, published an article that claimed that the human body itself had changed since Galen had studied it. 

After the abdication of Emperor Charles V, Vesalius continued at court in great favor with his son Philip II, who rewarded him with a pension for life by making him a count palatine. In 1555 he published a revised edition of De humani corporis fabrica.

In 1564 Vesalius went on a pilgrimage to the Holy Land, some said, in penance after being accused of dissecting a living body. He sailed with the Venetian fleet under James Malatesta via Cyprus. When he reached Jerusalem he received a message from the Venetian senate requesting him again to accept the Paduan professorship, which had become vacant on the death of his friend and pupil Fallopius. 

After struggling for many days with adverse winds in the Ionian Sea, he was shipwrecked on the island of Zakynthos. Here he soon died, in such debt that a benefactor kindly paid for his funeral. At the time of his death he was 49 years of age. He was buried somewhere on the island of Zakynthos (Zante).

For some time, it was assumed that Vesalius's pilgrimage was due to the pressures imposed on him by the Inquisition. Today, this assumption is generally considered to be without foundation and is dismissed by modern biographers. It appears the story was spread by Hubert Languet, a diplomat under Emperor Charles V and then under the Prince of Orange, who claimed in 1565 that Vesalius had performed an autopsy on an aristocrat in Spain while the heart was still beating, leading to the Inquisition's condemning him to death. The story went on to claim that Philip II had the sentence commuted to a pilgrimage. That story re-surfaced several times, until it was more recently revised.

Publications

De Humani Corporis Fabrica

Vesalius's Fabrica contained many intricately detailed drawings of human dissections, often in allegorical poses.

 

In 1543, Vesalius asked Johannes Oporinus to publish the book De humani corporis fabrica (On the fabric of the human body), a groundbreaking work of human anatomy he dedicated to Charles V and which many believe was illustrated by Titian's pupil Jan Stephen van Calcar. 

About the same time he published another version of his great work, entitled De humani corporis fabrica librorum epitome (Abridgement of the Structure of the Human Body) more commonly known as the Epitome, with a stronger focus on illustrations than on text, so as to help readers, including medical students, to easily understand his findings. The actual text of the Epitome was an abridged form of his work in the Fabrica, and the organization of the two books was quite varied. He dedicated it to Philip II of Spain, son of the Emperor.

The Fabrica emphasized the priority of dissection and what has come to be called the "anatomical" view of the body, seeing human internal functioning as a result of an essentially corporeal structure filled with organs arranged in three-dimensional space. His book contains drawings of several organs on two leaves. This allows for the creation of three-dimensional diagrams by cutting out the organs and pasting them on flayed figures. This was in stark contrast to many of the anatomical models used previously, which had strong Galenic/Aristotelean elements, as well as elements of astrology. Although modern anatomical texts had been published by Mondino and Berenger, much of their work was clouded by reverence for Galen and Arabian doctrines. 

Besides the first good description of the sphenoid bone, he showed that the sternum consists of three portions and the sacrum of five or six, and described accurately the vestibule in the interior of the temporal bone. He not only verified Estienne's observations on the valves of the hepatic veins, but also described the vena azygos, and discovered the canal which passes in the fetus between the umbilical vein and the vena cava, since named the ductus venosus. He described the omentum and its connections with the stomach, the spleen and the colon; gave the first correct views of the structure of the pylorus; observed the small size of the caecal appendix in man; gave the first good account of the mediastinum and pleura and the fullest description of the anatomy of the brain up to that time. He did not understand the inferior recesses, and his account of the nerves is confused by regarding the optic as the first pair, the third as the fifth, and the fifth as the seventh. 

In this work, Vesalius also becomes the first person to describe mechanical ventilation. It is largely this achievement that has resulted in Vesalius being incorporated into the Australian and New Zealand College of Anaesthetists college arms and crest.

Excerpts

When I undertake the dissection of a human pelvis I pass a stout rope tied like a noose beneath the lower jaw and through the zygomas up to the top of the head... The lower end of the noose I run through a pulley fixed to a beam in the room so that I may raise or lower the cadaver as it hangs there or turn around in any direction to suit my purpose; ... You must take care not to put the noose around the neck, unless some of the muscles connected to the occipital bone have already been cut away.

