Cerebral Hemispheres 2



Savant syndrome

January 26, 2014

Savant syndrome is one of the true mysteries of neuroscience. Many people were first exposed to this curious phenomenon when they watched the movie Rain Man. In it, Dustin Hoffman plays a character named Raymond Babbit, who is loosely based on Kim Peek. Peek was (Peek died in 2009) a savant who had a stunningly prodigious memory and the ability to read a book in an hour, retaining virtually all of the information he took in during that short time. Peek, like most other savants, also suffered from a neurological disorder that caused him to have difficulty with more mundane aspects of daily life like getting dressed or brushing his teeth. Intellectually, he had trouble understanding abstract concepts and engaging in normal reasoning. Yet, by some accounts he read and remembered the information from over 12,000 books.

Like Peek, most savants are exceptional in one or a few closely related areas, yet they suffer from a cognitive disorder that severely disrupts functioning in other areas. In most cases, a savant’s skill will involve art, music, mathematics, mechanics, spatial estimation, or calendar calculating, e.g. making rapid calculations regarding the day of the week given a particular date. The mystery, however, is what creates the exceptionality. The area of expertise is usually not something that the individual has had special training in, and thus it often seems like an innate ability has somehow been brought from the depths of the mind up to the surface. Strangely enough, this emergence usually coincides with some sort of developmental disorder or with another insult to the integrity of the brain.

In fact, there are multiple instances of a savant-like skill emerging from a person with no sort of developmental disability after he or she had some sort of traumatic brain event. This is known as acquired savant syndrome. For example, in 2006 a 39-year old man named Derek Amato experienced head trauma after hitting his head on the floor of a swimming pool. Despite having no training in piano playing (and little musical training in general), Amato discovered a few weeks after the accident that he was suddenly able to play the piano as if he had been taking lessons for years. Now, Amato is a professional piano player who has released multiple albums.

Savantism, and especially acquired savant syndrome, begs the question: do we all have these abilities locked up deep within our brain, but just don’t know how to free them? Some researchers, like Allan Snyder, think so. Snyder suggests that savants are able to access information in a raw form, before a “normal” brain would begin to categorize it, apply labels, and incorporate it into a larger picture. Although it is helpful for our brains to create this holistic view of something, it may also cause us to ignore details our brain decides are unimportant and/or distracting. Savants, then, might possess an attention to detail that many of us are incapable of displaying, and perhaps it is this attention to detail that allows for things like the creation of meticulous sculptures, memorization of large pieces of information, and the ability to do lengthy mathematical calculations in one’s head.

Snyder tried to test this hypothesis using transcranial magnetic stimulation (TMS). TMS involves the use of magnetic fields to transiently disrupt electrical activity in the brain. Although this sounds somewhat perilous, the side effects are minimal, and when the TMS stimulation stops, brain activity returns to normal relatively quickly. You can see a video of this procedure at the bottom of this post. TMS gives scientists a valuable tool, as they can disturb function in an awake patient, then see how that perturbation affects behavior. In the past, this was something that could only be done with surgery.

Snyder et al. asked participants to look at an image consisting of anywhere from 50 to 150 dots (see image to the right) for only 1.5 seconds, and then to estimate the number of dots that were there. Obviously, 1.5 seconds is too fast for someone to count the dots, but the rapid estimation (sometimes with precision) of large numbers of objects is something that has been documented in savants. Snyder et al. had the participants make estimates after applying TMS to their left anterior temporal cortex (a region hypothesized to be involved in savant syndrome) as well as after applying sham TMS (i.e. the machine was used in such a way that the participant might think TMS was being used, but there was no stimulation applied) as a control. The researchers found that, in 10 out of 12 participants, the ability to estimate the number of dots improved after TMS. Snyder et al. suggested that, by inhibiting activity in the anterior temporal cortex, they inhibited brain activity involved in holistic processing, allowing for a focus on detail that improved numerical estimation.

While the idea that savant-like skills are latent within each of us is intriguing, the explanation provided by Snyder et al. for why we can’t normally access them still will require much more work to be convincing. The skills displayed by some savants seem to be almost superhuman, and thus it’s difficult to understand how holistic processing dampens them to such a degree that they nearly disappear in most of us. Snyder’s hypothesis also doesn’t allow us to understand how someone with no training in a specific skill like piano playing can suddenly acquire that skill. Although the ability to pay attention to details may be important for the development of musical talent, such a talent at least has the appearance of requiring some deeper training as well. How someone can gain proficiency in an instrument without that training, regardless of how their brain processes details, is a puzzle.

Savant syndrome remains a very intriguing area for future research. For, it hints at some deep power hidden within the human brain, and also suggests that there may be a key to unlock that power in all of us. If that key is found, it would revolutionize our conceptualization of human potential.

Snyder A, Bahramali H, Hawker T, & Mitchell DJ (2006). Savant-like numerosity skills revealed in normal people by magnetic pulses. Perception, 35 (6), 837-45 PMID:16836048


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