Predictors of Responsivity to Interdisciplinary Pain Management.

Objective: This study investigated for whom interdisciplinary pain management (IPM) is most effective. Identification of predictors of treatment responsivity would facilitate development of patient-treatment matching algorithms to optimize outcomes. Design: Repeated measures prospective study of consecutive admissions to a two-week IPM program. Setting: Brisbane Pain Rehabilitation Service in Brisbane, Australia. Subjects: A total of 163 adults referred for chronic pain management. Methods: Self-report questionnaires and measures of physical performance were obtained at program entry and completion. Group-level analyses were performed using standard parametric statistics. Individual-level change was assessed using recommended criteria. Multivariate analysis of variance and logistic regression were used to examine outcomes and predictors of response. Results: Significant improvements were observed across psychological, social, and physical outcome domains. Up to 50% of participants had clinically meaningful improvements, while less than 10% deteriorated. Higher baseline depression, anxiety, stress, and pain catastrophizing scores predicted better group-level outcomes (Ps < 0.05). Participants with higher baseline depression scores were most likely to show significant individual-level improvement on at least one outcome (Ps < 0.05). Participants with nociceptive pain were more than four times more likely than those with neuropathic pain to show clinically meaningful improvement on multiple outcomes, while those participants who were older were more likely to be multidomain responders. Conclusions: Physical, psychological, and social outcomes all improved in a significant proportion of participants following the IPM. High baseline depression was a clinically reliable predictor of individual-level improvement. Individuals with nociceptive pain and those who were older, respectively, showed the largest response across multiple outcomes and domains.

Do injury characteristics predict the severity of acute neuropsychological deficits following sports-related concussion? A meta-analysis.

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.

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.

Return-to-driving expectations following mild traumatic brain injury.

AIM: Although individuals recovering from mild traumatic brain injury (MTBI) could pose a risk to road safety, little is known about their intentions regarding return-to-driving. Reported are the expectations of a sample of emergency department patients with MTBI regarding their recovery and return-to-driving. METHOD: Eighty-one patients with MTBI were recruited from an emergency department. Participants completed an 11-item questionnaire measuring expectations regarding recovery from injury; five of the items addressed return-to-driving. RESULTS: Only 48% of the sample intended to reduce their driving following their injury. However, those that did intend to reduce their driving nominated a mean duration of 16.59 days (SD = 31.68) of reduced exposure. A logistic regression found that previous head injury experience and an interaction between pain and previous head injury experience predicted intentions to reduce driving. Similarly, a multiple regression revealed that pain level contributed significantly to the variance in time estimates of return-to-driving. CONCLUSION: The finding that half the individuals recovering from MTBI do not intend to moderate their driving exposure post-injury is cause for concern, as another study has shown that driving performance is compromised in this group immediately after injury.

Assessment of drivers' ability to anticipate traffic hazards after traumatic brain injury.

OBJECTIVES: The aim of this study was to examine the effect of traumatic brain injury (TBI) on drivers' ability to anticipate traffic hazards. Slower anticipation of hazards has been associated with higher crash rates, but this driving skill has never been assessed after TBI. METHODS: The anticipatory ability of 31 drivers with TBI and 24 age-matched uninjured controls was assessed with a validated drivers' Hazard Perception Test. The Hazard Perception Test displayed videos of genuine traffic scenes filmed from the driver's perspective, and participants had to respond as soon as they anticipated a traffic hazard in a scene. The primary dependent measure was mean response latency. RESULTS: Participants with TBI were significantly slower to anticipate traffic hazards than controls (p<0.001). Within the TBI group, while hazard perception response times were significantly related to duration of post-traumatic amnesia (Spearman ρ=0.63; p<0.001), they were not significantly related to Glasgow Coma Scale scores (r=-0.19; p=0.33). Also, participants with a complicated mild TBI were significantly faster in anticipating traffic conflicts than participants with moderate to severe TBI (p=0.04). CONCLUSIONS: Individuals with TBI were slower to anticipate traffic hazards than age-matched uninjured controls. This finding signifies the need for hazard perception testing and training as part of driving rehabilitation after TBI.

