骨骼肌衰老与力量-速度的关系

背景：人类的衰老与神经肌肉系统的功能能力衰退有关，年龄增长所致的肌肉质量丢失和肌肉结构的变化直接导致骨骼肌的力量-速度关系发生变化，而这些变化直接影响了老年人的功能活动，使老年人的活动能力和自理能力丧失。 目的：综述肌肉的力量-速度关系随年龄变化的研究进展，探讨这些变化对老龄肌肉的功能产生的影响。 方法：应用计算机检索CNKI 期刊全文数据库、读秀学术搜索和Elsevier SD、Springer Link数据库(1980-01/2010-04)与骨骼肌衰老与力量-速度关系的相关的文献。纳入所述内容与骨骼肌力量-速度关系随年龄变化的规律，以及该变化对老龄肌肉产生的影响相关的文章，排除重复研究或Meta分析类文章。 结果与结论：共纳入骨骼肌衰老与力量-速度关系的相关文献46篇。经分析得出结论：肌肉的力量，尤其是爆发力和收缩速度随年龄增长而衰退，而这种衰退与老年人的活动能力和自理能力的丧失直接相关。爆发力的衰退与老年人的功能活动能力的丧失高度相关，改善老年人的肌肉爆发力可能会有效地改善老年人的功能活动能力，从而提高老年人的生活质量。     

小脑非运动功能异常的影像研究进展

现代神经成像技术已经能在活体上获得近似于真实的小脑与大脑结构功能连接特征。近年来的研究已发现小脑在认知、注意、情感和语言等非运动功能方面起到了重要作用。在神经精神疾病中,小脑异常也参与了神经认知损害。本文针对包括老化、癫痫和精神分裂症在内的典型小脑非运动功能异常,从结构、功能和脑连接角度综述了小脑的影像研究进展。对于探索小脑的非运动功能及其在老化和神经精神疾病中的病理生理机制具有重要的科学意义。     

分子神经科学系列讲座 第七讲突触可塑性的机制

学习和记忆是脑的基本功能 ,人和动物经过学习可以改变自身的行为 ,以适应不断变化的外界环境。为了调节各种适应性反应 ,神经系统的回路在整个生活过程中都是可变、可修饰或称为可塑的。突触的可塑性主要指突触连接在形态上和功能上的修饰。其主要变化可分为 :突触前修饰、突触后修饰、突触前或突触后结构的可塑性等。神经系统的可塑性变化可以影响到神经系统的生长发育、神经的损伤和修复以及学习记忆等多种脑功能。1海马是事件记忆的必要部位　　突触的可塑性主要指突触连接在形态上和功能上的修饰。ＤｏｎａｌｄＨｅｂｂ于 194 9年在著…     

胶质瘤功能连接网络的静息态脑磁图研究

目的通过静息态脑磁图评估胶质瘤对人类大脑功能连接网络的影响。方法本研究共采集20例胶质瘤患者及20例健康受试者的静息态脑磁图数据,在Delta频段,Theta频段,Alpha频段,Beta频段,低Gamma频段和高Gamma频段6个频段上分别构建网络,对比分析两组功能连接网络之间的差异。结果胶质瘤患者脑功能连接网络在Alpha频段呈现显著的小世界网络特性;与健康对照组相比较,胶质瘤患者功能连接在低Gamma和高Gamma频段出现显著下降(P<0.05),左侧半球胶质瘤在beta频段脑功能连接显著高于右侧(P<0.05),而性别、年龄对脑功能连接的影响并无统计学意义。结论胶质瘤患者大脑小世界网络特性出现改变;同时胶质瘤患者在低Gamma和高Gamma频段出现功能连接显著下降,左右大脑半球胶质瘤对患者Beta频段功能连接网络的影响有显著差异。     

脑白质疏松的治疗

脑MRI上的皮质下白质信号强度改变被称之为白质疏松，它在老年人的影像学研究中很常见，以前被认为是一种良性老龄化过程。然而，最近的研究发现脑白质疏松的存在与卒中、认知功能减退和痴呆的风险增高之间存在确切的联系。并且，流行病学研究显示白质疏松与年龄和其他一些可纠正的危险因素有关，包括吸烟、高血压、糖尿病，高同型兰胱氨酸血症，高脂血症和过量钦酒。尽管尚缺乏前瞻性研究的结果，但目前的证据提示对心血管疾病危险因素的积极治疗可以防止脑白质疏松及随之而来的卒中和痴呆的发生或进展。     

地中海饮食对老年脑心共病的影响

随着人口老龄化的加剧,老年人健康成为老龄化社会的重要问题。地中海饮食通过改变饮食模式延缓和预防疾病发生,有助于健康老龄化。本文综述地中海饮食模式相关概念及其与老年脑心共病如心血管病、认知功能障碍、抑郁症、慢性炎症等的关系,为国人老龄化的优化升级提供思考与借鉴,助力健康中国发展。     