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Other publications

In 1538, Vesalius wrote Epistola, docens venam axillarem dextri cubiti in dolore laterali secandam (A letter, teaching that in cases of pain in the side, the axillary vein of the right elbow be cut), commonly known as the Venesection Letter, which demonstrated a revived venesection, a classical procedure in which blood was drawn near the site of the ailment. He sought to locate the precise site for venesection in pleurisy within the framework of the classical method. The real significance of the book is his attempt to support his arguments by the location and continuity of the venous system from his observations rather than appeal to earlier published works. With this novel approach to the problem of venesection, Vesalius posed the then striking hypothesis that anatomical dissection might be used to test speculation. 

In 1546, three years after the Fabrica, he wrote his Epistola rationem modumque propinandi radicis Chynae decocti, commonly known as the Epistle on the China Root. Ostensibly an appraisal of a popular but ineffective treatment for gout, syphilis, and stone, this work is especially important as a continued polemic against Galenism and a reply to critics in the camp of his former professor Jacobus Sylvius, now an obsessive detractor. 

In February 1561, Vesalius was given a copy of Gabriele Fallopio's Observationes anatomicae, friendly additions and corrections to the Fabrica. Before the end of the year Vesalius composed a cordial reply, Anatomicarum Gabrielis Fallopii observationum examen, generally referred to as the Examen. In this work he recognizes in Fallopio a true equal in the science of dissection he had done so much to create. Vesalius' reply to Fallopio was published in May 1564, a month after Vesalius' death on the Greek island of Zante (now called Zakynthos).

Scientific findings

Skeletal system

• Vesalius believed the skeletal system to be the framework of the human body. It was in this opening chapter or book of De fabrica that Vesalius made several of his strongest claims against Galen's theories and writings which he had put in his anatomy books. In his extensive study of the skull, Vesalius claimed that the mandible consisted of one bone, whereas Galen had thought it to be two separate bones. He accurately described the vestibule in the interior of the temporal bone of the skull.
• In Galen's observation of the ape, he had discovered that their sternum consisted of seven parts which he assumed also held true for humans. Vesalius discovered that the human sternum consisted of only three parts.
• He also disproved the common belief that men had one rib fewer than women and noted that the fibula and tibia bones of the leg were indeed larger than the humerus bone of the arm, unlike Galen's original findings.

Muscular system

• Vesalius' most impressive contribution to the study of the muscular system may be the illustrations that accompany the text in De fabrica, which would become known as the "muscle men". He describes the source and position of each muscle of the body and provides information on their respective operation.

Vascular and circulatory systems

• Vesalius' work on the vascular and circulatory systems was his greatest contribution to modern medicine. In his dissections of the heart, Vesalius became convinced that Galen's claims of a porous Interventricular septum were false. This fact was previously described by Michael Servetus, a fellow of Vesalius, but never reached the public, for it was written down in the "Manuscript of Paris",^[15] in 1546, and published later in his Christianismi Restitutio (1553), a book regarded as heretical by the Inquisition. Only three copies survived, but these remained hidden for decades, the rest having been burned shortly after publication. In the second edition Vesalius published that the septum was indeed waterproof, discovering (and naming), the mitral valve to explain the blood flow.
• Vesalius believed that cardiac systole is synchronous with the arterial pulse.
• He not only verified Estienne's findings on the valves of the hepatic veins, but also described the azygos vein, and discovered the canal which passes into the fetus between the umbilical vein and vena cava.

Nervous system

• Vesalius defined a nerve as the mode of transmitting sensation and motion and thus refuted his contemporaries' claims that ligaments, tendons and aponeuroses were three types of nerve units.
• He believed that the brain and the nervous system are the center of the mind and emotion in contrast to the common Aristotelian belief that the heart was the center of the body. He correspondingly believed that nerves themselves do not originate from the heart, but from the brain.
• Upon studying the optic nerve, Vesalius came to the conclusion that nerves were not hollow.

