Mauricio A. Garcia-Barrera

The Neuropsychological Outcomes of Concussion: A Systematic Review of Meta-Analyses on the Cognitive Sequelae of Mild Traumatic Brain Injury

UNLABELLED Mild Traumatic Brain Injury (mTBI), also known as concussion, has become a growing public health concern, prevalent in both athletic and military settings. Many researchers have examined post-mTBI neuropsychological outcomes, leading to multiple meta-analyses amalgamating individual study results. OBJECTIVE Considering the plethora of meta-analytic findings, the next logical step stands as a systematic review of meta-analyses, effectively reporting key moderators that predict post-mTBI neuropsychological outcomes. METHOD A systematic review of reviews yielded 11 meta-analyses meeting inclusion criteria (i.e., English-language systematic reviews/meta-analyses covering post-mTBI observational cognitive research on late adolescents/adults), with their findings qualitatively synthesized based on moderator variables (i.e., cognitive domain, time since injury, past head injury, participant characteristics, comparison group, assessment technique, and persistent symptoms). RESULTS The overall effect sizes ranged for both general (range: .07-.61) and sports-related mTBI (range: .40-.81) and differed both between and within cognitive domains, with executive functions appearing most sensitive to multiple mTBI. Cognitive domains varied in recovery rates, but overall recovery occurred by 90 days postinjury for most individuals and by 7 days postinjury for athletes. Greater age/education and male gender produced smaller effects sizes, and high school athletes suffered the largest deficits post-mTBI. Control-group comparisons yielded larger effects than within-person designs, and assessment techniques had limited moderating effects. CONCLUSIONS Overall, meta-analytic review quality remained low with few studies assessing publication or study quality bias. Meta-analyses consistently identified adverse acute mTBI-related effects and fairly rapid symptom resolution. Future meta-analyses should better operationally define cognitive constructs to produce more consistent effect estimates across domains.

An empirical comparison of the therapeutic benefits of physical exercise and cognitive training on the executive functions of older adults: a meta-analysis of controlled trials.

UNLABELLED A robust body of aging-related research has established benefits of both physical exercise (PE) and cognitive training (CT) on executive functions related to the activities of daily living of older adults; however, no meta-analysis has compared these treatments. OBJECTIVE The current quantitative review involved a comparison of the overall effect sizes of PE and CT interventions on executive functions (Morris, 2008; pre-post-controlled effect size: d(ppc)), while also exploring contextual moderators of treatment outcomes. METHOD A systematic review identified 46 studies (23 PE, 21 CT, and 2 both) meeting inclusion criteria (i.e., controlled interventions, executive-related outcomes, mean ages 65+, information to calculate d(ppc)). RESULTS The weighted mean dppc values came to 0.12 (p < .01) for PE and 0.24 (p < .01) for CT. Treatment effects differed based on executive constructs for CT, with problem solving presenting the highest d(ppc) (0.47, p < .01). Notably, PE produced similar effect sizes across distinct executive functions. Treatment characteristics (e.g., session length/frequency) did not predict effect sizes. CT had a significant benefit on healthy participants (0.26, p < .01), but cognitively impaired samples did not experience a significant effect. CONCLUSIONS Both treatments improved executive functions, but CT presented a potential advantage at improving executive functions. Improvements in executive functions differed depending on construct for CT, whereas each construct produced similar, modest effect sizes for PE. Publication bias and study quality variability potentially bias these conclusions, as lower quality studies likely produced inflated effect sizes.

Blast-Related Mild Traumatic Brain Injury: A Bayesian Random-Effects Meta-Analysis on the Cognitive Outcomes of Concussion among Military Personnel

