Persistent adaptations in sensorimotor interneuron circuits in the motor cortex with a history of sport-related concussion

Abstract

Recent studies highlight a persistent increase in subsequent injury risk following a sport-related concussion (SRC) despite clinical recovery. However, markers of persistent alterations in sensorimotor integration have yet to be identified. One possibility is that compensatory adaptation following SRC may only be unmasked during transient periods of high task complexity in specific sensorimotor circuits. The current study used short-latency afferent inhibition (SAI) to investigate the long-term sequelae of sport-related concussion (SRC) in different short-latency sensorimotor circuits converging in the motor cortex. Specific sensorimotor circuits sensitive to posterior-anterior current with a positive phase lasting 120µs (PA₁₂₀) and anterior-posterior current with a positive phase lasting 30µs (AP₃₀) were assessed using controllable pulse parameter transcranial magnetic stimulation (cTMS) while young adults with and without a history of SRC were at rest or responded to valid and invalid sensorimotor cues. SAI was quantified as the ratio of the motor-evoked potential (MEP) elicited by peripherally conditioned cTMS stimuli to the unconditioned MEP for each cTMS configuration. Individuals with a SRC history demonstrated persistent adaptation in AP₃₀ SAI, but only in response to invalid cues. Persistent adaptation in AP₃₀ SAI was not apparent at rest or during simple sensorimotor transformations in response to valid cues. PA₁₂₀ SAI demonstrated similar responses at rest and in response to both valid and invalid cues, regardless of SRC history. AP₃₀-sensitive sensorimotor circuits may mark the long-term SRC sequelae and the increased susceptibility to momentary breakdowns in sensorimotor integration during periods of high cognitive-motor demands.

Keywords: Afferent inhibition; Cognitive-motor, transcranial magnetic stimulation (TMS); Concussion; Motor control; Sensorimotor integration.