Application Of Functional Near-Infrared Spectroscopy To Examine The Neurophysiology Of The Injured Adolescent Brain

Over 1.9 million children sustain a concussion in the US annually, with adolescents accounting for over 50% of these injuries. Common sequelae of concussion include neurocognitive deficits, which can negatively affect daily activities, and persist past symptom resolution, the primary method for gauging recovery. There are currently few methods for quantifying cognitive recovery after concussion in adolescents. Functional near-infrared spectroscopy (fNIRS) is a portable, optical, neuroimaging technology that can quantitatively assess cognitive deficits by measuring brain activation in the prefrontal cortex, a brain region implicated in cognition and undergoing rapid development in adolescence. fNIRS has been applied to adult populations; however, because of the variable rates of development, fNIRS findings in adults cannot be directly translated to adolescents. To quantify prefrontal cortical response in adolescence due to concussion or repetitive head acceleration event exposure (RHAEE) due to sport participation, three studies were undertaken. First, in a sample of uninjured high school soccer players, in which RHAEE was quantified over a season, fNIRS was used pre- and post-season to measure prefrontal cortical response during cognitive assessments. Adolescents with greater RHAEE displayed greater prefrontal cortical activation during the most cognitively complex portions of the assessments at post-season, compared to pre-season, indicating a reliance on aberrant neural networks after a season of RHAEE. This trend continued in the second study when, compared to uninjured youth, concussed adolescents displayed lower neural efficiency, a measure that contextualizes cortical activation with behavioral performance, during the dual motor-cognitive condition of a gait assessment, but not during simpler single-task conditions. Concussed adolescents also displayed less efficient motor unit recruitment during walking conditions compared to uninjured adolescents. Finally, in the third study during a validated simulated driving assessment, concussed adolescents displayed lower neural efficiency during certain distracted driving scenarios. Collectively, the studies suggest cognitive deficits in adolescents with greater RHAEE or a concussion can be identified via cortical activation and neural efficiency metrics from fNIRS and manifest during complex ecologically valid assessments that mimic real-world activities