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J Neurosci. 2014 Jun 4;34(23):7976-87. doi: 10.1523/JNEUROSCI.3022-13.2014.

Response normalization in the superficial layers of the superior colliculus as a possible mechanism for saccadic averaging.

Author information

Molecular and Cellular Pharmacology Training Program and.
Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53706 and.
Department of Psychiatry and Biobehavioral Sciences and Neurobiology, Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles, Los Angeles, California 90025


How does the brain decide where to look? Neuronal networks within the superior colliculus (SC) encode locations of intended eye movements. When faced with multiple targets, the relative activities of neuronal populations compete for the selection of a saccade. However, the computational principles underlying saccadic choices remain poorly understood. We used voltage imaging of slices of rat SC to record circuit dynamics of population responses to single- and dual-site electrical stimulation to begin to reveal some of the principles of how populations of neurons interact. Stimulation of two distant sites simultaneously within the SC produced two distinct peaks of activity, whereas stimulation of two nearby sites simultaneously exhibited a single, merged peak centered between the two sites. The distances required to produce merged peaks of activity corresponded to target separations that evoked averaging saccades in humans performing a corresponding dual target task. The merged activity was well accounted for by a linear weighed summation and a divisive normalization of the responses evoked by the single-site stimulations. Interestingly, the merging of activity occurred within the superficial SC, suggesting a novel pathway for saccadic eye movement choice.


global effect; nonlinear interactions; saccade direction; voltage imaging; weighted summation

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