Michael Gazzaniga


Michael Saunders Gazzaniga is an American cognitive neuroscientist and professor emeritus of psychology at the University of California, Santa Barbara. He is the founder and retired director of the SAGE Center for the Study of the Mind at UCSB.

Biography

In 1961, Gazzaniga graduated from Dartmouth College with a B.A in zoology. In 1964, he received a Ph.D. in psychobiology from the California Institute of Technology, where he carried out research on human split-brain patients for his doctoral thesis under Roger Sperry. In his subsequent work, Gazzaniga has made important advances in research concerning the laterization of brain function and communication between the left and right cerebral hemispheres.

Career

Gazzaniga's academic career began as an assistant professor of psychology at UCSB in 1967. Here he met a future life-long friend and collaborator, Colin Blakemore, a graduate student at the University of California Berkeley. Together they edited the Handbook of Psychobiology in 1975. In 1969 he moved to New York University graduate school as an assistant professor and in 1972 became a full professor. In 1973 he took a position as professor of psychology at the State University of New York at Stony Brook. That same year, at the invitation of Dartmouth neurosurgeon Donald Wilson, Gazzaniga began to study a new series of split-brain patients in New Hampshire with his graduate student, Joseph LeDoux. They put together a mobile lab and drove from New York to New Hampshire every month to test what became known as the "east-coast" series of split-brain patients, one of whom was patient P.S. Patient P.S. was the first split-brain patient whose right hemisphere could read. It could not speak, but it could spell out answers to questions. Gazzaniga's theory of the left hemisphere's interpreter was first formulated at this time. After he received his doctorate, LeDoux turned his efforts to what was then a mostly ignored field, emotion, and with meticulous research, gave it a firm foundation.
In 1977 Gazzaniga was offered a job at Cornell University Medical College when Fred Plum, the chairman of the neurology department, decided his residents needed some schooling in neuropsychology. He appointed Gazzaniga as the Director of the Division of Cognitive Neuroscience and a professor of Neurology and Psychology, where he stayed until 1988.
Meanwhile, in 1978, he and his good friend and colleague from Rockefeller University, Professor of Psychology George A. Miller, launched a new field of study by first giving it a name: Cognitive Neuroscience. Cognitive neuroscience integrates the methods of cognitive psychology with those of systems neuroscience to help understand how mental processes emerge from neural activity. With a small grant from the Sloan Foundation, Gazzaniga established the Cognitive Neuroscience Institute to begin a new program focused on research and on teaching the brain mechanisms involved with cognitive processes.
With continued funding from the Sloan Foundation, Gazzaniga extended the Cornell program to include a consortium of New York City universities to help establish the growing field of cognitive neuroscience and began a postdoctural training program. In 1982 he was elected Fellow of the Society of Experimental Psychologists in recognition for his studies on split-brain patients. In 1988, still making monthly trips to New Hampshire in the mobile camper lab, he was offered a professorship at Dartmouth Medical School.
From 1988 to 1992, he was the Andrew W. Thomson Jr. Professor of Psychiatry and the director of the Cognitive Neuroscience Program at Dartmouth Medical School. During that time, Gazzaniga founded the first cognitive neuroscience degree-granting program in the United States, founded and served as the first editor-in-chief of the Journal of Cognitive Neuroscience through 2003, and with help from the James S. McDonnell Foundation, initiated and ran the Summer Institute in Cognitive Neuroscience at Dartmouth. The summer camp brought together cognitive neuroscience graduate students, postdoctural researchers, and leaders in the various fields of cognitive neuroscience for a 2 week lecture and laboratory course each summer on a cutting edge topic.
After his time at Dartmouth Medical School, Gazzaniga moved to the University of California Davis in 1992 where he launched and served as the first Director of the Center for Neuroscience, where he continued to expand his pioneering research on brain function and cognitive processes.
In 1993, he founded, along with George R. Mangun, Steve Pinker, Patricia Reuter-Lorenz, Daniel Schacter and Art Shimamura, the Cognitive Neuroscience Society, a professional organization dedicated to advancing the field. The inaugural meeting was held in San Francisco in 1994. 1993 also marks the first summer that a 3 week stock-taking of the sub-specialty fields of cognitive neuroscience began. Eight leaders in each of the fields were invited for an intense meeting of self-examination and to write a chapter about their work. This stock-taking of the field continues to occur every 5 years. The result is the 6 volume series, The Cognitive Neurosciences, published by MIT Press.
In 1996, he returned to Dartmouth as the David T. McLaughlin Distinguished Professor of Psychological and Brain Sciences and as founding director of the Center for Cognitive Neuroscience. Under his leadership, Dartmouth was the first college to have a functional brain imaging center. He was elected to the American Academy of Arts and Sciences in 1997. Gazzaniga served as the Dean of the Faculty of Arts and Sciences at Dartmouth College from 2002 to 2004, while concurrently serving on the President's Council on Bioethics from 2002-2009. In 2005, he was elected to National Academy of Medicine.
In 2006, Gazzaniga became the founding Director of the Sage Center for the Study of the Mind at UC Santa Barbara, a role he took on after his time at Dartmouth. In 2007, The John D. and Catherine T. MacArthur Foundation appointed him director of The Law and Neuroscience Project, "the first systematic effort to bring together the worlds of law and science on questions of how courts should deal with recent breakthroughs in neuroscience as they relate to matters of assessing guilt, innocence, punishment, bias, truth-telling, and other issues." At UCSB, he continued to lead research efforts in cognitive neuroscience, while fostering the study of the mind's complex relationship with the brain.
In 2009, he delivered the Gifford Lectures on Mental Life at the University of Edinburgh. In 2011, he was elected to the National Academy of Sciences and received honorary doctorates from Dartmouth College and the University of Aberdeen. In 2019, Trinity College Dublin also awarded him with an honorary doctorate.
Over the course of his career, Gazzaniga's work has contributed to the development of experimental methods to study hemispheric specialization and the brain's role in cognitive functions such as language, reasoning, and facial recognition.
Gazzaniga's publication career includes books for a general audience such as The Social Brain, Mind Matters, Nature's Mind, The Ethical Brain ''Human and Who's in Charge?, which is based on the Gifford lectures he presented at the University of Edinburgh in 2009, and Tales From Both Sides of the Brain. 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 book is entitled The Consciousness Instinct: Unraveling the Mystery of How the Brain Makes Mind'', published by Farrar, Straus and Giroux in 2018.

