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Objective: Cognitive recovery from sports concussion may be incomplete after resolution of other symptoms. It was hypothesized that independent effects of the number of days since last concussion (Days) and total number of concussions (Number) would predict poorer cognitive functioning. Methods and procedures: Cognition was assessed in an NCAA Division I student-athlete population ( n = 87) using the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) battery. In a MANOVA, the five ImPACT Composite scores were dependent variables, with Group (Concussion, Unaffected) as the independent variable and prior number of concussions (Number) and days since last concussion (Days; 68-2495 days) entered as covariates. Outcomes and results: The hypothesis that Days and Number would each independently affect cognitive functioning (as assessed by ImPACT Composite scores) was only partly supported. A significant, multivariate, main effect of Days ( p = 0.01) indicated that more Days predicted better cognitive functioning overall ( p = 0.01). Univariate effects emerged such that more Days specifically predicted better visual memory ( p = 0.004) and faster reaction times ( p = 0.02). A trend toward a Group*Days*Number three-way interaction for reaction time emerged ( p = 0.06), such that smaller Number and more Days each predicted slower reaction time. Conclusions: Cognitive recovery following sports concussion may take far longer than was previously thought, the aetiology of cognitive reductions may be very complex and the ImPACT appears to be sensitive to subtle changes in cognition across time. [ABSTRACT FROM AUTHOR]

Two studies were conducted to assess the impact of methylphenidate on normal young adults in a fixed version of Sternberg's memory scanning task. Both studies yielded characteristic monotonic increases in reaction time (RT) and P3b latency as a function of memory load. Also, in both studies, methylphenidate speeded up RTs and decreased error rates and intrasubject RT variability. However, the slope of RT as a function of memory load, i.e. the rate of memory search, was not altered by the stimulant. In Study 1, P3b latency also was not affected by methylphenidate, a result suggesting that the stimulant brought about the decrease in RT by acting after the completion of evaluation, presumably by accelerating response processes. However, in Study 2, the drug significantly shortened P3b latency and the interval between RT and P3b latency. Thus, a speeding both evaluation as well as motor processes was achieved. A review of procedural differences between the two studies suggests some possible explanations. In combination, the two studies indicate that methylphenidate consistently shortened the timing of motor processes and, under some circumstances, the duration of evaluation processes as well. [ABSTRACT FROM AUTHOR]