Impaired Parahippocampal Gyrus-Orbitofrontal Cortex Circuit Associated with Visuospatial Memory Deficit as a Potential Biomarker and Interventional Approach for Alzheimer Disease

A Multimodal Meta-Analytical Evidence of Functional and Structural Brain Abnormalities Across Alzheimer's Disease Spectrum

BACKGROUND

Numerous neuroimaging studies have reported that Alzheimer's disease (AD) spectrum have been linked to alterations in intrinsic functional activity and cortical thickness (CT) of some brain areas. However, the findings have been inconsistent and the correlation with the transcriptional profile and neurotransmitter systems remain largely unknown.

METHODS

We conducted a meta-analysis to identify multimodal differences in the amplitude of low-frequency fluctuation (ALFF)/fractional ALFF (fALFF) and CT in patients with AD and preclinical AD compared to healthy controls (HCs), using the Seed-based d Mapping with Permutation of Subject Images software. Transcriptional data were retrieved from the Allen Human Brain Atlas. The atlas-based nuclear imaging-derived neurotransmitter maps were investigated by JuSpace toolbox.

RESULTS

We included 26 ALFF/fALFF studies comprising 884 patients with AD and 1,020 controls, along with 52 studies comprising 2,046 patients with preclinical AD and 2,336 controls. For CT, we included 11 studies comprising 353 patients with AD and 330 controls. Overall, compared to HCs, patients with AD showed decreased ALFF/fALFF in the bilateral posterior cingulate gyrus (PCC)/precuneus and right angular gyrus, as well as increased ALFF/fALFF in the bilateral parahippocampal gyrus (PHG). Patients with peclinical AD showed decreased ALFF/fALFF in the left precuneus. Additionally, patients with AD displayed decreased CT in the bilateral PHG, left PCC, bilateral orbitofrontal cortex, sensorimotor areas and temporal lobe. Furthermore, gene sets related to brain structural and functional changes in AD and preclincal AD were enriched for G protein-coupled receptor signaling pathway, ion gated channel activity, and components of biological membrane. Functional and structural alterations in AD and preclinical AD were spatially associated with dopaminergic, serotonergic, and GABAergic neurotransmitter systems.

CONCLUSIONS

The multimodal meta-analysis demonstrated that patients with AD exhibited convergent functional and structural alterations in the PCC/precuneus and PHG, as well as cortical thinning in the primary sensory and motor areas. Furthermore, patients with preclinical AD showed reduced functional activity in the precuneus. AD and preclinical AD showed genetic modulations/neurotransmitter deficits of brain functional and structural impairments. These findings may provide new insights into the pathophysiology of the AD spectrum.

Neural repair and regeneration interfaces: a comprehensive review

Neural interfaces play a pivotal role in neuromodulation, as they enable precise intervention into aberrant neural activity and facilitate recovery from neural injuries and resultant functional impairments by modulating local immune responses and neural circuits. This review outlines the development and applications of these interfaces and highlights the advantages of employing neural interfaces for neural stimulation and repair, including accurate targeting of specific neural populations, real-time monitoring and control of neural activity, reduced invasiveness, and personalized treatment strategies. Ongoing research aims to enhance the biocompatibility, stability, and functionality of these interfaces, ultimately augmenting their therapeutic potential for various neurological disorders. The review focuses on electrophysiological and optophysiology neural interfaces, discussing functionalization and power supply approaches. By summarizing the techniques, materials, and methods employed in this field, this review aims to provide a comprehensive understanding of the potential applications and future directions for neural repair and regeneration devices.

Loss of TDP-43 splicing repression occurs early in the aging population and is associated with Alzheimer's disease neuropathologic changes and cognitive decline

LATE-NC, the neuropathologic changes of limbic-predominant age-related TAR DNA-binding protein 43 kDa (TDP-43) encephalopathy are frequently associated with Alzheimer's disease (AD) and cognitive impairment in older adults. The association of TDP-43 proteinopathy with AD neuropathologic changes (ADNC) and its impact on specific cognitive domains are not fully understood and whether loss of TDP-43 function occurs early in the aging brain remains unknown. Here, using a large set of autopsies from the Baltimore Longitudinal Study of Aging (BLSA) and another younger cohort, we were able to study brains from subjects 21-109 years of age. Examination of these brains show that loss of TDP-43 splicing repression, as judged by TDP-43 nuclear clearance and expression of a cryptic exon in HDGFL2, first occurs during the 6th decade, preceding by a decade the appearance of TDP-43+ neuronal cytoplasmic inclusions (NCIs). We corroborated this observation using a monoclonal antibody to demonstrate a cryptic exon-encoded neoepitope within HDGFL2 in neurons exhibiting nuclear clearance of TDP-43. TDP-43 nuclear clearance is associated with increased burden of tau pathology. Age at death, female sex, high CERAD neuritic plaque score, and high Braak neurofibrillary stage significantly increase the odds of LATE-NC. Faster rates of cognitive decline on verbal memory (California Verbal Learning Test immediate recall), visuospatial ability (Card Rotations Test), mental status (MMSE) and semantic fluency (Category Fluency Test) were associated with LATE-NC. Notably, the effects of LATE-NC on verbal memory and visuospatial ability are independent of ADNC. However, the effects of TDP-43 nuclear clearance in absence of NCI on the longitudinal trajectories and levels of cognitive measures are not significant. These results establish that loss of TDP-43 splicing repression is an early event occurring in the aging population during the development of TDP-43 proteinopathy and is associated with increased tau pathology. Furthermore, LATE-NC correlates with high levels of ADNC but also has an impact on specific memory and visuospatial functions in aging that is independent of AD.