Research

Early research

Gazzaniga is known for his work in cognitive neuroscience. His research with split-brain patients has helped to understand the distinct roles of the left and right hemispheres of the brain. In split-brain patients the corpus callosum, the giant nerve bundle which connects the right and left hemispheres, had been severed to limit the transmission of nerve impulses across the brain in the hopes of decreasing previously intractable seizures. The original series of split-brain patients, whose callosotomies had been done in the 1930s in Rochester, New York had been previously tested, and no evidence was found that there was any disruption of the interhemispheric transfer of information after callosotomy. Later, however, Sperry and his graduate student Ron Myers found that severing the corpus callosum in monkeys did block the transfer of information.
As a first-year graduate student at Caltech, Gazzaniga, convinced by the monkey research that transfer of information would be interrupted, began to test the first California split-brain patient with a testing procedure that had not been done on the previous series of split-brain patients. He had to present information to one hemisphere only in order for his experiment to work. The anatomy of the optic nerve allowed Gazzaniga to communicate solely to one hemisphere or the other. Visual information flashed to the right side of the visual field of both eyes is sent to the left hemisphere, and visual information flashed to the left side of the visual field of both eyes is sent to the right hemisphere. He designed an apparatus that flashed a letter, number or symbol onto a screen to either the right or left visual field while the patient focused on a central point. By fixating on a central point, the quickly flashed figure could be isolated to a particular visual field.

Patient W.J.

Patient W.J. was a World War II paratrooper, the first of a series of patients that underwent a callosotomy on the West Coast.
He had developed grand mal seizures after a German soldier knocked him out with a rifle butt after a parachute jump behind enemy lines. When it was suggested that he might benefit from a callosotomy, he was having anywhere from one grand mal seizure a week to seven a day, each requiring a full day to recover. He was ready to risk it. The surgery, which severed his entire corpus callosum and anterior commissure, was a success. W.J. had no more seizures and said he felt no different than he did before surgery. Before surgery, Gazzaniga tested W.J.'s brain functions. This included identifying stimuli presented to the left and right visual fields and identifying objects placed in his hands that were hidden from view, all of which he could easily do. After he had the surgery, the test results were different. When a picture of an object was flashed to his right visual field and he was asked if he saw anything, he quickly named the object. When a picture was flashed to his left visual field, however, he denied seeing anything. Then a circle was flashed on the screen and he was asked to point to whatever he had seen with whichever hand he wished. When the circle was flashed to the right visual field, he pointed to where it had been with his right hand, which is controlled by the left hemisphere. When it was flashed to his left visual field, even though he denied seeing anything, he pointed to where it had been with his left hand, controlled by the right hemisphere. This seemingly simple test showed that each hemisphere saw a circle when it was shown in the opposite visual field, and each hemisphere, separate from the other, could guide the contralateral hand, which it controls, to point to the circle it had seen, but only the left hemisphere could talk about it. Neither hemisphere knew what the other had seen!
Another experiment revealed the right hemisphere's was adept at visualspatial relations. A card showing a pattern produced by a set of blocks was put on a table in front of W.J. He was asked to copy the pattern using a set of blocks with his left hand, which was quickly able to reproduce the pattern. When it was his right hand's turn, it fumbled around haphazardly. Indeed, seeing what his right hand was up to, the left hand kept trying to help the fumbling right hand. W.J. had to actually sit on his left hand to stop it from interfering: two different mental control systems were competing with each other to solve the problem.
These experiments opened the door to years of research by Gazzaniga and colleagues that has revealed that severing the callosum prevents the transfer of perceptual, sensory, motor, gnostic and other types of information between the left and right cerebral hemispheres. Extensive research has shown that many of the brains processes are lateralized, such as speech and language to the left hemisphere, along with analytical thinking and the capacity to interpret behavior and unconsciously driven emotional states, while visuospatial processing, facial recognition, attentional monitoring, and the ascribing of beliefs to others are right hemisphere processes.

