Vilayanur S Ramachandran

Vilayanur S Ramachandran
University of California, San Diego | UCSD · Department of Psychology

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116
Publications
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Publications

Publications (116)
Article
By studying an enigmatic condition called, “calendar synesthesia”, we explored the elusive boundary between perception, visual imagery, and the manner in which we construct an internal mental calendar by mapping time-sequences onto spatial maps. We use a series of demonstrations to establish that these calendars act more like real objects activatin...
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We report some new observations on what could be regarded as the world’s simplest visual illusion—the autokinetic effect. When a single dim spot of light is viewed in a completely dark room, it moves vividly in random directions. During steady fixation, perhaps subtle eye movements cause the image to move and a failure to correct for this using eye...
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Primates are especially good at recognizing facial expression using two contrasting strategies—an individual diagnostic feature (e.g., raise eyebrows or lower mouth corner) versus a relationship between features. We report several novel experiments that demonstrate a profound role of grouping and segmentation—including stereo—on recognition of faci...
Article
Grapheme-color synesthesia is a neurological phenomenon in which viewing a grapheme elicits an additional, automatic, and consistent sensation of color. Color-to-letter associations in synesthesia are interesting in their own right, but also offer an opportunity to examine relationships between visual, acoustic, and semantic aspects of language. Re...
Article
The sense of touch is mediated by the interaction of a soft material (i.e., skin) with the texture and chemistry of an object’s surface. Previous work designed to probe the limits of tactile perception has been limited to materials with surface asperities larger than the molecular scale; such materials may also have different bulk properties. We de...
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When we visualize a calendar, we have a vague impression of a rectangular grid hovering in front. But 1% of the population "see" vivid, crisp "calendar form" - e.g. an odd V shape as in subject ML. We found that (1) ML could "read off", months of her calendar - or alternate months - backward, unlike controls; (2) her eyes and index finger unconscio...
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The way we detect shape and depth from shading reveals some primeval rules
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Grapheme-color synesthesia is a neurological phenomenon in which letters and numbers (graphemes) consistently evoke particular colors (e.g., A may be experienced as red). These sensations are thought to arise through the cross-activation of grapheme processing regions in the fusiform gyrus and color area V4, supported by anatomical and functional i...
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Misophonia is a relatively unexplored chronic condition in which a person experiences autonomic arousal (analogous to an involuntary "fight-or-flight" response) to certain innocuous or repetitive sounds such as chewing, pen clicking, and lip smacking. Misophonics report anxiety, panic, and rage when exposed to trigger sounds, compromising their abi...
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Mirror neurons allow us to covertly simulate the sensation and movement of others. If mirror neurons are sensory and motor neurons, why do we not actually feel this simulation- like "mirror-touch synesthetes"? Might afferent sensation normally inhibit mirror representations from reaching consciousness? We and others have reported heightened sensory...
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Three coins are lined up with the middle coin at room temperature and flanking coins cooled down to 4 ° C. If digits 2 and 4 are placed on the outer coins and digit 3 on the middle coin, the latter also feels cold; a striking example of perceptual filling in of temperature. We show that if digits 2 and 4 are placed on a thermal grill with alternati...
Article
Between the two extreme ends of human sexuality - male and female - lie a poorly understood and poorly studied spectrum of ambiguously defined sexual identities that are very much a part of the human condition but defy rigid classification. "Bigender" is a recently formed sub-category of transgenderism, describing individuals who experience a blend...
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Full-text available
Three coins are lined up with the middle coin at room temperature and flanking coins cooled down to 4 degrees C. If digits 2 and 4 are placed on the outer coins and digit 3 on the middle coin, the latter also feels cold; a striking example of perceptual filling in of temperature. We show that if digits 2 and 4 are placed on a thermal grill with alt...
Article
Individuals with anorexia nervosa (AN) experience pronounced body image distortion in combination with a pernicious desire to maintain a dangerously low body weight. Relatively little is known, however, about the mechanism underlying body image distortion in AN. Despite having normal visual perception, individuals with AN both feel and see themselv...
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The claim that some individuals see colored halos or auras around faces has long been part of popular folklore. Here we report on a 23-year-old man (subject TK) diagnosed with Asperger's disorder, who began to consistently experience colors around individuals at the age of 10. TK's colors are based on the individual's identity and emotional connota...
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In 2001, Ramachandran and Hubbard introduced the cross-activation model of grapheme-colour synaesthesia. On the occasion of its 10-year anniversary, we review the evidence from experiments that have been conducted to test the model to assess how it has fared. We examine data from behavioural, functional magnetic resonance imaging (fMRI), anatomical...
