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Guillaume A. Rousselet, Jesse S. Husk, Patrick J. Bennett, Allison B. Sekuler; Differential effects of eccentricity on N170 for faces and houses. Journal of Vision 2004;4(8):913. doi: https://doi.org/10.1167/4.8.913.
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© ARVO (1962-2015); The Authors (2016-present)
The present study aimed to characterize more precisely the link between face processing and the N170, a posterior negative event-related component that is particularly pronounced for human faces. Using a forced choice procedure, observers discriminated faces from houses while high-density EEG (256 electrodes) recordings were collected. All stimuli were flashed for 80 ms at varying eccentricities (0, 3.5, 7 and 10.5 degrees, relative to fixation). Preliminary results revealed a clear N170 for both centrally presented faces and houses, but the N170 was much larger for faces than for houses. The N170 evoked by faces decreased in amplitude and increased in latency with stimulus eccentricity, an effect that mirrored the increase in RT observed at the behavioral level. However, the N170 evoked by houses was nearly invariant with stimulus eccentricity. Hence, the difference between the N170 evoked by faces and houses diminished with stimulus eccentricity, becoming marginal at 10? in some subjects. Our results demonstrate that the generators of the N170 to faces are more affected by stimulus eccentricity than the generators to other objects like houses. This result might reflect a foveal bias affecting the generators of the face N170. Such a bias could be due to cortical magnification or the involvement of different spatial frequency bands in face and house processing. These alternative hypotheses will be investigated in future experiments. In addition, subject-by-subject source analyses will be performed to determine the possible cortical origin of the N170 effect.
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