Oliver Sacks observed autistic twins who instantly guessed the exact number of matchsticks that had just fallen on the floor, saying in unison "111". To test the suggestion that normal individuals have the capacity for savant numerosity, we temporarily simulated the savant condition in normal people by inhibiting the left anterior temporal lobe of twelve participants with repetitive transcranial magnetic stimulation (rTMS). This site has been implicated in the savant condition. Ten participants improved their ability to accurately guess the number of discrete items immediately following rTMS and, of these, eight became worse at guessing as the effects of the pulses receded. The probability of as many as eight out of twelve people doing best just after rTMS and not after sham stimulation by chance alone is less than one in one thousand.
"To elucidate the mechanisms of memory, the study of variations in human behavior associated with impaired memory and perception (Savant syndrome, hyperthymesia and others) can also be important (Snyder et al., 2006). Another direction (Melkikh, 2014c) for experimental research is to determine where large amounts of information that are required for complex behaviors, such as the recognition of complex images and smells, are stored. "
"This hypothesis was verified by virtual lesion studies, showing that focal brain dysfunction produced behavioral facilitation related to the contralateral hemisphere (Hilgetag et al., 2001; Oliveri et al., 1999; Snyder et al., 2006). One study using TMS showed that the inhibition of the left anterior temporal lobe, the most frequently implicated site in emergent visual artistic skills after brain damage (Snyder et al., 2006), caused improvement of accuracies of approximate numerosity estimation. The authors' explanation for their result was that decreased inhibition of the left frontotemporal region caused compensatory activation in the contralateral parietal cortex, which in turn mediated the enhancement of visual numerosity estimation. "
[Show abstract][Hide abstract] ABSTRACT: Over the last two decades, evidence of enhancement of drawing and painting skills due to focal prefrontal damage has accumulated. It is of special interest that most artworks created by such patients were highly realistic ones, but the mechanism underlying this phenomenon remains to be understood. Our hypothesis is that enhanced tendency of realism was associated with accuracy of visual numerosity representation, which has been shown to be mediated predominantly by right parietal functions. Here, we report a case of left prefrontal stroke, where the patient showed enhancement of artistic skills of realistic painting after the onset of brain damage. We investigated cognitive, functional and aesthetic characteristics of the patient’s visual artistry and visual numerosity representation. Neuropsychological tests revealed impaired executive function after the stroke. Despite that, the patient’s visual artistry related to realism was rather promoted across the onset of brain damage as demonstrated by blind evaluation of the paintings by professional art reviewers. On visual numerical cognition tasks, the patient showed higher performance in comparison with age-matched healthy controls. These results paralleled increased perfusion in the right parietal cortex including the precuneus and intraparietal sulcus. Our data provide new insight into mechanisms underlying change in artistic style due to focal prefrontal lesion.
[Show abstract][Hide abstract] ABSTRACT: It seems that neurotypical individuals (people without autism) have a hidden ability for savant-like skills, and these special abilities can be accessible via top-down cortical disinhibition of the left fronto-temporal lobe by repetitive transcranial magnetic stimulation (rTMS). It is well known that enhanced visual function in striate and extrastriate areas is a common character in autists, savants and subjects with Asperger syndrome. In addition, visual cortex not only processes visual signals but also is involved in the processing of mathematical thinking and auditory signals among them. Here we argue about the essential (and more ancient) role of picture representation over linguistic representation in ASD and that extraordinary savant-like skills are due to the explicit predominance of the right hemisphere (a malfunction of top-down control processes) accompanied with prevalence of lower level detailed visual information in the right hemisphere. Our recently presented novel biophysical picture representation hypothesis (also called as intrinsic biophysical virtual visual reality) about visual perception and imagery is also briefly described and linked to the predominance of lower level and detailed visual representation in the right hemisphere that may be a common character in autism, savantism, and Asperger syndrome.
Cognitive Systems Research 06/2013; 22-23. DOI:10.1016/j.cogsys.2012.05.002 · 0.83 Impact Factor
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