Role of Prefrontal Cortex in Locomotor Learning

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 DESCRIPTION (provided by applicant): Gait function is a strong predictor of general health and quality of life in older adults and persons with movement disorders. However, our ability to restore healthy gait patterns through rehabilitation is limited by a lack of understanding about how the nervous system learns and stores new gait patterns. This proposal aims to advance our understanding of the brain structures that influence locomotor learning and investigate how activity in these structures can be manipulated with non-invasive stimulation to enhance learning. Specifically, we will focus on the prefrontal cortex and its role in strategic and adaptie locomotor learning. The prefrontal cortex has been implicated in cognitive function, gait modulation, and multiple mechanisms of motor learning (including strategic and adaptive learning). Here, we will investigate prefrontal contributions to locomotor learning and, importantly, whether we can manipulate prefrontal activity to enhance learning. Aim 1 examines how error size during adaptive locomotor learning affects the ability to explicitly recall a perturbation. We have observed that, during split-belt treadmill walking, abrupt adaptation leads to faster relearning (i.e., savings) while gradual adaptation does not. We think that savings might be absent following gradual adaptation because small errors provide little explicit information about the magnitude of the perturbation (i.e., difference between belt speeds). We also suspect that the abilities to detect a perturbation and determine whether it has been previously-experienced may be frontally-mediated, as persons with prefrontal lesions have difficulty detecting perturbations in upper extremity movements. Aim 2 investigates how excitatory (anodal) and inhibitory (cathodal) transcranial direct current stimulation (tDCS) of the prefrontal cortex affects explicit recall of a perturbation during adaptive locomotor learning and retention of what has been learned during strategic locomotor learning. This information could open a new avenue for gait rehabilitation by demonstrating that the prefrontal cortex can be stimulated with tDCS to enhance locomotor learning. In Aim 3, we study the effects of prefrontal tDCS on strategic locomotor learning in persons with cerebellar damage. Persons with cerebellar damage demonstrate adaptive motor learning impairments. Accordingly, alternative mechanisms are required to facilitate locomotor learning within this population. We will attempt to enhance strategic locomotor learning in persons with cerebellar damage using prefrontal tDCS. The goals of this proposal are to understand the role of the prefrontal cortex during adaptive and strategic locomotor learning and to investigate how to manipulate activity of the prefrontal cortex to enhance these learning mechanisms. The findings of this proposal could have a profound impact on gait rehabilitation by advancing the understanding of the neural mechanisms involved in locomotor learning and providing direct evidence that non-invasive brain stimulation can enhance strategic and adaptive locomotor learning.