Grant Number: 5R01EY003878-26
Project Title: Neural Control of Eye Movement
PI Information: PROFESSOR STEPHEN G. LISBERGER, sgl@phy.ucsf.edu,
Phone: 415-476-1062  

Abstract: DESCRIPTION (provided by applicant):
Visual motion signals in extrastriate visual area MT provide the primary sensory input that guides smooth pursuit eye movements. Because of the broad tuning of MT neurons for target direction and speed, many neurons are active in MT when a target moves with any given direction and speed: as a consequence, any given visual motion is represented in the brain by the discharge of a large population of neurons, called the "population response".

The long-term goal of this application is to understand how the population response is read by the motor system to provide commands for smooth pursuit eye movements. Prior work has allowed us to form the hypothesis that target speed is decoded from the population response in MT by performing a vector-averaging computation on an opponent motion signal, where the computation is biased toward estimating low speeds if the population response is noisy or has a low amplitude.

We now will ask how target direction is coded and decoded for pursuit. Direction has been chosen for analysis because it offers advantages for understanding how the decoding computation is done with neurons.

We will develop an analysis that is based on the mean and variation of individual neural and behavioral responses in awake, trained rhesus monkeys.

We will conduct behavioral experiments to determine how well pursuit can discriminate between targets moving in slightly different directions, for stimuli with and without directional noise.

We will record the mean and variation of neural responses in MT during the directional discrimination, and investigate co-variation of neural and behavioral responses as well as correlations between the responses of pairs of MT neurons.

Then, we will evaluate possible neural mechanisms for decoding target direction by computer simulations of a neural network model with a realistic population code and neuraly plausible decoding mechanisms.

Our proposed approach investigates the situation faced by the pursuit system in real life, when it must estimate target direction on the basis of individual responses of many neurons. It will provide us an understanding of the neural operations performed in neural circuits between the cerebral cortex and cerebellum, shedding light on the normal functions of pathways that are compromised in many strokes and motor disorders and potentially leading to new therapies for assisting in recovery from strokes.

Thesaurus Terms:
neural information processing, neuroregulation, sensory discrimination, smooth pursuit eye movement, visual perception, visual tracking computer data analysis, computer simulation, information system, motor neuron, neural transmission, neurophysiology, neuropsychology, sensorimotor system, time resolved data, visual stimulus Macaca mulatta, behavioral /social science research tag, electrode, oscillography, single cell analysis

Institution: UNIVERSITY OF CALIFORNIA SAN FRANCISCO
3333 California St., Ste 315, SAN FRANCISCO, CA 941430962
Fiscal Year: 2006
Department: PHYSIOLOGY
Project Start: 01-SEP-1981
Project End: 31-AUG-2009
ICD: NATIONAL EYE INSTITUTE
IRG: CVP

J Neurophysiol 97: 272-282, 2007. First published October 4, 2006; doi:10.1152/jn.00941.2005 0022-3077/07 $8.00

Responses of Neurons in the Medial Superior Temporal Visual Area to Apparent Motion Stimuli in Macaque Monkeys

Anne K. Churchland, Xin Huang and Stephen G. Lisberger
 
Howard Hughes Medical Institute, Department of Physiology, W. M. Keck Foundation Center for Integrative Neuroscience, and Neuroscience Graduate Program, University of California, San Francisco, California
 
Submitted 7 September 2006; accepted in final form 1 October 2006

Eye movement and neural recordings were obtained from three adult male rhesus monkeys (Macaca mulatta) that had been trained to fixate and pursue visual targets for fluid reward. Two of the monkeys provided the data from MST and one provided the data from MT. Using sterile surgical procedures, monkeys were implanted with head restraints and scleral search coils as described elsewhere (Churchland and Lisberger 2000 ; Ramachandran and Lisberger 2005 ).

After initial training, surgery was performed to implant recording cylinders over a 20-mm circular hole cut in the skull to allow access to MST for neural recordings. For each experimental session, the monkey sat in a primate chair affixed with a tube for dispensing fluid rewards.

Methods were approved in advance by the Institutional Animal Care and Use Committee at the University of California, San Francisco and were in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals.