Asymmetrical Activation in the Human Brain during Processing of Fearful Faces

Abstract

Traditional split-field studies and patient research indicate a privileged role for the right hemisphere in emotional processing [1-7], but there has been little direct fMRI evidence for this, despite many studies on emotional-face processing [8-10](see Supplemental Background). With fMRI, we addressed differential hemispheric processing of fearful versus neutral faces by presenting subjects with faces bilaterally [11-13]and orthogonally manipulating whether each hemifield showed a fearful or neutral expression prior to presentation of a checkerboard target. Target discrimination in the left visual field was more accurate after a fearful face was presented there. Event-related fMRI showed right-lateralized brain activations for fearful minus neutral left-hemifield faces in right visual areas, as well as more activity in the right than in the left amygdala. These activations occurred regardless of the type of right-hemifield face shown concurrently, concordant with the behavioral effect. No analogous behavioral or fMRI effects were observed for fearful faces in the right visual field (left hemisphere). The amygdala showed enhanced functional coupling with right-middle and anterior-fusiform areas in the context of a left-hemifield fearful face. These data provide behavioral and fMRI evidence for right-lateralized emotional processing during bilateral stimulation involving enhanced coupling of the amygdala and right-hemispheric extrastriate cortex.