Vilayanur S. Ramachandran

Vilayanur S. "Rama" Ramachandran (born 1951) is a neurologist best known for his work in the fields of behavioral neurology and psychophysics. He received a degree in medicine from Stanley Medical College in Madras, India, and later, a Ph.D. from the University of Cambridge. He is currently a professor of psychology and neuroscience at University of California, San Diego, the director of the Center for Brain and Cognition, and scientific advisor to the Beckley Foundation.

V. S. Ramachandran has published over 120 peer reviewed articles, and has authored two general reader science books as an introduction to his work and research. He writes regularly for Scientific American, and has appeared in both BBC and PBS documentaries. Newsweek magazine named him one of the "hundred most prominent people to watch in the next century".

He is married to Diane Rogers-Ramachandran and they have two boys, Mani and Jaya.^[1]

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Education

V.S. Ramachandran received his M.D. from Stanley Medical College in Madras, India in 1974 where he specialized in surgery. After receiving his M.D., he moved to the University of Cambridge, where he studied human psychophysics and neurophysiology under the direction of David Whitteridge, and received his Ph.D. in 1978. He then conducted post-doctoral research at Caltech, under the direction of Jack Pettigrew from 1978 to 1981. He was appointed Assistant Professor at the University of California, San Diego in 1983, and has been a full professor at UC San Diego since 1998.

Scientific career

Ramachandran's scientific work can be broken into two phases. From 1972 until the late 1980s, Ramachandran's work focused almost exclusively on visual perception, using the methods of psychophysics, which permit clear inferences about what someone is seeing, based on what they report. In the second half of his career, Ramachandran turned his attention towards cognitive neurology, and in particular towards a number of little-studied neurological syndromes.

Over the course of his scientific career, Ramachandran has published over 120 peer reviewed articles. Twenty of these have appeared in the highly prestigious scientific journal Nature, and many others have appeared in such journals as Science, Nature Neuroscience, Perception and Vision Research. In addition, Ramachandran is the author of two popular audience books, Phantoms in the Brain (1998, with Sandra Blakeslee) and A Brief Tour of Human Consciousness (2003, published in England under the Title The Emerging Mind) and is the editor of the Encyclopedia of the Human Brain (2002). He is also the author, with his wife Diane Rogers-Ramachandran, of the bi-monthly "Illusions" column in Scientific American Mind.

He is a member of All Souls College, Oxford, Neurosciences Institute in La Jolla, CA, and the Institute for Advanced Studies in Behavioral Sciences at Stanford University.

He obtained an honorary doctorate from Connecticut College, Gold medal from the Australian National University, the Ariens Kappers Medal from the Royal Nederlands Academy of Sciences and the Presidential Lecture Award from the American Academy of Neurology.

Visual psychophysics

Ramachandran began his scientific career while still in medical school, when he made observations on phenomena such as stereopsis, or how the two eyes combine information to allow us to see depth. He noticed that the sensation of depth could be generated using random dot stereograms even though the two images were rivaling due to different colored filters placed in front of each eye. This paper, Ramachandran's first, was published in Nature in 1972.

Ramachandran went on to make observations about how visual perception works, including in the domains of apparent motion (with Stuart Anstis), shape from shading, filling in, and interactions between color and motion (the latter two conducted in collaboration with Richard Gregory). Many of his visual illusions, including brief explanations of how they work are available on his website at Ramachandran illusions.

Behavioral neurology

In the late 1980s, Ramachandran turned his attention to neurology, which had fascinated him in medical school. Ramachandran is best known for his work on neurological syndromes such as phantom limbs and anosognosia, his invention of the mirror box, and his more recent work on synesthesia, all of which have figured prominently in his two general audience books.

Phantom limbs

Main article: Phantom limb

Ramachandran's approach has been to identify potential neural mechanisms, and then to test these potential mechanisms through the use of a few simple behavioral experiments. For example, he suggested that phantom limbs might be due to changes in the brain, rather than in the peripheral nerves. Due to the way that the surface of the body is represented in the brain, stimulation to the cheek should elicit phantom limb sensations if the brain had reorganized after amputation, but not if the changes were simply peripheral. Simply by showing that phantom limb sensations were elicited after stroking the cheek, Ramachandran was able to show that they were due to reorganization in the brain. Subsequent functional neuroimaging studies by Ramachandran's group, and by others, have demonstrated that this cortical reorganization occurs, and that the extent of cortical reorganization correlates with phantom limb pain.

