Biology subjects

Waters, A. B.

Publications and source records attributed to Waters, A. B..

3 recordsLinked to original sources

bioRxiv2018

Components of Executive Function Predict Regional Prefrontal Volumes

Objective: Designed to measure a diversity of executive functioning (EF) through classical neuropsychological tests, the Delis-Kaplan Executive Function Scale (D-KEFS) allows for the investigation of the neural architecture of EF. We examined how the D-KEFS Tower, Verbal Fluency, Design Fluency, Color-Word Interference, and Trail Making Test tasks related to regional frontal lobe volumes, quantifying how components of EF were represented in disparate neural networks. Method: Adults from the Nathan Kline Institute - Rockland Sample (NKI-RS), an open-access community study of brain development, with complete MRI (3T scanner) and D-KEFS data were selected for analysis (N = 478; ages 20-85). In a mixed-effects model predicting volume, D-KEFS task, D-KEFS score, region of interest (ROI; 13 frontal, 1 occipital control), were entered as fixed effects with intercepts for participants as random effects. Results: Unitary EF (average of D-KEFS scores) was positively associated with superior frontal, rostral middle frontal, and lateral orbitofrontal volumes; a negative association was observed with frontal pole volume (| z-score slope | range = 0.040 to 0.051). Diverse EF skills (individual D-KEFS task scores) were differentially associated with two or three ROIs, respectively, but to a stronger extent (| z-score slope | range = 0.053 to 0.103). Conclusions: The neural correlates found for the D-KEFS support the prefrontal modularity of EF at both the unitary (aspects of EF ability common to all tasks) and task (diverse EF skills) levels. The separation of task-general variance in neurocognition from task-specific variance can further evaluate neuropsychological tests as indices of brain integrity.

neuroscience↗

bioRxiv2018

A Meta-Analysis of Executive Functions in Frontal Cortex: Comparing Healthy and Neuropsychiatric Groups

BackgroundThe neural architecture of executive functions remains a topic of considerable clinical and academic interest in the clinical neurosciences, given its strength as a transdiagnostic predictor of adaptive functioning with high heritability. In recent years, meta-analyses have shown a consistent relationship between prefrontal cortex size and executive functioning task performance in healthy adults and lesion patients, with increases in measures of cortical size (i.e., volume or thickness) associated with better executive functioning performance. There is a gap in meta-analytic literature assessing these relationships in neuropsychiatric populations, their effects relative to healthy controls, and differential contributions of brains regions and neuropsychological paradigms.\n\nMethodsWe conducted a meta-analysis of published studies (k =30) that assessed the relationship between executive functions and frontal regions in vivo (N = 1935) for both healthy (20 samples) and neuropsychiatric (21 samples) adults. Random effects modeling was used to calculate mean effect sizes and CIs.\n\nResultsLarger volumes and thickness were associated with better executive functioning in both healthy (r =.35, 95% CI =.29 -.39) and neuropsychiatric populations (r =.47, 95% CI =.40 -.51), with the effect size for neuropsychiatric populations being significantly larger compared to healthy controls. While there was variability between tasks, there were no significant differences in effect size between neuropsychological paradigms or brain region classification.\n\nConclusionsThese results indicate the relationship between healthy adult performance on neuropsychological testing is less associated with cortical size compared to neuropsychiatric adults.

neuroscience↗

bioRxiv2017

On the Impact of Interhemispheric White Matter: Age, Executive Functioning, and Dedifferentiation in the Frontal Lobes

IntroductionIn middle age, declines in executive functioning (EF) are associated with decrements in the quality and/or quantity of white and grey matter. Recruitment of homologous regions has been identified as a compensatory mechanism for cognitive decline in later middle age, however research into neural substrates of EF has yet to be guided by dedifferentiation models. We hypothesized that frontal-parietal grey matter volume, interhemispheric white matter and intrahemispheric white matter fractional anisotropy (FA) will be predictive of EF. Further, we hypothesized that the comparative association between interhemispheric white matter and EF will increase with age, because of compensatory recruitment.\n\nMethodsNeurocognitive test data, DTI, and T1 MPRAGE scans (n = 444) were obtained from the NKI-Rockland Sample. Structural equation modeling was used to examine the relationship between age, EF, interhemispheric white matter (forceps minor; FM), intrahemispheric white matter (superior longitudinal fasciculus; SLF), and a frontal-parietal grey matter network. EF and grey matter were modelled as latent variables, with EF examined as the criterion. Additionally, a subsample of participants aged 55-85 (n = 168) was analyzed to examine the influence of age related compensatory mechanisms.\n\nResultsThere was a significant relationship between FM, grey matter, and EF, which was fully mediated by age. There was a significant relationship between SLF and EF, which was not mediated by age. For older adults, only the age-mediated pathway from FM to EF was significant.\n\nDiscussionUsing structural imaging data, support was found for age-related interhemispheric mechanisms of compensation, but not intrahemispheric mechanisms.\n\nKey points(1) Neural substrates of executive functioning are not static across the lifespan. (2) In older adults, white matter becomes more salient as a structural correlate of executive functioning, as recruitment needs increase. (3) While the importance of interhemispheric white matter is mediated by age, intrahemispheric recruitment remains consistent across the lifespan, and is not the primary mechanism of age-based compensation in community dwelling older adults.

neuroscience↗