CRCNS: investigating perceptual processing speed and its impact on choice behavior

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Project Summary/Abstract The goal of this project is to investigate the neural mechanisms whereby perceptual information guides the choice of where to look next; specifically, we propose to record neuronal activity during urgent decision making to examine with fine temporal resolution how perception informs motor planning. Neuroscientists normally study choice behavior with tasks in which a perceptual judgment is made and is followed by a motor report, but this approach has limitations. First, it allows various covert factors such as attention, anticipation, or task diffi- culty to be traded against each other, creating ambiguities that cannot be resolved via standard psychophysical metrics, i.e., reaction time and choice accuracy. And second, serialization suppresses the rapid, reciprocal inter- action between perceptual analysis and motor planning from which informed saccadic choices normally arise. Our approach is based on a recently developed task in which decisions are urgent and both of these problems are minimized. Our framework also includes a heuristic, physiologically grounded model that reproduces the subjects' rich behavior with great detail. Thus, we propose to study how perception informs motor planning using time pressure to engage these processes within their natural time scale and dynamics, and relate them quantitatively to psychophysical performance. Oculomotor activity will be recorded from monkeys trained to perform several variants of our urgent choice paradigm. In Aim 1 we will investigate the relationship between exogenous (or bottom-up) attention and motor planning by varying the relative salience of target and distracter during an urgent choice. We hypothesize that the reflexive, salience-driven form of attention acts through two specific mechanisms: acceleration of ongoing motor plans that are spatially congruent with it, and halting of those plans that are spatially incongruent. In Aim 2 we will investigate the relationship between attention, motor planning, and accumulation of sensory evidence by training monkeys to perform an urgent version of the well known random-dot motion discrimination task. In this case, because the locations of the two choice targets are dissociated from that of the stimulus to be discriminated, we expect to observe a tradeoff between stimulus-driven activity (signaling the deployment of attention to the stimulus) and target-driven activity (sig- naling the impending eye movement). Our previous and current preliminary results indicate that we will be able to resolve exquisitely orchestrated interactions between perceptual signals and ongoing motor activity that unfold very rapidly, within a few tens of ms, and are otherwise experimentally inaccessible. We will exploit this capability to draw essential functional distinctions between the frontal eye field (FEF) and the lateral intra- parietal area (LIP), and to determine the distinct contributions of classical cell types (visual, visuomotor, and motor) to perceptually guided choices within each of these key oculomotor structures. This work will provide critical insight about how perceptual information is dynamically incorporated into ongoing motor activity, and how this interaction determines saccadic-choice performance.