Effect of Repetitive, Subconcussive Impacts on Electrophysiological Measures of Attention.

OBJECTIVES: In this preliminary study, the auditory P3b response, when measured during a visually distracting task, was investigated as an index of change in cognitive function resulting from exposure to subconcussive impacts (SCIs) in collision sports over time. METHODS: Both pre- and postseason P3b responses were examined in seven first-year collegiate-level American football players. Comparisons were made between a group of seven third- and fourth-year players and a control group of seven noncontact athletes. RESULTS: No difference in P3b amplitude was revealed in pre- versus postseason data of the first-year players. Furthermore, no P3b amplitude differences were found when comparing first-year players with controls. P3b amplitudes of third- and fourth-year players versus first-year players were smaller along the midline electrode sites. CONCLUSIONS: Preliminary results suggest exposure to SCIs during the course of a season does not affect brain function negatively, as measured by the P3b response; however, differences between first-year players and the group of third- and fourth-year players suggest that exposure to hundreds of SCIs in multiple seasons leads to changes in brain activation patterns. Subtle effects such as difficulty with attentional resource allocation may develop. Longitudinal studies are necessary before definitive conclusions can be drawn.

Effects of complexity of visual distracters on attention and information processing speed reflected in auditory p300.

OBJECTIVES: The primary aim of this study was to assess the effects of continuous, visual distracters that change systematically in complexity on P300 responses generated by an auditory oddball paradigm. In addition, the type of attention given to the visual distracter was explored. It was hypothesized that P300 amplitudes would be smallest, latencies longest, and changes in scalp distribution greatest when the most complex visual distracter requiring active attention was used versus the simple visual distracter requiring passive attention. DESIGN: Auditory-evoked P300s were collected in a sample of 10 healthy adults (mean age = 19.90 years) using a two-toned oddball paradigm (1500 Hz "frequent" tone, probability of occurrence: 0.88, and 2000 Hz "rare" target tone, probability of occurrence: 0.12). The oddball paradigm was paired with three different visual distracters, increasing in complexity. The simplest was a black fixation cross on a white background that participants were asked to view passively as they performed the auditory task of counting the target stimulus. The second visual distracter increased in complexity by introducing color and motion, as tan and medium pink squares were alternated on the screen. Participants had to actively attend to the alternating squares by looking for a hidden text message while simultaneously counting the target auditory stimulus. The third visual distracter condition increased complexity again by introducing not only color and motion, but also biological relevance as participants viewed a mouth producing nonsense syllables. Participants had to actively attend to the moving mouth to determine what it was producing while simultaneously counting the rare auditory stimulus. RESULTS: The two more complex visual distracters that required active attention caused reductions in auditory-evoked P300 amplitudes relative to those recorded while the participants passively viewed a fixation cross. P300 amplitudes were similar whether the two more complex visual distracters (squares versus mouth) were used. P300 latencies and scalp distribution were not influenced by complexity of, or type of attention to, the visual distracter. Regardless of distracter condition, P300 amplitude was significantly smaller and P300 latency was significantly shorter at frontal sites when compared with central and parietal sites. CONCLUSIONS: Findings indicate that endogenous attentional resource allocation abilities can be effectively monitored through the addition of a complex, visually distracting task to a "classic" auditory P300 paradigm. Biological relevance of the distracting task does not seem to have an effect on the event-related potentials measured in this study, suggesting other aspects, such as whether or not a stimulus contains color or motion, may determine the efficiency of the distracter. Last, by increasing the complexity of, and amount of attention to, a visual distracter while evoking P300s using auditory stimuli, the cognitive load for the normal, healthy listener seems to be increased and the response amplitude subsequently reduced. Evoking P300s under similar conditions from disordered populations with subtle cognitive deficits (e.g., mild traumatic brain injury) may allow for increased diagnostic specificity and sensitivity over that found for P300s to classic, auditory oddball paradigms alone.

The effects of visual distracter complexity on auditory evoked p3b in contact sports athletes.

"Classic" P3b auditory oddball paradigms are insensitive to subtle deficits. An auditory oddball paradigm paired with visual distracters was used to compare football players with history of concussion, football players without history of concussion, and non-contact sport athletes. As hypothesized, increasing complexity of, and attention to, visual distracters reduced P3b amplitude. P3b amplitudes from non-contact athletes were larger than those from football players; however, players with and without a history of concussion were not significantly different. An auditory oddball paradigm with simple visual distracter improves sensitivity to cognitive deficits. Subconcussive impacts may contribute to brain damage frequently attributed to concussions.

Mild traumatic brain injury: effects on naming in word retrieval and discourse.

PRIMARY OBJECTIVE: To investigate differences between a group with mild traumatic brain injury (MTBI) and a control group relative to standard scores and error type during word retrieval in both naming and discourse tasks. METHODS AND PROCEDURES: Ten participants with MTBI were age-, gender- and education-matched with 10 participants without injury. Pre-experimental tasks for the participants with MTBI included the Scales of Cognitive Ability for Traumatic Brain Injury and the Raven's Coloured Progressive Matrices and both groups received the Peabody Picture Vocabulary Test-III. Experimental tasks included the Test of Adolescent/Adult Word Finding and the Test of Word Finding in Discourse. MAIN OUTCOMES AND RESULTS: Few participants (three on each experimental task) demonstrated psychometrically-based word retrieval deficits (standard score < 85); however, a significant difference in performance for the TAWF as compared to the TWFD was observed between groups. More word finding errors occurred with confrontational naming than with discourse tasks for both groups, with latency as the primary error type. CONCLUSIONS: Confrontational naming tasks may be more sensitive to subtle language difficulties occurring after MTBI. The study of adults with MTBI and their performance on semantically-based tasks offers important information for the advancement of therapeutic intervention and education.