Magnetization transfer imaging in normal aging,mild cognitive impairment,and Alzheimer's disease

The purpose of this study was to assess whether structural brain damage as detected by volumetric magnetization transfer imaging (MTI) is present in mild cognitive impairment (MCI) and Alzheimer's disease (AD) and, if so, whether these abnormalities are global in character or restricted to the temporal lobe. Volumetric MTI analysis of the whole brain and temporal and frontal lobes was performed in 25 patients with probable AD, in 13 patients with MCI, and in 28 controls. Magnetization transfer ratio (MTR) histograms were produced, from which we derived measures for structural brain damage and atrophy. The peak heights of the MTR histograms of MCI and AD patients were lower than those of controls for the whole brain and temporal and frontal lobes, reflecting structural brain damage. AD patients had more atrophy than controls in all regions that were studied. MCI patients differed from controls for temporal lobe atrophy only. Volumetric MTI demonstrates structural changes that are related to cognitive decline in large parts of the brain of AD patients. Moreover, structural changes also were observed in MCI patients, indicating that widespread brain damage can be demonstrated before patients are clinically demented.     

The impact of silent vascular brain burden in cognitive impairment in Parkinson’s disease

Background and purpose: White matter hyperintensities (WMHs) detected by magnetic resonance imaging (MRI) of the brain are associated with dementia and cognitive impairment in the general population and in Alzheimer’s disease. Their effect in cognitive decline and dementia associated with Parkinson’s disease (PD) is still unclear. Methods: We studied the relationship between WMHs and cognitive state in 111 patients with PD classified as cognitively normal (n = 39), with a mild cognitive impairment (MCI) (n = 46) or dementia (n = 26), in a cross‐sectional and follow‐up study. Cognitive state was evaluated with a comprehensive neuropsychological battery, and WMHs were identified in FLAIR and T2‐weighted MRI. The burden of WMHs was rated using the Scheltens scale. Results: No differences in WMHs were found between the three groups in the cross‐sectional study. A negative correlation was observed between semantic fluency and the subscore for WMHs in the frontal lobe. Of the 36 non‐demented patients re‐evaluated after a mean follow‐up of 30 months, three patients converted into MCI and 5 into dementia. Progression of periventricular WMHs was associated with an increased conversion to dementia. A marginal association between the increase in total WMHs burden and worsening in the Mini Mental State Examination was encountered. Conclusions: White matter hyperintensities do not influence the cognitive status of patients with PD. Frontal WMHs have a negative impact on semantic fluency. Brain vascular burden may have an effect on cognitive impairment in patients with PD as WMHs increase overtime might increase the risk of conversion to dementia. This finding needs further confirmation in larger prospective studies.     

Aberrant cerebral network topology and mild cognitive impairment in early Parkinson's disease

The aim of this study was to assess whether mild cognitive impairment (MCI) is associated with disruption in large‐scale structural networks in newly diagnosed, drug‐naïve patients with Parkinson's disease (PD). Graph theoretical analyses were applied to 3T MRI data from 123 PD patients and 56 controls from the Parkinson's progression markers initiative (PPMI). Thirty‐three patients were classified as having Parkinson's disease with mild cognitive impairment (PD‐MCI) using the Movement Disorders Society Task Force criteria, while the remaining 90 PD patients were classified as cognitively normal (PD‐CN). Global measures (clustering coefficient, characteristic path length, global efficiency, small‐worldness) and regional measures (regional clustering coefficient, regional efficiency, hubs) were assessed in the structural networks that were constructed based on cortical thickness and subcortical volume data. PD‐MCI patients showed a marked reduction in the average correlation strength between cortical and subcortical regions compared with controls. These patients had a larger characteristic path length and reduced global efficiency in addition to a lower regional efficiency in frontal and parietal regions compared with PD‐CN patients and controls. A reorganization of the highly connected regions in the network was observed in both groups of patients. This study shows that the earliest stages of cognitive decline in PD are associated with a disruption in the large‐scale coordination of the brain network and with a decrease of the efficiency of parallel information processing. These changes are likely to signal further cognitive decline and provide support to the role of aberrant network topology in cognitive impairment in patients with early PD. Hum Brain Mapp 36:2980–2995, 2015. © 2015 Wiley Periodicals, Inc.     

