Amygdala activation during masked presentation of emotional faces

Purpose: The amygdala has a central role in processing threat-related emotional cues. We investigated the involvement of the amygdala in emotional processing of masked fearful and angry faces, taking advantage of high T2* contrast at 3 T,

Methods: 9 Volunteers have been included so far in the study. Subjects were presented with alternating 30s blocks of masked fearful, angry, happy, neutral faces and a no-face control, presented twice per second in random order. Participants were instructed to observe the pictures and memorise the faces.

FMRI data were acquired at 3 Tesla (Intera, PMS) using single shot EPI (TR=3s, TE=30 ms, FA=90°). High in plane resolution reduced distortion (1282 matrix, voxel size 1.75mm*1.75mm*3.5mm). 25 axial slices were scanned 160 times, 10 per condition block, in addition to anatomical datasets (T1w 3DTFE, cubic voxels, 0.5mm; T1wIR. aligned with fMRI). fMRI data were processed using SPM2. Hypotheses were tested using a region of interest approach.

Results: Even without parallel imaging the amygdala region remained sufficiently undistorted. Activation of amygdalae responding to masked fearful faces correlated significantly with the number of fearful faces detected (p <0.05). Numbers of angry faces detected correlated with right amygdala activation (p <0.01). There was no correlation of activation and detection during presentation of happy faces.

Conclusion: Present results indicate a specific association between amygdala activation and detection of masked threat-related facial expression. Increased amygdala activation could facilitate visual processing of fearful and angry faces and make these threat-indicating stimuli more available for conscious information processing.