RESUMEN
INTRODUCTION: Metabolic syndrome (MetS) is a clustering of three or more cardiovascular risk factors (RF), including hypertension, obesity, high cholesterol, or hyperglycemia. MetS and its component RFs are more prevalent in older age, and can be accompanied by alterations in brain structure. Studies have shown altered functional connectivity (FC) in samples with individual RFs as well as in clinical populations that are at higher risk to develop MetS. These studies have indicated that the default mode network (DMN) may be particularly vulnerable, yet little is known about the overall impact of MetS on FC in this network. METHODS: In this study, we evaluated the integrity of FC to the DMN in participants with MetS relative to non-MetS individuals. Using a seed-based connectivity analysis approach, resting-state functional MRI (fMRI) data were analyzed, and the FC measures among the DMN seed (isthmus of the cingulate) and rest of the brain voxels were estimated. RESULTS: Participants with MetS demonstrated reduced positive connectivity between the DMN seed and left superior frontal regions, and reduced negative connectivity between the DMN seed and left superior parietal, left postcentral, right precentral, right superior temporal and right superior parietal regions, after accounting for age- and sex-effects. CONCLUSIONS: Our results suggest that MetS is associated with alterations in FC between the DMN and other regions of the brain. Furthermore, these results indicate that the overall burden of vascular RFs associated with MetS may, in part, contribute to the pathophysiology underlying aberrant FC in the DMN.
Asunto(s)
Encefalopatías/fisiopatología , Lóbulo Frontal/fisiopatología , Síndrome Metabólico/fisiopatología , Lóbulo Parietal/fisiopatología , Anciano , Encefalopatías/patología , Mapeo Encefálico/métodos , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Síndrome Metabólico/patología , Persona de Mediana Edad , Vías Nerviosas/fisiopatologíaRESUMEN
OBJECTIVE: Metabolic syndrome (MetS) refers to a cluster of risk factors for cardiovascular disease, including obesity, hypertension, dyslipidemia, and hyperglycemia. While sizable prior literature has examined associations between individual risk factors and quantitative measures of cortical thickness (CT), only very limited research has investigated such measures in MetS. Furthermore, the relative contributions of these risk factors to MetS-related effects on brain morphology have not yet been studied. The primary goal of this investigation was to examine how MetS may affect CT. A secondary goal was to explore the relative contributions of individual risk factors to regional alterations in CT, with the potential to identify risk factor combinations that may underlie structural changes. METHODS: Eighteen participants with MetS (mean age = 59.78 years) were age-matched with 18 healthy control participants (mean age = 60.50 years). CT measures were generated from T1-weighted images and groups were contrasted using whole-brain general linear modeling. A follow-up multivariate partial least squares correlation (PLS) analysis, including the full study sample with complete risk factor measurements (N = 53), was employed to examine which risk factors account for variance in group structural differences. RESULTS: Participants with MetS demonstrated significantly reduced CT in left hemisphere inferior parietal, rostral middle frontal, and lateral occipital clusters and in a right hemisphere precentral cluster. The PLS analysis revealed that waist circumference, high-density lipoprotein cholesterol (HDL-C), triglycerides, and glucose were significant contributors to reduced CT in these clusters. In contrast, diastolic blood pressure showed a significantly positive association with CT while systolic blood pressure did not emerge as a significant contributor. Age was not associated with CT. CONCLUSION: These results indicate that MetS can be associated with regionally specific reductions in CT. Importantly, a novel link between a risk factor profile comprising indices of obesity, hyperglycemia, dyslipidemia and diastolic BP and localized alterations in CT emerged. While the pathophysiological mechanisms underlying these associations remain incompletely understood, these findings may be relevant for future investigations of MetS and might have implications for treatment approaches that focus on specific risk factor profiles with the aim to reduce negative consequences on the structural integrity of the brain.
