Tests Of Information Processing Speed Research Articles

Skeletal muscle adiposity is a novel risk factor for poor cognition in African Caribbean women.

Skeletal muscle adiposity (myosteatosis) is recognized as a major risk factor for cardiometabolic diseases, and it increases with aging. The relationship of myosteatosis with cognitive impairment is unknown. The association of calf myosteatosis (measured by computed tomography-derived skeletal muscle density; higher values indicate less myosteatosis) with cognitive function was examined among 626 African Caribbean women who were aged 40 to 84 years, a population highly vulnerable to increased myosteatosis. Cognition was assessed by the Digit Symbol Substitution Test (DSST), a test of information processing speed (higher scores indicate better performance). Linear regression was used to assess the association of muscle density with DSST. Adjusting for age, education, muscle area, BMI, hypertension, diabetes, cardiovascular event history, lifestyle factors, lipid-lowering medication use, and menopausal status, a one-SD lower muscle density was associated with a 1.69-point lower DSST score (p = 0.002). BMI, diabetes, and hypertension interactions were not statistically significant, suggesting that the main association was not moderated by overall obesity or cardiometabolic diseases. These findings suggest that greater myosteatosis is associated with slower information processing speed, an early indicator of cognitive impairment. Further studies are needed to establish this association in this and other populations using an expanded battery of cognitive tests with longitudinal follow-up and to identify the biological mechanisms underlying this relationship.

Evaluation of major depressive disorder using 7 Tesla phase sensitive neuroimaging before and after mindfulness-based cognitive therapy

ObjectiveWe applied 7 Tesla phase sensitive imaging to evaluate the impact of brain iron levels on depression severity and cognitive function in individuals with major depressive disorder (MDD) treated with mindfulness-based cognitive therapy (MBCT). MethodsSeventeen unmedicated MDD participants underwent MRI, evaluation of depression severity, and cognitive testing before and after receiving MBCT, compared to fourteen healthy controls (HC). Local field shift (LFS) values, measures of brain iron levels, were derived from phase images in the putamen, caudate, globus pallidus (GP), anterior cingulate cortex (ACC) and thalamus. ResultsCompared to the HC group, the MDD group had significantly lower baseline LFS (indicative of higher iron) in the left GP and left putamen and had a higher number of subjects with impairment in a test of information processing speed. In the MDD group, lower LFS values in the left and right ACC, right putamen, right GP, and right thalamus were significantly associated with depression severity; and lower LFS in the right GP was correlated with worse performance on measures of attention. All MBCT participants experienced depression relief. MBCT treatment also significantly improved executive function and attention. MBCT participants with lower baseline LFS values in the right caudate experienced significantly greater improvement in depression severity with treatment; and those with lower LFS values in the right ACC, right caudate, and right GB at baseline performed better on measures of verbal learning and memory after MBCT. ConclusionsOur study highlights the potential contribution of subtle differences in brain iron to MDD symptoms and their successful treatment.

SKELETAL MUSCLE ADIPOSITY IS ASSOCIATED WITH LOWER COGNITION IN AFRICAN CARIBBEAN WOMEN

Abstract Objective Skeletal muscle adiposity (SMA) increases with aging and is recognized as a major risk factor for cardiometabolic diseases, disability, and mortality among older adults. Obesity is related to dementia and cognitive decline yet the relationship between SMA and cognition remains ill defined. The objective of this study was to assess SMA and cognitive function among African Caribbean women.Design and Methods Cross-sectional analysis of 448 African Caribbean women in the Tobago Health Study (mean age, 55 years; range, 39-84 years). Cognition was assessed by the Digit Symbol Substitution Test (DSST), a test of information processing speed with a range of 0-90; higher scores suggest better cognitive function (faster information processing speed). Calf SMA (muscle density) was assessed with computed tomography (Stratec XCT-2000). Linear regression was used to assess the association of SMA with DSST adjusted for age, education, muscle area, waist circumference, alcohol intake, smoking, physical activity, diabetes, and hypertension. Results Participants had a BMI of 30.7 kg/m2. Mean (SD) DSST scores and SMA were 39.2 (13.1) and 71.7 (5.3) mg/cm3, respectively. After full adjustment, we found that one SD greater skeletal muscle adiposity was associated with a 1.40 lower DSST score (p-value=0.025). Conclusions Our findings suggest that in African Caribbean women, greater SMA is associated with slower information processing speed, an early indicator of future dementia risk. Future studies using an expanded battery of cognitive tests and longitudinal follow-up should further advance our understanding of the role of SMA and dementia risk among African ancestry populations.

