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Early visual responses to upright and inverted faces

OBJECTIVE: The aim of this neuromagnetic study was to investigate neural substrates of face inversion effect at early latencies. METHODS: 306-channel whole-head MEG system was used to record visually evoked responses to centrally presented upright and inverted faces from eight subjects with available MRI scans. MEG responses to four face stimuli were analyzed: upright happy, upright neutral, inverted happy and inverted neutral. Spatio-temporal localization assumed multiple-current dipoles in a spherical volume conductor. RESULTS: Depending on subjects, up to four sources were identified during the first 140 ms after stimulus onset in the occipital, occipito-temporal, and parietal regions. Our preliminary results indicated bigger differences in locations of current dipoles for upright vs. inverted than for happy vs. neutral conditions. CONCLUSIONS: Face inversion effect was evident at early latencies not only by a delayed and decreased amplitude of evoked responses but also by shifts in source locations that were activated by upright and inverted faces, respectively.

MEG (magnetoencephalography); face processing; face inversion; facial expression change; multiple-current dipoles; spatio-temporal source localization

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