Asunto(s)
Mapeo Encefálico , Corteza Cerebral/diagnóstico por imagen , Síndrome Metabólico/diagnóstico por imagen , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Estudios de Cohortes , Femenino , Humanos , Imagenología Tridimensional , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Factores de Riesgo , Circunferencia de la CinturaRESUMEN
While antisaccade paradigms invoke circuitry associated with cognitive control and attention-deficit/hyperactivity disorder (ADHD), there is a dearth of functional magnetic resonance imaging (fMRI) investigations using antisaccade tasks among children with ADHD. Neural correlates associated with antisaccade performance were examined with fMRI in 11 children with ADHD (10 medicated) matched to 11 typically developing children. Significantly greater brain activation in regions in right dorsolateral prefrontal cortex and caudate nucleus was observed in children with ADHD relative to the control group. This pattern separated the children into their respective groups in a taxonomic manner. Sensitivity analyses probing comorbidity and medication-specific effects showed that results were consistent; however, the caudate nucleus difference was only detectable in the full sample, or in subsets with a more relaxed cluster threshold. Antisaccade performance did not significantly differ between the groups, perhaps as a result of greater brain activation or medication effects in the ADHD group. Thus, antisaccade paradigms may have sensitivity and specificity for the investigation of cognitive control deficits and associated neural correlates in ADHD, and may contribute towards the development of new treatment approaches for children with the disorder.
Asunto(s)
Trastorno por Déficit de Atención con Hiperactividad/diagnóstico , Trastorno por Déficit de Atención con Hiperactividad/metabolismo , Encéfalo/metabolismo , Desempeño Psicomotor/fisiología , Movimientos Sacádicos/fisiología , Trastorno por Déficit de Atención con Hiperactividad/psicología , Encéfalo/patología , Mapeo Encefálico/métodos , Núcleo Caudado/metabolismo , Núcleo Caudado/patología , Niño , Trastornos del Conocimiento/diagnóstico , Trastornos del Conocimiento/metabolismo , Trastornos del Conocimiento/psicología , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Masculino , Pruebas Neuropsicológicas , Estimulación Luminosa/métodos , Proyectos Piloto , Corteza Prefrontal/metabolismo , Corteza Prefrontal/patologíaRESUMEN
Our objective was to determine whether a Symbol Search paradigm developed for functional magnetic resonance imaging (FMRI) is a reliable and valid measure of cognitive processing speed (CPS) in healthy older adults. As all older adults are expected to experience cognitive declines due to aging, and CPS is one of the domains most affected by age, establishing a reliable and valid measure of CPS that can be administered inside an MR scanner may prove invaluable in future clinical and research settings. We evaluated the reliability and construct validity of a newly developed FMRI Symbol Search task by comparing participants' performance in and outside of the scanner and to the widely used and standardized Symbol Search subtest of the Wechsler Adult Intelligence Scale (WAIS). A brief battery of neuropsychological measures was also administered to assess the convergent and discriminant validity of the FMRI Symbol Search task. The FMRI Symbol Search task demonstrated high test-retest reliability when compared to performance on the same task administered out of the scanner (r=.791; p<.001). The criterion validity of the new task was supported, as it exhibited a strong positive correlation with the WAIS Symbol Search (r=.717; p<.001). Predicted convergent and discriminant validity patterns of the FMRI Symbol Search task were also observed. The FMRI Symbol Search task is a reliable and valid measure of CPS in healthy older adults and exhibits expected sensitivity to the effects of age on CPS performance.
