Correlation between gray/white matter volume and cognition in healthy elderly people

This study applied volumetric analysis and voxel-based morphometry (VBM) of brain magnetic resonance (MR) images to assess whether correlations exist between global and regional gray/white matter volume and the cognitive functions of semantic memory and short-term memory, which are relatively well preserved with aging, using MR image data from 109 community-dwelling healthy elderly individuals. We used the Information and Digit Span subtests of the Wechsler Adult Intelligent Scale-Revised as measures of semantic memory and short-term memory, respectively. We found significant positive correlations between the gray matter ratio, the percentage of gray matter volume in the intracranial volume, and performance on the Digit Span subtest, and between the regional gray matter volumes of the bilateral anterior temporal lobes and performance on the Information subtest. No significant correlations between performance on the cognitive tests and white matter volume were found. Our results suggest that individual variability in specific cognitive functions that are relatively well preserved with aging is accounted for by the variability of gray matter volume in healthy elderly subjects.     

Microstructural integrity of the corpus callosum linked with neuropsychological performance in adolescents

Background: Diffusion tensor imaging (DTI) has revealed microstructural aspects of adolescent brain development, the cognitive correlates of which remain relatively uncharacterized. Methods: DTI was used to assess white matter microstructure in 18 typically developing adolescents (ages 16–18). Fractional anisotropy (FA) and mean diffusion (MD) were evaluated within the splenium and body of the corpus callosum in relation to cognitive performance. Results: Visuospatial construction abilities were associated with white matter integrity in both the splenium and body of the corpus callosum, while only splenium integrity was associated with language and psychomotor function. Conclusion: Results suggest that, for typically developing adolescents, white matter coherence positively relates to visuospatial, psychomotor, and language skills. These findings may have implications for the cognitive functioning of clinical populations in which typical white matter development is altered.     

White matter development during adolescence as shown by diffusion MRI

Previous volumetric developmental MRI studies of the brain have shown white matter development continuing through adolescence and into adulthood. This review presents current findings regarding white matter development and organization from diffusion MRI studies. The general trend during adolescence (age 12–18 years) is towards increasing fractional anisotropy (FA) with age and decreasing mean diffusivity (MD) with age, findings primarily due to decreasing radial diffusivity with age. However, results of studies vary as to the regional specificity of such age-related changes, likely due in part to methodological issues. Another general trend is for FA to positively correlate and MD to negatively correlate with cognitive function. This trend is however region-specific, task-specific, and population-specific; some studies have in fact found negative correlations of FA and positive correlations of MD in specific regions with specific measures of cognitive performance. There are also published reports of sexual dimorphism in white matter development, indicating differing developmental trajectories between males and females as well as differing relationships developmentally between white matter architecture and cognitive function. There is a need for more research to further elucidate the development of white matter and its relation to cognitive function during this critical developmental period.     

The role of white matter hyperintensities and medial temporal lobe atrophy in age-related executive dysfunctioning

Various studies support an association between white matter hyperintensities (WMH) and deficits in executive function in nondemented ageing. Studies examining executive functions and WMH have generally adopted executive function as a phrase including various functions such as flexibility, inhibition, and working memory. However, these functions include distinctive cognitive processes and not all may be affected as a result of WMH. Furthermore, atrophy of the medial temporal lobe (MTA) is frequently observed in ageing. Nevertheless, in previous studies of nondemented ageing MTA was not considered when examining a relationship between white matter and executive function. The goal of the present study was to examine how WMH and MTA relate to a variety of executive functions, including flexibility, fluency, inhibition, planning, set shifting, and working memory. Strong correlations were observed between WMH and MTA and most of the executive functions. However, only MTA was related to flexibility and set shifting performance. Regression analysis furthermore showed that MTA was the strongest predictor of working memory, after which no further significant association with WMH was noted. Alternatively, both MTA and periventricular hyperintensities independently predicted inhibition performance. These findings emphasize the importance of MTA when examining age-related decline in executive functioning.     