Changes in theta activities in the left posterior temporal region,left occipital region and right frontal region related to mild cognitive impairment in Parkinson's disease patients

The aim of this study was to investigate changes in brain activity associated with mild cognitive impairment (MCI) in a large sample of nondemented Parkinson's disease (PD) patients and its relationship with specific neuropsychological deficits. Electroencephalography (EEG) and neuropsychological assessment were performed in a sample of 135 nondemented PD patients and 44 healthy controls. All patients underwent a neuropsychological battery to assess global cognitive function. Patients were classified according to their cognitive status as PD patients with MCI (n = 61) and without MCI (n = 74). EEG data were used to analyze the relative band power parameters for the following frequency bands: delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz) and beta (13–30 Hz). In addition, relative band power parameters were compared between groups and examined for correlations with neuropsychological performance. The relative theta band powers in three regions (O1, T5 and F4) exhibited statistically significant increases in PD patients with MCI. Beta band powers also exhibited obvious decreases in five regions (T5, T6, P3, P4 and C3) in the PD-MCI group compared with the normal control group. Furthermore, correlation analyses revealed that attention, visuospatial and executive functions were associated with theta power in local regions, mainly in the frontal region (F4). The present study demonstrated that changes in brain activities limited to distinct cognitive domains, especially the theta power in the frontal region, could serve as an electrophysiological marker of cognitive impairment in nondemented PD patients.     

Altered topological patterns of brain networks in mild cognitive impairment and Alzheimer's disease: a resting-state fMRI study

Recent studies have shown that cognitive and memory decline in patients with Alzheimer's disease (AD) is coupled with losses of small-world attributes. However, few studies have investigated the characteristics of the whole brain networks in individuals with mild cognitive impairment (MCI). In this functional magnetic resonance imaging (fMRI) study, we investigated the topological properties of the whole brain networks in 18 AD patients, 16 MCI patients, and 18 age-matched healthy subjects. Among the three groups, AD patients showed the longest characteristic path lengths and the largest clustering coefficients, while the small-world measures of MCI networks exhibited intermediate values. The finding was not surprising, given that MCI is considered to be the prodromal stage of AD. Compared with normal controls, MCI patients showed decreased nodal centrality mainly in the medial temporal lobe as well as increased nodal centrality in the occipital regions. In addition, we detected increased nodal centrality in the medial temporal lobe and frontal gyrus, and decreased nodal centrality mainly in the amygdala in MCI patients compared with AD patients. The results suggested a widespread rewiring in AD and MCI patients. These findings concerning AD and MCI may be an integrated reflection of reorganization of the brain networks accompanied with the cognitive decline that may lead to AD.     

Altered dynamic amplitude of low-frequency fluctuation in individuals at high risk for Alzheimer's disease

The brain's dynamic spontaneous neural activity is significant in supporting cognition; however, how brain dynamics go awry in subjective cognitive decline (SCD) and mild cognitive impairment (MCI) remains unclear. Thus, the current study aimed to investigate the dynamic amplitude of low-frequency fluctuation (dALFF) alterations in patients at high risk for Alzheimer's disease and to explore its correlation with clinical cognitive assessment scales, to identify an early imaging sign for these special populations. A total of 152 participants, including 72 SCD patients, 44 MCI patients and 36 healthy controls (HCs), underwent a resting-state functional magnetic resonance imaging and were assessed with various neuropsychological tests. The dALFF was measured using sliding-window analysis. We employed canonical correlation analysis (CCA) to examine the bi-multivariate correlations between neuropsychological scales and altered dALFF among multiple regions in SCD and MCI patients. Compared to those in the HC group, both the MCI and SCD groups showed higher dALFF values in the right opercular inferior frontal gyrus (voxel P < .001, cluster P < .05, correction). Moreover, the CCA models revealed that behavioural tests relevant to inattention correlated with the dALFF of the right middle frontal gyrus and right opercular inferior frontal gyrus, which are involved in frontoparietal networks (R = .43, P = .024). In conclusion, the brain dynamics of neural activity in frontal areas provide insights into the shared neural basis underlying SCD and MCI.     

