We propose experiments aimed toward understanding the neural circuits responsible for these percepts. Subjects can perceive their direction of self-motion from "optic flow" signals that are produced on their retinas during translation through the environment. An important problem for the visual system is to recover translation based motion cues when smooth gaze movements are made that generate additional, laminar motions on the retinas.

During the last grant period we found that extra-retinal and retinal cues produce shifts in the tuning curves of MSTd neurons that are tuned to the direction of heading.

In the first aim of the current proposal we plan to extend these findings with three new lines of research, examining translation compensation, the effects of 3D cues, and the coordinate frame used by MSTd to represent heading direction.

The second aim is to study the neural networks responsible for SFM perception. Observers can perceive the 3D shape of objects based purely on relative motion cues. Such displays are bistable, and this feature has allowed us to examine the neural correlates of SFM perception.

Based on work in the last grant period, we proposed a two-stage model; in the first stage motion signals are measured in Vi and in the second stage surfaces are represented from these motion signals by a circuit within MT.

In the current proposal we plan to test this model by examining its temporal dynamics. These studies are designed to gain knowledge of how the brain processes information, and will help to understand neurological deficits that occur with brain diseases.

Thesaurus Terms:
motion perception, neural information processing, visual cortex, visual pathway brain mapping, eye movement, form /pattern perception, head movement, psychophysics, visual stimulus, visual tracking Macaca mulatta, behavioral /social science research tag, human subject, microelectrode, single cell analysis, statistics /biometry

Institution: CALIFORNIA INSTITUTE OF TECHNOLOGY
Office of Sponsored Research, Mail Code 201-15
PASADENA, CA 91125
Fiscal Year: 2006
Department: NONE
Project Start: 01-SEP-1987
Project End: 28-FEB-2008
ICD: NATIONAL EYE INSTITUTE
IRG: VISB

J Neurophysiol 92: 553-566, 2004. First published March 3, 2004; doi:10.1152/jn.00030.2004 0022-3077/04 $5.00

Dorsal Neck Muscle Vibration Induces Upward Shifts in the Endpoints of Memory-Guided Saccades in Monkeys

Brian D. Corneil^1,2 and Richard A. Andersen<sup>1

1</sup>Division of Biology, California Institute of Technology, Pasadena, California 91125; and ²Departments of Physiology & Pharmacology and Psychology, University of Western Ontario, London, Ontario N6A 5K8, Canada
 
Submitted 9 January 2004; accepted in final form 28 February 2004

Experimental procedures
Two adult male rhesus monkeys (Macaca mulatta), weighing 7.5 and 10.5 kg, were used in these experiments following protocols approved by the Caltech Institutional Animal Care and Use Committee and in compliance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals.

Both monkeys underwent an aseptic surgery during which a scleral coil was implanted subconjunctivally (Judge et al. 1980 ) for monitoring the horizontal and vertical rotation of the eyes in space (henceforth referred to as eye position; Fuchs and Robinson 1966 ; torsional eye rotations were not measured), and a head post was secured to the skull by way of a dental acrylic pedestal for immobilizing the head during the experimental sessions.

Anesthesia was induced with ketamine hydrochloride and maintained with isoflurane. Antibiotics were administered pre- and postoperatively, and anti-inflammatories and analgesics were administered postoperatively. The monkeys' weights were monitored daily before and after surgery, and their general health was supervised by the university veterinarian.

Prior to the start of an experimental session, the monkeys were placed within a primate chair, and their heads restrained via the implanted head post. Within the chair, the monkeys rested on a perch with their trunk and hips facing forward.

The monkeys were placed within a dark, sound-attenuated experimental chamber, in the center of magnetic fields produced by 1-m field coils (CNC Engineering). The monkeys faced a hemispheric array of red light emitting diodes (LEDs; each 4.7 cd/m2) subtending about ±40° of the central visual field. These LEDs were arranged radially around a central LED, the fixation point (FP), which was located 50 cm straight ahead of the monkey.

Horizontal and vertical eye positions were each recorded at 1,000 Hz via a PLEXON system (Plexon, Dallas, TX), and all aspects of the experimental paradigms were controlled by customized real-time Labview programs interfacing with the hardware through a PXI box (National Instruments).

The monkeys were monitored throughout the experiment via an infrared camera and light-source, positioned behind the monkeys so that the infrared light source was not in their field of view.

Experimental paradigms
Monkeys were trained to perform a delayed-memory saccade task for a liquid reward. This task requires the monkey to look to the remembered location of a flashed target only when instructed (Fig. 1 A).