Sensory and motor cortices cooperate to provide the visual guidance of movement by processing visual inputs and providing voluntary modulation of how strongly those inputs reach sub-cortical motor circuits. The present proposal uses smooth pursuit eye movements to ask how visual and motor cortex interact to produce smooth pursuit eye movements. First, it will study the neural basis for ?gain-control?. In pursuit, the smooth eye movement region of the frontal eye fields (FEFSEM) modulates the strength of visual-drive for pursuit. Recordings from sensory area MT, motor area FEFSEM, and their brainstem targets will ask how gain control is represented a) when a target is perturbed during pursuit or fixation and b) for high-contrast and low- contrast visual stimuli, which produce high and low gains in the initiation of pursuit. Second, the research will evaluate the neural basis for pursuit latency. It will expand on preliminary data showing a trial-by-trial relationship between neural and pursuit latency in MT. It will ask whether latency or response amplitude in FEFSEM is better related to pursuit latency. It also will record from multiple single neurons in both structures to document how strongly the latencies are correlated across the population. Third, the proposed research will record simultaneously from multiple single neurons in MT and FEFSEM to determine the nature of the functional connectivity between the two areas, and to provide data that constrain how signals are transformed as they move from sensory to motor areas of the cortex. Integrated computational analyses will inform the experimental approaches by answering key questions such as: 1) how is the output from area MT used simultaneously to estimate the speed and direction of target motion and to determine how strongly the motor system should weight sensory evidence; 2) what is the functional connectivity among MT, FEFSEM, and the downstream motor system, and how can the system account for the mean, variation, and correlations among neural and behavioral responses; 3) How do MT and FEFSEM interact to control pursuit latency. The proposed research will make large steps towards understanding how multiple sites within the circuit for pursuit eye movements coordinate visual guidance of movement.
Humans use what they see to guide most of their movements. The relevant neural circuits involve all levels of the brain, from cortex to spinal cord. A better understanding of the operation of complete sensory-motor circuits will be important for improving human health in cases of stroke, neuro-degenerative motor disease, and developmental motor disorders. !
| Darlington, Timothy R; Beck, Jeffrey M; Lisberger, Stephen G (2018) Neural implementation of Bayesian inference in a sensorimotor behavior. Nat Neurosci 21:1442-1451 |
| Darlington, Timothy R; Tokiyama, Stefanie; Lisberger, Stephen G (2017) Control of the strength of visual-motor transmission as the mechanism of rapid adaptation of priors for Bayesian inference in smooth pursuit eye movements. J Neurophysiol 118:1173-1189 |
