The preservation of right cingulum fibers in subjective cognitive decline of preclinical phase of Alzheimer’s disease

IntroductionSubjective cognitive decline (SCD) with a positive amyloid burden has been recognized as the earliest clinical symptom of the preclinical phase of Alzheimers disease (AD), providing invaluable opportunities to improve our understanding of the natural history of AD and determine strategies for early therapeutic interventions.MethodsThe microstructure of white matter in patients showing SCD in the preclinical phase of AD (SCD of pre-AD) was evaluated using diffusion images, and voxel-wise fractional anisotropy (FA), mean diffusivity (MD), and axial and radial diffusivities were assessed and compared among participant groups. Significant clusters in the tracts were extracted to determine their associations with alterations in the cognitive domains.ResultsWe found that individuals with SCD of pre-AD may have subclinical episodic memory impairment associated with the global amyloid burden. Meanwhile, we found significantly reduced FA and λ1 in the right cingulum (cingulate and hippocampus) in AD dementia, while significantly increased FA and decreased MD as well as λ23 in the SCD of pre-AD group in comparison with the HC group.DiscussionIn conclusion, increased white matter microstructural integrity in the right cingulum (cingulate and hippocampus) may indicate compensation for short-term episodic memory in individuals with SCD of pre-AD in comparison with individuals with AD and healthy elderly individuals

Brain mechanisms underlying neuropsychiatric symptoms in Alzheimer’s disease: a systematic review of symptom-general and –specific lesion patterns

Abstract Neuropsychiatric symptoms (NPSs) are common in patients with Alzheimer’s disease (AD) and are associated with accelerated cognitive impairment and earlier deaths. This review aims to explore the neural pathogenesis of NPSs in AD and its association with the progression of AD. We first provide a literature overview on the onset times of NPSs. Different NPSs occur in different disease stages of AD, but most symptoms appear in the preclinical AD or mild cognitive impairment stage and develop progressively. Next, we describe symptom-general and -specific patterns of brain lesions. Generally, the anterior cingulate cortex is a commonly damaged region across all symptoms, and the prefrontal cortex, especially the orbitofrontal cortex, is also a critical region associated with most NPSs. In contrast, the anterior cingulate-subcortical circuit is specifically related to apathy in AD, the frontal-limbic circuit is related to depression, and the amygdala circuit is related to anxiety. Finally, we elucidate the associations between the NPSs and AD by combining the onset time with the neural basis of NPSs

Effects of blast furnace slag on the immobilization, plant uptake and translocation of Cd in a contaminated paddy soil

The potential toxicity of Cd to soil and rice plant severely threaten human health. This study was conducted to investigate the remediation effects of blast furnace slag (BFS) on the bioavailability of Cd in a contaminated paddy soil from a perspective of soil solution chemistry. Batch experiments, pot culture experiments, and principal analysis (PCA) were used to study the effects and mechanisms of BFS addition changing Cd chemical behavior and Cd toxicity. Results indicated that BFS facilitated Cd adsorption in soils, increased pH, Eh, and EC values in soil solution, whereas reduced dissolved Cd content. BFS amendment was efficient in decreasing root Cd intake and Cd upward transport in rice plant, with the Cd translocation factor in brown rice decreased by ∼ 75% (BFS treatment, 6‰ wt) relative to Cd treatment, which in turn increased rice biomass and grain yield. PCA indicated that the dissolved Cd concentration had a close relationship with soil pH and metal concentration in soil solution. Results from this study indicated that BFS had potential ability for either immobilization or remobilization of Cd in soils, and the findings have important implications for Cd-polluted soil remediation or other resource utilization with slag-based materials

Early frontal structural and functional changes in mild white matter lesions relevant to cognitive decline

White matter lesions (WMLs) are of considerable research interest because of their high prevalence and serious consequences, such as stroke and dementia. Most existing studies of WMLs have focused on severe WMLs, but mild WMLs, which are clinically and fundamentally significant, have been largely neglected. The present study is a comprehensive investigation on the injury pattern and on the anatomical, functional, and cognitive changes related to mild WMLs. These results may provide better understanding mild WMLs. Fifty-one human subjects with mild WMLs and 49 control participants completed serial neuropsychological tests and underwent a 3-T magnetic resonance imaging (MRI) scan that included diffusion tensor imaging, a resting-state functional MRI, and a structural MRI. We found declines in cognitive functions such as global function, executive function, and episodic memory in mild WMLs subjects. The white matter injuries in the mild WMLs subjects were mainly in the fibers that projected to frontal areas, while gray matter structures were relatively intact. The overall resting state function of the frontal area was significantly increased. The integrity of the neural fibers in the inferior fronto-occipital fasciculus and the inferior longitudinal fasciculus was significantly correlated with the cognitive scores in executive function and episodic memory in both the control and the mild WMLs group. These findings demonstrate that mild WMLs subjects exhibit abnormalities in both white matter structure and functional intrinsic brain activity and that such changes are related to several types of cognitive dysfunction

