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Nadine Kloth, Gillian Rhodes, Stefan Schweinberger; Watching the brain recalibrate: An ERP correlate of renormalization during face adaptation. Journal of Vision 2016;16(12):1236. doi: 10.1167/16.12.1236.
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© 2017 Association for Research in Vision and Ophthalmology.
The face perception system flexibly adjusts its neural responses to current face exposure, inducing aftereffects in the perception of subsequent faces. For instance, adaptation to expanded faces biases observers to perceive undistorted faces as compressed, and adaptation to compressed faces induces biases to perceive undistorted faces as expanded. Such distortion aftereffects have been proposed to result from renormalisation, in which the face perception system defines recent face characteristics as "normal" and evaluates subsequent faces relative to that. However, although consequences of adaptation are easily observed in behavioural aftereffects, it has proven difficult to observe renormalisation during adaptation itself. Here, we establish the occipitotemporal P2 ERP as an electrophysiological indicator of renormalisation. Participants adapted to sequences of four consecutive compressed, undistorted, or expanded faces with different identities, followed by a slightly compressed or expanded test face, which participants had to classify as undistorted or distorted. Unlike earlier studies, we analyzed not only the ERPs evoked by the test faces, but also by each of the four adaptors. We found that the P2 amplitudes evoked by consecutive adaptor faces exhibited an electrophysiological pattern of renormalisation during adaptation: P2 amplitudes evoked by both compressed and expanded adaptors significantly increased as adaptation proceeded: P2 amplitudes were consistently smallest for the first adaptor and significantly larger for both the second and third adaptor. Replicating earlier research, larger P2 amplitudes were also evoked by test faces for which adaptation had increased perceived normality. Specifically, after adaptation to expanded faces, P2 amplitudes were larger for expanded than compressed test faces. After adaptation to compressed faces, P2 amplitudes were larger for compressed than expanded test faces. We conclude that the sensitivity of the occipitotemporal P2 to the perceived deviation of a face from the current norm makes the component an excellent tool to demonstrate and study adaptation-induced renormalisation.
Meeting abstract presented at VSS 2016
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