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This Article Full Text Full Text (PDF) Supplemental Figures All Versions of this Article: 101/6/3199    most recent 90983.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Reyes-Puerta, V. Articles by Hoffmann, K.-P. PubMed PubMed Citation Articles by Reyes-Puerta, V. Articles by Hoffmann, K.-P.

Influence of Task Predictability on the Activity of Neurons in the Rostral Superior Colliculus During Double-Step Saccades

¹Department of General Zoology and Neurobiology and ²International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany; and ³Spinal Cord Injury Center, Balgrist University Hospital, Zurich, Switzerland

Submitted 2 September 2008; accepted in final form 20 March 2009

Target probability has been shown to modulate motor preparatory activity of neurons in the caudal superior colliculus (SC) of the primate. Here we tested whether top-down processes, such as task predictability, influence the activity of neurons also at the rostral pole of the SC (rSC), classically related to fixation. To investigate this, double-step saccade tasks were embedded in two different paradigms, one containing unpredictable and another containing predictable tasks. During predictable tasks the animals could develop some expectation about the forthcoming second target jump, i.e., anticipate when and where to make the second saccade. Neuronal responses were recorded during both paradigms and compared, revealing the influence of task predictability on the activity of rSC neurons during specific periods of fixation. In particular, neuronal activity stayed significantly lower during the fixation period between two successive saccades in predictable than in unpredictable tasks. In addition there was a learning effect within a session during predictable conditions, i.e., the intersaccadic activity was higher in the early than in the late trials. Further, reaction times for the second saccade were shorter in predictable than in unpredictable tasks. However, we demonstrated that this difference in reaction times cannot be solely accounted for by the reported difference in neural activity, which was mainly influenced by the predictability of the tasks. With these results we show that top-down processes such as predictability are imposed on the activity of neurons in the rostral pole of the primate SC.