Concept: Savant syndrome
Superior perception, peaks of ability, and savant skills are often observed in the autistic phenotype. The enhanced perceptual functioning model (Mottron et al., 2006a) emphasizes the increased role and autonomy of perceptual information processing in autistic cognition. Autistic abilities also involve enhanced pattern detection, which may develop through veridical mapping across isomorphic perceptual and non-perceptual structures (Mottron et al., 2009). In this paper, we elaborate veridical mapping as a specific mechanism which can explain the higher incidence of savant abilities, as well as other related phenomena, in autism. We contend that savant abilities such as hyperlexia, but also absolute pitch and synaesthesia, involve similar neurocognitive components, share the same structure and developmental course, and represent related ways by which the perceptual brain deals with objective structures under different conditions. Plausibly, these apparently different phenomena develop through a veridical mapping mechanism whereby perceptual information is coupled with homological data drawn from within or across isomorphic structures. The atypical neural connectivity characteristic of autism is consistent with a developmental predisposition to veridical mapping and the resulting high prevalence of savant abilities, absolute pitch, and synaesthesia in autism.
Individuals with autism who show high abilities are called savants. Whereas in their brains a disconnection in and between neural networks has been identified, savantism is yet poorly understood. Focusing on astrocyte domain organization, it is hypothesized that local astrocyte mega-organizations may be responsible for exerting high capabilities in brains of autistic savants. Astrocytes, the dominant glial cell type, modulate synaptic information transmission. Each astrocyte is organized in non-overlapping domains. Formally, each astrocyte contacting n-neurons with m-synapses via its processes generates dynamic domains of synaptic interactions based on qualitative computation criteria, and hereby it structures neuronal information processing. If the number of processes is genetically significantly increased, these astrocytes operate in a mega-domain with a higher complexitiy of computation. From this model savant abilities are deduced.
Although biological etiologies and diffuse anatomical changes have been provided as plausible explanations for the unusual behaviors observed in idiot savants, no neuropsychological case studies or explanations for these behaviors are found in the literature. We present a case in which the “diagnosis” of idiot savant was based on historical, clinical, and test data. To assess his calendar abilities, this individual was subsequently tested over a period of six months on his ability to determine the day of the week across approximately 1,000 years. For a period of approximately 100 years he was 100% accurate. The neuropsychological tests revealed marked deficits in all areas with performance generally in the lower 1-5th percentile of the population (e.g., Full Scale Intelligence Quotient [FSIQ] = 54). Tests of attention yielded the best scores although still deficient. General learning, coding, and executive function tests proved to be challenging. In contrast, tests of visuo-motor abilities were only of moderate difficulty for the individual. These findings are considered within the theoretical framework of Rimland (autism) and Squyres (memory).