Pauline Schaller¹ (), Lisa Stacchi¹, Peter de Lissa¹, Anne-Raphaëlle Richoz¹, Roberto Caldara¹; ¹University of Fribourg

Face processing in the human brain is relatively automatic, rapid, effortless, and very effective. However, this critical biological skill is markedly impaired when observers are confronted with less familiar other-race or inverted faces. Interestingly, on the one hand, when more sensitive neural adaptation paradigms are used, same-race upright faces elicit early larger N170 amplitudes compared to other-race faces. On the other hand, inverted same-race faces lead to a greater recognition impairment and elicit larger N170 amplitudes compared to inverted other-race faces. Yet, whether similar neurofunctional electrophysiological signatures for those impairments could also be found with fast periodic visual stimulation (FPVS) remains unknown. The FPVS is a fast, reliable, and highly sensitive method to isolate neural brain categorization responses. We thus recorded the electrophysiological signals of Western observers while they were viewing upright and inverted Western and Eastern faces by using an FPVS paradigm. The first experiment consisted in a stream of 6 Hz composed of either same- or other-race faces among which the faces of the alternate race were periodically embedded (oddball). In the second experiment, same- or other-race oddball faces were respectively embedded in object streams either in upright or inverted condition. Surprisingly, the race of the faces did not modulate the FPVS response in the upright conditions, regardless of whether faces were embedded in a stream of faces or objects. Critically, however, in the inverted condition, the neural response was significantly lower for same- than other-race faces, with the response to other-race faces remaining comparable to the upright condition. Our data show that face inversion affects the FPVS neural responses of the visual category human observers are more expert with. These findings contribute to a deeper understanding of the intricate mechanisms underlying neural processing in face perception and its interaction with race.

Acknowledgements: This work was supported with funding from the Swiss National Science Foundation awarded to Roberto Caldara (100019_189018).