Abstract The influence of education, occupation, and leisure activities on the passive and active components of reserve capacity remains unclear. We used the voxel-based morphometry (VBM) technique ...in a population-based sample of 331 nondemented people in order to investigate the relationship between these factors and the cerebral volume (a marker of brain reserve). The results showed a positive and significant association between education, occupation, and leisure activities and the cognitive performances on Isaac's set test. Among these factors, only education was significantly associated with a cerebral volume including gray and white matter ( p = 0.01). In voxel-based morphometry analyses, the difference in gray matter volume was located in the temporoparietal lobes and in the orbitofrontal lobes bilaterally (a p -value corrected <0.05 by false discovery rate FDR). Although smaller, the education-related difference in white matter volume appeared in areas connected to the education-related difference in gray matter volume. Education, occupation attainment, and leisure activities were found to contribute differently to reserve capacity. Education could play a role in the constitution of cerebral reserve capacity.
Background Many neuroimaging studies exploring the volumes of brain structures in obsessive-compulsive disorder (OCD) have been published in the past 2 decades. In this study, we attempted to provide ...a complete overview of structural alterations in OCD by meta-analyzing magnetic resonance imaging (MRI) data. Methods We conducted a systematic search of MRI studies that reported volumetric measurements in both OCD patients and healthy subjects. Data were entered into the meta-analysis through calculation of the standardized mean differences (SMDs) between the volumes of cerebral regions in OCD patients and the corresponding volumes in control subjects. We then performed a meta-regression to explore the influence of clinical covariates on effect sizes. Results Although no volumetric differences were found for the whole brain, intracranial region, gray matter, or prefrontal cortex, OCD patients did show a reduced volume of the left anterior cingulate cortex (ACC) and the left and right orbitofrontal cortex (OFC). No significant volumetric differences within the basal ganglia were observed, although the left and right thalamic volumes were significantly increased in OCD patients. The severity of obsessive or compulsive symptoms correlated significantly with the effect sizes for the left and right thalamus. Conclusions Our findings indicate volumetric differences between OCD patients and control subjects in the cortical and thalamic regions, suggesting that structural alteration of the thalamocortical pathways may contribute to the functional disruptions of frontosubcortical circuits observed in OCD.
Early-onset torsion dystonia (TOR1A/DYT1) is a devastating hereditary motor disorder whose pathophysiology remains unclear. Studies in transgenic mice suggested abnormal cholinergic transmission in ...the putamen, but this has not yet been demonstrated in humans. The role of the cerebellum in the pathophysiology of the disease has also been highlighted but the involvement of the intrinsic cerebellar cholinergic system is unknown. In this study, cholinergic neurons were imaged using PET with 18F-fluoroethoxybenzovesamicol, a radioligand of the vesicular acetylcholine transporter (VAChT). Here, we found an age-related decrease in VAChT expression in the posterior putamen and caudate nucleus of DYT1 patients versus matched controls, with low expression in young but not in older patients. In the cerebellar vermis, VAChT expression was also significantly decreased in patients versus controls, but independently of age. Functional connectivity within the motor network studied in MRI and the interregional correlation of VAChT expression studied in PET were also altered in patients. These results show that the cholinergic system is disrupted in the brain of DYT1 patients and is modulated over time through plasticity or compensatory mechanisms.
BACKGROUND AND PURPOSE—The aim of the present study was to evaluate the relationship between normal-appearing white matter (NAWM) integrity and postischemic stroke recovery in 4 main domains ...including cognition, mood, gait, and dependency.
METHODS—A prospective study was conducted, including patients diagnosed for an ischemic supratentorial stroke on a 3T brain MRI performed 24 to 72 hours after symptom onset. Clinical assessment 1 year after stroke included a Montreal Cognitive Assessment, an Isaacs set test, a Zazzo cancelation task, a Hospital Anxiety and Depression scale, a 10-meter walking test, and a modified Rankin Scale (mRS). Diffusion tensor imaging parameters in the NAWM were computed using FMRIB (Functional Magnetic Resonance Imaging of the Brain) Diffusion Toolbox. The relationships between mean NAWM diffusion tensor imaging parameters and the clinical scores were assessed using linear and ordinal regression analyses, including the volumes of white matter hyperintensities, gray matter, and ischemic stroke as radiological covariates.
RESULTS—Two hundred seven subjects were included (66±13 years old; 67% men; median National Institutes of Health Stroke Scale score, 3; interquartile range, 2–6). In the models including only radiological variables, NAWM fractional anisotropy was associated with the mRS and the cognitive scores. After adjusting for demographic confounders, NAWM fractional anisotropy remained a significant predictor of mRS (β=−0.24; P=0.04). Additional path analysis showed that NAWM fractional anisotropy had a direct effect on mRS (β=−0.241; P=0.001) and a less important indirect effect mediating white matter hyperintensity burden. Similar results were found with mean diffusivity, axial diffusivity, and radial diffusivity. In further subgroup analyses, a relationship between NAWM integrity in widespread white matter tracts, mRS, and Isaacs set test was found in right hemispheric strokes.
CONCLUSIONS—NAWM diffusion tensor imaging parameters measured early after an ischemic stroke are independent predictors of functional outcome and may be additional markers to include in studies evaluating poststroke recovery.
