Plasticity of sensorimotor behaviour

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The long term objective of my research program is to understand the neurological basis for behavioural plasticity in vertebrates. The short term objective of my research program is to determine how manipulation of sensory and supraspinal inputs to the spinal cord alter locomotor limb function and the strength of intact spinal pathways in rats. Spinal plasticity, in the form of strengthening of brainstem-spinal connections, underlies the recovery of breathing movements after unilateral spinal transection (hemisection) in the neck (cervical) region. This strengthening is enhanced by removal of sensory input to the spinal cord (spinal sensory denervation, SSD). The effects of SSD on behaviour other than breathing have not been quantified, although this would provide valuable insight into the plastic capabilities of spinal circuitry. My laboratory is well suited to address this problem because we can quantitatively assess sensorimotor, including locomotor, abilities in rats. In particular, we measure ground reaction forces (GRF), a novel and sensitive method for assessing overground locomotion in rats. We propose to investigate whether SSD alters locomotor limb function after hemisection and whether this is accompanied by altered strength in locomotor brainstem-spinal connections.  Specifically, AIM 1 tests the hypothesis that SSD improves forelimb locomotor function after cervical hemisection. We will measure forelimb function using GRF and kinematic analysis during 2 different locomotor tasks in groups of hemisected rats with and without SSD. AIM 2 tests the hypothesis that the effect of SSD is generalizable to other regions of the spinal cord, by applying the above approach to the thoracic spinal cord and measuring hindlimb function. Finally, AIM 3 tests the hypothesis that SSD increases the strength of brainstem connections to limb motoneurons after spinal hemisection. This will be accomplished by recording the amplitude of electrical signals in fore- and hindlimb motor nerves evoked by stimulation of brainstem pathways in hemisected rats with and without SSD. These experiments will provide important information regarding the potential of neural circuitry throughout the spinal cord to facilitate changes in motor behaviour.