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Michael Gazzaniga | |
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Born | Los Angeles, California, USA [1] | December 12, 1939
Alma mater | Dartmouth College, Caltech |
Known for | Split-brain research, cerebral lateralization, cognitive neuroscience |
Awards | Elected to the National Academy of Sciences, honorary doctorate from Trinity College Dublin |
Scientific career | |
Fields | Psychology, neuroscience |
Institutions | University of California, Santa Barbara, SAGE Center for the Study of the Mind |
Doctoral advisor | Roger Sperry |
Doctoral students | Joseph E. LeDoux |
Michael S. Gazzaniga (born December 12, 1939) is a professor of psychology at the University of California, Santa Barbara in the USA, where he heads the new SAGE Center for the Study of the Mind. [2] He is one of the leading researchers in cognitive neuroscience, the study of the neural basis of mind. [3] He is a member of the American Academy of Arts & Sciences, the Institute of Medicine, and the National Academy of Sciences. [3]
In 1961, Gazzaniga graduated from Dartmouth College in the USA. In 1964, he received a Ph.D. in psychobiology from the California Institute of Technology, where he worked under the guidance of Roger Sperry (who had primary responsibilities for initiating human split-brain research). In his subsequent work he has made important advances in our understanding of functional lateralization in the brain and how the cerebral hemispheres communicate with one another.
Gazzaniga's publication career includes books for a general audience such as The Social Brain, Mind Matters, Nature's Mind, The Ethical Brain and Who's in Charge?. He is also the editor of The Cognitive Neurosciences book series published by the MIT Press, which features the work of nearly 200 scientists and is a sourcebook for the field. His latest monograph is entitled Who's in Charge?: Free Will and the Science of the Brain. It was published by HarperCollins in 2011. [4]
Gazzaniga founded the Centers for Cognitive Neuroscience at the University of California, Davis and at Dartmouth College, the Neuroscience Institute, and the Journal of Cognitive Neuroscience , of which he is the Editor-in-Chief Emeritus. Gazzaniga was a member of U.S. President George W. Bush's Council on Bioethics. He was also the Director of the Law and Neuroscience Project, a project to study the intersection of law and neuroscience.
In 2009, he delivered the Gifford Lectures on Mental Life at the University of Edinburgh. [5] In 2019, Trinity College Dublin awarded him with an honorary doctorate. [6]
Gazzaniga's work is mentioned in the novel Peace on Earth by Stanisław Lem. It is also mentioned in Chapter 8 of Homo Deus by Yuval Noah Harari. [7]
In 2010 a tribute volume to the work of Gazzaniga was published, containing contributions by Joseph LeDoux, Stephen Kosslyn, Steven Pinker and others. [8]
Gazzaniga has led pioneering studies in learning and understanding split brained patients and how their brains work. [9] He has performed numerous studies and done large amounts of research on split brain patients to provide a higher quality understanding into the lives of those affected by this rare phenomenon. He has studied how people who have the two halves of the brain separated function in comparison to those who do not. Gazzaniga has looked into what bodily functions are controlled by each half of the brain. He has looked at what split brained patients are able to do as a result of their condition such as the ability to draw two different objects with each hand, an ability that a person with a non-split brain is unable to do. They study how those with split brain act emotionally and physically in comparison to those who do not have a split brain. Through Gazzaniga’s studies a much greater understanding of the split brain phenomenon has been brought to other physiologists as well as the general population of the world. [10] [11]
Patient W.J. was a World War II paratrooper who got hit in the head with a rifle butt, after which he started having seizures. Before his operation to try to fix the seizures, Gazzaniga tested his brain functions. This included presenting stimuli to the left and right visual fields and identifying objects in his hands that were out of view. He was able to perform these tasks perfectly and afterwards he had the surgery that split his corpus callosum and anterior commissure. After his surgery, he was brought in again for testing with Gazzaniga in which stimuli such as letters and light bursts were flashed to the left and right visual fields. The stimuli flashed to the right visual field were processed by the brain’s left hemisphere, which contains the language center, so he was able to press a button to indicate he saw the stimulus and could verbally report what he had seen. However, when the stimuli were flashed to the left visual field, and thus the right hemisphere, he would press the button, but could not verbally report having seen anything. When they modified the experiment to have him point to the stimulus that was presented to his left visual field and not have to verbally identify it, he was able to perform this task accurately. [12] [13]
Patient W.J.’s divided corpus callosum could also cause conflicts between the hemispheres. An example of this could be seen with his hands, where each hand was controlled by the opposite hemisphere, and there was no communication between the two. This would result in moments where one hand might reach out to open a car door while the other would try to stop that hand from opening the door. [13]
Patient P.S. was a teenage boy in whom it was shown that language comprehension was possible in the right hemisphere. When the word “girlfriend” was flashed to his left visual field, and thus his right hemisphere, he could not verbally say the name of his “crush”, but he then spelled out the name “Liz” with Scrabble tiles. This suggested that even though verbal language was not possible in the right hemisphere, there was a form of language possible through gesturing and left hand movements. [12] [13]
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.