Abdominal organs

• In De fabrica, he corrected an earlier claim he made in Tabulae about the right kidney being set higher than the left. Vesalius claimed that the kidneys were not a filter device for urine to pass through, but rather that the kidneys serve to filter blood as well, and that excretions from the kidneys travelled through the ureters to the bladder.
• He described the omentum, and its connections with the stomach, the spleen and the colon gave the first correct views of the structure of the pylorus.
• He also observed the small size of the caecal appendix in man and gave the first good account of the mediastinum and pleura.
• Vesalius admitted that due to a lack of pregnant cadavers he was unable to come to a significant understanding of the reproductive organs. However, he did find that the uterus had been falsely identified as having two distinct sections.

Heart

Through his work with muscles, Vesalius believed that a criterion for muscles was their voluntary motion. On this claim, he deduced that the heart was not a true muscle due to the obvious involuntary nature of its motion.

He identified two chambers and two atria. The right atrium was considered a continuation of the inferior and superior venae cavae, and the left atrium was considered a continuation of the pulmonary vein.

He also addressed the controversial issue of the heart being the centre of the soul. He wished to avoid drawing any conclusions due to possible conflict with contemporary religious beliefs.

• Base of the brain, showing the optic chiasma, cerebellum, olfactory bulbs, etc.
• Against Galen's theory and many beliefs he also discovered that there was no hole in the septum or heart.

Other achievements

• Vesalius disproved Galen's assertion that men have more teeth than women.
• Vesalius introduced the notion of induction of the extraction of empyema through surgical means.
• Due to his impressive study of the human skull and the variations in its features he is said to have been responsible for the launch of the study of physical anthropology.
• Vesalius always encouraged his students to check their findings, and even his own findings, so that they could better understand the structure of the human body.
• In addition to his continual efforts to study anatomy he also worked on medicinal remedies and came to such conclusions as treating syphilis with chinaroot.
• Vesalius claimed that medicine had three aspects: drugs, diet, and 'the use of hands'—mainly suggesting surgery and the knowledge of anatomy and physiology gained through dissection.
• Vesalius was a supporter of 'parallel dissections' in which an animal cadaver and a human cadaver are dissected simultaneously in order to demonstrate the anatomical differences and thus correct Galenic errors.

Scientific and historical impact

The influence of Vesalius' plates representing the partial dissections of the human figure posing in a landscape setting is apparent in the anatomical plates prepared by the Baroque painter Pietro da Cortona (1596–1669), who executed anatomical plates with figures in dramatic poses, most of them with architectural or landscape backdrops.
During the 20th century, the American artist, Jacob Lawrence created his Vesalius Suite based on the anatomical drawings of Andreas Vesalius.

"De Fabrica received a mixed reception when it first appeared; strict Galenists deplored its attacks on their master, while other anatomists, particularly in Italy, praised it as an important contribution—the reaction that was ultimately to carry the day," concludes Katharine Park her Commentary in the 1998 De Fabrica.

Vesalius was going up against the towering authority of a tradition stretching back to the ancients—here specifically the work of Galen — with only his experience on his side. He knew what his eyes saw and his hands felt, and concluded that traditional belief was wrong. In his publications we see Vesalius doing everything he can think of to bolster his authoritative image: publishing a huge monument to himself, but presenting the work using Galen’s own flowchart; presenting himself as personal physician to the emperor and having himself depicted in a commanding position on the title page of the book; augmenting his words with illustration after illustration and recommending the experiential road to all his students far and wide. His guarantee: if you doubt what I say and show here, do your own anatomy, see for yourself. Simultaneously, Vesalius’s work was part of one of the earliest known public health programs. The Council of Doges in Venice responded to the Bubonic Plague in the mid-14th century by directing the University of Padua Medical School to devote itself to discovering the causes of plague, how it spreads, how it develops in the individual, and if possible how victims might be cured. It ultimately took three centuries to find the solution, but with Venice leading the way plague was eventually eliminated as a major killer across Europe.

Cognitive neuroscience

From Wikipedia, the free encyclopedia

Cognitive neuroscience is the scientific field that is concerned with the study of the biological processes and aspects that underlie cognition, with a specific focus on the neural connections in the brain which are involved in mental processes. It addresses the questions of how cognitive activities are affected or controlled by neural circuits in the brain. Cognitive neuroscience is a branch of both neuroscience and psychology, overlapping with disciplines such as behavioral neuroscience, cognitive psychology, physiological psychology and affective neuroscience. Cognitive neuroscience relies upon theories in cognitive science coupled with evidence from neurobiology, and computational modeling.