Throughout their careers, many soldiers experience repeated blasts exposures from improvised explosive devices, which often involve head injury. Consequentially, blast-related mild Traumatic Brain Injury (mTBI) has become prevalent in modern conflicts, often occuring co-morbidly with psychiatric illness (e.g., post-traumatic stress disorder [PTSD]). In turn, a growing body of research has begun to explore the cognitive and psychiatric sequelae of blast-related mTBI. The current meta-analysis aimed to evaluate the chronic effects of blast-related mTBI on cognitive performance. A systematic review identified 9 studies reporting 12 samples meeting eligibility criteria. A Bayesian random-effects meta-analysis was conducted with cognitive construct and PTSD symptoms explored as moderators. The overall posterior mean effect size and Highest Density Interval (HDI) came to d = −0.12 [−0.21, −0.04], with executive function (−0.16 [−0.31, 0.00]), verbal delayed memory (−0.19 [−0.44, 0.06]) and processing speed (−0.11 [−0.26, 0.01]) presenting as the most sensitive cognitive domains to blast-related mTBI. When dividing executive function into diverse sub-constructs (i.e., working memory, inhibition, set-shifting), set-shifting presented the largest effect size (−0.33 [−0.55, −0.05]). PTSD symptoms did not predict cognitive effects sizes, βPTSD = −0.02 [−0.23, 0.20]. The results indicate a subtle, but chronic cognitive impairment following mTBI, especially in set-shifting, a relevant aspect of executive attention. These findings are consistent with past meta-analyses on multiple mTBI and correspond with past neuroimaging research on the cognitive correlates of white matter damage common in mTBI. However, all studies had cross-sectional designs, which resulted in universally low quality ratings and limited the conclusions inferable from this meta-analysis.

Theoretical and Statistical Derivation of a Screener for the Behavioral Assessment of Executive Functions in Children

The problem of valid measurement of psychological constructs remains an impediment to scientific progress, and the measurement of executive functions is not an exception. This study examined the statistical and theoretical derivation of a behavioral screener for the estimation of executive functions in children from the well-established Behavior Assessment System for Children (BASC). The original national standardization sample of the BASC-Teacher Rating Scales for children ages 6 through 11 was used (N = 2,165). Moderate-to-high internal consistency was obtained within each factor (.80-.89). A panel of experts was used for content validity examination. A confirmatory factor analysis model with 25 items loading on 4 latent factors (behavioral control, emotional control, attentional control, and problem solving) was developed, and its statistical properties were examined. The multidimensional model demonstrated adequate fit, and it was deemed invariant after configural, metric, and scalar measurement invariance tests across sex and age. Given its strong psychometric properties, with further tests of item validity, this instrument promises future clinical and research utility for the screening of executive functions in school-age children.

Planum temporale morphology in children with developmental dyslexia.

The planum temporale is a highly lateralized cortical region, located within Wernickes area, which is thought to be involved in auditory processing, phonological processing, and language. Research has linked abnormal morphology of the planum temporale to developmental dyslexia, although results have varied in large part due to methodological inconsistencies in the literature. This study examined the asymmetry of the planum temporale in 29 children who met criteria for dyslexia and 26 children whose reading was unimpaired. Leftward asymmetry of the planum temporale was found in the total sample and this leftward asymmetry was significantly reduced in children with dyslexia. This reduced leftward asymmetry in children with dyslexia was due to a planum temporale that is larger in the right hemisphere. This study lends support to the idea that planum temporale asymmetry is altered in children with developmental dyslexia.

Executive Functioning and Intelligence

Executive functioning and intelligence are two umbrella constructs with prominent similarities in the way each is conceptualized and measured. A key characteristic of frontal lobe syndrome post brain injury is relatively intact intellectual capacity with marked executive functioning impairment; however, accumulating research indicates a potentially more complex relationship between these two constructs than was previously suggested. This chapter examines the relationships between executive functioning and intelligence through a review of their definitions and empirical evidence. For this purpose, both psychometric studies and neurophysiologic approaches examining neurologic substrates, brain-lesioned patients and healthy controls were reviewed. Further, research examining the interactions between intelligence and executive functioning in developmental disorders is also discussed. The chapter ends with a discussion of the potential conclusions and implications that can be drawn about the relationship between these two elusive constructs.

Longitudinal applications of a behavioral screener of executive functioning: assessing factorial invariance and exploring latent growth.

This study included a replicated derivation of a behavioral screener for executive functions among children, longitudinal invariance analyses to evaluate measurement reliability across time, and latent growth modeling of 4 executive functions: problem solving, attentional control, behavioral control, and emotional control. The sample included 1,237 (52% female) participants age 6 to 11 years. Participants were tracked longitudinally for 3 years with 5 assessment waves, and new participants were recruited at each wave to compensate for attrition. As predicted, the 4-factor model was successfully replicated, with longitudinal invariance newly confirmed. These findings support this screener as a reliable childhood measure for executive functions, and latent growth modeling identified predictive qualities of gender and age on levels and changes in these constructs.

