Role of Cingulate Cortex in Eye Movement Control

Duke University, Durham NC

Investigators

Linked publications & trials

Abstract

DESCRIPTION (provided by applicant): This project seeks to understand the role of the limbic system in choosing movements for execution. Anatomical and physiological evidence suggest that, within the limbic system, posterior cingulate cortex (CGp) may integrate the sensory motor, and reward signals that guide the oculomotor system to shift gaze to a particular visual stimulus. The purpose of the proposed study is to determine whether CGp encodes the motivational significance of visually-guided saccades, or merely their spatial coordinates. This study has 3 goals. The first goal is to quantify the representation of the timing and spatial coordinates of visual and oculomotor events in CGp. To do this, both initial fixation position and target position will be varied while animal subjects perform reaction-time and delayed saccade tasks. Pilot data suggest that different subpopulations of CGp neurons signal the spatial coordinates of either sensory or motor events, and that these spatial representations are encoded in retinotopic and head-centered coordinates, respectively. The second goal is to determine whether CGp neurons encode the reward outcome of eye movements. Single CGp neurons will be studied while animal subjects either shift gaze to a single target while reward size is varied, or choose between gaze shifts of different reward value. Pilot data suggest the new finding that some CGp neurons encode the amount of reward delivered after a particular saccade. These data suggest that CGp neurons may assign motivational valence to visually-guided saccades based on the outcome of those movements. The third goal is to determine whether CGp activation signals the valence of sensory and motor events or the spatial coordinates of those events. Stimulation will be applied to CGp during fixation trials, and the choices animal subjects make on subsequent choice trials examined. If CGp activation assigns motivational valence to particular movements, then stimulation should bias future choices. Overall, this project may reveal important interactions between the limbic system and visuo-motor planning areas during behavioral guidance, and promises to yield data that may clarify the mechanisms underlying the emotional, cognitive, and motor deficits characterizing individuals with limbic system disorders.