Time course of allocation of spatial attention by acoustic cues in non-human primates.

Spatial attention mediates the selection of information from different parts of space. When a brief cue is presented shortly before a target [cue to target onset asynchrony (CTOA)] in the same location, behavioral responses are facilitated, a process called attention capture. At longer CTOAs, responses to targets presented in the same location are inhibited; this is called inhibition of return (IOR). In the visual modality, these processes have been demonstrated in both humans and non-human primates, the latter allowing for the study of the underlying neural mechanisms. In audition, the effects of attention have only been shown in humans when the experimental task requires sound localization. Studies in monkeys with the use of similar cues but without a sound localization requirement have produced negative results. We have studied the effects of predictive acoustic cues on the latency of gaze shifts to visual and auditory targets in monkeys experienced in localizing sound sources in the laboratory with the head unrestrained. Both attention capture and IOR were demonstrated with acoustic cues, although with a faster time course than with visual cues. Additionally, the effect was observed across sensory modalities (acoustic cue to visual target), suggesting that the underlying neural mechanisms of these effects may be mediated within the superior colliculus, a center where inputs from both vision and audition converge.