Brain MR kurtosis imaging study: Contrasting gray and white matter

This paper mainly focuses on characterization of different brain tissues such as White and Gray matter (WM and GM) using the relation between Diffusion Tensor Imaging and Diffusion Kurtosis Imaging parameters. Both Diffusion Tensor Imaging and Diffusion Kurtosis Imaging are the extension of Diffusion Weighted Imaging, which are widely applied for analysing micro fibre structure of human organs non-invasively. Diffusion Tensor Imaging assumes that the water diffusion is in Gaussian nature and Diffusion Kurtosis Imaging accounts the deviation of the Gaussian nature. This study, conducted a correlation and regression analysis between different parametric maps generated from Diffusion Kurtosis Images. For this we have chosen 200 regions of interest pixels drawn from brain MRIs. From the results, it is observed that there is a significant variation in the correlation results between Axial Diffusion and Kurtosis Fractional Anisotropy maps of Gray matter and White matter tissues. This can be employed for enhancing accuracy in MRI segmentation techniques and also as a potential tool for Neuro degenerative disease detection.     

Processing speed in normal aging: Effects of white matter hyperintensities and hippocampal volume loss

Changes in cognitive functioning are said to be part of normal aging. Quantitative MRI has made it possible to measure structural brain changes during aging which may underlie these decrements which include slowed information processing and memory loss. Much has been written on white matter hyperintensities (WMH), which are associated with cognitive deficits on tasks requiring processing speed and executive functioning, and hippocampal volume loss, which is associated with memory decline. Here we examine volumetric MRI measures of WMH and hippocampal volume loss together in relation to neuropsychological tests considered to be measures of executive functioning and processing speed in 81 non-demented elderly individuals, aged 75–90. Correlational analysis showed that when controlling for age, both greater WMH volume and smaller hippocampal volume were correlated with slower performances on most tests with the exception of a battery of continuous performance tests in which only WMH was correlated with slower reaction time (RT). We then performed a series of hierarchical multiple regression analyses to examine the independent contributions of greater WMH volume and reduced hippocampal volume to executive functioning and processing speed. The results showed that for the four measures requiring executive functioning and speed of processing, WMH volume and hippocampal volume combined predicted between 21.4% and 37% of the explained variance. These results suggest that WM integrity and hippocampal volume influence cognitive decline independently on tasks involving processing speed and executive function independent of age.     

Exposure to severe urban air pollution influences cognitive outcomes, brain volume and systemic inflammation in clinically healthy children

Exposure to severe air pollution produces neuroinflammation and structural brain alterations in children. We tested whether patterns of brain growth, cognitive deficits and white matter hyperintensities (WMH) are associated with exposures to severe air pollution. Baseline and 1 year follow-up measurements of global and regional brain MRI volumes, cognitive abilities (Wechsler Intelligence Scale for Children-Revised, WISC-R), and serum inflammatory mediators were collected in 20 Mexico City (MC) children (10 with white matter hyperintensities, WMH⁺, and 10 without, WMH⁻) and 10 matched controls (CTL) from a low polluted city. There were significant differences in white matter volumes between CTL and MC children - both WMH⁺ and WMH⁻ - in right parietal and bilateral temporal areas. Both WMH⁻ and WMH⁺ MC children showed progressive deficits, compared to CTL children, on the WISC-R Vocabulary and Digit Span subtests. The cognitive deficits in highly exposed children match the localization of the volumetric differences detected over the 1 year follow-up, since the deficits observed are consistent with impairment of parietal and temporal lobe functions. Regardless of the presence of prefrontal WMH, Mexico City children performed more poorly across a variety of cognitive tests, compared to CTL children, thus WMH⁺ is likely only partially identifying underlying white matter pathology. Together these findings reveal that exposure to air pollution may perturb the trajectory of cerebral development and result in cognitive deficits during childhood.     

White matter integrity and pictorial reasoning in high-functioning children with autism

The current study investigated the neurobiological role of white matter in visuospatial versus linguistic processing abilities in autism using diffusion tensor imaging. We examined differences in white matter integrity between high-functioning children with autism (HFA) and typically developing controls (CTRL), in relation to the groups’ response times (RT) on a pictorial reasoning task under three conditions: visuospatial, V, semantic, S, and V + S, a hybrid condition allowing language use to facilitate visuospatial transformations.     

