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Abstract:
Neuropsychological evaluations were performed on 81 patients
(ages 5-20) with Velocardiofacial Syndrome (VCFS). Strong evidence
of a Nonverbal Learning Disability was evidenced by significantly
higher Verbal IQ and reading than Performance IQ and math scores.
These findings might be explained by disturbed processing in the
dorsal visual pathway, an occipito-parietal stream specialized for
spatial ("where") perception of objects which terminates in the
parietal lobes (PPL) (Ungerleider & Mishkin,1982). PPL
dysfunction produces many visuospatial deficits, e.g. Gerstmann's
Syndrome from left hemisphere damage, which includes dyscalculia
and dysgraphia. Both are seen in VCFS along with a general
visuospatial deficit. Levy et al. (1999) identified left angular
gyrus as the basis for developmental dyscalculia in their 1H-MRS
study. Eliez et al., 2000 reported reduced left parietal volumes in
children with VCFS. Simon (1997) detailed four infant competencies
demonstrably sufficient to reproduce infants' behavior on primitive
numerical tasks. The critical abilities are object individuation
and spatiotemporal coding. Individuation deploys spatiotemporal
markers such as Object Files (Kahneman et al, 1992). Spatiotemporal
coding is evident in infants' detection of impossible object
appearances or disappearances without apparent detection of
impossible identity changes, i.e. preferential "whereness" over
"whatness' coding. Thus, converging evidence points to "where"
pathway processing as the mediator of some key cognitive deficits
in VCFS. This analysis will ground new cognitive neuroscience
research into the development of mathematical ability and
disability.
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