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Projects
Neural control of eye-head gaze shifts
Eye-head gaze shifts serve as a model system for understanding multi-segmental motion, as they combine motion across multiple body segments. One of the lessons we have learned over the last couple of years is that the brain initiates head motion well before eye motion, even though the eye usually moves first due to the comparative biomechanics of the eyes and head. These timing differences attest to a brainstem circuit that basically allows the brain to "hedge its bets" by initiating a head movement while still decided on whether to initiate an eye movement. This research project utilizes neurophysiological experiments in non-human primates (examining the role of brainstem and cortical areas in eye- head control), and behavioural experiments in humans. Both projects rely on the recording of electromyographic (EMG) activity from neck muscles as a means of reliably measuring the timing and patterning of muscle recruitment.
Neck EMG recordings in Cognitive Neuroscience
Our neurophysiological results have demonstrated that the brain initiates head motion in advance of gaze shifts. A surprising implication of this result is that that activity recorded from neck muscles should be related to activity within the oculomotor system, well in advance of eye motion. A number of projects are on-going in both humans and animals to test this idea, assessing both neural activity (e.g., within the superior colliculus) and neck EMG activity during the performance of well-studied behavioural tasks that vary the allocation of attention, expectation or reward, or aspects of decision-making. If true, the recording of neck muscle activity could provide a neurophysiology-quality signal in humans that greatly exceeds the temporal resolution available in fMRI experiments.
Neural representations of initial position
Muscles are not only motor organs. Neck muscles in particular have a very high density of proprioceptive organs which relay a kinesthetic sense of head-on-body position. In this project, we are testing whether the sense of head-on-body position influences the representation of motor plans in oculomotor areas such as the superior colliculus. Our preliminary results to date demonstrate that changes in body-under-head position has a profound influence on SC motor plans, demonstrating that this signal carries both motor commands and representations of initial body configuration. It remains to be determined precisely how this information is used in specifying the contribution of the eyes and head to a given gaze shift.
Techniques Back to top
To address our experimental questions, we employ a variety of advanced neurophysiological and behavioural techniques. These include extracellular recording and microstimulation, which are frequently combined with chronic recording of EMG activity from up to a dozen neck muscles. These combinations of neurophysiological techniques provide unparalleled insight into the neural control of eye-head gaze shifts. The results from our neurophysiological experiments allow us to refine our human psychophysical experiments, permitting testing of advanced concepts of neural control of movement in both human and animal subjects via sophisticated behavioural paradigms.
Facilities Back to top
Dr. Corneil's laboratories are housed within The Centre for Brain and Mind, which was founded as an inter- disciplinary venture between the University of Western Ontario and Robarts Research Institute. The Centre is recognized as one of the top international laboratories for the combination of sophisticated imaging, neurophysiological, and psychophysical techniques. Dr. Corneil's facilities comprise 2 state-of-the-art neurophysiological laboratories, and 1 human psychophysical laboratory, which has recently been renovated and upgraded via a $320K New Opportunities Award from the Canadian Foundation for Innovation and Ontario Innovation Trust. The Corneil lab is part of the CIHR Group for Action and Perception.