Gray matter density negatively correlates with duration of heroin use in young lifetime heroin-dependent individuals

Numerous studies have documented cognitive impairments and hypoactivity in the prefrontal and anterior cingulate cortices in drug users. However, the relationships between opiate dependence and brain structure changes in heroin users are largely unknown. In the present study, we measured the density of gray matter (DGM) with voxel-based morphometry in 30 lifetime heroin-dependent individuals who had abstained from drug use for 5 months, and 34 healthy participants. The DGM of the prefrontal, temporal and cingulate cortices significantly decreased in heroin addicts relative to the healthy group. Critically, partial correlation analysis, which controlled for age, education and gender factors as well as nicotine use and heroin abstinence duration, showed that the duration of heroin use negatively correlated with the DGM in heroin-dependent individuals. These results provide compelling evidence for structural abnormality in heroin-dependent individuals and further suggest that duration of heroin use is a critical factor leading to brain damage.     

Incidence of Specific Absolute Neurocognitive Impairment in Globally Intact Children with Histories of Early Severe Deprivation

Postnatal deprivation is associated with neurocognitive delay/dysfunction. Although “catch up” in global cognition following adoption has been reported, this study examined the incidence of specific absolute impairment in adopted children with intact global cognitive functioning. Eighty-five children (38 males, mean age = 112.8, SD = 30.3 months; range 61–209 months) raised from birth in orphanages underwent comprehensive neuropsychological evaluation. Fifty-four were deemed globally intact (IQ > 85). Of those deemed globally intact, 46% evidenced absolute impairment in at least one domain of functioning. Duration of stay in the orphanage was directly associated with incidence of impairment and number of domains affected. A substantial proportion of participants evidenced persistent, absolute impairment in one or more domains of neurocognitive function despite integrity of basic intellectual functions.     

Myelin breakdown mediates age-related slowing in cognitive processing speed in healthy elderly men

Background

To assess the hypothesis that in a sample of very healthy elderly men selected to minimize risk for Alzheimer’s disease (AD) and cerebrovascular disease, myelin breakdown in late-myelinating regions mediates age-related slowing in cognitive processing speed (CPS).

Materials and methods

The prefrontal lobe white matter and the genu of the corpus callosum myelinate later in brain development (late-myelinating white matter; LMWM) and are more vulnerable to breakdown due to the effects of normal aging. An in vivo MRI biomarker of myelin integrity (transverse relaxation rates; R₂) of LMWM was obtained for 38 very healthy elderly adult men (mean age = 66.3 years; SD = 6.0; range = 55–76). To evaluate regional specificity, we also assessed a contrasting early-myelinating region (splenium of the corpus callosum; SWM), which primarily contains axons involved in visual processing. CPS was assessed using the Trail Making Test.

Results

LMWM R₂ and CPS measures were significantly correlated (r = .515, p = .0009), but no significant association between R₂ and CPS was detected in the splenium (p = .409). LMWM R₂, but not SWM R₂, was a significant mediator of the relationship between age and CPS (p = .037).

Conclusions

In this very healthy elderly sample, age-related slowing in CPS is mediated by myelin breakdown in highly vulnerable late-myelinating regions but not in the splenium.     

Effects of dual task difficulty in motor and cognitive performance: Differences between adults and adolescents

In the present study our aim was to compare dual-task performance in thirteen adolescents and fifteen young adults while concurrently performing a cognitive and a motor task. The postural control variables were obtained under three different conditions: i) bipedal stance, ii) tandem stance and iii) unipedal stance. The cognitive task consisted of a backward digit span test in which the participants were asked to memorize a sequence of numbers and then repeat the number in reverse order at three different difficulty levels (i.e. with 3, 4 and 5 digits). The difficulty of the cognitive task was seen to have different effects on adolescents and young adults. Adolescents seem to prioritize postural control during high difficulty postural conditions while a cross-domain competition model appeared in easy postural conditions.     

The Neuropsychology of HIV/AIDS in Older Adults

Highly active antiretroviral therapy is allowing increasing numbers of adults to age with HIV. The neuropsychological effects of aging with HIV are reviewed through three types of studies. First, the separate effects of HIV and aging on cognition are examined in studies that compare younger adults with HIV with neurologically normal older adults. Second, studies examine the impact of aging within samples of adults with HIV only. Third, providing the most critical evidence, are studies that assess cognition in younger and older adults with HIV relative to younger and older adults without HIV. In general research findings are inconclusive. Large individual differences among older adults with HIV as well as co-factors (APOE4 and detectable viral load) may account for inconsistent findings in the literature. A subgroup of older adults with HIV may be at greater risk for cognitive impairment, especially in attention functioning.     