Diffusion MRI is extensively used to investigate changes in white matter microstructure. However, diffusion measures within white matter tissue can be affected by partial volume effects due to ...cerebrospinal fluid and white matter hyperintensities, especially in the aging brain. In previous aging studies, the cingulum bundle that plays a central role in the architecture of the brain networks supporting cognitive functions has been associated with cognitive deficits. However, most of these studies did not consider the partial volume effects on diffusion measures. The aim of this study was to evaluate the effect of free water elimination on diffusion measures of the cingulum in a group of 68 healthy elderly individuals. We first determined the effect of free water elimination on conventional DTI measures and then examined the effect of free water elimination on verbal fluency performance over 12 years. The cingulum bundle was reconstructed with a tractography pipeline including a white matter hyperintensities mask to limit the negative impact of hyperintensities on fiber tracking algorithms. We observed that free water elimination increased the ability of conventional DTI measures to detect associations between tissue diffusion measures of the cingulum and changes in verbal fluency in older individuals. Moreover, free water content and mean diffusivity measured along the cingulum were independently associated with changes in verbal fluency. This suggests that both tissue modifications and an increase in interstitial isotropic water would contribute to cognitive decline. These observations reinforce the importance of using free water elimination when studying brain aging and indicate that free water itself could be a relevant marker for age-related cingulum white matter modifications and cognitive decline.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The identification of biological and pathophysiological processes implicated in different forms of dementia is itself dependent on reliable descriptions of cognitive performance and capacities. ...However, traditional instruments are often unable to detect subtle declines in cognitive functions due to natural variation at the time of testing. Mobile technologies permit the repeated assessment of cognitive functions and may thereby provide more reliable descriptions of early cognitive difficulties that are inaccessible to clinic or hospital-based instruments. This assessment strategy is also able to characterize in real-time the dynamic associations between cognitive performance and specific daily life behaviors or activities. In a cohort of elderly rural residents, 60 individuals were administered neuropsychological and neuroimaging exams as well as a one-week period of electronic ambulatory monitoring of behavior, semantic memory performance, and daily life experiences. Whereas imaging markers were unrelated to traditional neuropsychological test scores, they were significantly associated with mobile assessments of semantic memory performance. Moreover, certain daily life activities such as reading or completing crossword puzzles were associated with increases in semantic memory performance over the subsequent hours of the same day. The revolution in mobile technologies provides unprecedented opportunities to overcome the barriers of time and context that characterize traditional hospital and clinical-based assessments. The combination of both novel and traditional methods should provide the best opportunity for identifying the earliest risk factors and biomarkers for Alzheimer's disease and other forms of dementia.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
While the neural correlates of age-related episodic memory decline have been extensively studied, the precise involvement of the Posterior Cingulate Cortex (PCC) and posterior parietal cortex (the ...precuneus and the angular gyrus), remains unclear. The present study examined functional and structural neural correlates of age-related episodic memory change assessed over 12 years in 120 older adults (range 76–90 years). Episodic memory performance was measured using the Free and Cued Selective Reminding Test (FCSRT); functional connectivity metrics were computed from resting-state fMRI images and structural connectivity metrics were assessed through microstructural properties of reconstructed tract using a native space pipeline. We found that FCSRT change was significantly associated with the functional connectivity between the ventral PCC and three parietal regions, the ventral superior, the inferior part of the precuneus, and the rostro dorsal part of the angular gyrus. This association was independent of hippocampal volume. In addition, we found the that change in FCSRT scores was associated with fractional anisotropy of the tract connecting the ventral PCC and the ventral superior part of the precuneus. Change in episodic memory in aging was therefore related to a combination of high functional connectivity and low structural connectivity between the ventral PCC and the ventral superior part of the precuneus.
While resting-state networks are able to rapidly adapt to experiences and stimuli, it is currently unknown whether metacognitive processes such as confidence in learning and psychological temperament ...may influence this process. We explore the neural traces of confidence in learning and their variability by: (1) targeting rs-networks in which functional connectivity (FC) modifications induced by a learning task were associated either with the participant’s performance or confidence in learning; and (2) investigating the links between FC changes and psychological temperament. Thirty healthy individuals underwent neuropsychological and psychometric evaluations as well as rs-fMRI scans before and after a visuomotor associative learning task. Confidence in learning was positively associated with the degree of FC changes in 11 connections including the cerebellar, frontal, parietal, and subcortical areas. Variability in FC changes was linked to the individual’s level of anxiety sensitivity. The present findings indicate that reconfigurations of resting state networks linked to confidence in learning differ from those linked to learning accuracy. In addition, certain temperament characteristics appear to influence these reconfigurations.
Objective Recent functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies based on the symptom provocation paradigm have explored neural correlates of the cognitive ...and emotional processes associated with the emergence of obsessive–compulsive disorder (OCD) symptoms. Although most studies showed the involvement of cortico–subcortical loops originating in the orbitofrontal cortex and the anterior cingulate cortex, an increased activity within numerous other regions of the brain has inconsistently been reported across studies. To provide a quantitative estimation of the cerebral activation patterns related to the performance of the symptom provocation task by OCD patients, we conducted a voxel-based meta-analysis. Methods We searched the PubMed and MEDLINE databases for studies that used fMRI and PET and that were based on the symptom provocation paradigm. We entered data into a paradigm-driven activation likelihood estimation meta-analysis. Results We found significant likelihoods of activation in cortical and subcortical regions of the orbitofrontal and anterior cingulate loops. The left dorsal frontoparietal network, including the dorsolateral prefrontal cortex and precuneus, and the left superior temporal gyrus also demonstrated significant likelihoods of activation. Conclusion Consistent results across functional neuroimaging studies suggest that the orbitofrontal and anterior cingulate cortices are involved in the mediation of obsessive–compulsive symptoms. Based on recent literature, we suggest that activations within the dorsal frontoparietal network might be related to patients’ efforts to resist the obsessive processes induced by the provocation task. Further research should elucidate the specific neural correlates of the various cognitive and emotional functions altered in OCD.
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