Wolfgang Kohler

Vilayanur S. Ramachandran

Vilayanur S. "Rama" Ramachandran is a neurologist best known for his work in the fields of behavioral neurology and psychophysics. He is currently the Director of the Center for Brain and Cognition, Professor in the Psychology Department and Neurosciences Program at the University of California, San Diego, and Adjunct Professor of Biology at the Salk Institute for Biological Studies.

Ramachandran initially obtained an M.D. at Stanley Medical College in Madras, India, and subsequently obtained a Ph.D. from Trinity College at the University of Cambridge. Ramachandran’s early work was on visual perception but he is best known for his experiments in behavioral neurology which, despite their apparent simplicity, have had a profound impact on the way we think about the brain.

Ramachandran has been elected to fellowships at All Souls College, Oxford, and the Royal Institution, London (which also awarded him the Henry Dale Medal). He gave the 2003 BBC Reith Lectures and was conferred the title of Padma Bhushan by the President of India in 2007. He has been called “The Marco Polo of neuroscience” by Richard Dawkins and "the modern Paul Broca" by Eric Kandel. Newsweek magazine named him a member of "The Century Club", one of the "hundred most prominent people to watch" in the 21st century.

Early life and education

V.S. Ramachandran was born in Tamil Nadu, India to an Indian diplomat, and spent much of his youth abroad, at posts in Asia and India. After receiving his M.D. from Stanley Medical College in Madras in 1974, he moved to Trinity College, Cambridge, where he obtained his Ph.D. in neuroscience and experimental psychology. He was then a postdoctoral fellow at the Physiology Department at Oxford University. His advisors were Oliver Braddick, Fergus Campbell, Horace Barlow, Colin Blakemore and (at Oxford) David Whitteridge. He then spent two years at Caltech, as a research fellow working with Jack Pettigrew. 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. While still in England, he collaborated with Richard Gregory.

Scientific career

Ramachandran has pursued two parallel careers; one in the study of visual perception, using the methods of psychophysics, which permit clear inferences about what someone is seeing, based on what they report, and the other in neurology, and in particular towards a number of neurological syndromes. He is credited with introducing the use of visual feedback as a treatment for phantom limb pain (the mirror box), rehabilitation after stroke, and RSD (complex regional pain syndrome). He is also known for his new experiments and speculations (together with Edward Hubbard and David Brang) in the field of synesthesia and for creating a new wave of interest in this long-ignored phenomenon. More recently his work has focused on the cause of autism.

Ramachandran has published over 180 papers in scientific journals. 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. He is author of the acclaimed book Phantoms in the Brain that has been translated into nine languages and formed the basis for a two part series on BBC Channel 4 TV (UK) and a 1-hour PBS special in the USA. He is the editor of the Encyclopedia of the Human Brain (2002), and is co-author of the bi-monthly "Illusions" column in Scientific American Mind. The two phases of his career can be summarized as follows:

Human vision

Ramachandran’s early research was on human visual perception using psychophysical methods to draw clear inferences about the brain mechanisms underlying visual processing.

He is credited with discovering several new visual effects and illusions; most notably perceived slowing of motion at equiluminance (when red and green are seen as equally bright), stereoscopic "capture" using illusory contours, stereoscopic learning, shape-from-shading, and motion capture. He invented (together with Richard Gregory) filling in of "artificial scotomas" and discovered a new "dynamic noise after effect". He also invented a class of stimuli (phantom contours) that selectively activate the magnocellular pathway in human vision and are now being used to diagnose dyslexia.

Ramachandran’s work (together with that of many other colleagues, including Patrick Cavanagh, Ken Nakayama, and Alan Gilchrist) initiated a "neo-gestalt" revolution in the study of vision – following the tradition of Irvin Rock, Bela Julesz, Julian Hochberg, and Richard Gregory (and the generation of Gestaltists prior to that: Kurt Koffka, Wolfgang Kohler, Stuart Anstis, and Max Wertheimer). This work helped inspire a new era of physiological experiments and AI modeling of visual processes.

