The orienting attention network is responsible for prioritizing sensory input through overt or covert shifts of attention among targets. The ability to disengage attention is essential for the proper functioning of this network. In addition to its importance for proper orienting, deficits in disengagement have been recently implicated in autism disorders. Despite its importance, the neural mechanisms underlying disengagement processing are still poorly understood. In this study, the involvement of the superior colliculus (SC) in disengagement was investigated in unrestrained rats that had been trained in a two-alternative light-guided spatial choice task. At each trial, the rats had to choose one of two paths, leading either to a large or a small reward, based on 1 (single-cue) or 2 (double-cue) lights. The task consisted of serial trials with single- and/or double-cue lights, and rats could acquire a large reward if the rats chose infrequent lights when infrequent cue lights were presented after preceding frequent cue lights. Experiment 1 included trials with either single- or double-cue lights, and infrequent trials with double-cue lights required both attentional disengagement and shift of attention from preceding frequent single-cue lights, while experiment 2 included only trials with single-cue lights requiring shifts of attention but not attentional disengagement. The results indicated that temporary inactivation of the SC by muscimol injections selectively impaired performance on trials requiring disengagement. No impairment was observed on the other trials, in which attention disengagement was not required. The results provide the first evidence that the SC is necessary for attentional disengagement.
Keywords: Attention; Autism; Disengagement; Orienting network; Superior colliculus; Temporary inactivation.
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