Are we ready to define cognitive worsening in MS? How different cutoffs detect future cognitive worsening after six years of follow-up

BackgroundAlthough cognitive evaluation has been incorporated in recent MS clinical trials, the definition of cognitive progression is not clear and recent data are questioning the 4-point cutoff using the SDMT at the individual level. We aimed to evaluate the behavior of cognitive performance over time using different cutoffs. MethodsCognitive performance over six years was analyzed in a cohort of 42 relapsing-remitting MS patients and 30 controls using verbal/visual memory and information processing speed tests. Fixed cutoffs were: 10% and 20% change (all tests) and a 4- and 8-point change (SDMT). The relative cutoff established by regression-based models was a 1SD change. ResultsThe distributions of “worsening”, “stability”, and “improvement” showed low concordance rates across the cutoffs (p < 0.001 for most comparisons). Most patients classified with worsening initially using fixed cutoffs had subsequent improvement in all cognitive tests, yielding a low sensitivity to predict later cognitive worsening. Using the relative cutoff, the proportion of patients with subsequent improvement was noticeably smaller. ConclusionsFixed cutoffs classify a high proportion of patients with cognitive improvement. Most patients categorized with worsening initially presented subsequent improvement. Instead, the relative cutoff generally had a better performance. These data raise concerns about how we are defining cognitive worsening so far, especially at the individual level.

Retinal Thinning in People With Well-Controlled HIV Infection.

Retinal measurements correlate with disease progression in patients with multiple sclerosis; however, whether they associate with neurologic disease in people with controlled HIV is unknown. Using spectral domain optical coherence tomography, we evaluated retinal differences between people with HIV and HIV-negative controls and investigated clinical correlates of retinal thinning. People with HIV on antiretroviral therapy for at least 1 year and HIV-negative controls recruited from the same communities underwent spectral domain optical coherence tomography, ophthalmic examination, brain MRI, and neuropsychological testing. Retinal nerve fiber layer (RNFL) and ganglion cell inner plexiform layer (GC-IPL) thicknesses were compared between groups using analysis of covariance with relevant clinical variables as covariates. Linear regression was used to explore associations of HIV history variables, cognitive domain scores, and MRI volume measurements within the HIV group. The HIV group (n = 69), with long-duration HIV infection (median time from diagnosis 19 years) and outstanding viral control have thinner retinal layers than HIV-negative controls (n = 28), after adjusting for covariates (GC-IPL: P = 0.002; RNFL: P = 0.024). The effect of HIV on GC-IPL thickness was stronger in women than in men (Women: P = 0.011; Men: P = 0.126). GC-IPL thickness is associated with information processing speed in the HIV group (P = 0.007, semipartial r = 0.309). No associations were found with retinal thinning and MRI volumes or HIV factors. People with HIV on antiretroviral therapy have thinning of the RNFL and GC-IPL of the retina, and women particularly are affected to a greater degree. This retinal thinning was associated with worse performance on tests of information processing speed.

