The Contribution of Pre-Existing Depression to the Acute Cognitive Sequelae of Mild Traumatic Brain Injury

Frontotemporal abnormalities and cognitive dysfunction, especially in verbal memory and information processing speed, occur in both mild traumatic brain injury (mTBI) and depression. Study 1 investigated the effect of depression on cognitive performance in a sample at risk of sustaining mTBI.Seventy-eight male undergraduates completed the Depression Anxiety Stress Scales (DASS), Digit Symbol Substitution Test (DSS), Hopkins Verbal Learning Test (HVLT), and Speed of Comprehension Test. A oneway analysis of covariance (using the top 25% and bottom 25% of DASS Depression subscale scorers) showed that HVLT recognition was significantly worse in the high scorers. Study 2 examined the effects of injury type and pre-existing depression on cognitive performance in a prospective emergency department sample (within 24 hours of injury). Fifty-eight participants with mTBI (29 with depression, 29 without depression) and 47 control participants (18 with depression, 29 without depression) completed the DSS, HVLT, and Speed of Comprehension Test. Participants with mTBI performed worse than controls (uninjured and orthopaedic-injured participants) on all tests. Participants with depression did not perform worse than participants without depression on the tests. However, there was a significant univariate interaction for HVLT recognition, participants in the mTBI group with depression exhibited worse recognition compared to participants without depression. Since word recognition was impaired in participants who were more depressed in both samples, this suggests that it is a consistent finding. More importantly, the results of Study 2 indicate that depression may interact with mTBI to impair word recognition during the acute phase after head injury

A recent mild traumatic brain injury can slow drivers’ perception of traffic hazards

Driving a vehicle is probably the most dangerous activity that most people do every day. No research has examined whether individuals recovering from a recent mild traumatic brain injury (MTBI) are safe to drive, despite cognitive impairment being a common consequence soon after MTBI. This study examined the acute effect of MTBI on drivers’ hazard perception (defined as drivers’ ability to search the road ahead to rapidly identify potentially dangerous traffic situations). Poorer hazard perception has been associated with higher car crash rates in a number of studies, and consequently several Australian states and the United Kingdom now test hazard perception in their driver licensing programs. Forty-two patients with MTBI and 43 patients with minor orthopedic injuries were recruited from the emergency department of a large metropolitan hospital within 24 hours of injury. Participants completed a computerized hazard perception test, in which they watched videos of genuine traffic scenes filmed from the drivers’ point of view. They were required to use the computer mouse to click on potential traffic hazards as early as possible. Participants with MTBI were significantly slower to detect traffic hazards than participants with minor orthopedic injuries. This study provides the first indication that within the acute stage post-injury, MTBI can be associated with impairment in a crash-related component of driving. The practical implication is that patients with MTBI should perhaps be advised to refrain from driving for at least the first 24 hours after injury

The effect of traumatic brain injury on drivers’ hazard perception

Individuals recovering from traumatic brain injury (TBI) often experience perceptual, cognitive, and motor deficits that adversely affect their driving. However, many individuals with TBI return to driving, despite evidence that they are at increased risk. This study examined the effects of TBI on drivers’ hazard perception, i.e. the ability to search the road ahead and quickly identify potentially dangerous traffic situations. Slower hazard perception has been associated with higher crash rates (e.g. Quimby et al., 1986), but hazard perception has never been assessed after TBI. A convenience sample of adults recovering from mild, moderate and severe TBI was recruited from the rehabilitation unit of a tertiary level hospital. Uninjured controls were recruited from the community. Participants completed a hazard perception test, in which they viewed videos of genuine traffic scenes filmed from the driver’s perspective and indicated as soon as they detected a potential traffic hazard (mean response latency was the main dependent measure). Participants also completed a simple spatial reaction time task, a digit symbol substitution task and several measures related to pre- and post-injury functioning. Preliminary results indicate that individuals with TBI were significantly slower to detect traffic hazards than controls. The findings may signify the need for hazard perception testing or training post-TBI before return to driving

Effects of memory load and distraction on performance and event-related slow potentials in a visuospatial working memory task

