Phantom limbs When an arm or leg is amputated, patients often continue to feel vividly the presence of the missing limb as a "phantom limb" (an average of 80%). Building on earlier work by
Ronald Melzack (McGill University) and Timothy Pons (NIMH), Ramachandran theorized that there was a link between the phenomenon of phantom limbs and
neural plasticity in the adult
human brain. To test this theory, Ramachandran recruited amputees, so that he could learn more about if phantom limbs could "feel" a stimulus to other parts of the body. In 1992, in collaboration with T.T. Yang, S. Gallen, and others at the Scripps Research Institute who were conducting
MEG research, Ramachandran initiated a project to demonstrate that there had been measurable changes in the somatosensory cortex of a patient who had undergone an arm amputation. Ramachandran theorized that there was a relationship between the cortical reorganization evident in the MEG image and the non-painful referred sensations he had observed in other subjects. Later researchers found that non-painful phantom limbs correlated less with motor or somatosensory plasticity than painful phantom limbs. Recent research has also shown that the peripheral nervous system is involved in painful phantom limb phenomena. Research continues into more precise mechanisms and explanations.
Mirror visual feedback/mirror therapy Writing in 2009,
John Colapinto (author of Ramachandran's profile Ramachandran thought that
phantom pain might be caused by the mismatch between different parts of an amputee's nervous systems: the
visual system says the limb is missing, but the
somatosensory system (processing body sensations such as touch and limb position) says the limb is still there. The so-called mirror box was a simple apparatus that uses a mirror reflecting an amputee's good arm so it appears to be the extension of the one missing: They put their surviving arm through a hole in the side of a box with a mirror inside, so that, peering through the open top, they would see their arm and its mirror image, as if they had two arms. Ramachandran then asked them to move both their intact arm and, in their mind, their phantom arm—to pretend that they were conducting an orchestra, say. The patients had the sense that they had two arms again. Ramachandran found that in some cases restoring movement to a paralyzed phantom limb reduced the pain experienced. In 1999 Ramachandran and Eric Altschuler expanded the mirror technique from amputees to improving the muscle control of stroke patients with weakened limbs. As Deconick et al. state in a 2014 review, the mechanism of improved motor control may differ from the mechanism of pain relief. Despite the introduction of mirror therapy in the late 1990s, little research was published on it before 2009, and much of the research since then has been of contested quality. Out of 115 publications between 2012 and 2017 about using mirror therapy to treat phantom limb pain, a 2018 review, found only 15 studies whose scientific results should be considered. From these 15 studies, the reviewers concluded that "MT seems to be effective in relieving PLP, reducing the intensity and duration of daily pain episodes. It is a valid, simple, and inexpensive treatment for PLP." Similarly, a 2017 review that studied a wider range of uses for mirror therapy, concluded, "Mirror therapy has been used to treat phantom limb pain, complex regional pain syndrome, neuropathy and low back pain. The mechanism of action of mirror therapy remains uncertain, and the evidence for clinical efficacy of mirror therapy is encouraging, but not yet definitive."
Mirror neurons Mirror neurons were first reported in a paper published in 1992 by a team of researchers led by
Giacomo Rizzolatti at the
University of Parma. According to Rizzolati, "Mirror neurons are a specific type of visuomotor neuron that discharge both when a monkey executes a motor act and when it observes a similar motor act performed by another individual." In 2000, Ramachandran made what he called some "purely speculative conjectures" that "mirror neurons [in humans] will do for psychology what DNA did for biology: they will provide a unifying framework and help explain a host of mental abilities that have hitherto remained mysterious and inaccessible to experiments." Ramachandran has suggested that research into the role of mirror neurons could help explain a variety of human mental capacities such as empathy, imitation learning, and the evolution of language. In a 2001 essay for
Edge, Ramachandran speculated that I suggested that in addition to providing a neural substrate for figuring out another persons intentions...the emergence and subsequent sophistication of mirror neurons in hominids may have played a crucial role in many quintessentially human abilities such as empathy, learning through imitation (rather than trial and error), and the rapid transmission of what we call "culture". (And the "great leap forward" — the rapid Lamarckian transmission of "accidental") one-of-a kind inventions. Ramchandran's speculations about the connection of mirror neurons with empathy have been contested by some authors and supported by others.