Article
In one common variant of time-space synaesthesia, individuals report the consistent experience of months bound to a spatial arrangement, commonly described as a circle extending outside of the body. Whereas the layout of these calendars has previously been thought to be relatively random and to differ greatly between synaesthetes, Study 1 provides...
Article
A student volunteer was asked to stand just behind a mannequin so that the student was looking at the back of the mannequin's plastic head. The experimenter stood off to one side and used her two hands to stroke and tap the back of the student's head in perfect synchrony with the back of the mannequin's head. After 1-2 min the majority of naive sub...
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We showed a grapheme-color synesthete three different examples of stimuli in which the graphemes were 'hidden'--as in puzzle pictures--and became visible as letters only after prolonged viewing. Intriguingly the subject saw the appropriate colors accurately long before the graphemes became consciously visible--a novel form of blindsight.
Article
To explore whether interpersonal and intermanual sensory referral occurs following anesthetic block of a limb and to test theories of disinhibition of mirror neuron activity and transcallosal referral. Case series. Outpatient surgery at the University of California San Diego Medical Center. Six patients who underwent orthopedic surgery. Patient ver...
Article
Some people report that they consistently and involuntarily associate time events, such as months of the year, with specific spatial locations; a condition referred to as time-space synesthesia. The present study investigated the manner in which such synesthetic time-space associations affect visuo-spatial attention via an endogenous cuing paradigm...
Article
When an object is partially hidden, the brain deftly reconstructs it as a visual whole
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A growing body of literature demonstrates impaired multisensory integration (MSI) in patients with schizophrenia compared to non-psychiatric individuals. One of the most basic measures of MSI is intersensory facilitation of reaction times (RTs), in which bimodal targets, with cues from two sensory modalities, are detected faster than unimodal targe...
Article
After amputation of an arm the sensory map of the body changes radically, causing the sensory input from face to 'invade' the original hand area in the brain. As a result, touching the face of the amputee evokes tactile sensations on the phantom. These sensory referrals from the face to phantom hand occur in a stable, topographically organized mann...
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How quirks of perception drive the evolution of species
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And other real-life tales from the bizarre realm of out-of-body experience
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Using aftereffects to probe visual function reveals how the eye and brain handle colors and contours
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Grapheme-color synesthesia is a heritable trait where graphemes ("2") elicit the concurrent perception of specific colors (red). Researchers have questioned whether synesthetic experiences are meaningful or simply arbitrary associations and whether these associations are perceptual or conceptual. To address these fundamental questions, ERPs were re...
Article
When non-psychiatric individuals compare the weights of two similar objects of identical mass, but of different sizes, the smaller object is often perceived as substantially heavier. This size-weight illusion (SWI) is thought to be generated by a violation of the common expectation that the large object will be heavier, possibly via a mismatch betw...
Article
After amputation of a limb, the majority of patients experience phantom sensations, such as phantom pain. Such patients provide an opportunity for the exploration of the perceptual correlates of recently discovered "mirror neurons," which fire not only when individuals move their own limb but when they watch the movements of the corresponding limb...
Article
Insights into the nuances of depth perception provided by our two eyes' slightly different views of the world
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Spontaneous mimicry, including that of emotional facial expressions, is important for socio-emotional skills such as empathy and communication. Those skills are often impacted in autism spectrum disorders (ASD). Successful mimicry requires not only the activation of the response, but also its appropriate speed. Yet, previous studies examined ASD di...
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Binocular vision gives us depth perception—and enables us to play some tricks
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The question of how the human brain combines disparate sensory inputs to construct a unified body image is of longstanding interest^1,2,3^ . We approached this subject by studying the unusual medical condition of apotemnophilia, in which otherwise mentally normal individuals express the strong and persistent desire for the amputation of a specific...
Article
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Apotemnophilia straddles the boundary between neurology and psychiatry. It is a condition in which individuals experience the strong and specific desire for amputation of a healthy limb. Research suggests this disorder may be of neurological origin, specifically that the body image centers of the brain lack a cortical representation for a particula...
Article
About 95 % of amputees experience phantoms which often emerge immediately after amputation but sometimes after weeks or months. In roughly two thirds of patients the phantom is extremely painful.
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Patients with unusual visual deficits provide insights into how we normally see
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Apotemnophilia, a disorder that blurs the distinction between neurology and psychiatry, is characterized by the intense and longstanding desire for amputation of a specific limb. Here we present evidence from two individuals suggestive that this condition, long thought to be entirely psychological in origin, actually has a neurological basis. We fo...
