Research Interests
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My research interests predominantly focus on the cortical control of movement in neurologically intact people and in individuals with movement disorders. Research projects generally fall into three categories: basic neurophysiology of the intact nervous system; evaluation of alterations in neurophysiological function in individuals with movement disorders due to neurological deficit; and research involving rehabilitation strategies designed to enhance motor performance.
Influence of afferent input on motor output
My previous research projects have used transcranial magnetic stimulation (TMS) to examine alterations in motor cortex excitability induced by afferent sensory input. I am interested in the applications of this to investigate bradykinesia and altered proprioceptive function in individuals with Parkinson's disease, as well as cortical reorganization induced by passive movement therapies in people with stroke.
Application of bilateral activation strategies in individuals post-stroke
A relatively new rehabilitation strategy to enhance function of the impaired limb in people with stroke is the use of bilateral training therapies. This project will examine the behavioral effects of bilateral upper limb training, and will also use various structural and functional imaging techniques to investigate the associated neurological mechanisms. The role of cortical projections from the intact hemisphere in the stroke recovery process will also be examined.
Stretch reflex response characteristics
A series of investigations is being conducted to more clearly define the pathways and receptors mediating the components of the stretch reflex response in various upper limb joints. As well as evaluating the effect of perturbation characteristics and task instruction on the reflex responses, contributions from cortical and multi-segmental spinal pathways are also being investigated. Alterations in these responses will also be examined in individuals with cortical and sub-cortical neurological deficits, such as Parkinson's disease and stroke.
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Selected Publications
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Lewis, GN, Byblow, WD. 2004. The effects of repetitive proprioceptive stimulation on corticomotor representation in intact and hemiplegic individuals. Clinical Neurophysiology. In press.
Byblow, WD, Lewis, GN, Stinear, JW, Carson RG. 2004. The modulation of excitability in corticospinal pathways during rhythmic movement. In Swinnen, S & Duysens, J (Eds.), Interlimb Coordination. Kluwer Academic Publishers.
Lewis, GN, Polych , MA , Byblow, WD. 2004. Proposed cortical and sub-cortical contributions to the long-latency stretch reflex in the forearm. Experimental Brain Research. In press.
Lewis, GN, Byblow, WD. 2004. Bimanual coordination dynamics in post-stroke hemiparetics. Journal of Motor Behavior. In press.
Lewis, GN, Byblow, WD. 2002. Altered sensorimotor integration in Parkinson's disease. Brain, 125: 2089-2099.
Lewis, GN, Byblow, WD, Carson, RG. 2001. Phasic modulation of corticomotor excitability during passive movement of the upper limb: effects of movement frequency and muscle specificity. Brain Research, 900 (2): 282-294
Lewis, GN, Byblow, WD, Walt, SE. 2000. Stride length regulation in Parkinson's disease: the use of extrinsic visual cues. Brain, 123 (10): 2077-2090.
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