• Grant Application - .pdf file

Abstract: DESCRIPTION (provided by applicant):
The long-term objective of the research program is to understand the neural integration of multiple motor systems. The oculomotor system has long served as a model for the study of neural control of movement. In the natural environment, however, an orienting response consists of multiple oculomotor and skeletomotor actions combined to form a complex yet coordinated movement. An integrated action ideal for scientific investigation is a coordinated eye-head movement because it builds on our advanced knowledge of the oculomotor system. The research also offers diagnostic value for spatial orientation deficits resulting from oculomotor, vestibular and cervical disorders. Recent experiments suggest that familiar oculomotor structures, such as the superior colliculus (SC) and pontomedullary reticular formation (PMRF), output a motor command to displace the line of sight (gaze shift) by a desired amplitude and direction. The gaze shift can be executed as a coordinated eye-head movement, implying that the outputs of these oculomotor structures also control premotor circuits that innervate the neck muscles. An association between neural discharge and extraocular motor neurons is demonstrated by recording activity during head-restrained saccades. In contrast, a relationship between spikes and neck motor neurons is only inferred by observing activity during coordinated eye-head movements. A direct evaluation of the activity with head movements has not been performed yet because, under ordinary circumstances, the eye and head components of the coordinated movement are temporally correlated. Hence, four specific aims are proposed to characterize activity and identify neurons associated with head movement control. Using behavioral tasks developed to temporally uncouple head movements from saccadic eye movements, SC neurons will be recorded for head movement related activity, both when no gaze shift is required (Specific Aim 1) and when a gaze shift is planned or being executed (Specific Aim 2). Similar manipulations will be employed to investigate the distribution of PMRF neurons that encode eye-only, head-only and coordinated eye-head movements (Specific Aim 3). Finally, anatomical techniques will be used to determine whether SC neurons send divergent axon collaterals or segregated projections to the eye and head control regions of PMRF (Specific Aim 4).

Thesaurus Terms:
eye movement, head movement, neuron, neuroregulation, reticular formation, superior colliculus
neurophysiology, saccade, vestibular apparatus, visual tracking
Macaca mulatta, behavior test, computer program /software, electrostimulus, laser, training

Institution: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
350 THACKERAY HALL
PITTSBURGH, PA 15260
Fiscal Year: 2006
Department: OTOLARYNGOLOGY
Project Start: 01-APR-2004
Project End: 31-MAR-2008
ICD: NATIONAL EYE INSTITUTE
IRG: CVP

J Neurophysiol 96: 2011-2024, 2006

Behavioral Evaluation of Movement Cancellation

Mark M. G. Walton¹ and Neeraj J. Gandhi<sup>1,2,3,4

1</sup>Departments of Otolaryngology, ²Neuroscience, ³Bioengineering, and ⁴Center for the Neural Basis of Cognition, University of Pittsburgh, Eye and Ear Institute, Pittsburgh, Pennsylvania

Submitted 15 December 2005; accepted in final form 23 May 2006

Surgical procedures
All experimental and surgical procedures were approved by the Institutional Animal Care and Use Committee at the University of Pittsburgh and complied with the guidelines of the Public Health Service Policy on Humane Care and Use of Laboratory Animals. Two rhesus monkeys (Macacca mulatta) underwent sterile surgery under isoflurane anesthesia for implantation of a Teflon-coated stainless steel coil for eye movement measurements using the magnetic search coil technique and an acrylic fixture on the skull to permit head restraint. These procedures have been described in detail previously (Gandhi and Bonadonna 2005 ).

Behavioral tasks
During experiments, the animals sat in a primate chair in a dimly lit room. Targets were presented on a light-emitting diode (LED) screen located 70 cm away from the animal. The LEDs were spaced at 2° intervals over a range of 96° horizontally and 80° vertically. Target presentation and data acquisition were controlled by custom software written in LabView RT (Bryant and Gandhi 2005 ). The vertical position of the eyelid was recorded (in arbitrary units) by taping a 5-mm diameter coil of Teflon-coated stainless steel wire to the outer surface of the lid. Care was taken to ensure that the coil and tape were placed such that they would not interfere with blinks or vision. The air-puff used to evoke blinks was monitored by a flow meter that was placed 10 cm away from the eye. Eye position, eyelid position, and air flow were sampled at 1 kHz.

Monkeys were trained to perform randomly interleaved visually guided target step and countermanding (or stop) saccade tasks for a liquid reward. In the target-step task (Fig. 1A), the monkey first fixated a red LED illuminated at the straight-ahead position.