Autonomic and neural correlates of dysregulated arousal in severe traumatic brain injury.

Severe traumatic brain injury (TBI) in adults is associated with abnormalities in arousal and emotional responsivity, which are observed physiologically, behaviourally and via self-report measures. While an accurate measure of physiological arousal is debated, Barry et al. (2005, 2007, 2008) have consistently shown an inverse relationship between skin conductance level (SCL), and mean alpha power (alpha) during an eyes-closed resting condition (EC), accompanied by an increase in SCL and corresponding decrease in alpha during eyes-open (EO). Thus, alpha may provide a novel index of autonomic arousal. This study aimed to elucidate the neural and autonomic correlates of arousal disturbances in TBI. Participants were 17 adults with TBI (13 males; mean age 46.50) and 22 matched controls (14 males; mean age 41.25). Mean alpha and SCL were recorded across two 2 minute conditions (EC and EO). Paralleling previous research (e.g., Barry et al., 2007), a significant decrease in alpha was found from EC to EO for the sample overall, but this was significantly reduced in TBI participants. Further, TBI participants showed diminished regional differences compared to controls. Lower SCLs across EC-EO were also found in TBI participants compared to controls. Contrasting expectations, an increase in SCL from EC to EO was not found. This study showed that examining simple alpha changes provides insight into TBI-related arousal disturbances. Importantly, our findings accord with the nature of TBI, which involves global and region-specific damage.