快速老化动物模型SAMP8小鼠及其相关研究进展

SAMP8鼠由日本京都大学竹田俊男教授开发成功，主要以学习记忆功能呈增龄性加速衰退，中枢神经系统如皮质、海马等部位发生病理改变为主，是一种比较理想的研究脑老化和痴呆的模型，亦是目前研究快速衰老的唯一哺乳类模式动物。行为学、形态学、神经生化和分子生物学为此提供了较充足的证据。SAMP8鼠可被广泛应用于阐明年龄相关的学习记忆功能改变及认知缺陷的基本机制，研究老化相关性疾病，评价治疗老化关联疾病和改善学习记忆机能的益智药物。但SAMP8所涉及的相关疾病主要是阿尔茨海默病，能否用于其他衰老相关性疾病如帕金森病仍需进一步研究。     

同型半胱氨酸与痴呆：国际共识声明

痴呆预防的关键是要从可干预的危险因素入手。其中,营养或依赖营养的危险因素尤为重 要,通过调整饮食结构或使用膳食补充剂,即可能降低危险因素水平。血浆总同型半胱氨酸（serum total homocysteine,tHcy）水平升高属于上述的一项危险因素,其反映了3种B族维生素（叶酸、维生素 B12、维生素B6）的功能状态。专家们回顾分析了近20年的文献证据,基于Bradford Hill标准并达成共识, 认为血浆总tHcy水平升高是老年人认知功能损害、痴呆和AD发生的可干预的危险因素。在各项临床 研究中,tHcy水平中度升高（在正常范围内）的老年人发生痴呆的相对危险度为1.15～2.5,人群归因 危险度为4.3％～31％。对老年人进行认知功能损害干预的试验表明,使用B族维生素可降低tHcy水 平,并显著减缓全脑和区域性脑萎缩的发展速度,以及认知功能下降的速度。该结果进一步支持老 年人群中常见的血浆总tHcy水平中度升高（>11 μmol/L）是导致年龄相关的认知功能损害和痴呆的 原因之一。因此,应避免低估老年人中总tHcy升高的公共卫生意义,毕竟应用B族维生素治疗是简单、 廉价和安全的,但仍需要进一步的试验来确定B族维生素能否减缓或预防有认知损害或痴呆风险人 群进展为痴呆。     

脑小血管病研究进展

近年来,随着人口老龄化的加剧,脑小血管病（cerebral small vessel disease,CSVD）也日益 增多。CSVD可引起一系列病理学、神经影像学变化及相关临床症状,是导致老年人认知功能下降和 功能缺失的一大原因,本文就近年来CSVD在病理学、临床和影像学特征及诊疗方面的研究进展进行 综述,以期为其进一步研究提供思路。     

脑小血管病的视网膜标志物

脑小血管病（CVSD）是老年人认知能力下降和功能丧失的主要原因,起病隐匿,临床表现不典型,且无法早期获得微血管病理改变,而视网膜血管与脑小血管有着相似的胚胎学起源、解剖学特征和生理特性,且视网膜在活体中可被直接观测到,是研究CSVD的一个有效切入点。本文围绕不同视网膜变化与CVSD的关系研究进行综述,探讨通过视网膜变化作为CSVD标志物的可能性,为CSVD的早期诊断及防治提供参考。     

The relationship between episodic long-term memory and white matter integrity in normal aging

It has been proposed that episodic long-term memory (LTM) declines in normal aging and may be affected by disruption of white matter networks. This was explored in 104 healthy adults aged 50-90 years in the GENIE study; white matter integrity was assessed using diffusion tensor imaging (DTI) in large regions of interest, with additional measures of white matter hyperintensities (WMH), normalized brain and hippocampal volumes. LTM was compared with executive function, working memory and information processing speed. LTM correlated significantly with DTI, WMH and whole brain volume, but not with hippocampal volume. Using linear regression, only DTI measures explained the variance (approximately 19%) in LTM; mediational analyses explored the extent to which other cognitive functions mediate the association between DTI changes and memory. The results suggest that reduced LTM performance in normal aging is related to reduced integrity of a distributed network dependent on white matter pathways supporting episodic memory.     

Cognitive correlates of 1H MRS measures in the healthy elderly brain

Ageing is associated with cognitive decline, with some studies indicating that this decline can be mostly accounted for by slowing of information processing speed. Whilst it is likely that this is associated with age-related changes in fronto-subcortical neuronal circuits, such changes are not visible on routine neuroimaging. We examined the integrity of this brain region using proton magnetic resonance spectroscopy (1H MRS) and hypothesised that functional changes measured by 1H MRS would be associated with cognitive performance. Fifty-nine healthy elderly subjects (age 58-85 years) underwent single-voxel 1H MRS in frontal white matter and occipito-parietal gray matter, and a comprehensive neuropsychological battery. The results showed a significant correlation between frontal white matter NAA/H2O and a composite measure of neuropsychological performance representing speed of information processing, attentional function and visual memory, controlling for age and sex. This research highlights the importance of the relationship between regional brain changes and cognitive function in the ageing brain, and suggests that MRS may be a sensitive marker of subclinical change in cognition.     