Main article: Mirror box

In order to alleviate phantom limb pain, Ramachandran developed the mirror box, in which patients place their good limb and the amputated limb, and imagine making mirror symmetric movements. Due to the visual feedback, patients feel their limbs to be moving, which helps to alleviate phantom limb pain. Recent neuroimaging studies suggest that this may be a result of reversing the remapping that leads to phantom limb pain.

Synesthesia

Main article: Synesthesia

More recently, Ramachandran studied the neural mechanisms of grapheme-color synesthesia, a condition in which viewing black and white letters or numbers on a page evokes the experience of seeing colors. Ramachandran (with then PhD student, Edward Hubbard) showed that some synesthetes (those who experience synesthesia) were better able to detect "embedded figures" composed of one letter or number (for example a triangle composed of 2s) on a background of another number (for example 5s). This is a difficult task for people who do not experience synesthesia. However, some synesthetes report that the colors they see help them to find and identify the embedded shape. Their performance on behavioral tasks show that some synesthetes are better at this task than non-synesthetes.

Based on his previous work on phantom limbs, Ramachandran suggested that synesthesia may arise from a similar cross-activation between brain regions. However, rather than being within a single sensory stream, this form of cross-activation would occur between sensory streams, and is thought to be due to genetic differences, rather than neural re-organization. In fMRI experiments, increased activity in a color selective region (hV4) was found in synesthetes compared to non-synesthetes when they viewed letters and numbers that evoked synesthetic colors, compared with symbols that did not.

Capgras delusion

Main article: Capgras delusion

In collaboration with then post-doctoral fellow, William Hirstein, Ramachandran also explored the neural mechanisms behind Capgras delusion, a delusion in which family members and other loved ones are thought to be replaced by impostors, which can occur after brain trauma. Based on the classical observations that Capgras usually occurs only for people that are close to the patient, and that the delusions tend to be absent if the person is only spoken to (e.g., via telephone), Ramachandran and Hirstein suggested that Capgras might be a result of a disconnection between the "fusiform face area", a region of the fusiform gyrus involved in face perception, and the amygdala which is involved in the emotional responses to familiar faces. Ramachandran and Hirstein hypothesized that because the neural machinery involved in recognizing faces is intact, the patient recognizes the person as looking like his or her loved one. However, since the connection between face recognition and the emotional centers in the amygdala are severed, the emotional response generated by the face is absent, leading to the delusion that the seen loved one must be an impostor. To test this theory, Ramachandran and Hirstein used the Galvanic skin response (GSR), which measures emotional arousal, to show that patients suffering from Capgras delusion did not show the appropriate GSR to familiar faces. Subsequent work has expanded on these findings, and suggested that concurrent damage to other brain regions involved in reality monitoring must also occur.

Mass media

Ramachandran's work in behavioral neurology has been widely reported by the mass media. He has appeared in numerous Channel Four and PBS documentaries. He has also been featured by the BBC, the Science Channel, Newsweek, and This American Life. He gave the 2003 Reith Lectures, entitled The Emerging Mind, which were created by Lord Reith, the founder of the BBC, for the popularization of science. In May 2006, he gave an after-dinner lecture on The Uniqueness of the Human Brain at the Almaden Research Center's Almaden Institute on cognitive computing.^[2]

Books by Ramachandran

• Phantoms in the Brain : Probing the Mysteries of the Human Mind, coauthor Sandra Blakeslee, 1998, ISBN 0-688-17217-2
• The Encyclopedia of the Human Brain (editor-in-chief) ISBN 0-12-227210-2
• The Emerging Mind, 2003, ISBN 1-86197-303-9
• A Brief Tour of Human Consciousness: From Impostor Poodles to Purple Numbers, 2005, ISBN 0-13-187278-8 (paperback edition)
• The Man with the Phantom Twin: Adventures in the Neuroscience of the Human Brain Due out January 10, 2008. ISBN 978-0-525-95023-3

See also

• Body image
• the mirror box
• Oliver Sacks
• Phantom limb
• Phonaesthesia
• Neuropathic pain
• Synesthesia
• Temporal lobe epilepsy

References

1. ^ Mani Gaia in the San Diego Union Tribune.
2. ^ Almaden Institute 2006. (video lecture online)