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 makes undistorted faces ap...
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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 makes undistorted faces appear compressed, and adaptation to compressed faces makes undistorted faces appear expanded. Such distortion aftereffects have been proposed to result from renormalization, in which the visual system constantly updates a prototype according to the adaptors' characteristics and evaluates subsequent faces relative to that. However, although consequences of adaptation are easily observed in behavioral aftereffects, it has proven difficult to observe renormalization during adaptation itself. Here we directly measured brain responses during adaptation to establish a neural correlate of renormalization. Given that the face-evoked occipito-temporal P2 event-related brain potential has been found to increase with face prototypicality, we reasoned that the adaptor-elicited P2 could serve as an electrophysiological indicator for renormalization. Participants adapted to sequences of four distorted (compressed or expanded) or undistorted faces, followed by a slightly distorted test face, which they had to classify as undistorted or distorted. We analysed ERPs evoked by each of the adaptors and found that P2 (but not N170) amplitudes evoked by consecutive adaptor faces exhibited an electrophysiological pattern of renormalization during adaptation to distorted faces: P2 amplitudes evoked by both compressed and expanded adaptors significantly increased towards asymptotic levels as adaptation proceeded. P2 amplitudes were smallest for the first adaptor, significantly larger for the second, and yet larger for the third adaptor. We conclude that the sensitivity of the occipito-temporal P2 to the perceived deviation of a face from the norm makes this component an excellent tool to study adaptation-induced renormalization.
Binaural Cue coding (BCC) offers a compact parametric representation of auditory spatial information. This representation can be applied to stereophonic or multi-channel audio compression. It allows to reconstruct the...
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ISBN:
(纸本)0780374029
Binaural Cue coding (BCC) offers a compact parametric representation of auditory spatial information. This representation can be applied to stereophonic or multi-channel audio compression. It allows to reconstruct the spatial image given a mono audio signal and spatial cues that require only a low data volume. This paper focuses on the extraction of the spatial cues from a stereophonic signal with a BCC analyzer. Results of a first subjective quality evaluation confirm that this technique is able to approximate the spatial image of critical reference signals. Thus BCC has the potential to offer highly efficient stereophonic or multi-channel coding, even at very low bit rates that currently permit coding of only one mono channel.
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