Identifying neural underpinnings of these complex processes is essential for advancing our knowledge of how the brain makes choices and how cognitive information is utilized in oculomotor behavior. Equally important, this knowledge will provide a better understanding such abnormal behaviors as oculomotor apraxia in which reflexive visually-guided saccades are preserved while saccades prompted by verbal commands are impaired and frontal lobe dysfunction in which the inability to make choice decisions is an important feature.

Both the latter disorders are of public health concern. In this project, we will collect neural data while saccades are generated as a choice response based on the pre-trained associations between color and spatial location: Animals will attend to visual stimuli of different colors delivered at the fovea and respond with an eye movement to a unique location associated with each color.

Experiments are designed to achieve the following specific aims: 1) To characterize neural signals in the superior colliculus (SC) and the cortical frontal eye fields (FEF) related to saccadic choice responses by recording from single neurons. Whether these signals are indeed necessary for saccadic choice responses will be determined by making reversible chemical lesions in the 2 structures. More specifically, by selectively inactivating the foveal portion of the FEF, we will test the hypothesis that the FEF is the place where sensory cue information given at the fovea is translated into the activation of neurons representing a target in the periphery.

2) To identify the source of cue-driven signals observed in the caudal SC. Given the fact that the FEF has abundant connections to this region, we will test the hypothesis that the FEF is the source of cognitive signals recorded in the SC. Reversible lesions will be made in FEF as a SC neuron with cue-driven signals is being recorded. Changes in the activation of the SC during choice response would support this hypothesis.

3) To examine the temporal relationship between the activities in pairs of FEF cells that code for the target location and others that code for non-target locations, while a choice decision is being made. This data will help to differentiate between 2 current models that attempt to explain the neural mechanisms underlying choice response.

Thesaurus Terms:
neural information processing, neurophysiology, neuroregulation, saccade, superior colliculus, visual pathway, visual perception brain electrical activity, extraocular muscle, motion perception, neural inhibition, neural initiation, neuroanatomy, sensorimotor system, tegmentum, visual feedback, visual field, visual stimulus Macaca mulatta, behavioral /social science research tag, computer data analysis, electrophysiology

Institution: SMITH-KETTLEWELL EYE RESEARCH INSTITUTE
SAN FRANCISCO, CA 94115
Fiscal Year: 2006
Department:
Project Start: 01-MAY-1986
Project End: 31-MAR-2009
ICD: NATIONAL EYE INSTITUTE
IRG: CVP

J Neurophysiol 91: 890-900, 2004. First published October 15, 2003; doi:10.1152/jn.00818.2003 0022-3077/04 $5.00

Properties of Saccadic Responses in Monkey When Multiple Competing Visual Stimuli Are Present

Kuniharu Arai, Robert M. McPeek and Edward L. Keller
 
The Smith-Kettlewell Eye Research Institute, San Francisco, California 94115

Submitted 20 August 2003; accepted in final form 10 October 2003

METHODS

Two male rhesus monkeys (Macaca mulatta) weighing between 4 and 7 kg were used in this study. All experimental protocols were approved by the Institutional Animal Care and Use Committee at the California Pacific Medical Center and complied with the guidelines of the Public Health Service policy on Humane Care and Use of Laboratory Animals.

Preparation
A scleral eye coil and a head-holder system were implanted under isoflurane anesthesia and aseptic surgical conditions. Anesthesia was induced with an intramuscular injection of ketamine. Heart rate, blood pressure, respiratory rate, and body temperature were monitored for the duration of the surgery. A coil made of four turns of Teflon-coated stainless steel wire was implanted under the conjunctiva of one eye using the procedure described by Fuchs and Robinson (1966 ), as modified by Judge et al. (1980 ). At the completion of the surgery, animals were returned to their home cages. Antibiotics (Cefazolin) and analgesics (Buprenex) were administered as needed during the recovery period under the direction of a veterinarian.

Behavioral procedures
Testing was performed in a dimly illuminated room. Data collection and storage were controlled by a custom real-time program running on a PC. Eye position and velocity were sampled at 1 kHz and digitally stored on disc. A Macintosh computer, which was interfaced with the PC, generated the visual displays using software constructed using the Video Toolbox library (Pelli 1997 ). Visual stimuli were presented on a 29-inch color cathode ray tube (Viewsonic GA29) in synchronization with the monitor's vertical refresh. The monitor had a spatial resolution of 800 by 600 pixels and a noninterlaced refresh rate of 75 Hz. The monitor was positioned 33 cm in front of the monkey and allowed stimuli to be presented in a field of view of approximately ±32° along the horizontal meridian and ±30° along the vertical meridian.

The monkeys were seated in a primate chair with their heads restrained for the duration of the testing sessions. They executed behavioral tasks for liquid reward and were allowed to work to satiation. Records of each animal's weight and health status were kept, and supplemental water was given as necessary. The animals typically worked for 5 days and were allowed controlled access to water on weekends.