Brain perfusion correlates of medial temporal lobe atrophy and white matter hyperintensities in mild cognitive impairment

Abstract Objective To assess the association of Medial Temporal lobe Atrophy (MTA) and White Matter Hyperintensities (WMHs) with gray matter perfusion in Mild Cognitive Impairment (MCI). Methods 56 MCI patients (age = 69.3 ± 7.0, 32 females) underwent brain MR scan and ^99mTc ECD SPECT. We evaluated MTA according to Scheltens' fivepoint scale on T1 MR images, and assessed WMHs using the rating scale for age-related white matter changes on T2-weighted and FLAIR MR images. We divided MCI into age-matched subgroups with high and low MTA and high and low WMHs load. We processed SPECT images with SPM2 following an optimized protocol and performed a voxel-based statistical analysis comparing high vs. low MTA and high vs. low WMHs, setting p-value at 0.001 uncorrected, thresholding cluster extent at 100 voxels, using proportional scaling and entering age and WMHs or MTA respectively as nuisance covariates. Results MCI with high compared with low MTA showed hypoperfusion in the left hippocampus and in the left parahippocampal gyrus. MCI with high compared with low WMHs showed a hypoperfusion area in the left insular region and superior temporal gyrus. Conclusions MTA in MCI is associated with hippocampal gray matter hypoperfusion while WMHs is associated with gray matter hypoperfusion in areas of the insula and temporal neocortex. These results confirm that MTA is associated with local functional changes and suggest that WMHs may be associated with remote brain cortical dysfunction.     

Brain function during multi-trial learning in mild cognitive impairment: a PET activation study

We explored functional brain changes with positron emission tomography (PET) in mild cognitive impairment (MCI) patients and elderly normal controls by employing an episodic memory task that included two successive encoding trials of semantically related word-pairs and final retrieval. Both groups demonstrated significant learning across the two trials. The control group showed predominantly left frontal activity during encoding, and right frontal plus left temporal activity during retrieval. However, the MCI patients recruited partly different brain regions. They failed to activate right frontal and left temporal areas during retrieval, and failed to show any different activation for encoding on the first and second trials, whereas the controls activated a region of posterior cingulate. There was indication of compensatory increases in rCBF of the occipital cortex during incremental learning and the left frontal lobe during retrieval in the patients. These results suggest different episodic memory processing in the MCI group, and a possible over-reliance on semantic processing. Subtle functional changes occur in the pre-Alzheimer brain before there are marked structural or behavioural abnormalities.     

Cognitive decline in AD and mild cognitive impairment is associated with global brain damage

OBJECTIVE: To investigate the relationships between structural damage in the whole brain, the temporal lobes, and the frontal lobes and cognitive decline at old age. The authors hypothesized that widespread brain damage as quantified using magnetization transfer imaging (MTI) is related to global cognitive decline, whereas regional damage to the temporal lobes is related to memory impairment, and regional damage to the frontal lobes is related to executive dysfunctioning. METHODS: Cognitive function of 22 patients with probable AD, 13 patients with mild cognitive impairment (MCI), and 28 elderly controls was assessed using an extensive neuropsychological test battery. Structural damage in the whole brain, the temporal lobes, and the frontal lobes was estimated using volumetric MTI analysis. Associations between MTI measures and neuropsychological tests were investigated using Pearson correlation analysis. RESULTS: MTI measures of the whole brain, as well as the temporal and the frontal lobes, were strongly associated with global cognitive deterioration and impairment in memory, orientation, language, praxis, gnosis, and executive functioning. However, there were no specific cognitive correlates of regional brain damage to the temporal and frontal lobes. CONCLUSIONS: Using whole brain volumetric magnetization transfer imaging, the authors demonstrated that cognitive decline in patients with mild cognitive impairment and AD is associated with widespread structural brain damage. As there were no specific relationships between regional brain damage and impairment of specific cognitive functions, pathology in AD and mild cognitive impairment is much more generalized than was expected.     

