Cognitive neuroscience

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."[8] 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,[9] although this has also been accredited to Alcmaeon.[10] 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.[11] Psychology, a major contributing field to cognitive neuroscience, emerged from philosophical reasoning about the mind.[12]

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.[13] The major criticism of phrenology is that researchers were not able to test theories empirically.[4]

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.[4] 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 caused by activity in the same place in the brain every time. Jackson proposed that specific functions were localized to specific areas of the brain,[14] which was critical to future understanding of the brain lobes.

According to the aggregate field view, all areas of the brain participate in every mental function.[5]

Pierre Flourens, a French experimental psychologist, challenged the localizationist view by using animal experiments.[4] He discovered that removing the cerebellum (brain) 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.[15] His approach has been criticised on the basis that the tests were not sensitive enough to notice selective deficits had they been present.[4]

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.[9] In 1861, French neurologist Paul Broca came across a man with a disability who was able to understand the 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. Additionally, Aphasia is a learning disorder which was also discovered by Paul Broca. According to, Johns Hopkins School of Medicine, Aphasia is a language disorder caused by damage in a specific area of the brain that controls language expression and comprehension.[16] This can often lead to the person speaking words with no sense known as "word salad" [17]

In 1870, German physicians Eduard Hitzig and Gustav Fritsch published their findings of 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.[6] 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.

At the start of the 20th century, attitudes in America were characterized 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 behavior. Behaviorism 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".[18]

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.[19]

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,[20][21] 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 the cortices of patients during surgery. The work of Sperry and Gazzaniga on split brain patients in the 1950s was also instrumental in the progress of the field.[9] The term cognitive neuroscience itself was coined by Gazzaniga and cognitive psychologist George Armitage Miller while sharing a taxi in 1976.[22]

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.[7] 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.[7]

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[23] 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.[24]

Before the 1980s, interaction between neuroscience and cognitive science was scarce.[25] 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[26]). In the late 1970s, neuroscientist Michael S. Gazzaniga and cognitive psychologist George A. Miller were said to have first coined the term "cognitive neuroscience."[27] 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.[28]

ARTMAP overview

Adaptive resonance theory (ART) is a cognitive neuroscience theory developed by Gail Carpenter and Stephen Grossberg in the late 1970s on aspects of how the brain processes information. It describes a number of neural network models which use supervised and unsupervised learning methods, and address problems such as pattern recognition and prediction.[29]

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".[30] 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"[31] 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".[32]

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".,[33]