Genetic influences on handedness: data from 25,732 Australian and Dutch twin families.

Handedness refers to a consistent asymmetry in skill or preferential use between the hands and is related to lateralization within the brain of other functions such as language. Previous twin studies of handedness have yielded inconsistent results resulting from a general lack of statistical power to find significant effects. Here we present analyses from a large international collaborative study of handedness (assessed by writing/drawing or self report) in Australian and Dutch twins and their siblings (54,270 individuals from 25,732 families). Maximum likelihood analyses incorporating the effects of known covariates (sex, year of birth and birth weight) revealed no evidence of hormonal transfer, mirror imaging or twin specific effects. There were also no differences in prevalence between zygosity groups or between twins and their singleton siblings. Consistent with previous meta-analyses, additive genetic effects accounted for about a quarter (23.64%) of the variance (95%CI 20.17, 27.09%) with the remainder accounted for by non-shared environmental influences. The implications of these findings for handedness both as a primary phenotype and as a covariate in linkage and association analyses are discussed.

Emergency department assessment of mild traumatic brain injury and the prediction of postconcussive symptoms: a 3-month prospective study.

OBJECTIVE: To investigate the utility of a brief emergency department (ED) bedside screen for the prediction of postconcussive symptoms at 3 months following mild traumatic brain injury (MTBI). PARTICIPANTS: One hundred patients with MTBI (78% men; mean age = 33.6 years); 2 control groups (each n = 100), a "minor nonhead injury" group (77% men; mean age = 32.2 years) and an "uninjured ED visitor" group (78% men; mean age = 33.6 years). MAIN MEASURES: Brief measures of neuropsychological functioning, acute pain, and postural stability were collected in the ED; telephone follow-up at 3 months using the Rivermead Post-Concussion Symptoms Questionnaire was undertaken. RESULTS: Neuropsychological deficits, acute pain, and postural instability in the ED were significantly associated with postconcussive symptoms at 3-month follow-up. A regression formula using 3 easily obtainable measures obtained during acute stage of injury-immediate and delayed memory for 5 words and a visual analog scale score of acute headache-provided 80% sensitivity and 76% specificity for the prediction of clinically significant symptoms at 3 months postinjury. CONCLUSION: A small combination of variables assessable in the ED may predict MTBI patients likely to experience persistent postconcussive symptoms.

Genetic covariation among facets of openness to experience and general cognitive ability.

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.

Common and specific genetic influences on EEG power bands delta, theta, alpha, and beta.

It is difficult to study the genetic basis of psychological function/dysfunction due to its etiological complexity. Instead, we studied a biological marker, EEG power, which is associated with various psychological phenotypes and is closer to gene function. Previous studies have consistently demonstrated high heritability of EEG band power, but less is known about how common or specific genes influence each power band. For 519 adolescent twin pairs, spectral powers were calculated for delta, theta, alpha, and beta bands at bilateral occipital and frontal sites. All four bands were entered into a multivariate genetic model, with occipital and frontal sites modelled separately. Variance was decomposed into additive (A) and dominant (D) genetic factors, and common (C) and unique (E) environmental factors. Band heritabilities were higher at occipital (0.75-0.86) than frontal sites (0.46-0.80). Both common and specific genetic factors influenced the bands, with common genetic and specific genetic factors having more influence in the occipital and frontal regions, respectively. Non-additive genetic effects on beta power and a common environment effect on delta, theta, and alpha powers were observed in the frontal region.

Genetic variation of individual alpha frequency (IAF) and alpha power in a large adolescent twin sample.