Many of his visual illusions, including brief explanations of how they work are available on his website at Ramachandran illusions

Cognitive neuroscience

Ramachandran’s forté is studying neurological syndromes to investigate neural mechanisms underlying human mental function. He is especially known for the simplicity and elegance of his experiments – usually using very 'low-tech' equipment to try and answer fundamental questions about how the brain functions. Ramachandran is best known for his work on neurological syndromes such as phantom limbs, autism, neglect, his invention of the mirror box, and his more recent work on synesthesia.

Phantom limbs

When an arm or leg is amputated patients continue to vividly feel the presence of the missing limb a "phantom limb". In the early 1990’s Ramachandran began using this phenomenon as a probe for exploring neural plasticity in the adult human brain. Ramachandran suggested that phantom limbs might be due to changes in the brain, rather than in the peripheral nerves. The input from the limb is mapped on to the somatosensory cortex in an orderly manner, forming a representation which is referred to as the somatosensory homonculus. Input from the hand is located next to the input from the arm, input from the foot is located next to input from the hand, and so on. One oddity is input from the face is located next to input from the hand. 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. For example if, after arm amputation, the face on the same side of the body is touched the patient feels sensations in his/her phantom arm; the sensations (touch, temperature, vibration, etc.) are referred from the face to phantom in an organized manner (the somatotopic arrangement). Ramachandran and colleagues first demonstrated this remapping by showing that stroking different parts of the face led to perceptions of being touched on different parts of the missing limb.

Ramachandran conjectured (and showed using MEG) that when the arm is amputated the vacated cortical territory corresponding to the missing arm is “invaded” by neurons which respond to stimulation of the face which normally would only go to the face region of the cortical homonculus. Signals from the face would then activate the original hand area of cortex and higher brain centers interpret this activation as arising from the phantom hand. The results show that brain maps are highly malleable; not fixed at birth as was previously believed.

Most patients with phantom arms feel that they can move their phantoms but in many the phantom is fixed or "paralyzed", often in a cramped position that is excruciatingly painful. Ramachandran suggested that this paralysis was because every time the patient attempted to move the paralyzed limb, he or she received sensory feedback (through vision and proprioception) that the limb did not move. This feedback stamped itself into the brain circuitry through a process of Hebbian learning, so that, even when the limb was no longer present, the brain had learned that the limb (and subsequent phantom) was paralyzed. In order to overcome this learned paralysis, Ramachandran created the mirror box in which a mirror is placed vertically in front of the patient and had patients look at the mirror reflection of the normal arm so that the reflection was optically superimposed on the felt location of the phantom (thus creating the visual illusion that the phantom had been resurrected). Remarkably if the patient now moved his normal hand while looking at the reflection, he not only saw the phantom move (as expected) but felt it to move as well. In some patients this seemed to abolish the pain in the phantom. In others the phantom disappeared entirely – along with the pain – for the first time in years. The clinical usefulness of this mirror visual feedback (MVF) procedure has now been confirmed by several groups using double-blind placebo controlled trials. In the same series of studies, Ramachandran also found that merely creating the visual illusion of seeing the phantom being touched (using mirrors) sometimes evoked touch sensations in the phantom. Ramachandran also used phantom limbs to explore the perceptual correlates of the mirror neuron system in humans. Sensory neurons in the brain are activated in response to that person being touched, and a certain proportion of these same neurons also fire when someone watches another person, being touched (mirror neurons) as if the neuron was “reading” the other persons mind or “empathizing”. But the person watching someone else being touched does not normally experience the touch delivered to the other person presumably because the skin on his own hand is sending a null signal (to the non-mirror neuron type sensory neurons) that vetoes the output of mirror neurons. Consistent with this theory, Ramachandran found that when a patient with a phantom arm watched another person’s intact hand being rubbed, he actually felt his phantom being rubbed. Massaging the other persons hand appeared to relieve the pain in the phantom, an observation that might have clinical implications if confirmed.

