UC San Diego

Williams syndrome is a neurodevelopmental disorder characterized by a set of compromised and preserved features in social and general cognition. Some behavioral manifestations of the disorder – especially hypersociality and inadequate responses to social interactions – imply the involvement of prefrontal cortical (PFC) areas underlying higher-order social and emotional processing. Using Golgi and immunohistochemical techniques, I have examined dendritic branching and distribution of neurofilament protein expressing neurons in two prefrontal areas: BA 11 in the orbital frontal cortex, largely responsible for emotional processing, and BA 10 in the frontopolar cortex, an area underlying executive cognitive functions.

The results suggest that the morphology of basal dendrites on the pyramidal neurons is altered in the cortex of WS, with differences that are layer-specific, prominent in both PFC areas, and display an overall pattern of dendritic organization that differentiates WS from other disorders. In particular, and unlike what was expected based on typically developing brains, basal dendrites in the two PFC areas did not display longer and more branched dendrites compared to motor, sensory and visual areas. Further analysis of layer III in BA 10 suggests a decrease in density of neurofilament protein expressing neurons (SMI-32) underlying long distance connections between PFC and other cortical areas.

This dissertation contributes to our understanding of the relationship between the structure and function of cortical areas underlying social cognition, and provides additional insights into the range of variation in PFC areas in developmental and psychiatric disorders.