The utility of injury characteristics for predicting the severity of post-concussion outcomes remains equivocal. The purpose of this meta-analysis was to quantify the predictive relationship between these variables to inform classification of acute injury severity. Thirty-one empirical samples of concussed athletes, for which rates of loss of consciousness and/or amnesia were reported, were included in a meta-analysis evaluating acute outcomes following sports-related concussion. Outcome measures of interest were neuropsychological tests first administered 1–10 days post-injury. Loss of consciousness and anterograde amnesia significantly predicted more severe neuropsychological deficits within 10 days of concussion in studies using pre-injury baseline, but not control group, comparisons. Retrograde amnesia significantly predicted acute neuropsychological dysfunction (d = -1.03) irrespective of comparison group. Although small sample sizes require conservative interpretation and future replication, the evidence suggests that retrograde amnesia, rather than loss of consciousness, may be used to classify the acute severity of concussion. (JINS, 2014, 20, 81–87)

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. (JINS, 2013, 19, 1–17).

Schizophrenia has been identified as a disorder of the frontostriatal system with impairments in both sustained and selective attention (Bradshaw, 2001). The Sustained Attention to Response Task (SART), which required occasional withholding of an ongoing frequent response when a specified digit occurred, was completed by patients with a clinical diagnosis of schizophrenia (N = 52) and matched controls (N = 46). Relative to controls, participants with schizophrenia responded less frequently and made more impulsive errors. Their correct responses were slower on average, with greater variability in timing. Speed of response was unrelated to neuroleptic medication dosage. The slow responses exhibited by patients with schizophrenia were interpreted as reflecting primarily motor frontostriatal circuit dysfunction, and dysfunction of the lateral orbitofrontal/anterior cingulate circuit is implicated in poor impulse control. To address the heterogeneity of symptoms in schizophrenia, symptom dimension scores (positive, negative and disorganised) were used to determine whether symptom dimensions were associated with differential performance on the SART. Higher negative symptoms were related to increased miss errors on the SART whereas higher disorganised and positive symptom scores were unrelated to performance on this measure. An association between negative symptoms and increased miss errors may be considered indicative of dysfunction of the anterior cingulate circuit, considered to be linked to response inattention, apathy, reduced initiative and focused attention. Implications of this research for understanding the neuroanatomical basis for schizophrenia and its subtypes are discussed.

Genetic and environmental sources of covariation among cognitive measures of verbal IQ, performance IQ (PIQ), academic achievement, 2-choice reaction time (CRT), inspection time (IT) and the 6 Openness facets of the NEO Personality Inventory-Revised (NEO PI-R) were examined. The number of twin and twin–sibling pairs ranged from 432 (182 MZ, 350 DZ/sibling) to 1023 (273 MZ, 750 DZ/sibling) for cognitive measures, and between 432 (90 MZ, 342 DZ/sibling) — 437 (91 MZ, 346 DZ/sibling) for Openness facets. Structural equation modeling best supported a model with a 3-factor additive genetic structure. A genetic general factor subsumed the 5 cognitive measures and 5 of the 6 Openness facets (Actions did not load significantly). A second additive genetic factor incorporated the 6 Openness facets, and a third additive genetic factor incorporated the 5 cognitive measures. Specific additive and dominance genetic effects were also evident, as were shared common and shared unique environmental influences, and specific unique environmental effects. The Openness facets of Ideas and Values evidenced the strongest phenotypic correlations with cognitive indices, particularly verbal measures. The genetic correlations among Openness facets and cognitive measures ranged from −.06 to .79. Results were interpreted as suggesting that Openness is related to general cognitive ability (g) through a genetic mechanism and that gengenders a minor but discernable disposition towards Openness for the majority of facets.

Simultaneous analysis of handedness data from 35 samples of twins (with a combined sample size of 21,127 twin pairs) found a small but significant additive genetic effect accounting for 25.47% of the variance (95% confidence interval [CI] 15.69–29.51%). No common environmental influences were detected (C = 0.00; 95% CI 0.00–7.67%), with the majority of the variance, 74.53%, explained by factors unique to the individual (95% CI 70.49–78.67%). No significant heterogeneity was observed within studies that used similar methods to assess handedness, or across studies that used different methods. At an individual level the majority of studies had insufficient power to reject a purely unique environmental model due to insufficient power to detect familial aggregation. This lack of power is seldom mentioned within studies, and has contributed to the misconception that twin studies of handedness are not informative.

This study examined the genetic and environmental relationships among 5 academic achievement skills of a standardized test of academic achievement, the Queensland Core Skills Test (QCST; Queensland Studies Authority, 2003a). QCST participants included 182 monozygotic pairs and 208 dizygotic pairs (mean 17 years ± 0.4 standard deviation). IQ data were included in the analysis to correct for ascertainment bias. A genetic general factor explained virtually all genetic variance in the component academic skills scores, and accounted for 32% to 73% of their phenotypic variances. It also explained 56% and 42% of variation in Verbal IQ and Performance IQ respectively, suggesting that this factor is genetic g. Modest specific genetic effects were evident for achievement in mathematical problem solving and written expression. A single common factor adequately explained common environmental effects, which were also modest, and possibly due to assortative mating. The results suggest that general academic ability, derived from genetic influences and to a lesser extent common environmental influences, is the primary source of variation in component skills of the QCST.

It has been suggested that twinning may influence handedness through the effects of birth order, intra-uterine crowding and mirror imaging. The influence of these effects on handedness (for writing and throwing) was examined in 3657 Monozygotic (MZ) and 3762 Dizygotic (DZ) twin pairs (born 1893–1992). Maximum likelihood analyses revealed no effects of birth order on the incidence of left-handedness. Twins were no more likely to be left-handed than their singleton siblings (n = 1757), and there were no differences between the DZ co-twin and siblingtwin covariances, suggesting that neither intra-uterine crowding nor the experience of being a twin affects handedness. There was no evidence of mirror imaging; the co-twin correlations of monochorionic and dichorionic MZ twins did not differ. Univariate genetic analyses revealed common environmental factors to be the most parsimonious explanation of familial aggregation for the writing-hand measure, while additive genetic influences provided a better interpretation of the throwing hand data.

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.