Abstract: DESCRIPTION (provided by applicant): To survive, animals must orient toward important stimuli while ignoring irrelevant ones. Our long-term goal is to understand how the brain selects targets for visual orienting, including saccadic eye movements and shifts of attention without eye movements. Saccade target selection lies at the interface between sensory and motor systems. This project probes the functions of two structures traditionally regarded as motor areas: the superior colliculus (SC), a subcortical region important for saccades, and the frontal eye field (FEF), an anatomically connected cortical region. Activity correlated with target selection has been observed in both areas. However, it is still debatable, particularly for the SC, whether these areas are involved in selecting where to look, or simply receive selection-related activity in preparation for generating a movement. We will test the hypothesis that these areas play functional roles in target selection by temporarily inactivating small regions of either the SC or FEF and testing performance in tasks that distinguish purely sensory or motor deficits from deficits in target selection. Comparisons will reveal how the two structures differ from each other in their contributions to target selection (Aim 1). We will also study the interactions of the SC and the FEF. It is usually assumed that the SC is under the control of cortical regions such as FEF, even though anatomical pathways also lead from the SC back to the FEF. We will test the hypothesis that SC activity influences target selection in the FEF, using single-unit recording and inactivation. This will reveal whether the two areas interact primarily in a feed-forward manner, or whether feedback from the SC influences cortical target selection (Aim 2). Evidence suggests that some of the same brain areas control both eye movements and attention shifts. We will test this hypothesis by investigating the consequences of temporarily disrupting activity in the SC or FEF on tasks requiring shifts of focal attention (Aim 3). These experiments will help to reveal the architecture of the visual orienting system, leading to a better understanding of human neurological syndromes that disrupt eye movements and attention.
Thesaurus Terms:
attention, cerebral cortex, neural information processing, neurophysiology, orientation, saccade, superior colliculus, visual field
brain electrical activity, central neural pathway /tract, visual stimulus
Macaca mulatta, electronic recording system, histology
Institution: SMITH-KETTLEWELL EYE RESEARCH INSTITUTE
SAN FRANCISCO, CA 94115
Fiscal Year: 2006
Department:
Project Start: 01-AUG-2003
Project End: 31-AUG-2007
ICD: NATIONAL EYE INSTITUTE
IRG: VISB

J Neurophysiol 88: 2019-2034, 2002;
0022-3077/02 $5.00
The Journal of Neurophysiology Vol. 88 No. 4 October 2002, pp. 2019-2034
Copyright ©2002 by the American Physiological Society
Saccade Target Selection in the Superior Colliculus During a Visual Search Task
Robert M. McPeek and Edward L. Keller
The Smith-Kettlewell Eye Research Institute, San Francisco, California 94115

Preparation
A scleral eye coil and a head-holder system were implanted under isofluorane 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. After 2-3 mo of training in behavioral tasks, described in the following text, the monkeys were prepared for chronic single-unit recording in a second aseptic surgery. A stainless steel recording chamber (12 mm ID), tilted 38° posterior from vertical, was positioned above a craniotomy centered on the midline. Antibiotics (Cefazolin) and analgesics (Buprenex) were administered as needed during the recovery period under the direction of a veterinarian.
Single-unit recording
We used standard methods to record single neurons in the superior colliculi of three rhesus monkeys. Neural activity was recorded using tungsten microelectrodes with impedances ranging from 0.8 to 2.5 M at 1 kHz lowered into the brain by a hydraulic microdrive. The microelectrode signal was amplified, band-pass filtered, and displayed on a digital storage oscilloscope. Action potentials were discriminated and converted into TTL pulses using a time-amplitude window discriminator. The computer data-acquisition system registered the occurrence of spikes with a resolution of 1 kHz, and the neural data were stored in register with the behavioral measurements.
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 disk. A Macintosh computer, which was interfaced with the PC, generated the visual displays with software constructed using the Video Toolbox library (Pelli 1997 ). Visual stimuli were presented on a 29-in color CRT (Viewsonic GA29) in synchronization with the monitor's vertical refresh. The monitor had a spatial resolution of 800 × 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 free access to water on weekends.