Brain electrical activity related to working memory was recorded at 15 scalp electrodes during a visuospatial delayed response task. Participants (N = 18) touched the remembered position of a target on a computer screen after either a 1 or 8 sec delay. These memory trials were compared to sensory trials in which the target remained present throughout the delay and response periods. Distracter stimuli identical to the target were briefly presented during the delay on 30% of trials. Responses were less accurate in memory than sensory trials, especially after the long delay. During the delay slow potentials developed that were significantly more negative in memory than sensory trials. The difference between memory and sensory trials was greater at anterior than posterior electrodes. On trials with distracters, the slow potentials generated by memory trials showed further enhancement of negativity whereas there were minimal effects on accuracy of performance. The results provide evidence that engagement of visuospatial working memory generates slow wave negativity with a timing and distribution consistent with frontal activation. Enhanced brain activity associated with working memory is required to maintain performance in the presence of distraction. © 1997 by the Massachusetts Institute of Technolog

Athletes’ age, sex and years of education moderate the acute neuropsychological impact of sports-related concussion: A meta-analysis

The objective of this study is to determine which pre-existing athlete characteristics, if any, are associated with greater deficits in functioning following sports-related concussion, after controlling for factors previously shown to moderate this effect (e.g., time since injury). Ninety-one independent samples of concussion were included in a fixed+systematic effects meta-analysis (n = 3,801 concussed athletes; 5,631 controls). Moderating variables were assessed using analogue-to-ANOVA and meta-regression analyses. Post-injury assessments first conducted 1-10 days following sports-related concussion revealed significant neuropsychological dysfunction, postural instability and post-concussion symptom reporting (d = -0.54, -1.10, and -1.14, respectively). During this interval, females (d = -0.87), adolescent athletes competing in high school competitions (d = -0.60), and those with 10 years of education (d = -1.32) demonstrated larger post-concussion neuropsychological deficits than males (d = -0.42), adults (d = -0.25), athletes competing at other levels of competition (d = -0.43 to -0.41), or those with 16 years of education (d = -0.15), respectively. However, these sub-groups' differential impairment/recovery beyond 10 days could not be reliably quantified from available literature. Pre-existing athlete characteristics, particularly age, sex and education, were demonstrated to be significant modifiers of neuropsychological outcomes within 10 days of a sports-related concussion. Implications for return-to-play decision-making and future research directions are discussed

The n-back as a dual-task: P300 morphology under divided attention

The n-back task was hypothesized to be a dual task, permitting the imposition of parametrically increasing attentional and working memory demands, while keeping constant the demands of an embedded matching subtask. Visual targets were presented for 200 ms every 2.2 s at pseudorandomly varying positions on a computer screen. Participants were required to remember the most recent 0, 1, 2, or 3 positions and responded with a choice button push to whether the current target position matched the position presented n items previously. P300 peak latency was constant across n-back tasks, reflecting constant perceptual and cognitive demands of the matching subtask. P300 peak amplitude decreased with increasing memory load, reflecting reallocation of attention and processing capacity away from the matching subtask to working memory activity. These data support a dual-task nature of the n-back, which should be considered when employing this paradigm

Test-retest reliability of a new form of the auditory verbal learning test (AVLT)

The equivalence between the original form (Form 1) of the Auditory Verbal Learning Test (AVLT), and a new form (Form 4) was examined in 51 normal adult subjects (20-67 years) of average estimated intelligence who were assessed in two separate sessions. Performance on the new form was equivalent to that on the original and most measures on the two tests showed significant positive correlations. Test-retest reliability of AVLT scores between sessions was also assessed, both globally and separately for Form 1 followed by Form 4 and for the reverse order. The most reliable measures on the AVLT were the total number of words learned over the five learning trials, (r = .77), and performance on the retention trial of the learning list following the presentation and performance of the distractor list (r = .70). These measures are sufficiently robust for use in clinical serial assessments

Interhemispheric control of manual motor activity

The interhemispheric control of manual motor processes is reviewed, focusing on the clinical evidence from patients with commissurotomies and with agenesis of the corpus callosum. There is little evidence for a role of the corpus callosum in transferring explicit motor commands. Rather, the corpus callosum seems important for transferring lateralised information (such as verbal or visuospatial activity) of the pre-motor variety. Also, the corpus callosum may become very significant when movement begins: there appears to be a transcallosal passage of corollary motor signals and feedback sensory signals that are used to control asynchronous bimanual movements and to inhibit the opposite hemisphere from interfering when a simple unimanual movement is required