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Lisa Stacchi, Meike Ramon, Joan Liu-Shuang, Roberto Caldara; Idiosyncratic Neural Signatures of Face Discrimination - A Fast Periodic Oddball Stimulation Study. Journal of Vision 2017;17(10):1259. doi: 10.1167/17.10.1259.
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Western observers typically deploy a triangular fixation pattern encompassing the eyes and mouth during face recognition. Nevertheless, this average gaze pattern does not reflect observers' idiosyncratic strategies, which highlight individual-specific preferences. Whether similar preferences exist at the neural level remains an open question. To this aim, we recorded observers' electrophysiological responses during fast-periodic oddball stimulation (Liu-Shuang et al., 2013). While observers fixated the center of the screen, faces were presented at a high frequency rate with changes in identity every seventh image. Relative to the observers' fixation location, the position of the faces differed in 10 sampling positions, uniformly covering all the internal facial features through different sequences of trials. At the group level, we observed that faces presented in the conventional central fixation position elicited stronger right-lateralized periodic electrophysiological responses for the oddball face, hereby replicating previous findings. Interestingly, we also observed viewing position dependency for the fundamental frequency of the base response (i.e. 6Hz). Its higher harmonics on the other hand elicited a centrally distributed response, while the oddball frequencies led to topographically more heterogeneous responses. At the individual level, we observed clear idiosyncratic differences as a function of visual sampling position – both in terms of amplitude, as well as topography. While some observers showed more right-lateralized responses, others were relatively more left-lateralized. These findings stress the need of carefully considering inter-individual variability, as well as controlling for stimulus parameters, such as its location within observers' visual field. The observed differences in lateralization also challenge the notion of a universal right-hemispheric dominance involved in face discrimination. Finally, the different topographies associated with base and oddball frequencies highlight the potential need to reconsider the nature of neural processes generated by the fast periodic oddball stimulation.
Meeting abstract presented at VSS 2017
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