Attention is the concentration of awareness on some phenomenon to the exclusion of other stimuli. It is a process of selectively concentrating on a discrete aspect of information, whether considered subjective or objective. William James (1890) wrote that "Attention is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration, of consciousness are of its essence." Attention has also been described as the allocation of limited cognitive processing resources. Attention is manifested by an attentional bottleneck, in terms of the amount of data the brain can process each second; for example, in human vision, only less than 1% of the visual input data can enter the bottleneck, leading to inattentional blindness.
Roger Wolcott Sperry was an American neuropsychologist, neurobiologist, cognitive neuroscientist, and Nobel laureate who, together with David Hunter Hubel and Torsten Nils Wiesel, won the 1981 Nobel Prize in Physiology and Medicine for his work with split-brain research. A Review of General Psychology survey, published in 2002, ranked Sperry as the 44th most cited psychologist of the 20th century.
Split-brain or callosal syndrome is a type of disconnection syndrome when the corpus callosum connecting the two hemispheres of the brain is severed to some degree. It is an association of symptoms produced by disruption of, or interference with, the connection between the hemispheres of the brain. The surgical operation to produce this condition involves transection of the corpus callosum, and is usually a last resort to treat refractory epilepsy. Initially, partial callosotomies are performed; if this operation does not succeed, a complete callosotomy is performed to mitigate the risk of accidental physical injury by reducing the severity and violence of epileptic seizures. Before using callosotomies, epilepsy is instead treated through pharmaceutical means. After surgery, neuropsychological assessments are often performed.
Hemispatial neglect is a neuropsychological condition in which, after damage to one hemisphere of the brain, a deficit in attention and awareness towards the side of space opposite brain damage is observed. It is defined by the inability of a person to process and perceive stimuli towards the contralesional side of the body or environment. Hemispatial neglect is very commonly contralateral to the damaged hemisphere, but instances of ipsilesional neglect have been reported.
Bicameral mentality is a hypothesis introduced by Julian Jaynes who argued human ancestors as late as the ancient Greeks did not consider emotions and desires as stemming from their own minds but as the consequences of actions of gods external to themselves. The theory posits that the human mind once operated in a state in which cognitive functions were divided between one part of the brain which appears to be "speaking", and a second part which listens and obeys—a bicameral mind, and that the breakdown of this division gave rise to consciousness in humans. The term was coined by Jaynes, who presented the idea in his 1976 book The Origin of Consciousness in the Breakdown of the Bicameral Mind wherein he made the case that a bicameral mentality was the normal and ubiquitous state of the human mind as recently as 3,000 years ago, near the end of the Mediterranean bronze age.
The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The median longitudinal fissure separates the human brain into two distinct cerebral hemispheres, connected by the corpus callosum. Although the macrostructure of the two hemispheres appears to be almost identical, different composition of neuronal networks allows for specialized function that is different in each hemisphere.
Hemianopsia, or hemianopia, is a loss of vision or blindness (anopsia) in half the visual field, usually on one side of the vertical midline. The most common causes of this damage are stroke, brain tumor, and trauma.
