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Abstract:
Abstract: Synchronization on a millisecond time scale is a
prominent feature of activity in mammalian cortices, and it has
been suggested to be crucial for feature binding and selection of
coherent perceptual information. Previous tests of this hypothesis
have employed stimuli with locally continuous contours. Here, we
have used random-dot patterns to investigate the effects of local
incoherence of stimuli on synchronization. Multi-unit activity and
local field potentials were recorded from areas 17 and PMLS in
anesthetized cats. Cells were driven with moving random-dot
patterns and gratings. In both areas, response strength was
comparable for gratings and dots, but directional tuning was less
specific for the latter. The synchrony observed with dot patterns
was weaker than that induced by gratings and, moreover, dots
eliminated gamma-band oscillations readily evoked with gratings.
When increasing levels of noise were introduced in the dot
patterns, leading to a decrease in coherence of visible motion,
firing rates were decreased in PMLS but not in area 17. In both
areas, synchronization was strongly affected by stimulus noise,
discharges being less precisely correlated at high noise levels.
These data show that the temporal patterning of neuronal activity
is strongly influenced by local coherence of visual stimuli. The
results are compatible with the notion that precise neuronal
synchronization may serve for the extraction of coherent perceptual
features.
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