Impairment in spatial navigation (SN) and structural network topology is not limited to patients with Alzheimer's disease (AD) dementia and can be detected earlier in patients with mild cognitive impairment (MCI). We recruited 32 MCI patients (65.91 ± 11.33 years old) and 28 normal cognition patients (NC; 69.68 ± 10.79 years old), all of whom underwent a computer-based battery of SN tests evaluating egocentric, allocentric, and mixed SN strategies and diffusion-weighted and T1-weighted Magnetic Resonance Imaging (MRI). To evaluate the topological features of the structural connectivity network, we calculated its measures such as the global efficiency, local efficiency, clustering coefficient, and shortest path length with GRETNA. We determined the correlation between SN accuracy and network topological properties. Compared to NC, MCI subjects demonstrated a lower egocentric navigation accuracy. Compared with NC, MCI subjects showed significantly decreased clustering coefficients in the left middle frontal gyrus, right rectus, right superior parietal gyrus, and right inferior parietal gyrus and decreased shortest path length in the left paracentral lobule. We observed significant positive correlations of the shortest path length in the left paracentral lobule with both the mixed allocentric-egocentric and the allocentric accuracy measured by the average total errors. A decreased clustering coefficient in the right inferior parietal gyrus was associated with a larger allocentric navigation error. White matter hyperintensities (WMH) did not affect the correlation between network properties and SN accuracy. This study demonstrated that structural connectivity network abnormalities, especially in the frontal and parietal gyri, are associated with a lower SN accuracy, independently of WMH, providing a new insight into the brain mechanisms associated with SN impairment in MCI.
- Klíčová slova
- clustering coefficient, graph theory, mild cognitive impairment, network topology, spatial navigation,
- Publikační typ
- časopisecké články MeSH
Patients with Alzheimer's disease (AD) related dementia and mild cognitive impairment experience difficulties with spatial navigation (SN). However, SN has rarely been investigated in individuals with subjective cognitive decline (SCD), a preclinical stage with elevated progression rate to symptomatic AD. In this study, 30 SCD subjects and 30 controls underwent cognitive scale (CS) evaluation, a 2D computerized SN test, and resting-state functional magnetic resonance imaging scanning. Two SN brain networks (ego-network and allo-network), each with 10 selected spherical regions, were defined. We calculated the average network functional connectivity (FC) and region-to-region FC within the two networks and evaluated correlations with SN performance. Compared with the controls, the SCD group performed worse in the SN test and showed decreased FC between the right retrosplenial and right prefrontal cortices in the ego-network, and between the right retrosplenial cortex and right hippocampus in the allo-network. The logistic regression model based on SN and FC measures revealed a high area under the curve of .880 in differentiating SCD individuals from controls. These results suggest that SN network disconnection contributes to spatial deficits in SCD, and SN and FC measures could benefit the preclinical detection of subjects with incipient AD dementia.
- Klíčová slova
- Allocentric, Egocentric, Functional connectivity, Spatial navigation, Subjective cognitive decline,
- MeSH
- Alzheimerova nemoc * diagnostické zobrazování MeSH
- ego MeSH
- kognitivní dysfunkce * diagnostické zobrazování MeSH
- lidé MeSH
- magnetická rezonanční tomografie MeSH
- mozek MeSH
- zmatenost MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Individuals with subjective cognitive decline (SCD) are at higher risk of incipient Alzheimer's disease (AD). Spatial navigation (SN) impairments in AD dementia and mild cognitive impairment patients have been well-documented; however, studies investigating SN deficits in SCD subjects are still lacking. This study aimed to explore whether basal forebrain (BF) and entorhinal cortex (EC) atrophy contribute to spatial disorientation in the SCD stage. In total, 31 SCD subjects and 24 normal controls were enrolled and administered cognitive scales, a 2-dimensional computerized SN test, and structural magnetic resonance imaging (MRI) scanning. We computed the differences in navigation distance errors and volumes of BF subfields, EC, and hippocampus between the SCD and control groups. The correlations between MRI volumetry and navigation distance errors were also calculated. Compared with the controls, the SCD subjects performed worse in both egocentric and allocentric navigation. The SCD group showed volume reductions in the whole BF (p < 0.05, uncorrected) and the Ch4p subfield (p < 0.05, Bonferroni corrected), but comparable EC and hippocampal volumes with the controls. In the SCD cohort, the allocentric errors were negatively correlated with total BF (r = -0.625, p < 0.001), Ch4p (r = -0.625, p < 0.001), total EC (r = -0.423, p = 0.031), and left EC volumes (r = -0.442, p = 0.024), adjusting for age, gender, years of education, total intracranial volume, and hippocampal volume. This study demonstrates that SN deficits and BF atrophy may be promising indicators for the early detection of incipient AD patients. The reduced BF volume, especially in the Ch4p subfield, may serve as a structural basis for allocentric disorientation in SCD subjects independent of hippocampal atrophy. Our findings may have further implications for the preclinical diagnosis and intervention for potential AD patients.
