Synchronization of neuronal activity during stimulus expectation in a direction discrimination task
S. Cardoso de Oliveira, A. Thiele & K.-P. Hoffmann
Journal of Neuroscience, 17:9248-9260, 1997
- The dorsal pathway of the primate brain, especially the middle temporal area (MT or V5) and the superior middle
temporal area (MST or V5a), is strongly involved in motion detection. The relation between neural firing rates
and psychophysical performance has led to the assumption that the neural code used by these areas consists of the
relative discharge rates of neuronal populations. As an additional neural code, temporal correlation of neural
activity has been suggested. Our study addresses the involvement of such a code in awake monkeys performing a motion
discrimination task. We found significant temporal correlations between simultaneously recorded pairs of units
in areas MT and MST and other extrastriate cortical areas. Units recorded from the same electrode were more frequently
synchronized than units recorded from different electrodes placed within the same or different cortical areas.
Activity synchronization was present in the expectation period before stimulus presentation and could not be induced
de novo by the stimulus. Rather, we found a contrast-dependent reduction of correlation strength on stimulus onset.
Correlation strength did not vary systematically with stimulus directions. We conclude that under the conditions
of this study, temporal decorrelation of MT and MST neurons could be used to detect the stimulus, but synchronization
does not convey specific information about its direction of motion and therefore is unlikely to contribute to performance
in our direction discrimination task. Activity synchronization in the period before stimulus onset could be related
to attentive expectation.
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