Measuring face-name integration with fast periodic visual stimulation

Abstract

Associating specific names to faces of familiar identity is crucial for social interactions. This is a difficult process, which can be severely disrupted in neurodegenerative disorders such as Alzheimer's disease or temporal epilepsy. An outstanding issue is whether face and name representations are kept separated in the human brain and associated through re-entrant interactions, or if they are integrated into common representation at higher stages. Here we addressed this issue with fast periodic stimulation in EEG. Healthy subjects (n=12) were exposed to randomly alternating face photographs and written names of a famous identity (base stimuli) at a fast rate (3.999 Hz, about 4 images per second) while recording their brain activity with high density (128 channels) scalp EEG. A change in identity (either presented as a face or a name) occurred every seven stimuli (i.e., 0.5713 Hz; oddball stimuli). Following a few minutes of recordings, there were significant electrophysiological responses at the frequency of a face identity change (i.e., 0.5713 and harmonics), suggesting integrated representations of faces and names. Experiment 2 (n=20) replicated these findings and added two control conditions: A face only condition in which the specific identity names presented at the base rate were replaced by other famous names, and a name only condition which followed the same principle for names. There were much weaker amplitudes at the periodic change of identity in control conditions. Most importantly, the sum of the two control conditions' activation was weaker than the effect found in the main condition, in particular over the left medial occipital region and extending to the posterior part of the left occipito-temporal region. Overall, these observations provide evidence for integrated face/name representations in the human brain, with a left occipito-temporal locus.