Preparing Non-Human Primates to Study Hand-Eye Coordination in Frontal Eye Fields (FEF) During Delayed Movement Task
Date of Award
Master of Science (MS)
ABSTRACT OF THE THESIS Preparing Non-Human Primates to Study Hand-Eye Coordination in Frontal Eye Fields (FEF) During Delayed Movement Task by Juliusz Cydzik Master of Science in Biomedical Engineering Washington University in St. Louis, 2023 Professor Lawrence Snyder, Chair Hand-eye coordination enables humans and non-human primates to use their hands and eyes to perform various tasks. We are interested in coordination at the systems level, where saccades and reaches are encoded. The parietal reach region (PRR), situated at the posterior end of the intraparietal sulcus (IPS) and overlapping portions of the medial intraparietal area (MIP) and V6a, is commonly attributed as an area which contains cells that encode the direction or endpoint of an upcoming reach, particularly for the contralateral arm . Similarly, the lateral intraparietal area (LIP), located midway along the lateral bank of the IPS, is commonly attributed as an area containing cells that encode the direction or endpoint of an upcoming saccade . Coordinated behavior is often stereotyped in research, many unimanual reach studies have brought forth findings based on stereotyped behavior in LIP and PRR, in the Free Choice task LIP cells encoded the direction or endpoint of an upcoming saccade. A stereotyped vi behavior is a behavior instructed by experimenters which always occurs in a manner that would be unlikely to happen in nature. We want to train subjects in non-stereotyped, bimanual reaching tasks to be able to study how saccadic behaviors are naturally coded in FEF. Animals naturally make a saccade first to one target and then the other on separate trials prior to a hand movement, creating different patterns of limb–gaze coordination on different trials . These results suggest that the parietal cortex plays at best only a permissive role in some aspects of eye–hand coordination and makes the role of LIP in saccade generation unclear. Previously LIP activity was attributed as an area that coded saccades as they reached targets, providing distinguishable activity between different targets. In our experiment, saccades could go to either arm’s target, yet LIP did not distinguish between those two cases (saccade to the target of the right arm versus saccade to the target of the left arm) prior to the actual onset of the saccade. Frontal eye fields (FEF) an area located in the frontal cortex, specifically in Brodmann’s area 8a in primates, receives projections from temporal and parietal cortices and has direct projections to the superior colliculus . One study which induced monkeys to make saccades in the absence of visual targets classified three types of perisaccadic activity in FEF and found that the activity could account for saccadic generation . More recently, a study found that responses in FEF are suppressed when the animal maintains fixation for longer durations during a visual foraging task . Based on the literature mentioned, we believe that FEF may play a role in saccade generation. We would like to determine if FEF encodes saccadic movements made to targets cued for the left hand versus targets cued for the right hand during a “bimanual apart task”. In this study we defined, assessed, and influenced saccadic behavior in one subject during the bimanual apart task. We found that non-human primate subjects preferred certain saccade targets vii over others in the bimanual apart task. This finding indicated that the subject needs further training for us to study saccade generation in FEF. We believed that we could alter behaviors, in particular choice making during a task by adding rewards and altering viii stimuli/targets. We trained non-human primates to choose both targets in the bimanual apart task for two of the target combinations used in the task. If we successfully train the subject to saccade to both targets on the remaining combinations with our Bimanual Apart Flash Period Task, the behavioral paradigm can serve as a useful task to study FEF. This model will allow us to test the hypothesis that FEF encodes upcoming saccades when animals reach for two targets.
Dan Moran Kurt Thoroughman