Parts of the brain play an important role in this field. Neurons play the most vital role, since the main point is to establish an understanding of cognition from a neural perspective, along with the different lobes of the cerebral cortex.

Methods employed in cognitive neuroscience include experimental procedures from psychophysics and cognitive psychology, functional neuroimaging, electrophysiology, cognitive genomics, and behavioral genetics.

Studies of patients with cognitive deficits due to brain lesions constitute an important aspect of cognitive neuroscience. The damages in lesioned brains provide a comparable basis with regards to healthy and fully functioning brains. These damages change the neural circuits in the brain and cause it to malfunction during basic cognitive processes, such as memory or learning. With the damage, we can compare how the healthy neural circuits are functioning, and possibly draw conclusions about the basis of the affected cognitive processes.

Also, cognitive abilities based on brain development are studied and examined under the subfield of developmental cognitive neuroscience. This shows brain development over time, analyzing differences and concocting possible reasons for those differences.

Theoretical approaches include computational neuroscience and cognitive psychology.

Historical origins

Timeline showing major developments in science that led to the emergence of the field cognitive neuroscience.

 

Cognitive neuroscience is an interdisciplinary area of study that has emerged from neuroscience and psychology. There were several stages in these disciplines that changed the way researchers approached their investigations and that led to the field becoming fully established. 

Although the task of cognitive neuroscience is to describe how the brain creates the mind, historically it has progressed by investigating how a certain area of the brain supports a given mental faculty. However, early efforts to subdivide the brain proved to be problematic. The phrenologist movement failed to supply a scientific basis for its theories and has since been rejected. The aggregate field view, meaning that all areas of the brain participated in all behavior, was also rejected as a result of brain mapping, which began with Hitzig and Fritsch’s experiments and eventually developed through methods such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Gestalt theory, neuropsychology, and the cognitive revolution were major turning points in the creation of cognitive neuroscience as a field, bringing together ideas and techniques that enabled researchers to make more links between behavior and its neural substrates.

Origins in philosophy

Philosophers have always been interested in the mind: "the idea that explaining a phenomenon involves understanding the mechanism responsible for it has deep roots in the History of Philosophy from atomic theories in 5th century B.C. to its rebirth in the 17th and 18th century in the works of Galileo, Descartes, and Boyle. Among others, it’s Descartes’ idea that machines humans build could work as models of scientific explanation." For example, Aristotle thought the brain was the body’s cooling system and the capacity for intelligence was located in the heart. It has been suggested that the first person to believe otherwise was the Roman physician Galen in the second century AD, who declared that the brain was the source of mental activity, although this has also been accredited to Alcmaeon. However, Galen believed that personality and emotion were not generated by the brain, but rather by other organs. Andreas Vesalius, an anatomist and physician, was the first to believe that the brain and the nervous system are the center of the mind and emotion. Psychology, a major contributing field to cognitive neuroscience, emerged from philosophical reasoning about the mind.

19th century

Phrenology

A page from the American Phrenological Journal

One of the predecessors to cognitive neuroscience was phrenology, a pseudoscientific approach that claimed that behavior could be determined by the shape of the scalp. In the early 19th century, Franz Joseph Gall and J. G. Spurzheim believed that the human brain was localized into approximately 35 different sections. In his book, The Anatomy and Physiology of the Nervous System in General, and of the Brain in Particular, Gall claimed that a larger bump in one of these areas meant that that area of the brain was used more frequently by that person. This theory gained significant public attention, leading to the publication of phrenology journals and the creation of phrenometers, which measured the bumps on a human subject's head. While phrenology remained a fixture at fairs and carnivals, it did not enjoy wide acceptance within the scientific community. The major criticism of phrenology is that researchers were not able to test theories empirically.

