Abstract: PURPOSE: Ample evidence supports that the right hemisphere is dominant in processing faces and therefore participants often have a left visual field advantage for face perception. However, the mechanism underlying the interhemispheric dynamic coordination in face processing, especially when the prime face was unconsciousness, remains poorly understood.
METHODS: By combining continuous flash suppression (CFS), visual priming and a time-resolved behavioral measurement, we investigate the visual field bias in face processing when the prime face was visible (conscious) and invisible (unconscious). In two experiments, a prime face or house at the center of the screen was presented visible or invisible to participants by using CFS. Subsequently, participants were asked to detect a congruent versus incongruent target that was presented at either right or left visual field. Moreover, we varied the prime-to-target SOA from 20 to 800ms in steps of 20ms to measure fine-scale temporal dynamics.
RESULTS: Behavioral oscillations were found in congruent versus incongruent conditions. Specifically, for detecting a face target, we found a right visual field bias at ~5 Hz for the visible prime condition and a left visual field bias at 6-8 Hz for the invisible prime condition. By contrast, no significant theta-band oscillations were found for detecting a house target in both visual fields.
CONCLUSIONS: These results support a general theta-band (3-8 Hz) temporal organization mechanism in face processing. The different theta-band oscillation effects suggest distinct neural mechanisms for interhemispheric dynamic coordination, depending on the visibility of the priming stimuli.

Key words: behavioral oscillation, face processing, priming, visual field bias, theta-band