   Courchesne, Eric  University of California, San Diego   3
years  Basic & Clinical  La Jolla   United States   La Jolla
State/Province Full:  United States  Recent MRI studies suggest
that the brain of a toddler with autism grows at an excessive
rate, leaving the child with an enlarged brain volume relative
to typically-developing toddlers. The frontal and temporal lobes
are sites of maximal brain enlargement. The frontal lobe plays
vital roles in higher-order cognitive, language, social, and
emotional functions, each of which is seriously deficient in
autistic subjects. One hypothesis to account for the enlargement
is that the autistic brain has an excessive number of neurons.
However, following the overgrowth phase, there is also evidence
of a premature growth arrest in frontal lobes. Thus, there is
the intriguing possibility that while there are an excessive
number of neurons in autism during early childhood in frontal
cortex, this phase is followed by a decline in numbers beginning
by preadolescence. Th