Abstract MP22: Myosteatosis Is Associated With Worse Cognition In African Caribbean Women

Introduction: Skeletal muscle adipose tissue infiltration (i.e. myosteatosis) increases with aging, and is recognized as a major risk factor for cardio-metabolic diseases. While it is known that visceral adiposity is related to dementia and cognitive decline, the relationship between myosteatosis and cognition is not well understood. Such studies are particularly needed among African ancestry women, who have greater myosteatosis and higher burden of Alzheimer’s Disease and Related Dementias compared with White women. Aim: The objective of this study was to assess if, among African Caribbean middle-aged and older women (aged 40-79), myosteatosis is associated with cognitive function. Methods: Data were collected on women (n=481) from the Tobago Health Study. Cognition was assessed by the Digit Symbol Substitution Test (DSST), a test of information processing speed; DSST is a fast, reliable and sensitive test that predicts onset of dementia. DSST was administered to participants by trained interviewers; scores ranged from 0 to 81 (lower score indicating cognitive decline). Peripheral Quantitative Computed Tomography (Stratec XCT-2000) was used to measure calf skeletal muscle density (MD), which was used as a proxy measure for the myosteatosis (lower MD reflects more adiposity). Linear regression was used to assess the association of muscle density with cognition and was adjusted for age, education, muscle area, waist circumference, alcohol intake, smoking, walking hours, diabetes and hypertension. Results for the primary predictor of interest (MD) were standardized with effects shown per standard deviation (SD). Results: Mean (SD) DSST scores were 38.8 (13.2). Overall, participants were aged 55.2 years and had a BMI of 30.7 kg/m 2 . Mean (SD) MD was 71.7((5.3) (mg/cm 3 ). As expected, in unadjusted analyses, the strongest predictors of lower DSST scores in these women were older age and lower education, higher waist circumference, diabetes and hypertension. After full adjustment, we found that a one SD increase in MD was associated with a 1.48 increase in DSST score (p-value=0.015). Conclusions: Our findings suggest that in African Caribbean women, greater myosteatosis is associated with slower information processing speed, an early indicator of future dementia risk. Future studies using expanded battery of cognitive tests and longitudinal follow-up are warranted to further advance our understanding of the novel role of myosteatosis in dementia risk among African ancestry women.

The Symbol Digit Modalities Test (SDMT) is sensitive but non-specific in MS: Lexical access speed, memory, and information processing speed independently contribute to SDMT performance

BackgroundThe Symbol Digit Modalities Test (SDMT) is the most sensitive metric of neurocognitive function in multiple sclerosis (MS), and is consistently interpreted as a measure of information processing speed (IPS). ObjectiveTo evaluate the cognitive psychometric profile captured by the SDMT to identify whether different cognitive processes independently underlie performance. MethodsThree samples of MS patients (total n=661; 185 research patients at MS center; 370 clinical patients at MS center; 106 persons with MS from the community) completed objective assessments of neuropsychological function across cognitive domains. Exploratory factor analysis (EFA) was used to derive latent cognitive factor scores, and operationalize cognitive domain composite scores, to understand the unique, shared and redundant contribution of different cognitive domains to SDMT performance using hierarchical multiple regression and commonality analysis. ResultsAcross three independent samples we provide converging strong evidence that the cognitive domains of Memory, IPS and Rapid Automatized Naming (lexical access speed) jointly and uniquely contribute to SDMT performance. ConclusionThe SDMT measures multiple cognitive processes, which likely explains the high degree of sensitivity to cognitive change in MS. Researchers and clinicians should interpret the SDMT as a multifarious measure of general cognition rather than a specific test of IPS.

