Nicole Barger

The importance of social and prosocial behavior is increasingly recognized in models of human cognitive and behavioral evolution. Yet, whether humans exhibit specializations in brain structures processing social behavior remains largely unknown. This project addresses the evolution and development of two ‘social brain’ structures. The amygdala modulates emotional behavior and is necessary for proper social affiliative behavior and memory. The superior temporal cortex is integrated into social perception and language circuits. Like most brain regions, neurons in the superior temporal cortex are produced predominantly in fetal development. Alternatively, recent data indicate new neurons may be added in the primate amygdala, postnatally. My first proposed paper uses stereology and functional genomic analysis to show that new neurons are added in the human amygdala into the third decade of life, longer than in African apes. My second paper compares human and ape neuron numbers to determine whether they are increased in either frontal or temporal lobe language areas, hypothesizing greater increase in the superior temporal language cortex based on its additional social functions. My third paper characterizes evolutionary variation in neural progenitor cells and brain immune cells that regulate progenitor number in the frontal and temporal cortex of fetal humans, macaques, and rats.