Human faces induce stronger involuntary orienting responses than other visual objects. We recently reported a significant increase in anti-saccade error rates for faces compared to cars and noise patterns, as well as faster pro-saccades compared to the other visual categories (Morand et al., 2010). However, when and where this preferential orienting response is taking place at the neural level remains to be clarified. To address this issue, we investigated the neural dynamics preceding the onset of pro-and anti-saccades elicited by human faces and non-face visual objects normalized for their low-level visual properties (i.e., amplitude spectra and contrast). We simultaneously recorded high-density evoked potentials (ERPs) and eye movements in adult observers as they performed randomly interleaved pro- and anti-saccades to a lateralized target. Pro- and anti-saccades directed to the same visual field significantly modulated the electrophysiological signals within the 100–140 ms time-period following target onset. These amplitude modulations were associated with distinct electrical scalp topographies. Faces triggering pro-saccades directed to the left and anti-saccades directed to the right (presented in the LVF) modulated the neurophysiological signals over the temporo-occipital electrodes (PO8 and P9) at 130–140 ms, which correspond to the right and left counterparts of the face-sensitive N170 component respectively. These neurophysiological modulations were not accompanied with topographic changes, but with an increase in response amplitude for faces. Our data show distinct electrophysiological signatures for pro- and anti-saccades occurring as early as 100 ms after target onset. We believe these to reflect distinct cortical networks, probably recruiting the FEF and DLPFC in their respective role in saccade programming. Critically, faces, compared to other visual objects impact upon saccade programming at several stages by modulating the magnitude of the cortical networks active prior to both pro- and anti-saccades execution. These observations provide the neural dynamics and mapping of the involuntary orienting responses for faces.
Supported by the Economic and Social Research Council and the Medical Research Council (RES-060-25-0010).