Correlates of intellectual ability with morphology of the hippocampus and amygdala in healthy adults

Several prior imaging studies of healthy adults have correlated volumes of the hippocampus and amygdala with measures of general intelligence (IQ), with variable results. In this study, we assessed correlations between volumes of the hippocampus and amygdala and full-scale IQ scores (FSIQ) using a method of image analysis that permits detailed regional mapping of this correlation throughout the surface contour of these brain structures. We delineated the hippocampus and amygdala in high-resolution magnetic resonance images of the brain from 34 healthy individuals. We then correlated FSIQ with overall volumes and with the surface morphologies of each of these structures. Hippocampus volumes correlated significantly and inversely with FSIQ independently of gender, age, socioeconomic status, and whole brain volume. Left and right hippocampus volumes correlated respectively with verbal and performance IQ subscales. Higher IQs were significantly associated with large inward deformations of the surface of the anterior hippocampus bilaterally. These findings suggest that a smaller anterior hippocampus contributes to an increased efficiency of neural processing that subserves overall intelligence.     

Microstructural integrity of white matter moderates an association between childhood adversity and adult trait anger

Amongst a number of negative life sequelae associated with childhood adversity is the later expression of a higher dispositional tendency to experience anger and frustration to a wide range of situations (i.e., trait anger). We recently reported that an association between childhood adversity and trait anger is moderated by individual differences in both threat-related amygdala activity and executive control-related dorsolateral prefrontal cortex (dlPFC) activity, wherein individuals with relatively low amygdala and high dlPFC activity do not express higher trait anger even when having experienced childhood adversity. Here, we examine possible structural correlates of this functional dynamic using diffusion magnetic resonance imaging data from 647 young adult men and women volunteers. Specifically, we tested whether the degree of white matter microstructural integrity as indexed by fractional anisotropy modulated the association between childhood adversity and trait anger. Our analyses revealed that higher microstructural integrity of multiple pathways was associated with an attenuated link between childhood adversity and adult trait anger. Amongst these pathways was the uncinate fasciculus (UF; ΔR ² = 0.01), which not only provides a major anatomical link between the amygdala and prefrontal cortex but also is associated with individual differences in regulating negative emotion through top-down cognitive reappraisal. These findings suggest that higher microstructural integrity of distributed white matter pathways including but not limited to the UF may represent an anatomical foundation serving to buffer against the expression of childhood adversity as later trait anger, which is itself associated with multiple negative health outcomes.     

Executive functions and social skills in survivors of pediatric brain tumor

Medical advances have resulted in increased survival rates for children with brain tumors. Consequently, issues related to survivorship have become more critical. The use of multimodal treatment, in particular cranial radiation therapy, has been associated with subsequent cognitive decline. Specifically, deficits in executive functions have been reported in survivors of various types of pediatric brain tumor. Survivors are left with difficulties, particularly in self-monitoring, initiation, inhibition, and planning, to name a few. Another domain in which survivors of pediatric brain tumor have been reported to show difficulty is that of social skills. Parents, teachers, and survivors themselves have reported decreased social functioning following treatment. Deficits in executive functions and social skills are likely interrelated in this population, as executive skills are needed to navigate various aspects of social interaction; however, this has yet to be studied empirically. Twenty-four survivors of pediatric brain tumor were assessed using a computerized task of executive functions, as well as paper-and-pencil measures of social skills and real-world executive skills. Social functioning was related to a specific aspect of executive functions, that is, the survivors' variability in response time, such that inconsistent responding was associated with better parent-reported and survivor-reported social skills, independent of intellectual abilities. Additionally, parent-reported real-world global executive abilities predicted parent-reported social skills. The implications of these findings for social skills interventions and future research are discussed.     

