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Abstract:
Correlated activity of pairs of neurons recorded
simultaneously in somatosensory area SII of alert behaving monkeys
was examined. During the recordings, the animal's focus of
attention switched between performing a tactile task and a visual
task. Tactile stimulation was identical when the monkey performed
the tactile and the visual tasks. The neurons of each pair were
recorded from different electrodes separated by at least 400
microns. Correlations were determined after applying a shift
predictor to correct for variations in evoked firing rate. Of the
total 559 neuron pairs examined, 384 (69%) showed significant
(p<0.05) synchronous firing, with the half-width of the
cross-correlation peak approximately 25 ms. For pairs with
significant synchronous firing, 67 (17%) showed a degree of
correlation which significantly covaried (p<0.05) with the
attentional state of the monkey (93% increased, 7 % decreased).
These results indicate that attention changes not only the mean
rate of firing of neurons (Hsiao et al., J. Neurophys. 7:444, 1993)
but, for a substantial fraction of neuron pairs, the degree of
synchronization with other neurons as well. This covariation
supports a possible functional role for synchronous firing in
attentional control as suggested by theoretical work (Niebur and
Koch, J. Comput. Neurosci. 1(1), 141, 1994). Supported by NIH
Grant: NS34086 and the Sloan Foundation
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