Mild cognitive impairment after lacunar infarction: voxel-based morphometry and neuropsychological assessment

BACKGROUND: The aim of the present study was to investigate whether there were differences in neuroradiological features, including white-matter lesions and gray-matter volumes, between patients with lacunar infarction with and without mild cognitive impairment of the vascular type (MCI-V). METHODS: A total of 40 patients with lacunar infarction were studied within 1 month after stroke. RESULTS: MCI-V was found in 22 patients, who in comparison with patients without cognitive impairment were significantly older and had fewer years of formal education. MRI subcortical hyperintensities especially in the basal ganglia (putamen and thalamus) were significantly more frequent in the MCI-V group. In the voxel-based morphometric study, patients with MCI-V showed more atrophy bilaterally in the middle temporal gyrus, right and left frontal and posterior bilateral occipitoparietal regions including the posterior cingulate as well as in the cerebellum. A region of interest analysis restricted to the parahippocampi and hippocampi showed further reduced bilateral parahippocampal gyrus and right hippocampus volume reductions in this group of patients. Finally, the amount of white-matter lesions among MCI-V showed negative correlations with gray-matter volume in frontal and temporal areas as well as with the thalamus and mesencephalon. CONCLUSIONS: The present findings provide support for an anatomical substrate of the MCI entity in patients with lacunar infarction. Both gray- and white-matter changes seem to contribute to the cognitive impairment of such patients.     

Complexity changes in preclinical Alzheimer’s disease: An MEG study of subjective cognitive decline and mild cognitive impairment

ObjectiveTo analyse magnetoencephalogram (MEG) signals with Lempel-Ziv Complexity (LZC) to identify the regions of the brain showing changes related to cognitive decline and Alzheimeŕs Disease (AD).MethodsLZC was used to study MEG signals in the source space from 99 participants (36 male, 63 female, average age: 71.82 ± 4.06) in three groups (33 subjects per group): healthy (control) older adults, older adults with subjective cognitive decline (SCD), and adults with mild cognitive impairment (MCI). Analyses were performed in broadband (2–45 Hz) and in classic narrow bands (theta (4–8 Hz), alpha (8–12 Hz), low beta (12–20 Hz), high beta (20–30 Hz), and, gamma (30–45 Hz)).ResultsLZC was significantly lower in subjects with MCI than in those with SCD. Moreover, subjects with MCI had significantly lower MEG complexity than controls and SCD subjects in the beta frequency band. Lower complexity was correlated with smaller hippocampal volumes.ConclusionsBrain complexity – measured with LZC – decreases in MCI patients when compared to SCD and healthy controls. This decrease is associated with a decrease in hippocampal volume, a key feature in AD progression.SignificanceThis is the first study to date characterising the changes of brain activity complexity showing the specific spatial pattern of the alterations as well as the morphological correlations throughout preclinical stages of AD.     

Spatial patterns of intrinsic brain activity in mild cognitive impairment and Alzheimer's disease: a resting-state functional MRI study

We used resting-state functional MRI to investigate spatial patterns of spontaneous brain activity in 22 healthy elderly subjects, as well as 16 mild cognitive impairment (MCI) and 16 Alzheimer's disease (AD) patients. The pattern of intrinsic brain activity was measured by examining the amplitude of low-frequency fluctuations (ALFF) of blood oxygen level dependent signal during rest. There were widespread ALFF differences among the three groups throughout the frontal, temporal, and parietal cortices. Both AD and MCI patients showed decreased activity mainly in the medial parietal lobe region and lentiform nucleus, while there was increased activity in the lateral temporal regions and superior frontal and parietal regions as compared with controls. Compared with MCI, the AD patients showed decreased activity in the medial prefrontal cortex and increased activity in the superior frontal gyrus and inferior and superior temporal gyri. Specifically, the most significant ALFF differences among the groups appeared in the posterior cingulate cortex, with a reduced pattern of activity when comparing healthy controls, MCI, and AD patients. Additionally, we also showed that the regions with ALFF changes had significant correlations with the cognitive performance of patients as measured by mini-mental state examination scores. Finally, while taking gray matter volume as covariates, the ALFF results were approximately consistent with those without gray matter correction, implying that the functional analysis could not be explained by regional atrophy. Together, our results demonstrate that there is a specific pattern of ALFF in AD and MCI, thus providing insights into biological mechanisms of the diseases.     

