High dimensional motor coding and motor dysfunction in rett syndrome

The National Institute of Neurological Disorders and Stroke (NINDS) awarded a $450,000 Project Grant under the Extramural Research Programs in the Neurosciences and Neurological Disorders (CFDA 93.853) to the University of Arkansas. The grant will fund research to better understand the neural mechanisms underlying healthy motor function and motor dysfunction in Rett syndrome, a neurological disorder. Specifically, the project will leverage high-dimensional geometry to investigate how disruption of the MECP2 gene affects population coding in the motor cortex and striatum, with the goal of identifying new treatment strategies. The research will be conducted by a team of three undergraduate students and one postdoctoral researcher, building on the success of the university's previous R15 grant in this area. The grant period runs from July 2024 through June 2027.

Abstract

The broad, long-term goals of the proposed research are to better understand the neural underpinnings of healthy motor function and motor dysfunction in rett syndrome and to promote undergraduate involvement in health-related research. Rett syndrome (RTT) is a neurological disorder, caused by disrupted function of the gene MECP2, typically resulting in severe cognitive and motor disability. What goes wrong in the motor signals sent from the brain to the body, leading to motor dysfunction in RTT, remains largely unknown. Based on our recent work in rodent models, together with the fact that seizures are prevalent in RTT, here we hypothesize that excessive synchrony among neurons in the motor system may disrupt motor coding by limiting the dimensionality of motor signals. The essential idea here is that extreme synchrony entails many neurons doing the same thing, which precludes the complexity of signals required for controlling complex body movements. A complete and quantitative understanding of this idea is best approached using the framework of high-dimensional geometry. In this framework, excessive synchrony causes a collapse of the motor coding subspace, which is likely to entangle signals and collapse the complexity of body movements. The proposed work has three promising potential outcomes. First, we leverage state-of-the-art ideas from high- dimensional geometry of population motor coding to advance RTT etiology. Second, we provide an important counter-example of what can go wrong when high-dimensional geometry is disrupted, thus advancing basic knowledge of motor systems neuroscience. Third, we will test new RTT treatment strategies with potential for future translation from lab to clinic. Our first specific aim is to determine how MECP2 dysfunction alters population coding in motor cortex and striatum. We hypothesize that excessive synchrony will result in reduced dimensionality of the population motor code, which manifests as motor dysfunction. Our second specific aim is to test two promising treatment strategies, one pharmacological, and one based on physical therapy. We hypothesize that these treatments will partially recover wild-type dimensionality of motor coding. To test these hypotheses, the proposed research would use high-density multi- electrode measurements to monitor the spiking activity of many single neurons in motor cortex and striatum of head-fixed mice as the animal runs on a computer controlled wheel. The research will be performed by a team of three undergraduate students and one postdoc. The proposed work would build upon the success of another recent R15 grant which resulted in a pnas publication including an undergraduate author.