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Abstract:
Neural firing in the visual cortex is highly irregular. Much work suggests that the spontaneous activity changes experienced by a cortical neuron are highly correlated with those experienced by its neighbors. We have previously shown that multiunit activity between distant sites in monkey visual cortex can display significant covariation during the performance of a visual task. In the present study, we recorded from electrodes separated by up to 10 mm in striate and extrastriate visual cortex under a variety of behavioral conditions including 1) actively performing a visual task, 2) relaxing between trials, 3) in light sleep, and 4) under general anesthesia. We recorded single and multiunit activity, as well as local field potentials. We were primarily interested to understand how identifiable events contribute to covariation observed in the various states. These included external events such as changes in the sensory stimulus, internal events such as spontaneous perceptual changes during binocular rivalry, behavioral events such as blinks and eye movements, and physiological events such as sleep spindles. We found that inter-site correlation was diminished during the visual task compared other states. It was particularly diminished during the perceptual instability accompanying binocular rivalry. Preliminary results also demonstrated significant anti-correlation between areas accompanying blinks and eye movements. A substantial portion of the common variability could not be accounted for by events we could identify. We will discuss these results in terms of the magnitude, frequency coherence, and spatial distribution of the covariation patterns.