Cortical thinning associated with mild cognitive impairment in Parkinson's disease

The aim of this study was to investigate patterns of cortical atrophy associated with mild cognitive impairment in a large sample of nondemented Parkinson's disease (PD) patients, and its relation with specific neuropsychological deficits. Magnetic resonance imaging (MRI) and neuropsychological assessment were performed in a sample of 90 nondemented PD patients and 32 healthy controls. All underwent a neuropsychological battery including tests that assess different cognitive domains: attention and working memory, executive functions, memory, language, and visuoperceptual‐visuospatial functions. Patients were classified according to their cognitive status as PD patients without mild cognitive impairment (MCI; n = 43) and PD patients with MCI (n = 47). Freesurfer software was used to obtain maps of cortical thickness for group comparisons and correlation with neuropsychological performance. Patients with MCI showed regional cortical thinning in parietotemporal regions, increased global atrophy (global cortical thinning, total gray matter volume reduction, and ventricular enlargement), as well as significant cognitive impairment in memory, executive, and visuospatial and visuoperceptual domains. Correlation analyses showed that all neuropsychological tests were associated with cortical thinning in parietotemporal regions and to a lesser extent in frontal regions. These results provide neuroanatomic support to the concept of MCI classified according to Movement Disorders Society criteria. The posterior pattern of atrophy in temporoparietal regions could be a structural neuroimaging marker of cognitive impairment in nondemented PD patients. All of the neuropsychological tests reflected regional brain atrophy, but no specific patterns were seen corresponding to impairment in distinct cognitive domains. © 2014 International Parkinson and Movement Disorder Society     

Quantitative analysis of gray- and white-matter volumes and glucose metabolism in Sturge-Weber syndrome

The progressive nature of Sturge-Weber syndrome is well known, but the mechanisms of focal cortical and subcortical degeneration in this disorder are poorly understood. In the present study, we assessed the structural and functional integrity of gray and white matter in unihemispheric Sturge-Weber syndrome using quantitative magnetic resonance imaging (MRI) volumetry and MRI-based partial volume correction of [18F]fluorodeoxyglucose positron emission tomographic (PET) images. Gray- and white-matter volumes and glucose metabolism were measured in three brain regions (parieto-occipital underneath the angioma, temporal, and frontal) in six children with Sturge-Weber syndrome (two infants, ages 6 and 9 months; four older children, ages 4 to 14 years), all with unilateral parieto-occipital leptomeningeal angiomatosis. The gray-matter volumes ipsilateral to the angioma were smaller in all children, with the posterior regions underneath the angioma the most affected. In the infants, the white-matter volumes were increased in the region of the angioma, whereas in the regions remote from the angioma in the infants and in all regions of the older children, there were large decreases in white-matter volume. The decreases of frontal and temporal white-matter volume were more pronounced than the corresponding gray-matter volume decreases. The PET studies showed severe hypometabolism in the parieto-occipitalregion underneath the angioma in all of the children. However, the two infants showed glucose hypermetabolism in the frontal and temporal cortical gray matter, whereas these regions had relatively preserved metabolism in the older patients. These results demonstrate differential involvement of gray and white matter in Sturge-Weber syndrome. Both structural and functional abnormalities extend well beyond the angioma, indicating widespread abnormalities of growth and development of the affected hemisphere. Furthermore, whereas increased white-matter volume underlying the angioma may be seen in infants, ipsilateral white-matter regions outside the angioma show volume loss both in infants and in older patients. Extensive gray- and white-matter volume loss and hypometabolism ipsilateral to the angioma likely contribute to the frequently observed progressive cognitive dysfunction in these patients, regardless of the extent of the angioma.     

