• Grant Application - .pdf format
  
  Abstract: DESCRIPTION (provided by applicant):
  Vision is an active process. We do not see the world directly; rather, we construct a representation of it from sensory inputs in combination with internal, non-visual signals. In the case of spatial perception, our representation of the visual scene takes into account our own movements. This allows us to perceive the world as stationary despite the constant eye movements that produce new images on the retina. How is this perceptual stability achieved? Our central hypothesis is that a corollary discharge of the eye movement command updates, or remaps, an internal representation when the eyes move. We have previously shown that single neurons in the lateral intraparietal area (LIP) and extrastriate visual cortex are activated by the remapped trace of a visual stimulus. These neurons fire in the single-step task, in which a saccade brings the receptive field onto a previously stimulated location. Remapping is also observed in the double-step task, in which the animal makes sequential saccades to two target locations. Our long-term goal is to discover the neural mechanisms that produce remapping. To achieve this we need to learn much more about the phenomenon and about the neural circuitry that supports it. The proposed experiments are designed to discover whether LIP neurons have equal access to visual information from the entire visual field; to determine whether remapping varies with hemifield or distance; to discover the source of remapped visual signals; and to determine the source of the corollary discharge signals used in remapping. The aim of the proposed work is to elucidate the neural circuitry that contributes to active vision.
  
  Thesaurus Terms:
  brain interhemispheric activity, eye movement, neural information processing, neuroanatomy, parietal lobe /cortex, vision, visual cortex
  corpus callosum, frontal lobe /cortex, saccade, sensory signal detection, space perception, visual field, visual fixation, visual perception, visual stimulus
  Macaca mulatta, behavior test, electronic recording system, microelectrode
  
  Institution: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
  350 THACKERAY HALL
  PITTSBURGH, PA 15260
  Fiscal Year: 2006
  Department: NEUROSCIENCE
  Project Start: 01-MAY-1998
  Project End: 31-AUG-2009
  ICD: NATIONAL EYE INSTITUTE
  IRG: CVP
  

J Neurophysiol 95: 2751-2767, 2006

Spatial Updating in Area LIP Is Independent of Saccade Direction

Laura M. Heiser and Carol L. Colby

Department of Neuroscience and Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania

Submitted 18 January 2005; accepted in final form 2 November 2005

Animals
Two adult male rhesus macaques (8.1–9.5 kg) were used in this study. Experimental protocols were approved by the University of Pittsburgh Institutional Animal Care and Use Committee and were certified to be in compliance with the guidelines in the Public Health Service Guide for the Care of Laboratory Animals.

At the outset of the experiment, both monkeys underwent sterile surgery under general anesthesia induced with ketamine and maintained with isofluorane. The top of the skull was exposed, bone screws were inserted around the perimeter of the exposed area, and an acrylic cap was used to cover the skull and embed the bone screws. A head-restraint bar was embedded in the cap, and scleral search coils were implanted around the eyes for the purpose of monitoring eye position (Judge et al. 1980 ). After initial training, a recording chamber (1.8 cm diam) was installed over area LIP.

Physiological methods
During recording sessions, the monkey sat in a darkened room with its head fixed in a primate chair, facing a tangent screen 25 cm away.