- Klíčová slova
- allocentric, basal forebrain, entorhinal cortex, spatial navigation, subjective cognitive decline,
- Publikační typ
- časopisecké články MeSH
PURPOSE: Our objectives were to assess the abnormalities of subcortical nuclei by combining volume and shape analyses and potential association with cognitive impairment. PATIENTS AND METHODS: Twenty-nine patients with severe ACS of the unilateral internal carotid artery and 31 controls were enrolled between January 2017 to August 2018. All participants underwent a comprehensive neuropsychological evaluation, blood lipid biochemical measurements, and structural magnetic resonance imaging (MRI) to measure subcortical volumes and sub-regional shape deformations. Basic statistics, correction for multiple comparisons. Seventeen ACS patients underwent carotid endarterectomy (CEA) within one week after baseline measurements, cognitive assessments and MRI scans were repeated 6 months after CEA. RESULTS: The ACS patients had higher apolipoprotein B/apolipoprotein A1 (ApoB/ApoA1) ratio and worse performance in all cognitive domains than controls. Moreover, the ACS patients showed more profound thalamic atrophy assessed by shape and volume analysis, especially in the medial dorsal thalamus. No significant differences were found in other subcortical nuclei after multiple comparisons correction. At baseline, thalamic atrophy correlated with cognitive impairment and ApoB/ApoA1 ratio. Furthermore, mediation analysis at baseline showed that the association of carotid intima-media thickness with executive functioning was mediated by thalamic volume. After CEA, cognitive improvement and increase in the bilateral medial dorsal thalamic volume were observed. CONCLUSION: Our study identified the distinct atrophy of subcortical nuclei and their association with cognition in patients with ACS. Assessments of the thalamus by volumetric and shape analysis may provide an early marker for cerebral ischemia and reperfusion after CEA.
- Klíčová slova
- asymptomatic carotid stenosis, cognitive impairment, endarterectomy, magnetic resonance imaging, thalamus,
- MeSH
- asymptomatické nemoci MeSH
- atrofie MeSH
- intimomediální šíře tepenné stěny MeSH
- karotická endarterektomie metody MeSH
- kognitivní dysfunkce * diagnóza etiologie MeSH
- lidé MeSH
- magnetická rezonanční tomografie metody MeSH
- neuropsychologické testy MeSH
- prognóza MeSH
- senioři MeSH
- stenóza arteria carotis * komplikace diagnóza chirurgie MeSH
- thalamus * diagnostické zobrazování patologie MeSH
- velikost orgánu MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Previous resting-state functional magnetic resonance imaging (rs-fMRI) studies frequently applied the spatial normalization on fMRI time series before the calculation of temporal features (here referred to as "Prenorm"). We hypothesized that calculating the rs-fMRI features, for example, functional connectivity (FC), regional homogeneity (ReHo), or amplitude of low-frequency fluctuation (ALFF) in individual space, before the spatial normalization (referred to as "Postnorm") can be an improvement to avoid artifacts and increase the results' reliability. We utilized two datasets: (1) simulated images where temporal signal-to-noise ratio (tSNR) is kept a constant and (2) an empirical fMRI dataset with 50 healthy young subjects. For simulated images, the tSNR is constant as generated in individual space but increased after Prenorm and intersubject variability of tSNR was induced. In contrast, tSNR was kept constant after Postnorm. Consistently, for empirical images, higher tSNR, ReHo, and FC (default mode network, seed in precuneus) and lower ALFF were found after Prenorm compared to those of Postnorm. Coefficient of variability of tSNR and ALFF was higher after Prenorm compared to those of Postnorm. Moreover, the significant correlation was found between simulated tSNR after Prenorm and empirical tSNR, ALFF, and ReHo after Prenorm, indicating algorithmic variation in empirical rs-fMRI features. Furthermore, comparing to Prenorm, ALFF and ReHo showed higher intraclass correlation coefficients between two serial scans after Postnorm. Our results indicated that Prenorm may induce algorithmic intersubject variability on tSNR and reduce its reliability, which also significantly affected ALFF and ReHo. We suggest using Postnorm instead of Prenorm for future rs-fMRI studies using ALFF/ReHo.