Voxel and surface-based topography of memory and executive deficits in mild cognitive impairment and Alzheimer’s disease

Mild cognitive impairment (MCI) and Alzheimer’s disease (AD) are associated with a progressive loss of cognitive abilities. In the present report, we assessed the relationship of memory and executive function with brain structure in a sample of 810 Alzheimer’s Disease Neuroimaging Initiative (ADNI) participants, including 188 AD, 396 MCI, and 226 healthy older adults (HC). Composite scores of memory (ADNI-Mem) and executive function (ADNI-Exec) were generated by applying modern psychometric theory to item-level data from ADNI’s neuropsychological battery. We performed voxel-based morphometry (VBM) and surface-based association (SurfStat) analyses to evaluate relationships of ADNI-Mem and ADNI-Exec with grey matter (GM) density and cortical thickness across the whole brain in the combined sample and within diagnostic groups. We observed strong associations between ADNI-Mem and medial and lateral temporal lobe atrophy. Lower ADNI-Exec scores were associated with advanced GM and cortical atrophy across broadly distributed regions, most impressively in the bilateral parietal and temporal lobes. We also evaluated ADNI-Exec adjusted for ADNI-Mem, and found associations with GM density and cortical thickness primarily in the bilateral parietal, temporal, and frontal lobes. Within-group analyses suggest these associations are strongest in patients with MCI and AD. The present study provides insight into the spatially unbiased associations between brain atrophy and memory and executive function, and underscores the importance of structural brain changes in early cognitive decline.     

Cortical hypometabolism associated with cognitive impairment of multiple system atrophy

IntroductionCognitive impairment is not uncommon in patients with multiple system atrophy (MSA). This study investigated the cortical metabolic changes of MSA and the cortical structure associated with cognitive impairment.MethodsThe study included probable/definite MSA patients who underwent fluorodeoxyglucose positron emission tomography and cognitive evaluation based on mini-mental status examination (MMSE). Cerebral metabolism of the entire MSA patients (n = 88) was compared with healthy controls (n = 19) by voxel-wise statistical parametric mapping. Eight brain regions of interest (ROIs) were selected accordingly: the dorsolateral prefrontal, medial superior frontal, insular, posterior parietal, precuneus, lateral temporal, medial temporal, and posterior cingulate regions. Using validated population-based norms, MSA patients were divided by MMSE z-scores into MSA with cognitive dysfunction (MSA-D, n = 30) and without cognitive dysfunction (MSA-ND, n = 58). Regional metabolism of the selected ROIs was compared between the MSA-D and MSA-ND groups by logistic regression models. Correlations between the regional metabolism of the selected ROIs and MMSE z-scores were analyzed with a linear regression model.ResultsVoxel-wise analysis showed hypometabolism in the frontal, temporal, parietal, and limbic areas in MSA patients than in controls. ROI-based comparisons showed that metabolism in the posterior cingulate (P = 0.006) and medial temporal (P = 0.039) regions was significantly lower in the MSA-D than in the MSA-ND group. The degree of posterior cingulate metabolism correlated significantly with MMSE z-score (P = 0.023).ConclusionsMSA shows fronto-temporo-parietal cortical involvement. Hypometabolism of the limbic regions is associated with cognitive impairment in MSA.     

Brain network hierarchy reorganization in Alzheimer's disease: A resting‐state functional magnetic resonance imaging study

Hierarchy is a fundamental organizational principle of the human brain network. Whether and how the network hierarchy changes in Alzheimer''s disease (AD) remains unclear. To explore brain network hierarchy alterations in AD and their clinical relevance. Forty‐nine healthy controls (HCs), 49 patients with mild cognitive impairment (MCI), and 49 patients with AD were included. The brain network hierarchy of each group was depicted by connectome gradient analyses. We assessed the network hierarchy changes by comparing the gradient values in each network across the AD, MCI, and HC groups. Whole‐brain voxel‐level gradient values were compared across the AD, MCI, and HC groups to identify abnormal brain regions. Finally, we examined the relationships between altered gradient values and clinical features. In the secondary gradient, the posterior default mode network (DMN) gradient values decreased significantly in patients with AD compared with HCs. Regionally, compared with HCs, both MCI and AD groups showed that most of the brain regions with increased gradient values were located in anterior DMN, while most of the brain regions with decreased gradient values were located in posterior DMN. The decrease of gradients in the left middle occipital gyrus was associated with better logical memory performance. The increase of gradients in the right middle frontal gyrus was associated with lower rates of dementia. The network hierarchy changed characteristically in patients with AD and was closely related to memory function and disease severity. These results provide a novel view for further understanding the underlying neuro‐mechanisms of AD.     

