While studies among adults implicate the amygdala and interconnecting brain regions in encoding emotional stimuli, few studies have examined whether developmental changes occur within this emotional-memory network during adolescence. The present study examined whether adolescents and adults differentially engaged the amygdala and hippocampus during successful encoding of emotional pictures, with either positive or negative valence. Eighteen adults and twelve adolescents underwent event-related fMRI while encoding emotional pictures. Approximately 30 min later, outside the scanner, subjects were asked to recall the pictures seen during the scan. Age group differences in brain activity in the amygdala and hippocampus during encoding of the pictures that were later successfully and unsuccessfully recalled were separately compared for the positive and negative pictures. Adolescents, relative to adults, demonstrated enhanced activity in the right amygdala during encoding of positive pictures that were later recalled compared to not recalled. There were no age group differences in amygdala or hippocampal activity during successful encoding of negative pictures. The findings of preferential activity within the adolescent right amygdala during successful encoding of positive pictures may have implications for the increased reward and novelty seeking behavior, as well as elevated rates of psychopathology, observed during this distinct developmental period.
Keywords: adolescents; adults; amygdala; encoding; hippocampus; positive stimuli.