Executive functions and intraindividual variability following concussion.

The long-term outcomes of executive functions and intraindividual variability (IIV; i.e., trial-to-trial or across-task variability in cognitive performance) following concussion are unclear due to inconsistent and limited research findings, respectively. Objective: Responding to these gaps in scientific understanding, the current study aimed to assess the utility of both executive functions and IIV at predicting concussion history. Method: Altogether 138 self-identified athletes (Mage = 19.9 ± 1.91 years, 60.8% female, 19.6% with one concussion, 18.1% with two or more concussions) completed three executive-related cognitive tasks (i.e., n-back, go/no-go, global–local). Ordinal logistic regression analyses examined the joint effect of person-mean and IIV as predictors of concussion status. Results: Only mean response time for the global–local task predicted the number of past concussions, while no IIV variables reached unique significance. Conclusions: IIV research on concussion remains limited; however, the preliminary results do not indicate any additional value of IIV indices above mean performances at predicting past concussion. For executive functions, shifting appears most sensitive at detecting concussion group differences, with past researchers identifying post concussion impairment in attentional processing.

Screening for Conduct Disorder in an Adolescent Male Sample from Colombia

This study assessed the validity, reliability, and utility of a screening measure for detecting the signs or symptoms of Conduct Disorder in male adolescents from schools in Medellín, Colombia. A first study examined the differences between 70 male offender adolescents (aged 12-16 years) attending alternative education institutions, and 68 (sex, age, and socioeconomic status (SES)-matched) adolescent controls attending regular schools. A CD checklist (CD-CL) was constructed to be used by mothers (CD-CL-M) and for self-report by adolescents (CD-CL-SR). The validity of the screener for CD diagnosis was supported by significant differences between groups (ANOVA, p < .001). The CD-CL-SR had better sensitivity/specificity with a diagnostic cut-off point of 5 (sensitivity = 95.3% and specificity = 90.5%) than the CD-CL-M. A second study used the CD-CLSR with a random sample of 190 male adolescents (aged 12 to 16 years) from schools of low, middle and high SES. Reliability as assessed by Cronbach’s alpha was 0.86. An epidemiological cut point of 5 classified 35.5% of the adolescents assessed as probable CD cases. A psychometric cut point at T score > 59 (85th percentile) estimated 16.8% of the sample as probable CD cases. A psychometric cut point at T score > 64 (90th percentile) revealed that 10.5% of the sample would be severe CD cases. Some significant differences (p < 0.001) in proportions of CD adolescents were found between age and SES groups. It was concluded that such a high frequency of conduct problems in adolescence argues for the need for preventive programs in Colombian schools.

Using Multivariate Base Rates to Interpret Low Scores on an Abbreviated Battery of the Delis–Kaplan Executive Function System

Objective Executive function consists of multiple cognitive processes that operate as an interactive system to produce volitional goal-oriented behavior, governed in large part by frontal microstructural and physiological networks. Identification of deficits in executive function in those with neurological or psychiatric conditions can be difficult because the normal variation in executive function test scores, in healthy adults when multiple tests are used, is largely unknown. This study addresses that gap in the literature by examining the prevalence of low scores on a brief battery of executive function tests. Method The sample consisted of 1,050 healthy individuals (ages 16-89) from the standardization sample for the Delis-Kaplan Executive Function System (D-KEFS). Seven individual test scores from the Trail Making Test, Color-Word Interference Test, and Verbal Fluency Test were analyzed. Results Low test scores, as defined by commonly used clinical cut-offs (i.e., ≤25th, 16th, 9th, 5th, and 2nd percentiles), occurred commonly among the adult portion of the D-KEFS normative sample (e.g., 62.8% of the sample had one or more scores ≤16th percentile, 36.1% had one or more scores ≤5th percentile), and the prevalence of low scores increased with lower intelligence and fewer years of education. Conclusions The multivariate base rates (BR) in this article allow clinicians to understand the normal frequency of low scores in the general population. By use of these BRs, clinicians and researchers can improve the accuracy with which they identify executive dysfunction in clinical groups, such as those with traumatic brain injury or neurodegenerative diseases.