Impact of cognitive exertion on autonomic reactivity in individuals with persistent post-concussive symptoms
R. Davis Moore1, Adam Harrison1, Steven Broglio2, Troy Herter3
1University of South Carolina, 2NeuroTrauma Research Laboratory, 3Universty of South Carolina
Objective:
Examine the impact of cognitive exertion on autonomic reactivity in symptomatic and asymptomatic individuals with history of concussion and controls without history of concussion.
Background:
Following concussive head injuries, many individuals continue to experience physical, cognitive, and emotional symptoms that can persist for months or years. Recent studies suggest that concussive head injuries can also produce persistent dysfunction of the autonomic nervous system. However, it remains unclear if acute bouts of cognitive exertion moderate autonomic dysfunction in individuals with persistent post-concussion symptoms.
Design/Methods:
A cross-sectional design was used to investigate autonomic reactivity in 23 individuals without history of concussion (HC-) and 35 individuals with history of concussion, including 20 symptomatic (HCx-S) and 15 asymptomatic (HCx-A). Participants were classified based on clinical history and symptom reports obtained from a comprehensive questionnaire of their medical history and the Rivermead Post-Concussion Questionnaire (RPQ). Participants initially completed a seated, six-minute resting assessment with eyes open in the dimly lit room. They then completed a continuous reaching variant of the traditional Go/NoGo task. Continuous electrocardiography was recorded and utilized to compute time-domain metrics of heart rate variability (HRV) during the resting assessment and cognitive task.
Results:
HCx-S participants reported greater symptom burden on the RPQ and performed significantly worse on the Go/NoGo task compared to HC- and HCx-A participants. While HRV metrics failed to reveal any significant differences between HCx-S, HCx-A, and HC- participants during resting assessment (p’s > 0.8), HCx-S participants exhibited significantly greater HRV than HCx-A and HC- participants during the Go/NoGo task (p’s < 0.03).
Conclusions:
Increased HRV in HCx-S participants compared to HC- and HCx-A participants during the Go/NoGo task indicates that concussion may induce greater autonomic reactivity, characterized by higher levels of vagal/parasympathetic tone. This may reflect impairments in the capacity of the autonomic nervous system to efficiently adapt to situational demands.