Patterning of individual variability in neurocognitive health among South African women exposed to childhood maltreatment

There are individual differences in health outcomes following exposure to childhood maltreatment, yet constant individual variance is often assumed in analyses. Among 286 Black, South African women, the association between childhood maltreatment and neurocognitive health, defined here as neurocognitive performance (NP), was first estimated assuming constant variance. Then, without assuming constant variance, we applied Goldstein’s method (Encyclopedia of statistics in behavioral science, Wiley, 2005) to model “complex level-1 variation” in NP as a function of childhood maltreatment. Mean performance in some tests of information processing speed (Digit-symbol, Stroop Word, and Stroop Color) lowered with increasing severity of childhood maltreatment, without evidence of significant individual variation. Conversely, we found significant individual variation by severity of childhood maltreatment in tests of information processing speed (Trail Making Test) and executive function (Color Trails 2 and Stroop Color-Word), in the absence of mean differences. Exploratory results suggest that the presence of individual-level heterogeneity in neurocognitive performance among women exposed to childhood maltreatment warrants further exploration. The methods presented here may be used in a person-centered framework to better understand vulnerability to the toxic neurocognitive effects of childhood maltreatment at the individual level, ultimately informing personalized prevention and treatment.

Neurocognitive functioning in patients with conversion disorder/functional neurological disorder.

Neurocognitive symptoms are common in individuals with somatic symptom and related disorders (SSRD), but little is known about the specific impairments in neurocognitive domains in patients with conversion disorder (CD)/functional neurological disorder (FND). This study examines neurocognitive functioning in patients with CD/FND compared to patients with other SSRD. The sample consisted of 318 patients. Twenty‐nine patients were diagnosed with CD/FND, mean age 42.4, standard deviation (SD) = 13.8 years, 79.3% women, and 289 patients had other SSRD (mean age 42.1, SD = 13.3, 60.2% women). Patients completed a neuropsychological test battery that addressed a broad range of neurocognitive domains, including information processing speed, attention and executive functioning. Patients with CD/FND had clinically significant neurocognitive deficits in all neurocognitive domains based on normative data comparison. Patients with CD/FND also performed significantly worse than patients with other SSRD on information processing speed (Digit Symbol Substitution Test (V = .115, p = .035), Stroop Color–Word Test (SCWT) card 1 (V = .190, p = .006), and SCWT card 2 (V = .244, p < .001). No CD/FND vs. other SSRD differences were observed in other neurocognitive domains. These findings indicate the patients with CD/FND perform worse on information processing speed tests compared to patients with other SSRD.

Changes in functional brain networks and neurocognitive function in Chinese gynecological cancer patients after chemotherapy: a prospective longitudinal study

BackgroundPrevious neurocognitive assessments in non-central nervous system cancers highlight the high incidence of neurocognitive dysfunction in this study population. However, there have been few studies exploring neurocognitive dysfunction induced by chemotherapy in gynecological cancer patients. This prospective longitudinal study was conducted to assess neurocognitive functioning and functional brain networks in Chinese gynecological cancer patients pre- and post-chemotherapy, while additionally including age-matched healthy subjects as the control group.MethodsAll research participants were evaluated using a resting-state functional magnetic resonance imaging and neurocognition assessment. Behavioral data were conducted using SPSS for descriptive statistics, correlation and comparison analyses. Preprocessing of MRI (Magnetic Resonance Imaging) data and network analyses were performed using GRETNA (Graph Theoretical Network Analysis).ResultsA total of 40 subjects joined this study, with 20 subjects in each group. With the exception of the mean of psychomotor speed, there was no significant difference pre-chemotherapy between patients and healthy controls in neurocognitive test mean scores (Ps > 0.05). During the post-chemotherapy assessment, there were significant differences in the mean scores of neurocognitive tests (including Digit Span tests, verbal memory, immediate recall, delayed recall, and information processing speed tests) (all Ps < 0 .05). Longitudinal graph analysis revealed statistically significant differences in the patient group, with significant decreases in both local efficiency (P < 0.01) and global efficiency (P = 0.04). Lower raw TMT-A scores were significantly associated with lower local efficiency (r = 0.37, P = 0.03). Lower verbal memory scores were statistically significant and associated with lower global efficiency (r = 0.54, P = 0.02) in the patient group, but not in the healthy control group.ConclusionsThis study found that the risk of brain function and neurocognitive changes following chemotherapy could potentially guide patients in making appropriate treatment decisions, and this study may identify a cohort that could be suited for study of an intervention.