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Central post-stroke pain (CPSP) is often resistant to treatment. We have previously proposed that caloric vestibular stimulation might alleviate it. We conducted a single blind placebo controlled investigational study of caloric vestibular stimulation (CVS) in nine patients with CPSP. Participants rated their pain levels before and after the proced...
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A few simple experiments untangle the mysteries behind the Barber Pole Illusion
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When you hoist two items of equal weight, your brain may be doing some heavy lifting
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Even when we consciously know two lines are the same length, why can't we help seeing them as different?
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How does the brain sort out contradictory images?
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How visual-processing systems shape our feelings about what we see
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The feeling of being touched on a fake hand illuminates how the brain makes assumptions about the world
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Camouflage in fish and other animals provides insights into visual perception
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Studies of perception show the importance of being upright
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How the eyes can see movement where it does not exist
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In an early description of the mu rhythm, Gastaut and Bert [Gastaut, H. J., & Bert, J. (1954). EEG changes during cinematographic presentation. Clinical Neurophysiology, 6, 433-444] noted that it was blocked when an individual identified himself with an active person on the screen, suggesting that it may be modulated by the degree to which the indi...
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How the brain sees through the perceptual hurdles of tinted glass, shadows and all things transparent
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Autism is a complex disorder, characterized by social, cognitive, communicative, and motor symptoms. One suggestion, proposed in the current study, to explain the spectrum of symptoms is an underlying impairment in multisensory integration (MSI) systems such as a mirror neuron-like system. The mirror neuron system, thought to play a critical role i...
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The target article discusses a model of how brain circuits mediate social behaviors such as imitation and mindreading. Hurley suggests potential mechanisms for development of shared circuits. We propose that empirical studies can be designed to differentiate the influence of genetic and learning-based factors on the development of shared circuits....
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How the brain constructs one's inner sense of gender identity is poorly understood. On the other hand, the phenomenon of phantom sensations -the feeling of still having a body-part after amputation -has been much studied. Around 60% of men experience a phantom penis post-penectomy. As transsexuals report a mismatch between their inner gender identi...
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Startling deceptions demonstrate how tactile information is processed in the brain
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What uncertainty tells us about the brain
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People spontaneously mimic a variety of behaviors, including emotional facial expressions. Embodied cognition theories suggest that mimicry reflects internal simulation of perceived emotion in order to facilitate its understanding. If so, blocking facial mimicry should impair recognition of expressions, especially of emotions that are simulated usi...
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Abstract The current study investigated the properties of stimuli that lead to the activation of the human mirror neuron system, with an emphasis on those that are critically relevant for the perception of humanoid robots. Results suggest that robot actions, even those without objects, may activate the human mirror neuron system. Additionally, both...
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Reflections on the familiar and yet deeply enigmatic nature of the looking glass
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Central post-stroke pain syndrome develops in a minority of patients following a stroke. The most usual causative lesion involves the lateral thalamus. The classic presentation is of severe, unrelenting pain that involves the entire contralateral half of the body. It is largely refractory to current treatments. We found that in two patients with th...
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Studies of perception show the importance of being upright
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The discovery of the mirror neuron system (MNS) has led researchers to speculate that this system evolved from an embodied visual recognition apparatus in monkey to a system critical for social skills in humans. It is accepted that the MNS is specialized for processing animate stimuli, although the degree to which social interaction modulates the f...
Article
The mechanism by which humans perceive others differs greatly from how humans perceive inanimate objects. Unlike inanimate objects, humans have the distinct property of being "like me" in the eyes of the observer. This allows us to use the same systems that process knowledge about self-performed actions, self-conceived thoughts, and self-experience...
Article
Here we outline a simple method of using two mirrors which allows one to stand outside oneself. This method demonstrates that registration of vision with touch and proprioception is crucial for the perception of the corporeal self. Our method may also allow the disassociation of taste from touch, proprioception, and movement.
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Studies of the mirror neuron system can help know the causes of autism, a mental developmental disorder and help the researchers to find out a way to treat it. Studies of people with autism show a lack of mirror neuron activity in several regions of the brain. Mirror neurons may enable humans to see themselves as others see them, which may be an es...
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What do the Mona Lisa and President Abraham Lincoln have in common?
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Grapheme-color synesthesia is an automatic, involuntary experience of seeing colors when viewing numbers, letters or words on a printed page. Previous research has demonstrated that synesthesia is a genuine perceptual phenomenon, but crucially, all of these experiments have used high-contrast letters and numbers. Our synesthete, JC, anecdotally rep...
Article
Synesthesia is a condition in which certain otherwise normal individuals see colors when they hear tones, or, when they look at black-and-white numbers, each number is tinged with a specific color (eg 5 is red and 2 is green). We constructed a display in which a random matrix of 5s had a vertical column of 2s 'embedded' in it. This was shown in fra...
