Cerebral Blood Flow Changes Associated With Attribution of Emotional Valence to Pleasant, Unpleasant, and Neutral Visual Stimuli in a PET Study of Normal Subjects

Observing and assigning emotional value to unpleasant stimuli produced activations in subcortical limbic regions, whereas evaluation of pleasant stimuli produced activations in cortical limbic areas. These findings are consistent with the notion of a subcortical and archaic danger recognition system and a system detecting pleasantness in events and situations that is phylogenetically younger, involving primarily the prefrontal cortex.