To further clarify the mode of genetic transmission on individual alpha frequency (IAF) and alpha power, the extent to which individual differences in these alpha indices are influenced by genetic factors were examined in a large sample of adolescent twins (237 MZ, 282 DZ pairs; aged 16). EEG was measured at rest (eyes closed) from the right occipital site, and a second EEG recording for 50 twin pairs obtained approximately 3 months after the initial collection, enabled an estimation of measurement error. Analyses confirmed a strong genetic influence on both IAF (h(2)=0.81) and alpha power (h(2)=0.82), and there was little support for non-additive genetic (dominance) variance. A small but significant negative correlation (-0.18) was found between IAF and alpha power, but genetic influences on IAF and alpha power were largely independent. All non-genetic variance was due to unreliability, with no significant variance attributed to unique environmental factors. Relationships between the alpha and IQ indices were also explored but were generally either non-significant or very low. The findings confirm the high heritability for both IAF and alpha power, they further suggest that the mode of genetic transmission is due to additive genetic factors, that genetic influences on the underlying neural mechanisms of alpha frequency and power are largely specific, and that individual differences in alpha activity are influenced little by developmental plasticity and individual experiences.

Handedness in twins: joint analysis of data from 35 samples.

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.

Perceptual speed does not cause intelligence, and intelligence does not cause perceptual speed.

There is ongoing debate whether the efficiency of local cognitive processes leads to global cognitive ability or whether global ability feeds the efficiency of basic processes. A prominent example is the well-replicated association between inspection time (IT), a measure of perceptual discrimination speed, and intelligence (IQ), where it is not known whether increased speed is a cause or consequence of high IQ. We investigated the direction of causation between IT and IQ in 2012 genetically related subjects from Australia and The Netherlands. Models in which the reliable variance of each observed variable was specified as a latent trait showed IT correlations of -0.44 and -0.33 with respective Performance and Verbal IQ; heritabilities were 57% (IT), 83% (PIQ) and 77% (VIQ). Directional causation models provided poor fits to the data, with covariation best explained by pleiotropic genes (influencing variation in both IT and IQ). This finding of a common genetic factor provides a better target for identifying genes involved in cognition than genes which are unique to specific traits.

Executive control of working memory in schizophrenia.

There is considerable evidence that working memory impairment is a common feature of schizophrenia. The present study assessed working memory and executive function in 54 participants with schizophrenia, and a group of 54 normal controls matched to the patients on age, gender and estimated premorbid IQ, using traditional and newer measures of executive function and two dual tasks-Telephone Search with Counting and the Memory Span and Tracking Task. Results indicated that participants with schizophrenia were significantly impaired on all standardised measures of executive function with the exception of a composite measure of the Trail Making Test. Results for the dual task measures demonstrated that while the participants with schizophrenia were unimpaired on immediate digit span recall over a 2-min period, they recalled fewer digit strings and performed more poorly on a tracking task (box-crossing task) compared with controls. In addition, participants with schizophrenia performed more poorly on the tracking task when they were required to simultaneously recall digits strings than when they performed this task alone. Contrary to expectation, results of the telephone search task under dual conditions were not significantly different between groups. These results may reflect the insufficient complexity of the tone-counting task as an interference task. Overall, the present study showed that participants with schizophrenia appear to have a restricted impairment of their working memory system that is evident in tasks in which the visuospatial sketchpad slave system requires central executive control.

Multivariate genetic analysis of academic skills of the Queensland core skills test and IQ highlight the importance of genetic g.

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.

Comparability, reliability, and practice effects on alternate forms of the Digit Symbol Substitution and Symbol Digit Modalities tests.

The present study examined the comparability of 4 alternate forms of the Digit Symbol Substitution test and the Symbol Digit Modalities (written) test, including the original versions. Male contact-sport athletes (N = 112) were assessed on 1 of the 4 forms of each test. Reasonable alternate form comparability was demonstrated through establishing normality of form distributions and conducting pairwise form comparisons of means, variability, and intraclass correlations. Nonetheless, alternate forms are likely an insufficient means of controlling practice in speeded measures at brief (1-2 weeks) retest intervals. Reliable change indices demonstrated that practice must be accounted for in individual retesting.

Severity of sports-related concussion and neuropsychological test performance.

Concussion severity grades according to the Cantu, Colorado Medical Society, and American Academy of Neurology systems were not clearly related to the presence or duration of impaired neuropsychological test performance in 21 professional rugby league athletes. The use of concussion severity guidelines and neuropsychological testing to assist return to play decisions requires further investigation.

