Grant: CIHR Fellowship

Movement related deficits after stroke are extremely common. It has been shown that deficits are related to an imbalance between the stroke affected and non-affected sides of the brain. Past research has focused on the possibility that hyperexcitability of the non-affected motor cortex furthers movement related disability after stroke. Constraining the unaffected limb has been associated with functional recovery of the affected limb, perhaps by reducing this imbalance. However, the mechanisms associated with these changes is unknown. Recently, studies mimicking constraint of the unaffected limb by numbing the non-affected hand, either by restricting blood flow or application of a local anesthetic, show transient increases in motor ability in the affected hand. While numbing reduces movement of the affected limb it also reduces the amount of sensory information arriving at the brain from the non-affected limb. It is likely that this reduction in sensory information changes the interaction between the two hemispheres via connections between the sensory and motor cortices that are essential for accurate movements, yet very little research has investigated the role of the non-affected sensory cortex. The purpose of the proposed research is to investigate how changes in non-affected sensory cortex influence sensorimotor processing in the affected cortex and whether these changes can be consolidated with motor learning. In contrast to past work, we will alter sensory processing in the non-affected cortex at the level of the brain using transcranial magnetic stimulation rather than in the periphery by numbing the hand. Importantly, understanding whether improved motor ability following sensory disruption in the non-affected hemisphere is mediated at the level of sensory cortex will allow rehabilitation interventions for individuals with stroke to be refined and improved. Our findings may offer a novel method with which to stimulate motor recovery after stroke.