Asunto(s)
Atención/fisiología , Encéfalo/irrigación sanguínea , Cognición/fisiología , Imagen por Resonancia Magnética , Reconocimiento Visual de Modelos/fisiología , Simbolismo , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Pruebas de Inteligencia , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Oxígeno/sangreRESUMEN
Cognitive control is required for flexible responses in changing environments and can be assessed by measuring antisaccade error rate. Considerable variance in antisaccade error rate is observed in healthy participants, which motivated the current study to explore the cognitive factors affecting antisaccade performance. Relationships exist between prosaccade latency and antisaccade error rate, with faster prosaccade latencies linked to more antisaccade errors. Individual differences in working memory also impact saccadic performance. The current study tested the relationships among prosaccade latency, antisaccade error rate, and working memory in 153 healthy participants. Correlation and multiple regression analyses demonstrated that prosaccade latency predicted antisaccade error rate, and working memory moderated this relationship. These results may help elucidate individual differences in cognitive control among healthy individuals.
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Individualidad , Memoria a Corto Plazo/fisiología , Tiempo de Reacción/fisiología , Movimientos Sacádicos/fisiología , Adolescente , Cognición/fisiología , Femenino , Humanos , Masculino , Pruebas Neuropsicológicas , Estimulación Luminosa , Adulto JovenRESUMEN
Hypertension may increase risk for dementia possibly because of its association with decreased cortical thickness. Disturbed cerebral autoregulation is one plausible mechanism by which hypertension impacts the cerebral structure, but the associations among hypertension, brain perfusion, and cortical thickness are poorly understood. The current sample consisted of 58 older adults with varying levels of vascular disease. Diagnostic history of hypertension and antihypertensive medication status was ascertained through self-report, and when available, confirmed by medical record review. All participants underwent arterial spin labeling and T1-weighted magnetic resonance imaging to quantify total and regional cortical perfusion and thickness. Analysis of covariance adjusting for medical variables showed that participants with hypertension exhibited reduced temporal and occipital brain perfusion and total and regional cortical thickness relative to those without hypertension. The effects of hypertension on total brain perfusion remained unchanged even after adjustment for age, although no such pattern emerged for cortical thickness. Decreased total brain perfusion predicted reduced thickness of the total brain and of the frontal, temporal, and parietal lobe cortices. Antihypertensive treatment was not associated with total cerebral perfusion or cortical thickness. This study provides initial evidence for the adverse effects of a diagnostic history of hypertension on brain hypoperfusion and reduced cortical thickness. Longitudinal studies are needed to investigate the role of hypertension and its interaction with other contributing factors (e.g., age) in the manifestation of cerebral hypoperfusion and reduced cortical thickness.
Asunto(s)
Corteza Cerebral/patología , Circulación Cerebrovascular/fisiología , Demencia Vascular/etiología , Hipertensión/fisiopatología , Flujo Sanguíneo Regional/fisiología , Anciano , Presión Sanguínea , Corteza Cerebral/fisiopatología , Demencia Vascular/diagnóstico , Demencia Vascular/fisiopatología , Progresión de la Enfermedad , Femenino , Estudios de Seguimiento , Humanos , Hipertensión/complicaciones , Hipertensión/diagnóstico , Imagen por Resonancia Magnética , Masculino , Persona de Mediana EdadRESUMEN
During childhood, verbal learning and memory are important for academic performance. Recent functional MRI studies have reported on the functional correlates of verbal memory proficiency, but few have reported the underlying structural correlates. The present study sought to test the relationship between fronto-temporal white matter integrity and verbal memory proficiency in children. Diffusion weighted images were collected from 17 Black children (age 8-11 years) who also completed the California Verbal Learning Test. To index white matter integrity, fractional anisotropy values were calculated for bilateral uncinate fasciculus. The results revealed that low anisotropy values corresponded to poor verbal memory, whereas high anisotropy values corresponded to significantly better verbal memory scores. These findings suggest that a greater degree of myelination and cohesiveness of axonal fibers in uncinate fasciculus underlie better verbal memory proficiency in children.
