Abstract
In the antisaccade task, which is considered a sensitive assay of cognitive function, a salient visual cue appears and the participant must look away from it. This requires sensory, motor-planning, and cognitive neural mechanisms, but what are their unique contributions to performance, and when exactly are they engaged? Here, by manipulating task urgency, we generate a psychophysical curve that tracks the evolution of the saccadic choice process with millisecond precision, and resolve the distinct contributions of reflexive (exogenous) and voluntary (endogenous) perceptual mechanisms to antisaccade performance over time. Both progress extremely rapidly, the former driving the eyes toward the cue early on (∼100 ms after cue onset) and the latter directing them away from the cue ∼40 ms later. The behavioral and modeling results provide a detailed, dynamical characterization of attentional and oculomotor capture that is not only qualitatively consistent across participants, but also indicative of their individual perceptual capacities.
Highlights
Neuroscience aims to explain macroscopic behavior based on the microscopic operation of distinct neural circuits, and this requires carefully designed tasks that expose the relationship between the two
Akin to an athlete anticipating the trajectory of a ball that must be caught or struck, the participant in the compelled antisaccade task must begin programming a movement in advance of the relevant sensory information, and must quickly interpret the later arriving visual cue to modify the developing motor plan(s) on the fly
By making the antisaccade task urgent, focusing on processing time, and developing a mechanistic model that is firmly grounded on the neurophysiology of saccadic choices, we were able to resolve the opposing influences of endogenous and exogenous mechanisms on the oculomotor response with unprecedented sharpness
Summary
Neuroscience aims to explain macroscopic behavior based on the microscopic operation of distinct neural circuits, and this requires carefully designed tasks that expose the relationship between the two. In the case of the antisaccade task (Coe and Munoz, 2017; Munoz and Everling, 2004), in which participants are instructed to withhold responding to a visual cue in favor of programming a saccade to a diametrically opposed location, performance relies heavily on frontal cortical mechanisms associated with cognitive control (Guitton et al, 1985; Everling and Fischer, 1998; Munoz and Everling, 2004; Condy et al, 2007; Luna et al, 2008; Hakvoort Schwerdtfeger et al, 2012), and the paradigm is considered to be a sensitive assay of impulsivity and executive function in general. On the other hand, programming a saccade away from a cue is a top-down or endogenous process that
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