Localizationist view

The localizationist view was concerned with mental abilities being localized to specific areas of the brain rather than on what the characteristics of the abilities were and how to measure them. Studies performed in Europe, such as those of John Hughlings Jackson, supported this view. Jackson studied patients with brain damage, particularly those with epilepsy. He discovered that the epileptic patients often made the same clonic and tonic movements of muscle during their seizures, leading Jackson to believe that they must be occurring in the same place every time. Jackson proposed that specific functions were localized to specific areas of the brain, which was critical to future understanding of the brain lobes.

Aggregate field view

According to the aggregate field view, all areas of the brain participate in every mental function.

Pierre Flourens, a French experimental psychologist, challenged the localizationist view by using animal experiments. He discovered that removing the cerebellum in rabbits and pigeons affected their sense of muscular coordination, and that all cognitive functions were disrupted in pigeons when the cerebral hemispheres were removed. From this he concluded that the cerebral cortex, cerebellum, and brainstem functioned together as a whole. His approach has been criticised on the basis that the tests were not sensitive enough to notice selective deficits had they been present.

Emergence of neuropsychology

Perhaps the first serious attempts to localize mental functions to specific locations in the brain was by Broca and Wernicke. This was mostly achieved by studying the effects of injuries to different parts of the brain on psychological functions. In 1861, French neurologist Paul Broca came across a man who was able to understand language but unable to speak. The man could only produce the sound "tan". It was later discovered that the man had damage to an area of his left frontal lobe now known as Broca's area. Carl Wernicke, a German neurologist, found a patient who could speak fluently but non-sensibly. The patient had been the victim of a stroke, and could not understand spoken or written language. This patient had a lesion in the area where the left parietal and temporal lobes meet, now known as Wernicke's area. These cases, which suggested that lesions caused specific behavioral changes, strongly supported the localizationist view.

Mapping the brain

In 1870, German physicians Eduard Hitzig and Gustav Fritsch published their findings about the behavior of animals. Hitzig and Fritsch ran an electric current through the cerebral cortex of a dog, causing different muscles to contract depending on which areas of the brain were electrically stimulated. This led to the proposition that individual functions are localized to specific areas of the brain rather than the cerebrum as a whole, as the aggregate field view suggests. Brodmann was also an important figure in brain mapping; his experiments based on Franz Nissl’s tissue staining techniques divided the brain into fifty-two areas.

20th century

Cognitive revolution

At the start of the 20th century, attitudes in America were characterised by pragmatism, which led to a preference for behaviorism as the primary approach in psychology. J.B. Watson was a key figure with his stimulus-response approach. By conducting experiments on animals he was aiming to be able to predict and control behaviour. Behaviourism eventually failed because it could not provide realistic psychology of human action and thought – it focused primarily on stimulus-response associations at the expense of explaining phenomena like thought and imagination. This led to what is often termed as the "cognitive revolution".

Neuron doctrine

In the early 20th century, Santiago Ramón y Cajal and Camillo Golgi began working on the structure of the neuron. Golgi developed a silver staining method that could entirely stain several cells in a particular area, leading him to believe that neurons were directly connected with each other in one cytoplasm. Cajal challenged this view after staining areas of the brain that had less myelin and discovering that neurons were discrete cells. Cajal also discovered that cells transmit electrical signals down the neuron in one direction only. Both Golgi and Cajal were awarded a Nobel Prize in Physiology or Medicine in 1906 for this work on the neuron doctrine.

Mid-late 20th century

Several findings in the 20th century continued to advance the field, such as the discovery of ocular dominance columns, recording of single nerve cells in animals, and coordination of eye and head movements. Experimental psychology was also significant in the foundation of cognitive neuroscience. Some particularly important results were the demonstration that some tasks are accomplished via discrete processing stages, the study of attention, and the notion that behavioural data do not provide enough information by themselves to explain mental processes. As a result, some experimental psychologists began to investigate neural bases of behaviour. Wilder Penfield created maps of primary sensory and motor areas of the brain by stimulating cortices of patients during surgery. The work of Sperry and Michael Gazzaniga on split brain patients in the 1950s was also instrumental in the progress of the field. The term cognitive neuroscience itself was coined by Gazzaniga and cognitive psychologist George Armitage Miller while sharing a taxi in 1976.