Generalizability of demographically corrected Zambian neuropsychological norms to South African women

Objective: Demographically corrected norms typically account for the effects of age, education, and in some cases, sex and other factors (e.g. race/ethnicity). However, generalizability of normative standards to different countries and ethnic groups is not universal. This study sought to determine whether demographically specific Zambian neuropsychological norms would generalize to a group of South African women.Method: 212 English-Xhosa bilingual, South African (SA) women were administered a comprehensive neuropsychological (NP) test battery in either English or Xhosa. We examined rates of “impairment” using Global Deficit Scores (GDS) based upon published, demographically corrected norms from a nearby African country (Zambia). Using multiple regression, we examined the extent to which Zambian norms “corrected” for the effects of age and education in this SA sample.Results: Compared to the normative standards from Zambia, the South African women performed somewhat worse than expected on a few test measures and better than expected on others, but their GDS and associated “impairment” rates were close to what was seen in Zambia. Demographically corrected Zambian norms adequately adjusted for the effects of age and years of education in this sample of SA women, with the exception that Zambian norms appeared to “under correct” for the positive effects of years of education on tests of information processing speed.Conclusions: Demographically corrected norms developed for Zambia may adequately adjust for the effects of age in SA women. Further research is needed to determine whether additional corrections for education are needed in SA, especially for tests of information processing speed.

A clinical screening tool for objective and subjective cognitive disorders in multiple sclerosis.

Cognitive dysfunction is common in multiple sclerosis (MS). Deficits can affect attention, concentration, planning, and memory. They can have severe functional consequences in many domains. Cognitive complaints are frequently associated with other confounding factors (fatigue, anxiety, depression, or treatment side effects). In most cases, cognitive assessment is proposed after a spontaneous complaint, but determining the extent of discomfort perceived by the patient, the influence of coexisting factors, or the optimal timing for a more complete neuropsychological assessment is difficult. The objective of this work was to evaluate the feasibility and relevance of a fast global assessment of both objective and subjective cognitive dysfunction in MS. MS patients underwent a brief cognitive assessment including 7 visual analogue scales (VASs) asking about the patient's subjective level of discomfort in various domains, a memory test (Barbizet's lion story), a commonly used test of information processing speed (Symbol Digit Modalities Test [SDMT]) and self-reporting questionnaires for fatigue and mood (Fatigue Severity Scale [FSS] and Hospital Anxiety and Depression Scale [HADS]). Spearman correlation coefficients among scores were estimated. The mean age of the 73 patients included was 48.3 (SD 11.1) years; 78% were females and 52.8% had the remittent-recurrent MS form, 8.3% the primary progressive form, and 38.9% the secondary progressive form. In less than 20min, this brief cognitive assessment was able to identify symptoms and quantify discomfort level. Symptoms of fatigue and anxiety frequently coexisted with cognitive complaints. We found modest correlations between scores on the VAS fatigue and the FSS and between scores on the VAS mood and the HADS. Analytical evaluation revealed that most patients had similar SDMT and recall profiles; however, a small proportion showed a dissociation between these 2 tests, which validated the inclusion of both tests in the assessment. Accounting for coexisting factors (e.g., anxiety and fatigue) and their functional repercussions is essential for prioritizing these problems within the context of multidisciplinary patient treatment. Considering the possible multifactorial character of cognitive dysfunction in MS, it is essential to ask patients about their experiences and to take into account cognitive complaints in the follow-up of patients. The assessment tool we propose is simple and easy to use in a clinical setting and provides the information necessary for requesting (or not) a more complete neuropsychological assessment.

