The Persistent Influence of Concussive Injuries on Cognitive Control and Neuroelectric Function

Context: Increasing attention is being paid to the deleterious effects of sport-related concussion on cognitive and brain health. Objective: To evaluate the influence of concussion incurred during early life on the cognitive control and neuroelectric function of young adults. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: Forty young adults were separated into groups according to concussive history (0 or 1+). Participants incurred all injuries during sport and recreation before the age of 18 years and were an average of 7.1 ± 4.0 years from injury at the time of the study. Intervention(s): All participants completed a 3-stimulus oddball task, a numeric switch task, and a modified flanker task during which event-related potentials and behavioral measures were collected. Main Outcome Measure(s): Reaction time, response accuracy, and electroencephalographic activity. Results: Compared with control participants, the concussion group exhibited decreased P3 amplitude during target detection within the oddball task and during the heterogeneous condition of the switch task. The concussion group also displayed increased N2 amplitude during the heterogeneous version of the switch task. Concussion history was associated with response accuracy during the flanker task. Conclusions: People with a history of concussion may demonstrate persistent decrements in neurocognitive function, as evidenced by decreased response accuracy, deficits in the allocation of attentional resources, and increased stimulus-response conflict during tasks requiring variable amounts of cognitive control. Neuroelectric measures of cognitive control may be uniquely sensitive to the persistent and selective decrements of concussion.

Nicotine Deprivation Effects on the Dissociated Components of Simple Reaction Time

The effect of smoking abstinence on the dissociated components of a simple reaction-time response was investigated. 7 subjects completed two experimental sessions conducted one week apart. Each experimental session was comprised of two tests. The first test consisted of abstinent baseline measures, while the second test was administered after smoking either an investigator-supplied nicotinised or denicotinised cigarette. A within-subjects design was utilized which permitted each subject to be their own control. Interestingly, the smoking of either experimenter-controlled cigarette (nicotinised or denicotinised) reliably decreased the subjects' desire to smoke. More importantly, however, was that only the nicotinised cigarette had any influence on simple reaction time. Moreover, this decrease in reaction time was isolated within the premotor or cognitive processes. In fact, there was no evidence that the smoking of a nicotinised cigarette had any effect on the motor-time component of this task. These findings are relevant for two reasons, (1) performance decrements due to smoking abstinence were independent of the urge or craving to smoke and (2) nicotine affects cognitive and motor processes of a simple reaction-time task differently.

Conditioning Reaction Time: Evidence for a Process of Conditioned Automatization

The classical conditioning of the standard, simple reaction time (RT) in 140 college men and women is described. Consequent to an anticipatory instructed conditioning procedure, two experimental and two control groups acquired voluntary, controlled US(light)-URTR (unconditioned reaction-time response) associations which then served as the foundation for subsequent classical conditioning when a novel CS (auditory click) was simultaneously paired with the US. Conditioned reaction-time responses (CRTRs) occurred significantly more often during test trials in the two experimental groups than in the two control groups. Statistical and introspective findings support the notion that observed CRTRs may be products of cognitively unconscious conditioned automatization whereby the conditioning of relatively slow, voluntary, and controlled US-URTR associations leads to the acquisition of relatively fast, involuntary, and automatic CS-CRTR associations.

Reaction Time, Response Errors, and G

Humphreys (1989) hypothesized that psychometric g is more highly correlated with the number of response errors on elementary cognitive tasks than with the reaction time (RT) measures themselves. Although Humphreys' hypothesis may well hold for relatively complex RT tasks, results of a recent study do not substantiate his hypothesis with regard to some of the simplest tasks. In this study, the average correlation ( r) between g and number of response errors was .05, compared to -.20 for median RT and -.23 for intraindividual differences in RT (measured as the standard deviation of RTs over trials). Even after correction for attenuation, the average r between g and errors is lower (.02) than the average correlations between g and the RT measures.