Phasic electrodermal activity during the standardized assessment of concussion (SAC)

Context: The long-term effects of concussion on brain function during cognitive tasks are not fully understood and neuroimaging findings are equivocal. Some images show hyperactivation of prefrontal brain regions in previously concussed individuals relative to controls, suggesting increased cognitive resource allocation. Others show prefrontal hypoactivation and hyperactivation in other regions as a presumed compensatory mechanism. Given the relationship between sympathetic arousal and neural activation, physiologic measures of arousal, such as electrodermal activity, may provide additional insight into the brain's functional changes in those with a history of concussion. Objective: To quantify differences in electrodermal activity during a commonly used standardized neurocognitive assessment between individuals with or without a history of concussion. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: Seven asymptomatic individuals with a self-reported history of physician-diagnosed, sport-related concussion (number of previous concussions = 1.43 ± 0.53; time since most recent concussion = 0.75 to ± years, median = 3 years) and 10 individuals without a history of concussion participated in this study. Main Outcome Measure(s): All participants wore bilateral wrist electrodermal activity sensors during the Standardized Assessment of Concussion. We measured normalized phasic (reactive) electrodermal activity during each test element (orientation, immediate recall, concentration, delayed recall). Results: A significant group-by-test element interaction was present (P = .003). Individuals with a history of concussion had greater phasic activity during delayed recall (P < .001). Delayed-recall phasic activity was greater in both groups relative to the other elements. Conclusions: Delayed recall resulted in greater physiologic arousal in previously concussed individuals relative to healthy control participants, supporting previous neuroimaging findings of increased prefrontal cortex activity during memory tasks after concussion. Given similar task performance and arousal patterns across the test, our results suggest that previously concussed individuals incur additional cognitive demands in a short-delay recall task.