We present a multilevel approach to developing potential explanations
of cognitive impairments and psychopathologies common to individuals with
chromosome 22q11.2 deletion syndrome. Results presented support our
hypothesis of posterior parietal dysfunction as a central determinant of
characteristic visuospatial and numerical cognitive impairments.
Converging data suggest that brain development anomalies, primarily tissue
reductions in the posterior brain and changes to the corpus callosum, may
affect parietal connectivity. Further findings indicate that dysfunction
in “frontal” attention systems may explain some executive
cognition impairments observed in affected children, and that there may be
links between these domains of cognitive function and some of the serious
psychiatric conditions, such as attention-deficit/hyperactivity
disorder, autism, and schizophrenia, that have elevated incidence rates in
the syndrome. Linking the neural structure and the cognitive processing
levels in this way enabled us to develop an elaborate
structure/function mapping hypothesis for the impairments that are
observed. We show also, that in the case of the
catechol-O-methyltransferase gene, a fairly direct relationship
between gene expression, cognitive function, and psychopathology exists in
the affected population. Beyond that, we introduce the idea that variation
in other genes may further explain the phenotypic variation in cognitive
function and possibly the anomalies in brain development.
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