Asunto(s)
Encéfalo/anatomía & histología , Memoria , Percepción del Habla , Sustancia Blanca/anatomía & histología , Anisotropía , Niño , Análisis por Conglomerados , Imagen de Difusión por Resonancia Magnética , Femenino , Humanos , Modelos Lineales , Masculino , Pruebas NeuropsicológicasRESUMEN
In childhood, excess adiposity and low fitness are linked to poor academic performance, lower cognitive function, and differences in brain structure. Identifying ways to mitigate obesity-related alterations is of current clinical importance. This study examined the effects of an 8-month exercise intervention on the uncinate fasciculus, a white matter fiber tract connecting frontal and temporal lobes. Participants consisted of 18 unfit, overweight 8- to 11-year-old children (94% Black) who were randomly assigned to either an aerobic exercise (n = 10) or a sedentary control group (n = 8). Before and after the intervention, all subjects participated in a diffusion tensor MRI scan. Tractography was conducted to isolate the uncinate fasciculus. The exercise group showed improved white matter integrity as compared to the control group. These findings are consistent with an emerging literature suggesting beneficial effects of exercise on white matter integrity.
Asunto(s)
Terapia por Ejercicio , Lóbulo Frontal/patología , Sobrepeso/terapia , Lóbulo Temporal/patología , Sustancia Blanca/patología , Niño , Imagen de Difusión Tensora , Femenino , Humanos , Masculino , Sobrepeso/patología , Resultado del TratamientoRESUMEN
Aerobic fitness is associated with white matter integrity (WMI) in adults as measured by diffusion tensor imaging (DTI). This study examined the effect of an 8-month exercise intervention on WMI in children. Participants were 18 sedentary, overweight (BMI≥85th percentile) 8- to 11-year-old children (94% Black), randomly assigned to either an aerobic exercise (n=10) or sedentary attention control group (n=8). Each group was offered an instructor-led after-school program every school day for approximately 8 months. Before and after the program, all subjects participated in DTI scans. Tractography was conducted to isolate the superior longitudinal fasciculus and investigate whether the exercise intervention affected WMI in this region. There was no group by time interaction for WMI in the superior longitudinal fasciculus. There was a group by time by attendance interaction, however, such that higher attendance at the exercise intervention, but not the control intervention, was associated with increased WMI. Heart rate and the total dose of exercise correlated with WMI changes in the exercise group. In the overall sample, increased WMI was associated with improved scores on a measure of attention and improved teacher ratings of executive function. This study indicates that participating in an exercise intervention improves WMI in children as compared to a sedentary after-school program.
Asunto(s)
Ejercicio Físico , Lóbulo Frontal/patología , Fibras Nerviosas Mielínicas/patología , Sobrepeso/terapia , Lóbulo Parietal/patología , Niño , Cognición/fisiología , Femenino , Humanos , Masculino , Pruebas Neuropsicológicas , Sobrepeso/patología , Sobrepeso/psicología , Aptitud Física , Resultado del TratamientoRESUMEN
OBJECTIVE: Children who are less fit reportedly have lower performance on tests of cognitive control and differences in brain function. This study examined the effect of an exercise intervention on brain function during two cognitive control tasks in overweight children. DESIGN AND METHODS: Participants included 43 unfit, overweight (BMI ≥ 85th percentile) children 8- to 11-years old (91% Black), who were randomly divided into either an aerobic exercise (n = 24) or attention control group (n = 19). Each group was offered a separate instructor-led after-school program every school day for 8 months. Before and after the program, all children performed two cognitive control tasks during functional magnetic resonance imaging (fMRI): antisaccade and flanker. RESULTS: Compared to the control group, the exercise group decreased activation in several regions supporting antisaccade performance, including precentral gyrus and posterior parietal cortex, and increased activation in several regions supporting flanker performance, including anterior cingulate and superior frontal gyrus. CONCLUSIONS: Exercise may differentially impact these two task conditions, or the paradigms in which cognitive control tasks were presented may be sensitive to distinct types of brain activation that show different effects of exercise. In sum, exercise appears to alter efficiency or flexible modulation of neural circuitry supporting cognitive control in overweight children.