Brian D. Corneil
Associate Professor
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(Joint Appointment with Psychology) |
Accurate movements in the real world involve remarkably complex sensory and motor processing. Sensory signals relaying the position of a goal in the external world must be integrated with the body's current configuration to produce an accurate high-level motor command. This motor command must then be decomposed into the appropriate muscular commands to move various body segments in a coordinated fashion. The major goal of my research is to gain insights into how the brain accomplishes these feats in such a seemingly effortless way. Our model system to approach this question are gaze shifts, which are rapid and coordinated movements of the eyes and head. A common example of a gaze shift occurs when drivers look over their shoulders to check their blind spot. Like many movements, gaze shifts can be flexibly altered depending on various cognitive demands. The exact same gaze shift can be generated using just the eyes, by pairing eye movement with a large head movement, or any combination of eye-head coordination in between. The key hypothesis of my work is that the brainstem oculomotor structures are endowed with two thresholds: a gaze threshold that is surpassed only when a commitment to a gaze shift is made, and a lower head threshold that can drive the head without gaze shifts prior to this commitment. Inputs from higher cortical centres achieve flexible eye-head coupling by manipulating levels of brainstem activity relative to these differential thresholds. Another aspect of eye-head gaze control is that knowledge of the current position of the head relative to the body is a prerequisite for accurate movement. Given the major sense organs in the head (e.g., eyes, ears, vestibular organs), sensory information from neck muscles that uniquely relates head-on-body position is required for many movements. My work also investigates how such sensory information is incorporated into the neural control of eye-head gaze shifts at various oculomotor centers throughout the neuraxis.
Corneil, B.D., Elsley, J.K. (2005) Countermanding Eye-Head Gaze Shifts in Humans: Marching orders are delivered to the head first. J Neurophysiol Articles in Press. Musallam, S., Corneil, B.D., Greger, B., Scherberger, H., Andersen, R.A. (2004) Cognitive control signals for neural prosthetics. Science Corneil, B.D., Olivier, E., Munoz, D.P. (2004) Visual responses on neck muscles reveal selective gating that prevents express saccades. Neuron 42(5): 831-841.305(5681): 258-262 Corneil, B.D., Andersen, R.A. (2004) Dorsal neck muscle vibration induces upward shifts in the endpoints of memory-guided saccades in monkeys. J Neurophysiol 92: 553-566. Corneil, B.D., Olivier, E., Munoz, D.P. (2002) Neck muscle responses to stimulation of monkey superior colliculus. I. Topography and manipulation of stimulation parameters. J. Neurophysiol. 88:1980-1999.