Сегментация спонтанной речи и индивидуальность эксперта

The paper focuses on the findings of the psycholinguistic tests with German and Russian spontaneous speech in order to detect possible interrelations between the nature of division of spontaneous speech into sentences (their average length) and individual specifics of the expert who carries out this division. The kit of stimulating material consisted of the text part subject to the expert segmentation and the text part that included a five-factor personality questionnaire, information processing speed tests and two tests connected with the working memory capacity. The segmentation was conducted on the basis of the text information alone, without any reliance on the sound. Despite the research hypothesis, the capacity of the expert’s working memory demonstrated no connection with the average sentence length in either Russian or German. The information processing rate also had no effect on the sentence length. Nevertheless, it was established that during annotation of the German spontaneous speech, significant impact on the sentence length was made by the level of neuroticism, that is, experts with a higher score (more emotional) had a tendency to break the text into shorter statements. Using the material of the Russian language, the interrelation between the average sentence length and the “self-control – impulsiveness” proved statistically significant – that is, experts more prone to the self-regulation of their behavior tended to divide the text into longer sentences. The analysis of the sentence length revealed statistically significant correlations (from moderate to strong) in the average sentence length in diverse texts as they were marked by the same expert; notably, this phenomenon was observed on the material of both the German and Russian languages. This fact evidences that the sentence length is individual for each expert and remains stable regardless of external factors, such as the language or the text type.

Cognitive assessment in patients with multiple sclerosis: From neuropsychological batteries to ecological tools.

Cognitive impairment (CI) is frequent in patients with multiple sclerosis (PwMS) and could negatively affect family social and vocational activities. Detecting CI is clinically relevant, so the emerging question is the strategy for assessing cognition in MS. An update on cognitive assessment in PwMS with use of standard neuropsychological (NP) tests and ecological tools. The minimal cognitive assessment in MS should include at least NP tests assessing information processing speed (IPS) and verbal and visuospatial episodic memory. The IPS could be easily and quickly evaluated with symbol digit substitution tests by using paper for the oral version of the Symbol Digit Modalities Test or a laptop for the Computerised Speed Cognitive Test. The comprehensive NP battery must be performed by a qualified neuropsychologist to adequately characterize the extent and severity of CI in PwMS. The quiet and controlled environment used for this standardized assessment could be a limitation for generalizing the results because it does not reflect real daily life conditions. Thus, this context could decrease the ability to detect some cognitive deficits that could occur only in more complex situations. Thus, ecological evaluation seems a complementary and promising approach for detecting cognitive abnormalities in daily activities. Recent efforts have been made to detect and characterize cognitive deficits in PwMS. Some IPS and episodic memory NP tests have been validated in MS and should be proposed to patients in the clinical setting. Besides NP tests, ecological tools are becoming important for detecting cognitive dysfunction in everyday-like conditions. Further research is needed to validate relevant tools for monitoring cognition in MS and the ability to detect clinically meaningful change in longitudinal studies.

Deconstructing the symbol digit modalities test in multiple sclerosis: The role of memory

BackgroundThe Symbol Digit Modalities Test (SDMT) is a sensitive measure of impaired cognition in people with MS. While the SDMT is primarily considered a test of information processing speed, other components such as visual scanning and oral-motor ability have also been linked to performance. The objective of this study was to determine the role of memory in the performance of the SDMT. MethodsTwo version of a modified computerized SDMT (c-SDMT) were employed, a fixed and a variable. For each group 50 MS and 33 healthy control (HC) participants were recruited. In the fixed c-SDMT, the symbol-digit code is kept constant for the entire test whereas in the variable version, it changes eight times. Unlike the traditional SDMT which records the correct number of responses, the c-SDMT presented here measures the mean response time (in seconds) for the eight trials. ResultsMS participants were slower than HC on the fixed (p < 0.001) and variable (p = 0.005) c-SDMT. Trend analysis showed performance improvement on the fixed, but not on the variable c-SDMT in both MS and HC groups. Furthermore, immediate visual memory recall was associated with the fixed (β = −0.299, p = 0.017), but not variable (B = −0.057, p = 0.260) c-SDMT. Immediate verbal memory was not associated with either versions of the c-SDMT. ConclusionsGiven that the fixed and variable c-SDMTs are identical in every way apart from the fixity of the code, the ability of participants to speed up responses over the course of the fixed version only points to the contribution of incidental visual memory in test performance.