"Broken Mirrors" theory of autism In 1999, Ramachandran, in collaboration with then post-doctoral fellow Eric Altschuler and colleague Jaime Pineda, hypothesized that a dysfunction of
mirror neuron activity might be responsible for some of the symptoms and signs of autism spectrum disorders. Between 2000 and 2006 Ramachandran and his colleagues at UC San Diego published a number of articles in support of this theory, which became known as the "Broken Mirrors" theory of autism. Ramachandran and his colleagues did not measure mirror neuron activity directly; rather they demonstrated that children with ASD showed abnormal EEG responses (known as
Mu wave suppression) when they observed the activities of other people. In
The Tell-Tale Brain (2010), Ramachandran states that the evidence for mirror-neuron dysfunction in autism is "compelling but not conclusive."
Neural basis of synesthesia Ramachandran was one of the first scientists to theorize that grapheme-color synesthesia arises from a cross-activation between brain regions. Ramachandran and his graduate student, Ed Hubbard, conducted research with
functional magnetic resonance imaging that found increased activity in
the color recognition areas of the brain in synesthetes compared to non-synesthetes. Ramachandran has speculated that conceptual metaphors may also have a neurological basis in cortical cross-activation. As of 2015, the neurological basis of synesthesia had not been established.
Xenomelia (apotemnophilia) In 2008, Ramachandran, along with David Brang and
Paul McGeoch, published the first paper to theorize that
apotemnophilia is a neurological disorder caused by damage to the right
parietal lobe of the brain. This rare disorder, in which a person desires the amputation of a limb, was first identified by
John Money in 1977. Building on medical case studies that linked brain damage to syndromes such as
somatoparaphrenia (lack of limb ownership), the authors speculated that the desire for amputation could be related to changes in the right parietal lobe. In 2011, McGeoch, Brang and Ramachandran reported a functional imaging experiment involving four subjects who desired lower limb amputations. MEG scans demonstrated that their right superior parietal lobules were significantly less active in response to tactile stimulation of a limb that the subjects wished to have amputated, as compared to age- and sex-matched controls. The authors introduced the word
xenomelia to describe this syndrome, which is derived from the Greek for "foreign" and "limb".
"Phantom sex" theory of gender incongruence In 2008, Ramachandran, along with McGeoch, published the first paper to theorize that
gender dysphoria is caused by "a mis-match between the brain's hardwired gender-specific body image and the external somatic gender". The authors surveyed a group of
trans women about their experiences of phantom penile sensations following
gender-affirming surgery, as well as a group of
trans men. Responses showed that trans women experienced phantom penile sensations at significantly lower rates than
cis men who have undergone a
penectomy. Conversely, trans men experienced phantom penile sensations at equal rates to cis men. In 2017, Laura Case, Brang, Ramachandran, and some other authors, found that trans men experience altered brain activity in regions associated with xenomelia when their breasts are touched. They found alterations of white matter in these regions of the brain too.
Obsessive-compulsive disorder (OCD) Ramachandran, with
Baland Jalal and colleagues, conducted the first studies using the
rubber hand illusion to investigate self-representation in
obsessive-compulsive disorder (OCD). In these studies, contaminating a rubber hand with fake feces during the illusion led participants without OCD to report OCD-like disgust. Follow-up work with Jalal and Richard McNally found that OCD patients were more susceptible to the illusion, sometimes even when visual and tactile cues were out of sync, suggesting a more flexible body image. The research also explored using the illusion as an indirect exposure technique, offering a potential gentler alternative to traditional treatments. In 2017, Ramachandran and Jalal found that individuals with OCD symptoms felt disgust simply by watching an experimenter contaminate himself—and relief, after self-contamination, by watching him wash his hands. In 2021, these findings were extended to a clinical OCD population. Exploring clinical implications, and working with Jalal and Barbara Sahakian, they found that individuals with contamination fears showed improved symptoms after watching brief daily smartphone videos of themselves touching fake feces or washing their hands for one week. ==Popularity==