September 2011
Volume 11, Issue 11
Free
Vision Sciences Society Annual Meeting Abstract  |   September 2011
Superior colliculus inactivation impairs covert selective attention to motion but does not alter gain modulation of motion signals in areas MT and MST
Author Affiliations
  • Richard Krauzlis
    Systems Neurobiology Laboratory, Salk Institute for Biological Studies, USA
  • Alexandre Zenon
    Systems Neurobiology Laboratory, Salk Institute for Biological Studies, USA
Journal of Vision September 2011, Vol.11, 167. doi:10.1167/11.11.167
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      Richard Krauzlis, Alexandre Zenon; Superior colliculus inactivation impairs covert selective attention to motion but does not alter gain modulation of motion signals in areas MT and MST. Journal of Vision 2011;11(11):167. doi: 10.1167/11.11.167.

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Abstract

Superior colliculus (SC) inactivation causes large deficits in covert selective attention, but the mechanisms are not known. One possibility is that SC inactivation disrupts attention-related mechanisms in sensory areas of cerebral cortex. To test this idea, we recorded neuronal activity in areas MT and MST during a covert attention task involving motion, before and during SC inactivation. A rhesus macaque performed a motion change detection task, which required him to report if the motion direction in a cued patch changed, while ignoring changes in a simultaneously presented foil patch. The two patches were placed at symmetric locations across the fixation point and changes occurred after a variable delay during maintained fixation. The task was to report the change in the cued patch by pressing a button, and make no response if the motion change occurred in the foil patch. We first confirmed that MT and MST neurons had higher firing rates when the cued stimulus, rather than the foil, was placed in their receptive fields, similar to the cue-related gain changes found in previous studies. Next, we used muscimol, a GABA agonist, to focally and reversibly inactivate the SC during the task. Consistent with our previous results, SC inactivation caused a dramatic decrease in the ability of the animal to correctly detect motion changes in the affected visual field, and an increase in the number of erroneous responses to uncued events occurring in the unaffected field. Finally, we recorded MT and MST units before and during SC inactivation, and found that SC inactivation did not alter the cue-related gain modulation in firing rates, even though large deficits in selective attention were observed at the same time. These results suggest that SC activity contributes to covert selective attention by means that are largely independent of gain modulation of sensory signals.

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