Gaze Control Lab

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Research

The overall goal of our research is to understand how the brain produces accurate and coordinated movements. Since humans and other primates are primarily visual animals, they require a refined oculomotor system to rapidly change the line of sight (gaze shifts). The oculomotor system remains one of the best understood motor systems in humans. Small gaze shifts are carried out via saccadic eye movements, while larger gaze shifts require coordinated movements of the eyes and head.


To better understand the natural capabilities of the oculomotor system, we consider both the neuromuscular control of the eyes and head. Because the head is a heavy and complex structure, we record neck muscle activity via electromyography (EMG). Neck EMG signals enable excellent insights into the underlying neural control on a millisecond timescale, and provide a signal that can be recorded and compared in human and non-human primates.


Current projects

1. Neural control of orienting. A recurring theme in our research is that orienting head movements are not as tightly controlled as saccades. Even though the head usually moves after the start of a saccadic gaze shift, neck EMG recordings show that the brain recruits neck muscles much earlier. These timing differences arise because of brainstem circuits which allow the brain to “hedge its bets” by initiating neck muscle recruitment while still deciding on whether to commit to a gaze shift. A number of projects in human and non-human primates combine neck EMG recordings with neurophysiological approaches (e.g., recording or stimulation) to investigate how the oculomotor cortex and brainstem control eye-head gaze shifts. Recent work has also expanded this line of thinking into pupillometry.

Representative publications:

Lehmann, S.J. and Corneil, B.D. (2016) Transient pupil dilation after sub-saccadic microstimulation of primate Frontal Eye Fields J Neurosci 36: 3765-3776. Lehmann_and_Corneil_2016.pdf


Corneil, B.D., Munoz, D.P. (2014) Overt responses during covert orienting. Neuron 82: 1230-1243 Corneil_and_Munoz_2014.pdf



2. EMG recordings for cognitive neuroscience. Our understanding of the neural control of eye-head gaze shifts has implications for cognitive neuroscience. Since the head is not subjected to the same timing constraints as the eye, close assessment of neck muscle activity may provide a direct and objective measure of developing oculomotor activity, independent of gaze shifts. This idea is readily transferable to human, suggesting that recordings of neck muscle activity in humans may provide a quantifiable measure of the oculomotor activity on a millisecond basis. Recent work has also expanded this line of thinking into the control of upper limb movements.


Representative publications:

Atsma J, Maij F, Gu C, Medendorp WP, Corneil BD (2018) Active braking of whole-arm reaching movements provides single-trial neuromuscular measures of movement cancellation J Neurosci 38: 4367-4382. Atsma_et_al_2018.pdf


Gu G, Wood DK, Gribble PL, Corneil BD (2016) A trial-by-trial window into sensorimotor transformations in the human motor periphery. J Neurosci 36: 8273-8282. Gu_et_al_2016.pdf


Corneil BD, Munoz DP, Chapman BB, Admans T, Cushing SL (2008) Neuromuscular consequences of reflexive covert orienting. Nat. Neurosci. 11(1): 13-15. Corneil_et_al_2008.pdf


3. Effects of inactivation on the oculomotor network. The oculomotor system is composed of numerous interconnected areas spanning the cortex and brainstem. Another direction of research in our lab investigates how temporarily inactivating one node of the network influences the activity of other areas. Current projects are inactivating the frontal eye fields via cryogenic techniques or TMS, and investigating the effect on activity within the superior colliculus.


Representative publications:

Peel TR, Dash S, Lomber SG, Corneil BD (2017) Frontal eye field inactivation diminishes superior colliculus activity, but delayed saccadic accumulation governs reaction time increases. J Neurosci 37: 11715-11730. Peel_et_al_2017.pdf


Peel TR, Hafed ZM, Dash S, Lomber SG, Corneil BD (2016) A causal role for the cortical frontal eye fields in microsaccade generation. PLOS Biol 14(8): e1002532. Peel_et_al_2016.pdf


4. An animal model of TMS. Transcranial magnetic stimulation (TMS) provides a non-invasive way of stimulating the human brain. Although widely used as a tool in basic research, and thought to have some clinical potential, little is known on how exactly TMS effects neural activity, and how such an effect influences behaviour. Motivated by our findings on neck EMGs above, we are now combining TMS with neurophysiological recordings throughout the oculomotor system. The availability of an animal model will potentiate development of more efficacious stimulation parameters, perhaps in combination with pharmacological therapies, without exposing humans to risk.


Representative publications:

Gu C and Corneil BD (2014) Transcranial magnetic stimulation of the prefrontal cortex in awake nonhuman primates evokes a polysynaptic neck muscle response that reflects oculomotor activity at the time of stimulation J. Neurosci. 34: 14803-14815. Gu_and_Corneil_2014.pdf


Goonetilleke SG, Gribble PL, Mirsattari SM, Doherty TJ, Corneil BD (2011) Neck muscle responses evoked by transcranial magnetic stimulation of the human frontal eye fields Eur. J. Neurosci. 33: 2155-2167. Goonetilleke_et_al_2011.pdf


Techniques

We employ a variety of advanced neurophysiological and behavioural techniques in both humans and non-human primates, including extracellular recording and microstimulation, cryogenic inactivation, TMS, pupillometry, and the recording of neck muscle activity via electromyography. These techniques are frequently combined to give additional insights into our experimental questions.


Facilities

Our facilities include 2 state-of-the-art animal neurophysiological laboratories, and 1 human neurophysiological laboratory. They are housed within The Brain and Mind Institute at the Robarts Research Institute and the University of Western Ontario, close to a  3T and a 7T MRI. The Institute is recognized as one of the top international centres combining sophisticated imaging, neurophysiological, and psychophysical techniques.