Hemispheric and visual field differences in face processing: MEG/EEG evidence for an early right hemisphere/left visual field specificity

Abstract

Event Abstract Back to Event Hemispheric and visual field differences in face processing: MEG/EEG evidence for an early right hemisphere/left visual field specificity Elias Mouchlianitis1* and Rik Henson1 1 Cognition and Brain Sciences Unit, Medical Research Council (MRC), United Kingdom Clinical data suggest that the right hemisphere may be specialised for processing faces [1]. Using Divided Visual Field presentations, our recent fMRI data [2] supported a relative lateralisation of the Occipital Face Area (OFA). More specifically, faces produced greater activity in right OFA than did houses when these stimuli were presented to the Left Visual Field (LVF), but not when they were presented to the RVF, whereas the left OFA showed no evidence for a face vs house preference in either visual field. In the present study, we used MEG/EEG to identify temporal components of this LVF-rOFA face preference. We used concurrent 306 channel Elekta-Neuromag MEG and 70 channel EEG recordings, and a 2x2 repeated measures design, with factors visual field (LVF vs. RVF) and stimulus category (faces vs. houses). Three-dimensional “Space-Time” Statistical Parametric Maps (SPMs), reflecting statistical tests at each point in a 2D scalp topography that is tiled over time, showed a significant two-way interaction from approximately 140-190ms that survived correction for multiple comparisons (using Random Field Theory) in each of the EEG, Magnetometer and Root-Mean Square (RMS) Planar Gradiometer data. Further analyses, averaged across this time window, were conducted on specific left and right hemisphere gradiometers , defined independently by the maxima associated with face-processing in a previous study [3]. The gradiometer RMS showed the same pattern found in the rOFA in our prior fMRI data [2], with the RH sensor showing greater activity for faces than houses in LVF but not RVF; a pattern not found in the LH sensor. Future analysis will attempt multimodal source reconstruction of these MEG, EEG and fMRI data. For the moment, our MEG data suggest that the right hemisphere specialisation for face-processing occurs relatively early in the face-processing pathway (OFA) and relatively early in time (coincident with the basic M/N170 component associated with face-processing).