Attentional shift occurs when directing attention to a point increases the efficiency of processing of that point and includes inhibition to decrease attentional resources to unwanted or irrelevant inputs. Shifting of attention is needed to allocate attentional resources to more efficiently process information from a stimulus. Research has shown that when an object or area is attended, processing operates more efficiently. Task switching costs occur when performance on a task suffers due to the increased effort added in shifting attention. There are competing theories that attempt to explain why and how attention is shifted as well as how attention is moved through space in attentional control.
Elkhonon Goldberg is a neuropsychologist and cognitive neuroscientist known for his work in hemispheric specialization and the "novelty-routinization" theory.
The Herrmann Brain Dominance Instrument (HBDI) is a system to measure and describe thinking preferences in people, developed by William "Ned" Herrmann while leading management education at General Electric's Crotonville facility. It is a type of cognitive style measurement and model, and is often compared to psychological pseudoscientific assessments such as the Myers-Briggs Type Indicator, Learning Orientation Questionnaire, DISC assessment, and others.
In human neuroanatomy, brain asymmetry can refer to at least two quite distinct findings:
Elizabeth Kerr Warrington FRS is a British neuropsychologist specialised in the study of dementia. She holds a PhD in Psychology visual processing and is now an emeritus professor of clinical neuropsychology at the University College London. She formerly worked as the Head of the Department of Neuropsychology at the National Hospital for Neurology and Neurosurgery where she is also a member of the Dementia Research Centre. She was made a Fellow of the Royal Society in 1986.
In neuroscience, functional specialization is a theory which suggests that different areas in the brain are specialized for different functions.
Emotional lateralization is the asymmetrical representation of emotional control and processing in the brain. There is evidence for the lateralization of other brain functions as well.
Dichotic listening is a psychological test commonly used to investigate selective attention and the lateralization of brain function within the auditory system. It is used within the fields of cognitive psychology and neuroscience.
The left-brain interpreter is a neuropsychological concept developed by the psychologist Michael S. Gazzaniga and the neuroscientist Joseph E. LeDoux. It refers to the construction of explanations by the left brain hemisphere in order to make sense of the world by reconciling new information with what was known before. The left-brain interpreter attempts to rationalize, reason and generalize new information it receives in order to relate the past to the present.
Disconnection syndrome is a general term for a collection of neurological symptoms caused – via lesions to associational or commissural nerve fibres – by damage to the white matter axons of communication pathways in the cerebrum, independent of any lesions to the cortex. The behavioral effects of such disconnections are relatively predictable in adults. Disconnection syndromes usually reflect circumstances where regions A and B still have their functional specializations except in domains that depend on the interconnections between the two regions.
Dual consciousness is a hypothetical concept in neuroscience. It is proposed that it is possible that a person may develop two separate conscious entities within their one brain after undergoing a corpus callosotomy. The idea first began circulating in the neuroscience community after some split-brain patients exhibited the alien hand syndrome, which led some scientists to believe that there must be two separate consciousnesses within the brain's left and right hemispheres in competition with one another once the corpus callosum is severed.
Of Two Minds: The Revolutionary Science of Dual-Brain Psychology is a book written by the American psychiatrist Fredric Schiffer wherein he proposes that each person behaves as if there are two minds within the person, and that by recognizing and relating to the two separate minds, the therapist can promote healing and understanding of problems such as depression, anxiety, addictive behavior and delusional thoughts. The author writes that by "two minds in one person" he means that a "part of an individual ...has a unique set of memories, motivations, and behaviors alongside another part of him which has a different unique set of memories, motivations and behaviors." The author locates a "mind" in each of the two physical halves (hemispheres) of the brain. and he "maintains that one hemisphere can be more immature than the other and that this imbalance leads to different mental disorders." During his counseling, as an exercise he has his patients cover all of one eye, and the inner half of the other eye, which the author feels selectively stimulates one cerebral hemisphere more than the other – activating the thoughts and feelings of that hemisphere – which allows one to "'talk' to each half of the brain separately, to learn which is less mature, and to bring the two hemispheres into harmony."
Michael Gazzaniga is the Director of the SAGE Center for the Study of Mind at the University of California, Santa Barbara.
Michael Gazzaniga is one of the leading intellectuals in cognitive neuroscience.