Aggravated cognitive and brain functional impairment in mild cognitive impairment patients with type 2 diabetes: a resting-state functional MRI study

Type 2 diabetes mellitus is a metabolic disorder and a risk factor for dementia and mild cognitive impairment (MCI), which could also increase the risk of progression from MCI to dementia. The present study evaluated the spontaneous neuronal activity of 31 patients with MCI using resting-state functional MRI. The patients were divided into two groups (17 MCI patients without diabetes, and 14 patients with type 2 diabetes who were considered as the MCI-DM group) and 17 well-matched healthy controls were also recruited. The amplitude of low-frequency fluctuations (ALFF) of spontaneous blood oxygen level dependent signals was then applied to assess neuroimaging changes. To further investigate the impact of type 2 diabetes on cognition, the correlation of ALFF and the neuropsychological tests for the MCI-DM and MCI group were calculated. MCI-DM patients showed diffused ALFF changes in a variety of brain regions that were significantly related to cognitive performance, including the frontal lobe, the temporal lobe, the hippocampus, the amygdala, and the precuneus during a resting state; whereas, the alterations were much less pronounced in the MCI patients without diabetes. These findings provide new insights into understanding essential of diabetes mellitus and may help to clarify the relationship between diabetes mellitus and dementia

Differences in functional brain activation and hippocampal volume among amnestic mild cognitive impairment subtypes

Patients with amnestic mild cognitive impairment (aMCI) often display deficits in episodic memory. Amnestic MCI is now recognized as a prodromal form of Alzheimer's disease. Various aMCI clinical subtypes have been identified as ingle-domain (SD) or multi-domain (MD). The various subtypes represent heterogeneous syndrome indicating the probability of progression to AD, impaired cognitive domains and so on. To examine the characteristics of brain regions of aMCI subtypes is likely to be important for early diagnosis and prediction to AD. This study investigated brain functional activation and hippocampal atrophy during a visually complex scene encoding in 20 individuals with aMCI-SD, 14 individuals with aMCI-MD and 25 healthy controls. During the encoding task, aMCI-MD patients had reduced activation in right superior medial frontal, right inferior and middle temporal, right middle occipital and left inferior frontal regions compared to controls. The different active brain regions between aMCI-MD and aMCI-SD patients are the right middle occipital and left middle cingulum regions. The aMCI-MD group had significantly lower left hippocampus volumes compared to the aMCI-SD group and controls, but there was no difference between aMCI-SD patients and the control group in terms of left hippocampus atrophy. The findings provide evidence that aMCI may represent a heterogeneous group. The aMCI-MD patients displayed more severe hippocampcal atrophy and fMRI activation changes than aMCI-SD. The aMCIMD may represent a more advanced prodromal stage of AD

The Contribution of Genetic Factors to Cognitive Impairment and Dementia: Apolipoprotein E Gene, Gene Interactions, and Polygenic Risk

Alzheimer’s disease (AD) is a progressive neurodegenerative disease. Although it has been studied for years, the pathogenesis of AD is still controversial. Genetic factors may play an important role in pathogenesis, with the apolipoprotein E (APOE) gene among the greatest risk factors for AD. In this review, we focus on the influence of genetic factors, including the APOE gene, the interaction between APOE and other genes, and the polygenic risk factors for cognitive function and dementia. The presence of the APOE ε4 allele is associated with increased AD risk and reduced age of AD onset. Accelerated cognitive decline and abnormal internal environment, structure, and function of the brain were also found in ε4 carriers. The effect of the APOE promoter on cognition and the brain was confirmed by some studies, but further investigation is still needed. We also describe the effects of the associations between APOE and other genetic risk factors on cognition and the brain that exhibit a complex gene–gene interaction, and we consider the importance of using a polygenic risk score to investigate the association between genetic variance and phenotype

Leisure activities as reserve mediators of the relationship between loneliness and cognition in aging.

Previous studies have found that loneliness affects cognitive functions in older persons. However, the influence of loneliness on different cognitive fields and the internal mechanism of the relationship are unclear. A total of 4772 older persons aged above 50 years (Mean = 65.31, SD = 6.96, 57.7% female) were included in this study. All the participants completed the characteristics scale, as well as the loneliness scale, leisure activity scale, and cognitive function tests in six domains. The results showed that 17.6% of participants had high loneliness, while 16.7% of participants had low loneliness. Associations were observed between higher levels of loneliness and lower scores in general cognitive ability, memory, and executive functions. Mediation analysis suggested that leisure activities, encompassing mental, physical, and social activities, were associated with cognitive functions in the context of loneliness. These results indicate that leisure activities may play a significant role in the relationship between loneliness and cognitive functions in older adults. The study highlights the importance of considering leisure activities in this demographic to potentially mitigate the adverse cognitive effects associated with loneliness