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Abstract:
It has been suggested that amygdala response to
threat-related stimuli is fast and automatic, but there is no
direct evidence that such response is independent from spatial
attention. We used event-related fMRI in 12 normal subjects to
examine whether the amygdala and other related brain areas might be
differentially activated by expression of fear in faces when these
appear outside or within the focus of attention. Subjects had to
match pairs of stimuli at pre-specified locations in the presence
of irrelevant stimuli at other locations. Faces or houses appeared
at relevant or irrelevant locations in an unpredictable order.
Orthogonal to this, faces had either fearful or neutral
expressions. Activation of fusiform gyri by faces was strongly
affected by spatial attention. By contrast, a left amygdala
response to fearful faces was independent of attentional condition.
In addition, right fusiform activity was greater for fearful than
neutral faces, independent of attentional effects. These results
show distinct influences on face processing from emotion and
attention, and suggest obligatory processing of threat-related
stimuli in the amygdala.
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