Investigating the effects of arousal state on cognitive performance in individuals with and without mild head injury

We examined the cognitive and emotional sequelae following mild head injury (MHI; e.g., concussion) in high-functioning individuals and whether persons with MHI pre~ent, both physiologically and via self-report, in a manner different from (i.e., underaroused) that of persons who have no history of head injury. We also investigated the effect arousal state ~as on the cognitive performance of this population. Using a quasiexperimental research design (N = 91), we examined changes in attention, working memory, and cognitive flexibility (subtests ofthe WAIS-III, 1997,WMS-III, 1997, & DKEFS, 2002) as a function of manipulated arousal (i.e., induced psychosocial stress/activation; reduced activation/relaxation). In addition to self-reported arousal and state anxiety (State-Trait Anxiety Inventory; Speilberger, 1983a) measures, physiological indices of arousal state (i.e., electrodermal responsivity, heart rate, and respiration activity) were recorded (via Polygraph Professional Suite, 2008) across a 2.5 hour interval while completing various cognitive tasks. Students also completed the Post-concussive Symptom Checklist (Gouvier et aI., 1992). The results demonstrate that university students who report a history ofMHI (i.e., "altered state of consciousness") experience significantly lower levels of anxiety, were physiologically underaroused, and were less responsive to stressors in their environment, compared to their non-~HI cohorts. As expected, cognitive flexibility (but not other neuropsychological measures of cognition) was advantaged with increased stress, and disadvantaged with reduced stress, in persons with reported MHI, but not for those without reported MHI which provided limited support for our hypothesis. Further, university students who had no complaints related to their previous MHI endorsed a greater number of traditional post-concussive symptoms in terms of intensity, duration and frequency as compared to students who did not report a MHI. The underarousal in traumatic brain injury has been associated with (ventromedial prefrontal cortex) VMPFC disruption and may be implicated in MHI generally. Students who report sustaining a previous MHI may be less able to physiologically respond and/or cognitively appraise, stressful experiences as compared to their no-MHI cohort and experience persistent, long-lasting consequences despite the subtle nature of a history of head injury.

Interaction between stress and immunity during a week leading to competition in young athletes

This study examined changes in the salivary concentrations of immunoglobulin A (sIgA), cortisol (sC), testosterone (sT) and testosterone-to-cortisol ratio (T/C) in 23 competitive swimmers, 11-15 years old, during a week leading to competition as compared to a control (non-competitive) week. Results showed no effect of week or day, and no significant week-by-day interaction for sIgA, sC and T/C. In contrast, sT significantly decreased during the week of competition, along with a 7%, non-significant decrease in the weekly T/C. The latter suggests that the swimmers were in a catabolic state due to their training, but this did not have a negative effect on their performance Since sC did not change over the two weeks and according to the sport anxiety scale, competition stress was relatively low in these peri-pubertal athletes, it is concluded that in the absence of high cortisol levels mucosal immunity is unaffected in young athletes prior to competition.