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Abstract:
In a previous fMRI study, Irwin et al. (1996) reported
amygdala activation in female subjects during the presentation of
emotionally-negative visual pictures. The present study explored
several issues related to this finding, including whether the
activation (1) extends to male subjects and (2) reflects stimulus
arousal properties or is valence-specific. Subjects passively
viewed alternating blocks of negative, neutral, and positive
pictures in one of two counterbalanced orders. Negative and
positive (including erotic) pictures were equated for arousal and
chosen from the IAPS stimulus set (Lang et al., 1988). Neutral
pictures were generated to equate for the presence of human figures
across valence categories. Echoplanar functional images were
acquired from three coronal slices centered on the amygdala using
an asymmetric spin echo pulse sequence. Statistical t-maps revealed
amygdala activation in the negative vs. neutral, positive vs.
neutral, and negative vs. positive contrasts. The activation was
evident in male subjects but was more right-hemisphere dominant in
females. These results suggest that the human amygdala is involved
in evaluating emotionally-arousing scenes, including positive ones,
but may play a special role in processing negative valence.
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