Trisha Kesar, PT, Ph.D.
Division of Physical Therapy
Department of Rehabilitation Medicine
Emory University School of Medicine
Most stroke survivors have persistent mobility deficits that reduce community participation and quality of life. A complex array of direct and indirect connections between cortical and spinal circuits play important roles in motor control and post-stroke motor recovery. However, circuit dysfunctions underlying post-stroke impairments remain poorly understood, limiting the development of neurobiology-informed therapies. Our long-term goal is to identify key neuromotor control circuits that can be facilitated using pharmacological, regenerative, or behavioral treatments to improve walking function in stroke survivors. Ongoing studies in our lab are conducting the first comprehensive characterization of the physiology and behavioral correlates of direct and indirect descending motor pathway activity in individuals with post-stroke mobility deficits. The lateral corticospinal tract (CST) and a parallel system comprising non-CST pathways that travels indirectly (e.g. cortico-reticulo-spinal system) are both crucial for normal motor control. A cortical or sub-cortical stroke lesion can disrupt both CST and non-CST descending pathways, causing motor control impairments. Transcranial magnetic stimulation (TMS) and Hoffman reflexes have been previously used to probe corticospinal and spinal reflex circuits. However, in isolation, neither TMS nor PNS can specifically quantify activity in descending projections that modulate LMN excitability, the final common output for motor control. Short-latency facilitation (SLF) and long-latency facilitation (LLF) are neurophysiologic techniques, wherein pairing of subthreshold TMS of M1 with PNS measures the excitability of direct, fast-conducting and indirect, slower descending projections onto spinal LMNs. In this seminar, I will present preliminary results related to the use of SLF and LLF as novel indices to parse out activity in two descending systems important for post-stroke motor control.
Host: Richard Nichols, Ph.D.