The role of cognitive load on lateralized motor control processes

Project Summary/Abstract Upper limb physical rehabilitation post stroke tends to focus mainly on remediating deficits related to motor execution of the impaired arm. This approach can be problematic due to two major reasons: (1) efficient movement requires both intact cognition and motor execution, and (2) previous research shows that movement deficits depend on the side of brain damage; importantly, these deficits are present even in the “unimpaired”, ipsilesional arm. While there is a large body of evidence on the lateralization of motor control processes, research on lateralized cognitive processes is limited. Previous studies show that right brain damage produces larger deficits in cognitive processes, such as working memory and action selection, than left brain damage. Our preliminary studies examining hemisphere-specific deficits in motor execution demonstrate that ipsilesional arm movement planning deficits in individuals with left brain damage are highly correlated with functional independence. Surprisingly, this relationship was not found in individuals with right brain damage. Based on our preliminary studies and prior literature, we hypothesize that increased cognitive load produces functionally limiting deficits in the control of movement that differ based on the side of brain damage. We predict that with increased cognitive load, movement deficits will be larger with right than left brain damage. Additionally, we predict that functional independence will be correlated with cognitive deficits in right hemisphere damaged individuals and with motor execution deficits in left hemisphere damaged individuals. We will utilize a novel paradigm that integrates a cognitive challenge with an upper limb reaching task. This method provides a more real-world design for studying how cognitive load affects functional movement compared to dual-task paradigms that involve a cognitively-challenging task in parallel with the motor task. We will recruit 36 chronic stroke survivors with severe hemiparesis for our studies. They will each complete two tasks on a virtual reality motion tracking system, which are designed to assess deficits in ipsilesional arm motor execution and cognitive aspects of movement. We will also use standardized clinical assessments of ipsilesional arm function and functional independence. This proposal assembles an investigative team comprised of experts in cognitive neuroscience and stroke rehabilitation to accomplish the following aims: (1) To determine whether ipsilesional arm deficits in motor control are affected by cognitive load differently in left and right hemisphere damaged stroke survivors with severe contralesional paresis; (2) To determine whether deficits in ipsilesional arm motor execution and cognitive aspects of movement predict functional independence differently between left and right hemisphere damaged stroke survivors with severe contralesional paresis. The results of these studies will be used to develop personalized rehabilitation strategies that account for hemisphere-specific deficits in motor control, and will be particularly useful for severely impaired stroke survivors who depend exclusively on their ipsilesional arm to conduct activities of daily living.