ERP 'old/new' effects: memory strength and decisional factor(s).

Event-related potentials (ERPs) were recorded while subjects made old/new recognition judgments on new unstudied words and old words which had been presented at study either once ('weak') or three times ('strong'). The probability of an 'old' response was significantly higher for strong than weak words and significantly higher for weak than new words. Comparisons were made initially between ERPs to new, weak and strong words, and subsequently between ERPs associated with six strength-by-response conditions. The N400 component was found to be modulated by memory trace strength in a graded manner. Its amplitude was most negative in new word ERPs and most positive in strong word ERPs. This 'N400 strength effect' was largest at the left parietal electrode (in ear-referenced ERPs). The amplitude of the late positive complex (LPC) effect was sensitive to decision accuracy (and perhaps confidence). Its amplitude was larger in ERPs evoked by words attracting correct versus incorrect recognition decisions. The LPC effect had a left>right, centro-parietal scalp topography (in ear-referenced ERPs). Hence, whereas, the majority of previous ERP studies of episodic recognition have interpreted results from the perspective of dual-process models, we provide alternative interpretations of N400 and LPC old/new effects in terms of memory strength and decisional factor(s).

Genetic sources of covariation among P3(00) and online performance variables in a delayed-response working memory task.

Genetic and environmental sources of covariation among the P3(00) and online performance elicited in a delayed-response working memory task, and psychometric IQ assessed by the multidimensional aptitude battery, were examined in an adolescent twin sample. An association between frontal P3 latency and task performance (phenotypic r=-0.33; genotypic r=-0.49) was indicated, with genes (i.e. twin status) accounting for a large part of the covariation (>70%). In contrast, genes influencing P3 amplitude mediated only a small part (2%) of the total genetic variation in task performance. While task performance mediated 15% of the total genetic variation in IQ (phenotypic r=0.22; genotypic r=0.39) there was no association between P3 latency and IQ or P3 amplitude with IQ. The findings provide some insight into the inter-relationships among psychophysiological, performance and psychometric measures of cognitive ability, and provide support for a levels-of-processing genetic model of cognition where genes act on specific sub-components of cognitive processes.

Working memory correlates of three symptom clusters in schizophrenia.

This study was designed to examine whether discrete working memory deficits underlie positive, negative and disorganised symptoms of schizophrenia. Symptom dimension ratings were assigned to 52 outpatients with schizophrenia (ICD-10 criteria), using items drawn from the Positive and Negative Syndrome Scale (PANSS). Linear regression and correlational analyses were conducted to examine whether symptom dimension scores were related to performance on several tests of working memory function. Severity of negative symptoms correlated with reduced production of words during a verbal fluency task, impaired ability to hold letter and number sequences on-line and manipulate them simultaneously, reduced performance during a dual task, and compromised visuospatial working memory under distraction-free conditions. Severity of disorganisation symptoms correlated with impaired visuospatial working memory under conditions of distraction, failure of inhibition during a verbal fluency task, perseverative responding on a test of set-shifting ability, and impaired ability to judge the veracity of simple declarative statements. Severity of positive symptoms was uncorrelated with performance on any of the measures examined. The present study provides evidence that the positive, negative and disorganised symptom dimensions of the PANSS constitute independent clusters, associated with unique patterns of working memory impairment.

Driving after concussion: the acute effect of mild traumatic brain injury on drivers' hazard perception.

OBJECTIVE: 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, which is defined as drivers' ability to search the road ahead to rapidly identify potentially dangerous traffic situations. Poorer hazard perception has been associated with higher crash rates in a number of studies. METHOD: 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 driver's point of view. They were required to use the computer mouse to click on potential traffic hazards as early as possible. RESULTS: Participants with MTBI were significantly slower to respond to traffic hazards than participants with minor orthopedic injuries (p = .03, d = .48). CONCLUSIONS: This study provides the first indication that within the acute stage postinjury, MTBI is associated with impairment in a crash-related component of driving. This suggests that patients with MTBI should be advised to refrain from driving for at least the first 24 hours' postinjury.