title: Competitive integration of visual and goal-related signals on neuronal accumulation rate: a correlate of oculomotor capture in the superior colliculus.
abstract: The mechanisms that underlie the integration of visual and goal-related signals for the production of saccades remain poorly understood. Here, we examined how spatial proximity of competing stimuli shapes goal-directed responses in the superior colliculus (SC), a midbrain structure closely associated with the control of visual attention and eye movements. Monkeys were trained to perform an oculomotor-capture task [Theeuwes, J., Kramer, A. F., Hahn, S., Irwin, D. E., & Zelinsky, G. J. Influence of attentional capture on oculomotor control. Journal of Experimental Psychology. Human Perception and Performance, 25, 1595-1608, 1999], in which a target singleton was revealed via an isoluminant color change in all but one item. On a portion of the trials, an additional salient item abruptly appeared near or far from the target. We quantified how spatial proximity between the abrupt-onset and the target shaped the goal-directed response. We found that the appearance of an abrupt-onset near the target induced a transient decrease in goal-directed discharge of SC visuomotor neurons. Although this was indicative of spatial competition, it was immediately followed by a rebound in presaccadic activation, which facilitated the saccadic response (i.e., it induced shorter saccadic RT). A similar suppression also occurred at most nontarget locations even in the absence of the abrupt-onset. This is indicative of a mechanism that enabled monkeys to quickly discount stimuli that shared the common nontarget feature. These results reveal a pattern of excitation/inhibition across the SC visuomotor map that acted to facilitate optimal behavior-the short duration suppression minimized the probability of capture by salient distractors, whereas a subsequent boost in accumulation rate ensured a fast goal-directed response. Such nonlinear dynamics should be incorporated into future biologically plausible models of saccade behavior.
authors.affiliation: Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada. brian.white@queensu.ca
authors.forename: Brian J
authors.initials: BJ
authors.lastname: White
authors.forename: Robert A
authors.initials: RA
authors.lastname: Marino
authors.forename: Susan E
authors.initials: SE
authors.lastname: Boehnke
authors.forename: Laurent
authors.initials: L
authors.lastname: Itti
authors.forename: Jan
authors.initials: J
authors.lastname: Theeuwes
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Munoz
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D005133:Eye Movements / Q000502:physiology*; D006040:Goals; D006801:Humans; D008253:Macaca mulatta; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D013223:Statistics as Topic; D013477:Superior Colliculi / Q000166:cytology* / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*