The amygdala and its place in the cerebral hemisphere.

Developmental, gene expression, connectional, and neuron morphology evidence converges to suggest that cell groups of the amygdalar region participate in at least four distinct, though interrelated, functional systems associated with differentiated corticostriatopallidal projections. The amygdala is neither a structural nor a functional unit; instead, it is a collection of adjacent cell groups in the medial temporal lobe and adjacent regions of the caudal piriform lobe that was defined on gross anatomic terms.