Control of the temporal development of Alzheimer's disease pathology by the MR1/MAIT cell axis

BACKGROUND

Neuroinflammation is an important feature of Alzheimer's disease (AD). Understanding which aspects of the immune system are important in AD may lead to new therapeutic approaches. We study the major histocompatibility complex class I-related immune molecule, MR1, which is recognized by an innate-like T cell population called mucosal-associated invariant T (MAIT) cells.

METHODS

Having found that MR1 gene expression is elevated in the brain tissue of AD patients by mining the Agora database, we sought to examine the role of the MR1/MAIT cell axis in AD pathology. Brain tissue from AD patients and the 5XFAD mouse model of AD were used to analyze MR1 expression through qPCR, immunofluorescence, and flow cytometry. Furthermore, mice deficient in MR1 and MAIT cells were crossed with the 5XFAD mice to produce a model to study how the loss of this innate immune axis alters AD progression. Moreover, 5XFAD mice were also used to study brain-resident MAIT cells over time.

RESULTS

In tissue samples from AD patients and 5XFAD mice, MR1 expression was substantially elevated in the microglia surrounding plaques vs. those that are further away (human AD: P < 0.05; 5XFAD: P < 0.001). In 5XFAD mice lacking the MR1/MAIT cell axis, the development of amyloid-beta plaque pathology occurred at a significantly slower rate than in those mice with MR1 and MAIT cells. Furthermore, in brain tissue from 5XFAD mice, there was a temporal increase in MAIT cell numbers (P < 0.01) and their activation state, the latter determined by detecting an upregulation of both CD69 (P < 0.05) and the interleukin-2 receptor alpha chain (P < 0.05) via flow cytometry.

CONCLUSIONS

Together, these data reveal a previously unknown role for the MR1/MAIT cell innate immune axis in AD pathology and its potential utility as a novel therapeutic target.

Machine-Based Learning Shifting to Prediction Model of Deteriorative MCI Due to Alzheimer's Disease - A Two-Year Follow-Up Investigation

OBJECTIVE

The aim of the present work was to investigate the features of the elderly population aged ≥65 yrs and with deteriorative mild cognitive impairment (MCI) due to Alzheimer's disease (AD) to establish a prediction model.

METHODS

A total of 105 patients aged ≥65 yrs and with MCI were followed up, with a collection of 357 features, which were derived from the demographic characteristics, hematological indicators (serum Aβ1-40, Aβ1-42, P-tau and MCP-1 levels, APOE gene), and multimodal brain Magnetic Resonance Imaging (MRI) imaging indicators of 116 brain regions (ADC, FA and CBF values). Cognitive function was followed up for 2 yrs. Based on the Python platform Anaconda, 105 patients were randomly divided into a training set (70%) and a test set (30%) by analyzing all features through a random forest algorithm, and a prediction model was established for the form of rapidly deteriorating MCI.

RESULTS

Of the 105 patients enrolled, 41 deteriorated, and 64 did not come within 2 yrs. Model 1 was established based on demographic characteristics, hematological indicators and multi-modal MRI image features, the accuracy of the training set being 100%, the accuracy of the test set 64%, sensitivity 50%, specificity 67%, and AUC 0.72. Model 2 was based on the first five features (APOE4 gene, FA value of left fusiform gyrus, FA value of left inferior temporal gyrus, FA value of left parahippocampal gyrus, ADC value of right calcarine fissure as surrounding cortex), the accuracy of the training set being 100%, the accuracy of the test set 85%, sensitivity 91%, specificity 80% and AUC 0.96. Model 3 was based on the first four features of Model 1, the accuracy of the training set is 100%, the accuracy of the test set 97%, sensitivity100%, specificity 95% and AUC 0.99. Model 4 was based on the first three characteristics of Model 1, the accuracy of the training set being 100%, the accuracy of the test set 94%, sensitivity 92%, specificity 94% and AUC 0.96. Model 5 was based on the hematological characteristics, the accuracy of the training set is 100%, the accuracy of the test set 91%, sensitivity 100%, specificity 88% and AUC 0.97. The models based on the demographic characteristics, imaging characteristics FA, CBF and ADC values had lower sensitivity and specificity.

CONCLUSION

Model 3, which has four important predictive characteristics, can predict the rapidly deteriorating MCI due to AD in the community.

