The Effect of Mild Traumatic Brain Injury on Corticospinal Excitability During Complex Action Preparation

The long-term goal of this research is to understand the neural mechanisms underlying lingering functional movement deficits post-mild traumatic brain injury (mTBI) to design novel neurorehabilitation interventions for improving motor recovery and maximizing patient care. The overall objective of this pilot project is to investigate the neurophysiology of complex action preparation and its alterations after mTBI.

• Sponsor
  Medical University of South Carolina NC NM4R Pilot Project
  $37,500

• Principal investigator
  Deborah A. Barany
  Assistant professor
  Department of Kinesiology

• Co-principal investigators
  Robert C. Lynall
  Associate professor
  Department of Kinesiology

  Jing Xu
  Assistant professor
  Department of Kinesiology

• Active since
  July 2023

Abstract

Mild traumatic brain injury (mTBI) results from biomechanical forces to the head, often leading to persistent functional brain abnormalities in the absence of any structural damage. This incomplete neurobiological recovery may underlie long-term functional deficits, even when the patient is considered clinically asymptomatic or fully recovered. In particular, mTBI patients exhibit prolonged reaction times, especially for tasks requiring more complex and cognitively demanding action preparation. Given that these deficits are closely associated with an increased risk of future neurological or musculoskeletal injury, there is a critical need to identify the neurobiological mechanisms underlying complex action preparation as a first step toward enhanced rehabilitation recommendations or interventions to enhance functional recovery.

The long-term goal of this research is to understand the neural mechanisms underlying lingering functional movement deficits post-mTBI to design novel neurorehabilitation interventions for improving motor recovery and maximizing patient care. The overall objective of this pilot project is to investigate the neurophysiology of complex action preparation and its alterations after mTBI. To achieve this objective, transcranial magnetic stimulation (TMS) will be used to probe corticospinal excitability during the reaction time period while participants perform upper-limb obstacle-avoidance reaches with their right arm. In some blocks of trials, the reaches will require explicit planning of movement trajectories, which induces a significant reaction time cost.

Two cohorts will be tested on this task: (1) young healthy adults without a history of mTBI and (2) patients with a recent mTBI who are clinically asymptomatic. The central hypothesis is that the timecourse of corticospinal excitability will depend on planning of explicit movement trajectories and that corticospinal excitability for these complex movements will be altered in mTBI patients. The first aim is to test the hypothesis that changes in corticospinal excitability underlie reaction time differences for planning explicit movement trajectories. The pattern of changes observed will help distinguish whether trajectory planning representations lead to increased neural activity throughout the reaction time period or sharper neural tuning to support complex movement.

The second aim is to test the hypothesis that increased reaction time for complex tasks in mTBI is related to specific deficits in motor planning and corticospinal excitability. The preliminary data generated from this work will be used in a subsequent application that aims to link longterm neurophysiological changes and residual motor deficits post-mTBI, and test a novel timing-dependent neuromodulation intervention. This work is significant because it will help to clarify the functional relevance of corticospinal modulation for complex action preparation and inform novel rehabilitation approaches for improving functional motor outcomes after neurological injury.