Neural Correlates of Spatial Attention Deployment and Perceptual Decision Making

PROJECT SUMMARY Each of the 4-5 quick eye movements (saccades) that we generate every second is the result of a target selection process that combines perceptual and motor planning signals modulated by attention mechanisms, which prioritize the potential targets. The overarching goal of this project is to reveal how these attention

mechanisms are instantiated in the activity of the frontal eye field (FEF), a key oculomotor area. Specifically, I propose to record neuronal activity from recognized neuronal types in FEF while monkeys perform two novel visuomotor tasks. Many studies have investigated how oculomotor neurons contribute to visuomotor choices.

However, most have relied on serialized tasks where a perceptual judgment is made first and a motor report is made subsequently, and given this structure, the resulting behavioral metrics (accuracy and RT) confound the contributions of perceptual, motor, and attentional processes to each choice. An effective solution to this

limitation is to impose urgency which, in essence, means that motor plans are always initiated first, before the task-relevant sensory cue is evaluated. Time pressure yields a novel psychophysical curve, the “tachometric curve”, which is unique in its ability to resolve the contributions of distinct perceptual signals to the saccadic

choice process as it unfolds in time. Each of my two Specific Aims implements a novel, urgent decision-making paradigm. In both cases the general strategy is to record FEF activity and, using the time-resolved behavioral information provided by the tachometric curve, compare the neuronal responses evoked before and after

perceptual information arrives to the circuit. In Aim 1, I plan to use an urgent version of the classic random dot motion (RDM) discrimination task to determine whether the spatially selective activity in FEF represents the location where attention is deployed or, alternatively, the amount of sensory evidence that has accumulated in

favor of a choice toward that location. These two functions, attentional deployment and evidence accumulation, represent entirely distinct theoretical constructs — but are readily confounded in standard, non-urgent tasks. The proposed dissociation would represent a key conceptual advance. In Aim 2, I plan to use SpotChase, a

gamified, dynamic urgent task, to investigate how visuomotor performance depends on selection history effects. It is now well established that visuomotor choices are determined not only by ongoing stimulus-driven and goal-driven signals, but also by past events (stimuli, actions, rewards, etc.) recently experienced.

However, the impact of such selection histories is likely to be much stronger under natural viewing conditions than in trial-based laboratory tasks. Because SpotChase is highly dynamic but still permits rigorous behavioral quantification (specifically, construction of tachometric curves), it will afford a much more comprehensive

characterization of the neural basis of selection history effects under more relevant behavioral conditions. Preliminary data promise significant advances in both Aims.