Aberrant Cross-Tissue Functional Connectivity in Alzheimer’s Disease: Static, Dynamic, and Directional Properties

Background: BOLD signals in the gray matter (GM) and white matter (WM) are tightly coupled. However, our understanding of the cross-tissue functional network in Alzheimer’s disease (AD) is limited. Objective: We investigated the changes of cross-tissue functional connectivity (FC) metrics for the GM regions susceptible to AD damage. Methods: For each GM region in the default mode (DMN) and limbic networks, we obtained its low-order static FC with any WM region, and the high-order static FC between any two WM regions based on their FC pattern similarity with multiple GM regions. The dynamic and directional properties of cross-tissue FC were then acquired, specifically for the regional pairs whose low- or high-order static FCs showed significant differences between AD and normal control (NC). Moreover, these cross-tissue FC metrics were correlated with voxel-based GM volumes and MMSE in all participants. Results: Compared to NC, AD patients showed decreased low-order static FCs between the intra-hemispheric GM-WM pairs (right ITG-right fornix; left MoFG-left posterior corona radiata), and increased low-order static, dynamic, and directional FCs between the inter-hemispheric GM-WM pairs (right MTG-left superior/posterior corona radiata). The high-order static and directional FCs between the left cingulate bundle-left tapetum were increased in AD, based on their FCs with the GMs of DMN. Those decreased and increased cross-tissue FC metrics in AD had opposite correlations with memory-related GM volumes and MMSE (positive for the decreased and negative for the increased). Conclusion: Cross-tissue FC metrics showed opposite changes in AD, possibly as useful neuroimaging biomarkers to reflect neurodegenerative and compensatory mechanisms.

Functional Network Connectivity Reveals the Brain Functional Alterations in Breast Cancer Survivors

Different neurological and psychiatric disorders such as vertebrobasilar insufficiency, chronic pain syndrome, anxiety, and depression are observed in more than 90% of patients after treatment for breast cancer and may cause alterations in the functional connectivity of the default mode network. The purpose of the present study is to assess changes in the functional connectivity of the default mode network in patients after breast cancer treatment using resting state functional magnetic resonance imaging (rs-fMRI). Rs-fMRI was performed using a 3.0T MR-scanner on patients (N = 46, women) with neurological disorders (chronic pain, dizziness, headaches, and/or tinnitus) in the late postoperative period (>12 months) after Patey radical mastectomy for breast cancer. According to the intergroup statistical analysis, there were differences in the functional connectivity of the default mode network in all 46 patients after breast cancer treatment compared to the control group (p < 0.01). The use of rs-fMRI in in breast cancer survivors allowed us to identify changes in the functional connectivity in the brain caused by neurological disorders, which correlated with a decreased quality of life in these patients. The results indicate the necessity to improve treatment and rehabilitation methods in this group of patients.

The Visuospatial and Sensorimotor Functions of Posterior Parietal Cortex in Drawing Tasks: A Review

Drawing is a comprehensive skill that primarily involves visuospatial processing, eye-hand coordination, and other higher-order cognitive functions. Various drawing tasks are widely used to assess brain function. The neuropsychological basis of drawing is extremely sophisticated. Previous work has addressed the critical role of the posterior parietal cortex (PPC) in drawing, but the specific functions of the PPC in drawing remain unclear. Functional magnetic resonance imaging and electrophysiological studies found that drawing activates the PPC. Lesion-symptom mapping studies have shown an association between PPC injury and drawing deficits in patients with global and focal cerebral pathology. These findings depicted a core framework of the fronto-parietal network in drawing tasks. Here, we review neuroimaging and electrophysiological studies applying drawing paradigms and discuss the specific functions of the PPC in visuospatial and sensorimotor aspects. Ultimately, we proposed a hypothetical model based on the dorsal stream. It demonstrates the organization of a PPC-centered network for drawing and provides systematic insights into drawing for future neuropsychological research.

The Role of Gut Microbiota in Chronic Itch-Evoked Novel Object Recognition-Related Cognitive Dysfunction in Mice

The high incidence of patients with chronic itch highlights the importance of fundamental research. Recent advances in the interface of gut microbiota have shed new light into exploring this phenomenon. However, it is unknown whether gut microbiota plays a role in chronic itch in rodents with or without cognitive dysfunction. In this study, the role of gut microbiota in diphenylcyclopropenone (DCP)-evoked chronic itch was investigated in mice and hierarchical cluster analysis of novel object recognition test (ORT) results were used to classify DCP-evoked itch model in mice with or without cognitive dysfunction (CD)-like phenotype and 16S ribosomal RNA (rRNA) gene sequencing was used to compare gut bacterial composition between CD (Susceptible) and Non-CD phenotypes (Unsusceptible) in chronic itch mice. Results showed that the microbiota composition was significantly altered by DCP-evoked chronic itch and chronic itch induced novel object recognition-related CD. However, abnormal gut microbiota composition induced by chronic itch may not be correlated with novel object recognition-related CD.