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Abstract:
Abstract: While lesion and functional imaging studies have
demonstrated the involvement of the human orbitofrontal cortex in
processing emotion, this has been investigated at the single-cell
level only in nonhuman animals. We recorded single-cell activity
from two epileptic patients with chronically implanted depth
electrodes located in the ventral and dorsal medial prefrontal
cortex. Awake subjects passively viewed 60 (80) digital pictures of
facial expressions and 90 (67) pictures of emotionally arousing
scenes in multiple sessions over several days. We recorded
electrophysiological activity from 16 (24) spatially separate sites
from each subject, in addition to autonomic indices. Multiple
tetrode contacts along electrode shafts permitted cluster isolation
of >100 neurons per subject, and responses were analyzed in
relation to emotion category, valence, and arousal of the stimuli.
We found statistically significant modulations of firing rates in a
subset of neurons that were specific to certain negative emotions,
especially fear. The findings provide evidence in humans that
single cells in the orbitofrontal cortex participate in encoding
the emotional significance of visual stimuli. Supported by grants
to R.A. from the Sloan Foundation, the EJLB Foundation, and the
Center for Consciousness Studies.
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