Stroke rehabilitation

In 1994 Ramachandran suggested that visual feedback may also help accelerate recovery of arm (and leg) function after paralysis from stroke. In 1998 Ramachandran (and his colleague Eric Altschuler) tested MVF on nine patients with stroke and observed striking recovery in many of them. This finding has also now been replicated in a number of groups including some who have used virtual reality instead of mirrors. More recently MVF has also been found to promote recovery from complex regional pain syndrome (RSD).

Taken collectively, these results (together with the work of Michael Merzenich, Jon Kaas, Paul Bach-y-Rita, Alvaro Pascal-Leone, and others) have ushered in a new approach to brain function and neurological rehabilitation. The old picture of the brain as a set of autonomous modules hardwired at birth has been replaced with the view that the so-called brain modules are in a state of dynamic equilibrium with each other and with the sensory input. Many neurological disorders - but not all - may result from a shift in this equilibrium rather than permanent destruction of neural tissue. This is not only of considerable theoretical interest but also clinically useful because it implies that relatively simple procedures may be enormously effective in rehabilitation of brain function.

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

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.

Pathophysiology of autism

Ramachandran's group was the first to suggest and show experimentally in 1999, that a loss of mirror neurons may be the key deficit in autism that explains many of the symptoms and signs of the disorder (collaborators included Ramachandran's students and colleagues: Lindsay Oberman, Eric Altschuler, and Jaime Pineda). These observations have now been confirmed by several groups.

Awards and honors

In 2005 Ramachandran was awarded the Henry Dale Medal and elected to an honorary life fellowship by the Royal Institution of Great Britain. His other honors and awards include fellowships from All Souls College, Oxford, and the Center for Advanced Study in the Behavioral Sciences at Stanford University, the Neurosciences Institute, La Jolla, California and the Athenaeum Club, London. He has also received two honorary doctorates (DSc, honoris causa), the annual Ramon y Cajal award from the International Neuropsychiatry Society, and the Ariens-Kappers medal from the Royal Netherlands Academy of Sciences for Landmark contributions to Neuroscience. Most recently, in 2007, the President of India conferred on him the third highest civilian award and honorific title in India, the Padma Bhushan.

Visiting professorships

Invited plenary lectures

Ramachandran has presented numerous plenary lectures around the world including at the inaugural conference of the Cognitive Neuroscience Society, the keynote to the inaugural annual Dementia Congress, the Alfred Deakin lectures to the government of Australia, the keynote Presidential lecture to the American Academy of Neurology, the inaugural address of the University of Bristol’s new Neurosciences Department, and even the Getty Museum of Art. In 1995 he gave the Decade of the Brain lecture at the 25th annual (Silver Jubilee) meeting of the Society for Neuroscience. Separately, yet under the same title, he gave the Decade of the brain lecture to the National Institute of Mental Health and Library of Congress. Ramachandran has also delivered the Dorcas Cummings plenary lecture in Cold Spring Harbor, Fred Attneave memorial lecture to the University of Oregon, the Oliver-Sharpey lecture to the Royal College of Physicians in London, the Jonas Salk Memorial lecture at the Salk Institute, and the Rabindranath Tagore lecture at the Center for the foundations of science in New Delhi. In 2003 he gave the annual BBC Reith Lectures and was the first physician/psychologist to give the lectures since they were begun by Bertrand Russell in 1949. More recently, he completed a public lecture to the Royal Society in London. On July 14th, 2008, he gave the inaugural lecture at the Asian College of Journalism, in Chennai, India.

Genealogy

Ramachandran is the grandson of Sir Alladi Krishnaswamy Iyer, Governor General of Madras and co-architect of the Constitution of India.

Media coverage

Ramachandran's work in behavioral neurology has been widely reported by the media. He has appeared in numerous Channel 4 and PBS documentaries. He has also been featured by the BBC, the Science Channel, Newsweek, and This American Life. He gave the 2003 Reith Lecture, entitled The Emerging Mind, which were created in honor of Lord Reith, the founder of the BBC.

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, 2008, not yet published. ISBN 978-0-525-95023-3

See also

References

External links

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