- Klíčová slova
- fMRI methods, fMRI preprocessing, reliability, resting-state fMRI, spatial normalization,
- Publikační typ
- časopisecké články MeSH
Brain white matter fiber bundles in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) have abnormalities not usually seen in unaffected subjects. Ideal algorithm of the localization-specific properties in white matter integrity might reveal the changes of tissue properties varying along each tract, while previous studies only detected the mean DTI parameters of each fiber. The aim of this study was to investigate whether these abnormalities of nerve fiber tracts are localized to specific regions of the tracts or spread throughout and to analyze which of the examined fiber tracts are involved in the early stages of Alzheimer's disease. In this study, we utilized VBA, TBSS as well as AFQ together to comprehensively investigate the white matter fiber impairment on 25 CE patients, 29 MCI patients and 34 normal control (NC) subjects. Two tract profiles, fractional anisotropy (FA) and mean diffusivity (MD), were extracted to evaluate the white matter integrity at 100 locations along each of 20 fiber tracts and then we validated the results with 27 CE patients, 21 MCI patients and 22 NC from the ADNI cohort. Also, we compare the AFQ with VBA and TBSS in our cohort. In comparison with NC, AD patients showed widespread FA reduction in 25% (5 /20) and MD increase in 65%(13/20) of the examined fiber tracts. The MCI patients showed a regional FA reduction in 5% (1/20) of the examined fiber tracts (right cingulum cingulate) and MD increase in 5%(1/20) of the examined fiber tracts (left arcuate fasciculus). Among these changed tracts, only the right cingulum cingulate showed widespread disruption of myelin or/and fiber axons in MCI and aggravated deterioration in AD, findings supported by FA/MD changes both by the mean and FA changes by point wise methods and TBSS. And the AFQ findings from ADNI cohort showed some similarity with our cohort, especially in the pointwise comparison of MD profiles between AD vs NC. Furthermore, the pattern of white matter abnormalities was different across neuronal fiber tracts; for example, the MCI and AD patients showed similar FA reduction in the middle part of the right cingulum cingulate, and the anterior part were not damaged. However, the left arcuate fasciculus showed MD elevation located at the temporal part of the fibers in the MCI patients and expanding to the temporal and middle part of the fibers in AD patients. So, the AFQ may be an alternative complementary method of VBA and TBSS, and may provide new insights into white matter degeneration in MCI and its association with AD.
- Klíčová slova
- Alzheimer's disease, Automated fiber quantification, Diffusion tensor imaging, Mild cognitive impairment, Pointwise comparison,
- MeSH
- Alzheimerova nemoc diagnostické zobrazování patologie MeSH
- bílá hmota diagnostické zobrazování patologie MeSH
- interpretace obrazu počítačem metody MeSH
- lidé středního věku MeSH
- lidé MeSH
- nervová vlákna patologie MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- zobrazování difuzních tenzorů metody MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Impairment of spatial navigation (SN) skills is one of the features of the Alzheimer's disease (AD) already at the stage of mild cognitive impairment (MCI). We used a computer-based battery of spatial navigation tests to measure the SN performance in 22 MCI patients as well as 21 normal controls (NC). In order to evaluate intrinsic activity in the subcortical regions that may play a role in SN, we measured ALFF, fALFF, and ReHo derived within 14 subcortical regions. We observed reductions of intrinsic activity in MCI patients. We also demonstrated that the MCI versus NC group difference can modulate activity-behavior relationship, that is, the correlation slopes between ReHo and allocentric SN task total errors were significantly different between NC and MCI groups in the right hippocampus (interaction F = 4.44, p = 0.05), pallidum (F = 8.97, p = 0.005), and thalamus (F = 5.95, p = 0.02), which were negative in NC (right hippocampus, r = -0.49; right pallidum, r = -0.50; right thalamus, r = -0.45; all p < 0.05) but absent in MCI (right hippocampus, r = 0.21; right pallidum, r = 0.32; right thalamus r = 0.28; all p > 0.2). These findings may provide a novel insight of the brain mechanism associated with SN impairment in MCI and indicated a stage specificity of brain-behavior correlation in dementia. This trial is registered with ChiCTR-BRC-17011316.
- MeSH
- dospělí MeSH
- funkční zobrazování neurálních procesů MeSH
- globus pallidus diagnostické zobrazování patofyziologie MeSH
- hipokampus diagnostické zobrazování patofyziologie MeSH
- kognitivní dysfunkce diagnostické zobrazování patofyziologie psychologie MeSH
- lidé středního věku MeSH
- lidé MeSH
- magnetická rezonanční tomografie MeSH
- neuropsychologické testy MeSH
- prostorová navigace fyziologie MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- thalamus diagnostické zobrazování patofyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Deep gray matter structures are associated with memory and other important functions that are impaired in Alzheimer's disease (AD) and mild cognitive impairment (MCI). However, systematic characterization of the subregional atrophy and deformations in these structures in AD and MCI still need more investigations. In this article, we combined complex volumetry- and vertex-based analysis to investigate the pattern of subregional structural alterations in deep gray matter structures and its association with global clinical scores in AD (n = 30) and MCI patients (n = 30), compared to normal controls (NCs, n = 30). Among all seven pairs of structures, the bilateral hippocampi and nucleus accumbens showed significant atrophy in AD compared with NCs (p < 0.05). But only the subregional atrophy in the dorsal-medial part of the left hippocampus, the ventral part of right hippocampus, and the left nucleus accumbens, the posterior part of the right nucleus accumbens correlated with the worse clinical scores of MMSE and MOCA (p < 0.05). Furthermore, the medial-ventral part of right thalamus significantly shrank and correlated with clinical scores without decreasing in its whole volume (p > 0.05). In conclusion, the atrophy of these four subregions in bilateral hippocampi and nucleus accumbens was associated with cognitive impairment of patients, which might be potential target regions of treatment in AD. The surface analysis could provide additional information to volume comparison in finding the early pathological progress in deep gray matter structures.
- Klíčová slova
- Alzheimer’s disease, deep gray matter structures, mild cognitive impairment, surface alteration, vertex analysis,
- Publikační typ
- časopisecké články MeSH