Incident Heart Failure and Cognitive Decline: The Atherosclerosis Risk in Communities Study

BackgroundCognitive impairment is found in a significant proportion of patients with heart failure (HF). Although cognitive impairment may be a consequence of HF, early signs of cognitive impairment may also indicate subclinical vascular disease, and thus a risk factor for future cardiovascular events. Methods and ResultsThe Atherosclerosis Risk in Communities Study is a prospective cohort study of the development of atherosclerosis. Cox proportional hazards regression was used to examine the association between mean 6-year change in cognitive function and incident HF in 7962 white and 1933 African-American men and women aged 46 to 70 years and free of clinical stroke. Scores were obtained for the Delayed Word Recall Test, the Digit Symbol Substitution Test (DSST), and the Word Fluency Test. There was a significantly increased risk of developing HF during the mean 12.6-year follow-up period after adjustment for age, gender, race, and education for those in the quartile with the greatest decline in DSST scores (hazard ratio [HR] = 1.17, P = .009), and in the quartile with the lowest baseline DSST scores (HR = 1.43, P < .001). ConclusionsThe results suggest that relatively low performance on a test of information processing speed may serve as an indicator of HF risk in middle age.

Influence of Antipsychotic and Anticholinergic Loads on Cognitive Functions in Patients with Schizophrenia.

Many patients with schizophrenia show cognitive impairment. There is evidence that, beyond a certain dose of antipsychotic medication, the antipsychotic daily dose (ADD) may impair cognitive performance. Parallel to their D2 receptor antagonism, many antipsychotics show a significant binding affinity to cholinergic muscarinic receptors. Pharmacological treatment with a high anticholinergic daily dose (CDD) significantly impairs attention and memory performance. To examine the relationships between individual cognitive performance and ADD and/or CDD, we conducted a retrospective record-based analysis of a sample of n = 104 in patients with a diagnosis of schizophrenia, all of whom had completed a comprehensive neuropsychological test battery. To calculate the individual ADD and CDD, the medication at the time of testing was converted according to equivalence models. After extracting five principal cognitive components, we examined the impact of ADD and CDD on cognitive performance in the medicated sample and subgroups using multiple regression analysis. Finally, locally weighted scatterplot smoothing (Loess) was applied to further explore the course of cognitive performance under increasing dosage. Results showed significant negative effects of ADD on performance in tests of information processing speed and verbal memory. No effects were found for CDD. The potential neuropsychopharmacological and clinical implications are discussed.

Cannabis-induced alterations in brain activation during a test of information processing speed in patients with MS.

ObjectiveThe objective of this article is to determine the functional brain correlates of information processing speed in multiple sclerosis (MS) patients who smoke cannabis and those who are drug naïve.MethodsTwo neurologically and demographically matched samples of MS patients were enrolled, those who smoked cannabis daily (n = 20) and those who were cannabis naïve (n = 19). All participants completed the Brief Repeatable Battery of Neuropsychological Tests and underwent fMRI testing during which they were administered a modified version of the Symbol Digit Modalities Test (mSDMT).ResultsThe cannabis group responded slower in nine of 11 blocks of the mSDMT (p < 0.001), showing a trend toward a slower response time (p < 0.08), but did not differ in the accuracy of response (p < 0.18). Both groups displayed activation in a prefrontal cortex-parietal network associated with information processing speed. When compared to the cannabis-naïve group, cannabis users showed less activation in the right (p = 0.009) and left (p = 0.001) thalami and increased activation in the anterior cingulate (p = 0.006).ConclusionRegular cannabis use in MS patients is associated with slower information processing speed and a pattern of cerebral activity that differs from cannabis-naïve individuals, most notably in a bilateral reduction of thalamic activity.