Executive dysfunction in mild cognitive impairment is associated with changes in frontal and cingulate white matter tracts

Mild cognitive impairment (MCI) may affect multiple neuropsychological domains. While amnestic MCI is associated with Alzheimer's disease, patterns of brain pathology in non-amnestic subtypes have been less studied. Twenty-three patients with attention/executive MCI (a/e MCI), seen at a university-based memory clinic, and 23 normal controls, matched according to age, gender, and education, were included in this study. All subjects were assessed with a neuropsychological test battery, including tests of memory, attention and executive function, and underwent magnetic resonance imaging. Diffusion tensor imaging derived white matter (WM) tract radial and mean diffusivity (DR and MD) were assessed using Tract-Based Spatial Statistics, and cortical thickness (CTH) was assessed using FreeSurfer. This study investigated changes of WM DR/MD and CTH in subjects with a/e MCI, and associations between these changes and different a/e subfunctions. WM DR/MD underlying rostral middle frontal, medial orbitofrontal, caudal anterior cingulate, posterior cingulate, retrosplenial and entorhinal cortices was higher for the a/e MCI than the control group, but CTH was not different from controls in any of the regions. WM DR/MD underlying superior frontal, rostral middle frontal, lateral/medial orbitofrontal and retrosplenial cortices were significantly associated with inhibition/switching performance, while caudal middle frontal CTH was significantly associated with attention and divided attention in the patient group. We conclude that increased WM DR/MD in frontal and cingulate regions and cortical thinning in caudal middle frontal region are both associated with executive dysfunction in MCI.     

Aβ and cognitive change: Examining the preclinical and prodromal stages of Alzheimer's disease

BackgroundHigh β-amyloid (Aβ) is associated with faster memory decline in healthy individuals and adults with mild cognitive impairment (MCI). However, longer prospective studies are required to determine if Aβ-related memory decline continues and whether it is associated with increased rate of disease progression.MethodsHealthy controls (HCs; n = 177) and adults with MCI (n = 48) underwent neuroimaging for Aβ and cognitive assessment at baseline. Cognition was reassessed 18 and 36 months later.ResultsCompared with low-Aβ HCs, high-Aβ HC and MCI groups showed moderate decline in episodic and working memory over 36 months. Those with MCI with low Aβ did not show any cognitive decline. Rates of disease progression were increased in the high-Aβ HC and MCI groups.ConclusionsIn healthy individuals, high Aβ likely indicates that Alzheimer's disease (AD)-related neurodegeneration has begun. Once commenced, the rate of decline in cognitive function remains constant across the preclinical and prodromal stages of AD.     

Lesion patterns and mechanism of cerebral infarction caused by severe atherosclerotic intracranial internal carotid artery stenosis

The hippocampus is believed to have close relationship with many cerebral cortexes and constitute memory network to modulate and facilitate communication, which makes it especially interesting and meaningful in the study of functional connectivity in mild cognitive impairment (MCI). However, functional connectivity between the hippocampus and other brain regions remains unclear in MCI. Furthermore, the longitudinal changes of the hippocampal connectivity have not been reported. In the study, resting state functional MRI (fMRI) was used to examine changes in hippocampal connectivity comparing 14 patients and 14 healthy age-matched controls. We found that functional connectivity between the hippocampus and a set of regions was disrupted in MCI, these regions are: the right frontal lobe, the bilateral temporal lobe and the right insular. While, the left posterior cingulate cortex, precuneus, hippocampus, caudate and right occipital gyrus showed increased connectivity to the hippocampus in MCI. Additionally, we traced the seven MCI patients and compared the hippocampal connectivity in initial stage and 3 years later stage. Several regions presented decreased connectivity to the hippocampus after 3 years. Finally, the hippocampal connectivity with some regions showed significant correlation with the cognitive performance of patients. Based on these findings, the decreased hippocampal connectivity might indicate reduced integrity of hippocampal cortical memory network in MCI. In addition, the increased hippocampal connectivity suggested compensation for the loss of memory function. With the development of the disease, the hippocampal connectivity may lose some compensation and add some more disruption due to the pathological changes.