Effects of low-spatial frequency components of fearful faces on fusiform cortex activity.

Emotive faces elicit neural responses even when they are not consciously perceived. We used faces hybridized from spatial frequency-filtered individual stimuli to study processing of facial emotion. Employing event-related functional magnetic resonance imaging (fMRI), we show enhanced fusiform cortex responses to hybrid faces containing fearful expressions when such emotional cues are present in the low-spatial frequency (LSF) range. Critically, this effect is independent of whether subjects use LSF or high-spatial frequency (HSF) information to make gender judgments on the hybridized faces. The magnitude of this fusiform enhancement predicts behavioral slowing in response times when participants report HSF information of the hybrid stimulus in the presence of fear in the unreported LSF components. Thus, emotional modulation of a face-responsive region of fusiform is driven by the low-frequency components of the stimulus, an effect independent of subjects' reported perception but evident in an incidental measure of behavioral performance.