My co-workers and I are interested in the neural mechanisms and computational principles used by the brain to generate accurate movements in three-dimensional space, from sensation to cognition to behaviour. We focus on the following scientific questions: How do we represent and remember the spatial locations of things that we have seen? How are these sensory signals about target location in external space converted into patterns of muscle activity (in body space)? When there are many different ways to perform a movement, how and why do we choose the one that we do? How does the brain control the direction of movements? How does it hold final position after a movement? How are movements of two or more body segments properly coordinated?
We have had considerable success answering these questions for eye movements, and have now turned our attention to coordinated eye + head gaze shifts, and eye-hand coordination. Our approach is based on the following sequence of methods:
Theory. Our field has been strongly influenced by concepts from engineering. As a result, we express our hypotheses and ideas in rigorous mathematical models of neural control systems. These models allow us to simulate predicted behaviours using computers.
Behaviour. In order to understand the brain, it is critical to understand the behaviours that it generates. To test our theoretical models we measure the three-dimensional axes of rotation of the eye, head, and joints in humans during various behavioral paradigms. We are one of a very few labs in the world capable of this technology.
Neurophysiology. Some critical questions (especially those relevent to medicine and health) cannot be answered by theory or observation - they can only be answered by examining the brain itself. Therefore, we also directly study the neural mechanisms for these visual-motor behaviours using fMRI, single-unit recording, microstimulation, and pharmacological injection.
Although students may focus on any one of these areas, they are encouraged to gain exposure to all three. It is the vital interplay between these approaches that promotes an exciting and cooperative research environment.
Crawford, J.D., Ceylan, M.Z., Klier, E.M. and Guitton, D. (1999) Three-dimensional eye-head coordination during gaze saccades in the primate. The Journal of Neurophysiology, 81: 1760-1782.
Klier, E.M. and Crawford, J.D. (1998) The human oculomotor system accounts for 3-D eye orientation in the visual-motor transformation for saccades. The Journal of Neurophysiology, 80: 2274-2294.
Henriques, D.Y.P., Klier, E.M, Smith, M.A., Lowy, D, and Crawford, J.D. (1998) Gaze centered remapping of remembered visual space in an open-loop pointing task. The Journal of Neuroscience, 18: 1583-1594.
Neurophysiology, animal biology and physiology