Abstract
Despite the broad interest in the role of selective attention in human face perception, there has been little focus on characterizing attentional modulation of this critical brain function in a dynamic visual environment. Here we exploited fast periodic visual stimulation to separately characterise the impact of attentional enhancement and suppression on generic face categorization. We recorded 128 channel EEG while participants viewed a 6Hz stream of object images (e.g., buildings, animals, objects, etc.) with a face image embedded as every 5th image in the sequence (i.e., OOOOFOOOOFOOOOF…). Stimulating the visual system this way elicits a response at exactly 6Hz, reflecting processing common to both face and object images, and a response at 6Hz/5 (i.e., 1.2 Hz), reflecting a differential response to faces as compared to objects. We measured this face-selective response while manipulating the focus of task-based attention: On Attend Faces trials, participants responded to instances of female faces in the sequence; on Attend Objects trials, they responded to instances of guitars, and on Baseline trials, they performed an orthogonal task, monitoring a central fixation cross for colour changes. We inspected indices of attentional enhancement (Attend Face–Baseline) and attentional suppression (Baseline–Attend Objects) on right and left occipito-temporal electrodes separately. We observed that during the orthogonal task, face-specific activity was predominantly centred over the occipito-temporal region of the face-preferred hemisphere (right hemisphere in 13/15 observers). Where task-based attentional suppression was comparable across the left and right hemispheres, task-based attentional enhancement was much more prominent in the non face-preferred hemisphere (left hemisphere in 13/15 observers). These results suggest the left and right face-selective cortical regions may support face categorization in distinct ways – where the face-preferred hemisphere (typically right) may be mandatorily engaged by faces, the non face-preferred hemisphere (typically left) may be flexibly recruited to serve current tasks demands.
Meeting abstract presented at VSS 2017