Article
We have recently noticed our own inability to perform a number of interbodypart coordination tasks. The inability to perform these tasks indicates an intriguing central processing limitation on movement control, and study of these tasks should be helpful in understanding the neural mechanisms of motor control.
Article
How can an imaginary square look more real than a box with actual lines?
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Full-text available
Autism spectrum disorders (ASD) are largely characterized by deficits in imitation, pragmatic language, theory of mind, and empathy. Previous research has suggested that a dysfunctional mirror neuron system may explain the pathology observed in ASD. Because EEG oscillations in the mu frequency (8-13 Hz) over sensorimotor cortex are thought to refle...
Article
Grapheme-color synesthetes experience specific colors associated with specific number or letter characters. To determine the neural locus of this condition, we compared behavioral and fMRI responses in six grapheme-color synesthetes to control subjects. In our behavioral experiments, we found that a subject's synesthetic experience can aid in textu...
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Videnskaben om kunsten En neurologisk teori om den aestetiske oplevelse "Alle ønsker at forstå kunsten. Hvorfor ikke forsøge at forstå fuglens sang?" – Pablo Picasso Hvis en etolog fra Mars skulle finde på at lande på jorden og give sig til at observere os menne-sker, ville mange dele af den menneskelige natur forbløffe ham, men naeppe nogen mere e...
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In this commentary we discuss a predictive sensorimotor illusion, the size-weight illusion, in which the smaller of two objects of equal weight is perceived as heavier. We suggest that Grush's emulation theory can explain this illusion as a mismatch between predicted and actual sensorimotor feedback, and present preliminary data suggesting that the...
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Subjects perceived touch sensations as arising from a table (or a rubber hand) when both the table (or the rubber hand) and their own real hand were repeatedly tapped and stroked in synchrony with the real hand hidden from view. If the table or rubber hand was then 'injured', subjects displayed a strong skin conductance response (SCR) even though n...
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People with synesthesia—whose senses blend together—are providing valuable clues to understanding the organization and functions of the brain
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Several recent lines of inquiry have pointed to the amygdala as a potential lesion site in autism. Because one function of the amygdala may be to produce autonomic arousal at the sight of a significant face, we compared the responses of autistic children to their mothers' face and to a plain paper cup. Unlike normals, the autistic children as a who...
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The study of phantom limbs has received tremendous impetus from recent studies linking changes in cortical topography with perceptual experience. Systematic psychophysical testing and functional imaging studies on patients with phantom limbs provide 2 unique opportunities. First, they allow us to demonstrate neural plasticity in the adult human bra...
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Words such as 'consciousness' and 'self' actually encompass a number of distinct phenomena that are loosely lumped together. The study of neurological syndromes allows us to explore the neural mechanisms that might underlie different aspects of self, such as body image and emotional responses to sensory stimuli, and perhaps even laughter and humour...
Article
Laughter (and humor) involves the gradual build-up of expectation (a model) followed by a sudden twist or anomaly that entails a change in the model--but only as long as the new model is non-threatening--so that there is a deflation of expectation. The loud explosive sound is produced, we suggest, to inform conspecifics that there has been a 'false...
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Almost everyone who has a limb amputated will experience a phantom limb--the vivid impression that the limb is not only still present, but in some cases, painful. There is now a wealth of empirical evidence demonstrating changes in cortical topography in primates following deafferentation or amputation, and this review will attempt to relate these...
Article
Psychophysical evidence is given for the existence of two distinct systems in human vision: a fast, sign-invariant system concerned with extracting contours and a slower, sign-sensitive system concerned with assigning surface color. A class of stimuli we developed seems to selectively activate the fast, contour system. This stimulus is formed by ad...
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Patients with Capgras syndrome regard people whom they know well such as their parents or siblings as imposters. Here we describe a case (DS) of this syndrome who presents several novel features. DS was unusual in that his delusion was modality-specific: he claimed that his parents were imposters when he was looking at them but not when speaking to...
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Neurological syndromes in which consciousness seems to malfunction, such as temporal lobe epilepsy, visual scotomas, Charles Bonnet syndrome, and synesthesia offer valuable clues about the normal functions of consciousness and 'qualia'. An investigation into these syndromes reveals, we argue, that qualia are different from other brain states in tha...
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Patients with right hemisphere strokes sometimes vehemently deny their paralysis. I describe three new experiments that were designed to determine the extent and depth of this denial. Curiously, when asked to perform an action with their paralyzed arm, they often employ a whole arsenal of grossly exaggerated 'Freudian defense mechanisms' to account...