Brain mapping

New brain mapping technology, particularly fMRI and PET, allowed researchers to investigate experimental strategies of cognitive psychology by observing brain function. Although this is often thought of as a new method (most of the technology is relatively recent), the underlying principle goes back as far as 1878 when blood flow was first associated with brain function. Angelo Mosso, an Italian psychologist of the 19th century, had monitored the pulsations of the adult brain through neurosurgically created bony defects in the skulls of patients. He noted that when the subjects engaged in tasks such as mathematical calculations the pulsations of the brain increased locally. Such observations led Mosso to conclude that blood flow of the brain followed function.

Emergence of a new discipline

Birth of cognitive science

On September 11, 1956, a large-scale meeting of cognitivists took place at the Massachusetts Institute of Technology. George A. Miller presented his "The Magical Number Seven, Plus or Minus Two" paper while Noam Chomsky and Newell & Simon presented their findings on computer science. Ulric Neisser commented on many of the findings at this meeting in his 1967 book Cognitive Psychology. The term "psychology" had been waning in the 1950s and 1960s, causing the field to be referred to as "cognitive science". Behaviorists such as Miller began to focus on the representation of language rather than general behavior. David Marr concluded that one should understand any cognitive process at three levels of analysis. These levels include computational, algorithmic/representational, and physical levels of analysis.

Combining neuroscience and cognitive science

Before the 1980s, interaction between neuroscience and cognitive science was scarce. Cognitive neuroscience began to integrate the newly laid theoretical ground in cognitive science, that emerged between the 1950s and 1960s, with approaches in experimental psychology, neuropsychology and neuroscience. (Neuroscience was not established as a unified discipline until 1971). In the very late 20th century new technologies evolved that are now the mainstay of the methodology of cognitive neuroscience, including TMS (1985) and fMRI (1991). Earlier methods used in cognitive neuroscience include EEG (human EEG 1920) and MEG (1968). Occasionally cognitive neuroscientists utilize other brain imaging methods such as PET and SPECT. An upcoming technique in neuroscience is NIRS which uses light absorption to calculate changes in oxy- and deoxyhemoglobin in cortical areas. In some animals Single-unit recording can be used. Other methods include microneurography, facial EMG, and eye tracking. Integrative neuroscience attempts to consolidate data in databases, and form unified descriptive models from various fields and scales: biology, psychology, anatomy, and clinical practice. In 2014, Stanislas Dehaene, Giacomo Rizzolatti and Trevor Robbins, were awarded the Brain Prize "for their pioneering research on higher brain mechanisms underpinning such complex human functions as literacy, numeracy, motivated behaviour and social cognition, and for their efforts to understand cognitive and behavioural disorders". Brenda Milner, Marcus Raichle and John O'Keefe received the Kavli Prize in Neuroscience “for the discovery of specialized brain networks for memory and cognition" and O'Keefe shared the Nobel Prize in Physiology or Medicine in the same year with May-Britt Moser and Edvard Moser "for their discoveries of cells that constitute a positioning system in the brain". In 2017, Wolfram Schultz, Peter Dayan and Ray Dolan were awarded the Brain Prize "for their multidisciplinary analysis of brain mechanisms that link learning to reward, which has far-reaching implications for the understanding of human behaviour, including disorders of decision-making in conditions such as gambling, drug addiction, compulsive behaviour and schizophrenia".

Major contributors to the field

Hubel and Wiesel – 1960s

David H. Hubel and Torsten Wiesel, both neurophysiologists, studied the visual system in cats to better understand sensory processing. They performed experiments which demonstrated the specificity of the responding of neurons. Their experiments showed that neurons fired rapidly at some angles, and not so much at others. A difference was also found in light and dark settings. Their studies gave rise to the idea of complex visual representations being formed from relatively simple stimuli. 

They also discovered the simple cell and complex cell. These exist in the primary visual cortex and respond differentially to differently oriented presentations of light.

Recent trends

Recently the foci of research have expanded from the localization of brain area(s) for specific functions in the adult brain using a single technology, studies have been diverging in several different directions: exploring the interactions between different brain areas, using multiple technologies and approaches to understand brain functions, and using computational approaches. Advances in non-invasive functional neuroimaging and associated data analysis methods have also made it possible to use highly naturalistic stimuli and tasks such as feature films depicting social interactions in cognitive neuroscience studies.