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Zusammenfassung:
Salient visual stimuli often subjectively disappear following the abrupt onset of a spatially separated pattern (Generalized Flash Suppression, GFS). Unlike other forms of induced perceptual suppression such as monocular or binocular rivalry, the vanishing stimulus is not replaced by a competing pattern, but simply disappears and remains continuously invisible for up to several seconds. In agreement with studies measuring single cell activity during binocular rivalry (Leopold Logothetis, 1996; Gail et al., 2004), we reported previously that only a small minority of neurons in V1 showed activity changes corresponding to the subjective disappearance of a stimulus during GFS, while this fraction was slightly higher in area V4 (Wilke, 2003). In all cases, perceptual modulation was considerably smaller than in a control condition where the stimulus was physically removed. In the present study, we investigate the expression of perceptual suppression in the local field potential (LFP), comparing it to the changes in spiking activity observed at the same recording sites. Using transdural multielectrode recording techniques, we simultaneously measured spiking activity (single- and multi-unit) and local field potentials in areas V1, V2 and V4 in three monkeys reporting subjective target visibility during GFS. We found that perceptual suppression was more reliably expressed in the multiunit signal compared with single cells. In all visual areas, the magnitude of the evoked LFP response to the suppressing pattern was often correlated with the visibility. We examined band-limited power (BLP) of the local field potential, and found perception-related modulation to be variable, both in its magnitude and in the band in which it was expressed. Modulation in the gamma band (30 to 80 Hz) generally covaried with spiking activity on a trial by trial basis.