Patient P.S.

Patient P.S. at age 20 months developed a high fever and had many right-sided seizures, which became generalized, with a seizure focus over the left temporal region. He appeared to develop normally until age 10 when generalized seizures recurred spontaneously and became intractable. At age 14 he had a complete surgical section of the corpus callosum. He was also the first split-brain patient studied from the east coast series who had a full callosotomy with an intact anterior commissure. He had absolutely no interhemispheric transfer of visual information, and although only his left hemisphere could speak, he was the first split-brain patient in that series who demonstrated extensive language comprehension in the right hemisphere. For example, if he were asked to name an object in a picture presented to his left visual field, while he could not answer with speech, he spelled out the appropriate word with Scrabble tiles using his left hand. Every time, every picture. Even though he was right-handed, he could also roughly write words with his left hand. P.S.'s right hemisphere's verbal skills are unusual. Review studies on 3 series of patients who had had brain bisection found that right hemisphere language in split-brain patients happens infrequently. It is almost always attributable to early left-hemisphere brain damage, but see Patient J.W. below.
Gazzaniga and his graduate student Joseph LeDoux realized that P.S. presented them with the opportunity to directly question his right hemisphere: Would it be able to answer subjective and personal questions and, more specifically, did it possess its own sense of identity? To do this, they verbally asked, "Who blank?" then flashed the rest of the sentence "are you?" to his left visual field only and thus his right hemisphere. He spelled out "Paul" with his left hand using the tiles.
With the next question, they asked, “Would you spell your favorite blank” and then flashed “girl” to his left visual field. He shrugged and shook his head: His left hemisphere had seen nothing. But then he giggled and blushed. The right hemisphere saw and read the word “girl” and the right hemisphere’s comprehension of the word caused him to blush and giggle like most young teenage boys would have at the question. Meanwhile, the left hemisphere, which had not seen "girl," had no clue why he was blushing and giggling. Then his left hand reached out for 3 Scrabble tiles and spelled out the name “Liz.”
Another telling question asked the right hemisphere what job he would pick. He spelled out “automobile race” with his left hand, though shortly after the end of the session, he was asked the entire question out loud, and his left speaking hemisphere answered, “Oh, be a draftsman.” Each hemisphere had a separate goal. The experimental session ended after asking the right hemisphere to spell out its mood. The left hand spelled out "good."
The above experiments not only demonstrated that in some split-brain patients the right hemisphere was capable of language comprehension, but were also suggestive that P.S.'s right hemisphere was separately conscious: It had a sense of self, it knew who and what it liked, it had its own goals and was able to generate answers to ambiguous questions.
P.S. is most well known for an experiment using a simultaneous concept test, which led to the discovery of a major left hemisphere capacity. In this test, a picture of a snow scene was flashed exclusively to PS’s left hemisphere while simultaneously a picture of a chicken’s foot was flashed exclusively to his right hemisphere. A choice of four cards, a lawnmower, a rake, a shovel and a pick were in front of his left hand, and four cards in front of his right hand, an apple, a toaster, a hammer and a chicken head. PS was asked to pick which picture card best related to the stimuli he had seen. With his right hand, guided by his left hemisphere, he picked the chicken to match the chicken’s foot. With his left hand, guided by his right hemisphere, he picked the shovel to match the snow scene.
When PS asked why he did what he just did, he replied without hesitation, “I saw a claw and I picked the chicken, and you have to clean out the chicken shed with a shovel.” While the experimenters knew why PS’s right hemisphere had picked the shovel, his left speaking hemisphere did not. It had not seen the snow scene. What it did see was his left hand pointing to the shovel. The left hemisphere's answer, however, was not "I don't know." Thus, whatever his answer would be for why his left hand was pointing to the shovel, it would be a guess, a story that would cover as much of the incoming information to the left hemisphere as possible. The same results were obtained after many different trials: The left hemisphere could accurately report why it had picked the answer it had and continued on to include the right hemisphere's behavioral response as part of the story. These results suggested to LeDoux and Gazzaniga that they may be observing a basic mental mechanism in the left hemisphere that we all possess. They suggested that “the conscious verbal self is not always privy to the origin of our actions, and when it observes the person behaving for unknown reasons, it attributes cause to the action as if it knows for certain, but in fact it does not. It is as if the verbal self looks out and sees what the person is doing, and from that knowledge it interprets a reality.” Thinking about P.S. and his blushing when the right hemisphere was asked about his favorite girl, they wondered if emotional states of one hemisphere could influence the affective tone of the other. And then they met patient V.P.

