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Abstract:
The amygdala may play a key role in an aversive fear network
that enables rapid response to danger. Although recent case reports
suggest that processing of nonverbal threat stimuli is disrupted by
bilateral amygdalar lesions, it remains unclear whether similar
deficits occur with unilateral lesions of the amygdala. To address
this question, we administered tests of facial and vocal emotion
and examined whether certain emotions (e.g., fear, anger, etc.)
were differentially disrupted by right or left temporal removals
involving the amygdala. Our Ss included 25 patients who underwent
anterior temporal resections (12 Left, 13 Right) for treatment of
nonlesional, epilepsy. All patients were left language dominant and
had approximately 45-55% of the amygdala removed, based on
quantitative measures of amygdala volume from pre and post-surgical
MRI. We found that unilateral ablations of the anterior temporal
lobe did not induce deficits in decoding fear or anger expressions,
either facial or prosodic. Nor were there significant correlations
between amygdala volume and emotion errors. These findings suggest
that unilateral lesions involving at least 50% of the amygdala are
not sufficient to induce pervasive disruption of networks involved
in detection of threat. The discrepancy between our findings and
those of previous case reports of "bilateral" lesions will be
discussed in terms of extent of amygdalar removal, chronicity of
lesions, and experimental task demands.
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