Parent rating of executive function in fetal alcohol spectrum disorder: A review of the literature and new data on Aboriginal Canadian children

Aboriginal children in Canada are at high risk of fetal alcohol spectrum disorder (FASD) but there is little research on the cognitive impact of prenatal alcohol exposure (PAE) in this population. This paper reviews the literature on parent report of executive functioning in children with FASD that used the Behavior Rating Inventory of Executive Function (BRIEF). New data on the BRIEF is then reported in a sample of 52 Aboriginal Canadian children with FASD for whom a primary caregiver completed the BRIEF. The children also completed a battery of neuropsychological tests. The results reveal mean scores in the impaired range for all three BRIEF index scores and seven of the eight scales, with the greatest difficulties found on the Working Memory, Inhibit and Shift scales. The majority of the children were reported as impaired on the index scores and scales, with Working Memory being most commonly impaired scale. On the performance-based tests, Trails B and Letter Fluency are most often reported as impaired, though the prevalence of impairment is greater for parent ratings than test performance. No gender difference is noted for the parent report, but the boys had slightly slower intellectual functioning and were more perseverative than the girls on testing. The presence of psychiatric comorbidity is unrelated to either BRIEF or test scores. These findings are generally consistent with prior studies indicating that parents observe considerable executive dysfunction in children with FASD, and that children with FASD may have more difficulty with executive functions in everyday life than is detected by laboratory-based tests alone.     

Dynamic testing of learning potential in adults with cognitive impairments: A systematic review of methodology and predictive value

Dynamic testing includes procedures that examine the effects of brief training on test performance where pre‐ to post‐training change reflects patients’ learning potential. The objective of this systematic review was to provide clinicians and researchers insight into the concept and methodology of dynamic testing and to explore its predictive validity in adult patients with cognitive impairments. The following electronic databases were searched: PubMed, PsychINFO, and Embase/Medline. Of 1141 potentially relevant articles, 24 studies met the inclusion criteria. The mean methodological quality score was 4.6 of 8. Eleven different dynamic tests were used. The majority of studies used dynamic versions of the Wisconsin Card Sorting Test. The training mostly consisted of a combination of performance feedback, reinforcement, expanded instruction, or strategy training. Learning potential was quantified using numerical (post‐test score, difference score, gain score, regression residuals) and categorical (groups) indices. In five of six longitudinal studies, learning potential significantly predicted rehabilitation outcome. Three of four studies supported the added value of dynamic testing over conventional testing in predicting rehabilitation outcome. This review provides preliminary support that dynamic tests can provide a valuable addition to conventional tests to assess patients’ abilities. Although promising, there was a large variability in methods used for dynamic testing and, therefore, it remains unclear which dynamic testing methods are most appropriate for patients with cognitive impairments. More research is warranted to further evaluate and refine dynamic testing methodology and to further elucidate its predictive validity concerning rehabilitation outcomes relative to other cognitive and functional status indices.     

Developmental changes in effects of risk and valence on adolescent decision-making

Recent research on risky decision-making in adults has shown that both the risk in potential outcomes and their valence (i.e., whether those outcomes involve gains or losses) exert dissociable influences on decisions. We hypothesised that the influences of these two crucial decision variables (risk and valence) on decision-making would vary developmentally during adolescence. We adapted a risk-taking paradigm that provides precise metrics for the impacts of risk and valence. Decision-making in 11–16 year old female adolescents was influenced by both risk and valence. However, their influences assumed different developmental patterns: the impact of valence diminished with age, while there was no developmental change in the impact of risk. These different developmental patterns provide further evidence that risk and valence are fundamentally dissociable constructs and have different influences on decisions across adolescence.     

Assessment of cognition in an adolescent Indigenous population

The assessment of cognition in Indigenous populations is often complicated by cultural and language differences and unfamiliarity with the assessment process. Cognitive tasks are being developed that reduce the impact of these factors. These processes need to be evaluated in different cultural and ethnic groups to determine whether they are appropriate. Such an assessment was recently used in two studies of cognition of 237 Indigenous Australian adolescents (age: M = 16.06 ± 2.16 years). The tasks were completed appropriately, with response times and error rates increasing for difficult tasks. Duration and error rates decreased for the round‐based tasks, in line with performance in non‐Indigenous samples. There were no gender effects. Age associations occurred in some tasks, but significant correlations were only of a small magnitude. Although the battery appeared to be completed appropriately in this study, more work needs to be conducted examining the influence of demographic factors to ensure that control data can be most appropriately matched in future studies.