Patient V.P.

At the age of 6, Patient V.P. had recurrent seizures following febrile illnesses that included measles and scarlet fever. Over the following years she developed grand mal, petit mal and myoclonic episodes that did not abate with multiple anticonvulsants. When she was 27, Dr. Mark Rayport, founding chairman of the Department of Neurological Surgery at the Medical College of Ohio, performed a partial anterior callosal section in early April 1979, and in a second operation 7 weeks later, completed the section of her callosum.
Four months after her surgery, her right hemisphere could write simple answers and was able to carry out verbal commands. For example, if the command “smile” was flashed to her right hemisphere, V.P. could do it. Ask her why she was smiling and her left hemisphere would assert some made up answer. So V.P. was the second split-brain patient in the East Coast series whose right hemisphere had some verbal capacity. Gazzaniga wondered if he could create a mood state in the right hemisphere, study whether the left hemisphere was aware of it, and if so, how would it deal with it?
A previous experiment with split-brain monkeys had shown that emotional states appear to transfer between the hemispheres subcortically, that is, areas not affected by callosotomy, so it seemed possible. Gazzaniga showed V.P's right hemisphere a scary clip from a movie where a man pushed another man off a balcony and threw a fire bomb on top of him. Then she was asked what she had seen. She said, “I don’t really know what I saw. I think just a white flash.” When asked if it made her feel any emotions she answered, “I don’t really know why, but I’m kind of scared. I feel jumpy, I think maybe I don’t like this room, or maybe it’s you.” She said to one of the research assistants, “I know I like Dr. Gazzaniga, but right now I’m scared of him for some reason.” She felt the emotional response to the video her right hemisphere had seen but had no idea what caused it. She looked around to come up with an hoc answer. Gazzaniga explained, "The left-brain interpreter had to explain why she felt scared. The information it received from the environment was that I was in the room asking questions and that nothing else was wrong. The first makes-sense explanation it arrived at was that I was scaring her."
Gazzaniga later called this capacity to interpret behavior and unconsciously driven emotional states 'the Interpreter.' This system takes the chaos of both internally and externally generated information that is constantly bombarding each of us and tries to make sense of it all. It weaves a story about events, even felt emotions that can go beyond the actual available information or it can ignore pertinent information. Gazzaniga postulates that the interpreter underlies the human drive to seek explanations for why events occur. This system has proven to be helpful for survival, but also is not always accurate.

Patient J.W.

Patient J.W. suffered a concussive head trauma at age 13, after which he began to have brief absence spells that went untreated. At 19, he experienced his first grand mal seizure. The frequency of the seizures increased and were intractable with medication. In 1979, when he was 26 years old, he underwent a two-stage callosotomy. Immediately following both surgeries, his right hemisphere had the capacity to understand spoken and written language, meaning that he had a right hemisphere semantic system, but was unable to speak. For example, the left hand could make a picture-word correspondence: Lateralize a picture of a bird to J.W.'s right hemisphere and his left hand would point to the written word "bird." Lateralize the word "zebra" to his right hemisphere and his left hand would point to a picture of a zebra. Unexpectedly eleven years later, while evaluating visual field stabilizing equipment, J.W.'s right hemisphere started to vocally name pictures that were presented to his right hemisphere. Over the following several years, this ability continued to increase. Up until then, the previously reported post-callosotomy dynamic periods of right hemisphere language capacity suggested that the right hemisphere could only develop language skills in the absence of the left hemisphere when there had been damage to the left hemisphere in childhood. Another interpretation of the data was that observations of right hemisphere language development were restricted by the limited life span of postoperative adult patients. J.W. was the first split-brain patient to demonstrate an increasing ability for right hemisphere speech many years after his callosotomy. While long-term functional plasticity has been suggested in adults, documentation of such is scarce.

Awards