Neural Control of Posture in Individuals with Persisting Postconcussion Symptoms

INTRODUCTION Postural instability has been shown to characterize individuals who suffered from long-term symptoms after mild traumatic brain injury (mTBI). However, recordings of neural processes during postural control are difficult to realize with standard neuroimaging techniques. Thus, we used functional NearInfraRed Spectroscopy (fNIRS) to investigate brain oxygenation of individuals with persistent post-concussion symptoms (pPCS) during postural control in altered environments. METHODS We compared brain oxygenation and postural sway during balance control in three groups: individuals suffering from pPCS, individuals with a history of mTBI but without pPCS, and healthy controls. Individuals were investigated during postural control tasks with 6 different conditions: (i) eyes opened, (ii) eyes closed, and (iii) blurred visual input, each while standing (a) on a stable and (b) an unstable surface. RESULTS In all groups, during the eyes closed / unstable surface condition as compared to the other conditions, the postural sway increased as well as the brain oxygenation in frontal brain cortices. In the most difficult balance condition, as compared to the other two groups, subjects with pPCS applied more force over time to keep balance as measured by the force plate system with a significantly greater activation in frontopolar / orbitofrontal areas of the right hemisphere. CONCLUSIONS As subjects with pPCS applied more force over time to control balance, we propose that with regards to cognitive processes the increase of cerebral activation in these individuals indicates an increase of attention-demanding processes during postural control in altered environments.