Upper extremity impairments are extremely disabling for individuals with chronic stroke. A specific impairment that is often overlooked is associated reactions, which refers to involuntary activity in one limb in response to voluntary movement in another. Associated reactions can greatly interfere with activities of daily life, and impair balance reactions during gait. Unfortunately, rehabilitative efforts rarely address associated reactions, which may even be exacerbated by the current high-intensity exercise trend in rehabilitation. This proposal seeks to understand the underlying neural mechanisms of associated reactions, which can lead to more targeted interventions in the future that reduce their presence. We hypothesize that associated reactions are due to an increased reliance on brainstem pathways following stroke-induced damage to the corticospinal tracts. The brainstem pathways branch extensively at the spinal cord, causing stereotypical muscle co-activations in flexion or extension patterns, preventing an individual from performing isolated movement at a single joint. We will first seek to characterize if associated reactions in the upper extremity elicited from a lower extremity effort follow previously described patterns of brainstem-driven muscle co-activation and movement patterns by measuring EMG activity and kinematics. Next, we will determine the influence of lower extremity efforts on volitional upper extremity reaching movements to determine if individuals have the neural resources available to overcome the associated reactions. Lastly, we will use diffusion tensor imaging to determine the extent of damage to corticospinal tracts, and correlate this with measures of associated reactions. This will allow us to link changes in brain morphometry with quantitative engineering measures of motor behavior, which will not only explain neural mechanisms, but can be developed into a powerful prognostic tool of motor impairments as well. Through the aims of this project, we will elucidate the underlying neural mechanisms responsible for associated reactions, allowing rehabilitative efforts to be more targeted and effective.
|Effective start/end date||1/1/15 → 12/31/16|
- American Heart Association Midwest Affiliate (15PRE22990027)
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