Both Low and High 24-Hour Diastolic Blood Pressure Are Associated With Worse Cognitive Performance in Type 2 Diabetes: The Maastricht Study.

Hypertension and diabetes are both risk factors for cognitive decline, and individuals with both might have an especially high risk. We therefore examined linear and nonlinear (quadratic) associations of 24-h blood pressure (BP) with cognitive performance in participants with and without type 2 diabetes. We also tested the association of nocturnal dipping status with cognitive performance. This study was performed as part of the Maastricht Study, an ongoing population-based cohort study. Cross-sectional associations of 24-h BP (n = 713, of whom 201 had type 2 diabetes) and nocturnal dipping status (n = 686, of whom 196 had type 2 diabetes) with performance on tests for global cognitive functioning, information processing speed, verbal memory (immediate and delayed word recall), and response inhibition were tested using linear regression analysis and adjusted for demographics, vascular risk factors, cardiovascular disease, depression, and lipid-modifying and antihypertensive medication use. After full adjustment, we found quadratic (inverted U-shaped) associations of 24-h diastolic blood pressure (DBP) with information processing speed (b for quadratic term = -0.0267, P < 0.01) and memory (immediate word recall: b = -0.0180, P < 0.05; delayed word recall: b = -0.0076, P < 0.01) in participants with diabetes, but not in those without. No clear pattern was found for dipping status. This study shows that both low and high 24-h DBP are associated with poorer performance on tests of information processing speed and memory in individuals with type 2 diabetes.

Disconnection of network hubs and cognitive impairment after traumatic brain injury.

Traumatic brain injury affects brain connectivity by producing traumatic axonal injury. This disrupts the function of large-scale networks that support cognition. The best way to describe this relationship is unclear, but one elegant approach is to view networks as graphs. Brain regions become nodes in the graph, and white matter tracts the connections. The overall effect of an injury can then be estimated by calculating graph metrics of network structure and function. Here we test which graph metrics best predict the presence of traumatic axonal injury, as well as which are most highly associated with cognitive impairment. A comprehensive range of graph metrics was calculated from structural connectivity measures for 52 patients with traumatic brain injury, 21 of whom had microbleed evidence of traumatic axonal injury, and 25 age-matched controls. White matter connections between 165 grey matter brain regions were defined using tractography, and structural connectivity matrices calculated from skeletonized diffusion tensor imaging data. This technique estimates injury at the centre of tract, but is insensitive to damage at tract edges. Graph metrics were calculated from the resulting connectivity matrices and machine-learning techniques used to select the metrics that best predicted the presence of traumatic brain injury. In addition, we used regularization and variable selection via the elastic net to predict patient behaviour on tests of information processing speed, executive function and associative memory. Support vector machines trained with graph metrics of white matter connectivity matrices from the microbleed group were able to identify patients with a history of traumatic brain injury with 93.4% accuracy, a result robust to different ways of sampling the data. Graph metrics were significantly associated with cognitive performance: information processing speed (R(2) = 0.64), executive function (R(2) = 0.56) and associative memory (R(2) = 0.25). These results were then replicated in a separate group of patients without microbleeds. The most influential graph metrics were betweenness centrality and eigenvector centrality, which provide measures of the extent to which a given brain region connects other regions in the network. Reductions in betweenness centrality and eigenvector centrality were particularly evident within hub regions including the cingulate cortex and caudate. Our results demonstrate that betweenness centrality and eigenvector centrality are reduced within network hubs, due to the impact of traumatic axonal injury on network connections. The dominance of betweenness centrality and eigenvector centrality suggests that cognitive impairment after traumatic brain injury results from the disconnection of network hubs by traumatic axonal injury.