Objective measurement of face discrimination with a fast periodic oddball paradigm

J Liu-Shuang1, K Torfs2, A Norcia3, B Rossion4

1University of Louvain, Belgium
2Institute of Neuroscience, University of Louvain, Belgium
3Department of Psychology, Stanford University, CA, United States
4Institute of Research in Psychology, University of Louvain, Belgium
Contact: joan.liu@uclouvain.be

We present a novel paradigm using fast periodic oddball stimulation to objectively and efficiently quantify individual face discrimination. We recorded EEG in 20 observers presented with 60-second sequences containing a base-face (A) contrast-modulated at a frequency of 5.88 Hz. Oddball-faces (B,C…) were introduced at fixed intervals (every 5th stimuli or 5.88 Hz/5 = 1.18 Hz: AAAABAAAACAAAAD…). Face discrimination was indexed by responses at this oddball frequency. High-level face processing was targeted by manipulating size (face size randomly varied every 5.88 Hz cycle), orientation (upright vs. inverted, Experiment 1) and contrast (normal contrast vs. contrast-reversed, Experiment 2). In both experiments, normal faces evoked highly significant responses at 1.18 Hz and its harmonics on right occipito-temporal channels. Inversion and contrast-reversal significantly reduced oddball responses, while the basic 5.88 Hz response did not differ between conditions. In Experiment 3, we tested prosopagnosic patient PS [Rossion et al., 2003, Brain, 126:2381-95], who is specifically impaired at face discrimination [Busigny et al., 2010, Neuropsychologia, 48:2051-67]. Although PS’ basic response to faces was similar to young controls (N=11), her right occipito-temporal oddball response was absent. These observations underline the usefulness of fast periodic oddball stimulation to measure face discrimination on a neural level.

Up Home