Cognitive correlates of H MRS measures in the healthy elderly brain

Ageing is associated with cognitive decline, with some studies indicating that this decline can be mostly accounted for by slowing of information processing speed. Whilst it is likely that this is associated with age-related changes in fronto-subcortical neuronal circuits, such changes are not visible on routine neuroimaging. We examined the integrity of this brain region using proton magnetic resonance spectroscopy (1H MRS) and hypothesised that functional changes measured by 1H MRS would be associated with cognitive performance. Fifty-nine healthy elderly subjects (age 58-85 years) underwent single-voxel 1H MRS in frontal white matter and occipito-parietal gray matter, and a comprehensive neuropsychological battery. The results showed a significant correlation between frontal white matter NAA/H2O and a composite measure of neuropsychological performance representing speed of information processing, attentional function and visual memory, controlling for age and sex. This research highlights the importance of the relationship between regional brain changes and cognitive function in the ageing brain, and suggests that MRS may be a sensitive marker of subclinical change in cognition.     

Thalamic structures and associated cognitive functions: Relations with age and aging

The thalamus, with its cortical, subcortical, and cerebellar connections, is a critical node in networks supporting cognitive functions known to decline in normal aging, including component processes of memory and executive functions of attention and information processing. The macrostructure, microstructure, and neural connectivity of the thalamus changes across the adult lifespan. Structural and functional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) have demonstrated, regional thalamic volume shrinkage and microstructural degradation, with anterior regions generally more compromised than posterior regions. The integrity of selective thalamic nuclei and projections decline with advancing age, particularly those in thalamofrontal, thalamoparietal, and thalamolimbic networks. This review presents studies that assess the relations between age and aging and the structure, function, and connectivity of the thalamus and associated neural networks and focuses on their relations with processes of attention, speed of information processing, and working and episodic memory.     

Cerebral imaging in healthy aging: contrast with Alzheimer disease

With age, the brain undergoes both structural and functional alterations. Overall, the literature consistently reports global brain atrophy in normal adults, generally more pronounced in frontal areas. As a result of different methodologies and inclusion criteria, other brain areas have been the matter of conflicting findings, notably the hippocampus. Regarding resting-state PET studies, they have consistently highlighted a metabolic deterioration of the frontal and anterior cingulated cortices. By contrast, relatively few investigations have sought to identify those areas that remain intact with aging, or undergo the least deterioration. We report a study designed to establish a comprehensive profile of both structural and functional changes in the aging brain, using up-to-date voxel-based methodology in 45 optimally healthy subjects aged 20-83 years. One of the main findings is that the lesser structural deterioration of the anterior hippocampal region, together with the lesser functional alteration of the posterior cingulate cortex, appear to mark the parting of the ways between normal aging and Alzheimer's disease, which is characterized by early and prominent deterioration of both structures. This paper also deals with studies set out to establish the relationship between changes in episodic memory retrieval in normal aging on the one hand and gray matter volume and 18FDG uptake on the other hand. Frontal areas dysfunction is involved in memory decline in older subjects, at least in some conditions, a finding which clearly contrasts with that found in Alzheimer's disease where the hippocampus plays a key role. Finally, compensatory mechanisms are reviewed through activation studies which often show supplementary activations in old subjects compared to young as well as in Alzheimer's disease patients compared to healthy elderly subjects. Paradoxically, those mechanisms seem to be underpinned, at least partially, by frontal areas in both populations, but researches are needed to better identify which subregions are involved.     

Brain biomarkers and cognition across adulthood

Understanding the associations between brain biomarkers (BMs) and cognition across age is of paramount importance. Five hundred and sixty‐two participants (19–80 years old, 16 mean years of education) were studied. Data from structural T1, diffusion tensor imaging, fluid‐attenuated inversion recovery, and resting‐state functional magnetic resonance imaging scans combined with a neuropsychological evaluation were used. More specifically, the measures of cortical, entorhinal, and parahippocampal thickness, hippocampal and striatal volume, default‐mode network and fronto‐parietal control network, fractional anisotropy (FA), and white matter hyperintensity (WMH) were assessed. z‐Scores for three cognitive domains measuring episodic memory, executive function, and speed of processing were computed. Multiple linear regressions and interaction effects between each of the BMs and age on cognition were examined. Adjustments were made for age, sex, education, intracranial volume, and then, further, for general cognition and motion. BMs were significantly associated with cognition. Across the adult lifespan, slow speed was associated with low striatal volume, low FA, and high WMH burden. Poor executive function was associated with low FA, while poor memory was associated with high WMH burden. After adjustments, results were significant for the associations: speed‐FA and WMH, memory‐entorhinal thickness. There was also a significant interaction between hippocampal volume and age in memory. In age‐stratified analyses, the most significant associations for the young group occurred between FA and executive function, WMH, and memory, while for the old group, between entorhinal thickness and speed, and WMH and speed, executive function. Unique sets of BMs can explain variation in specific cognitive domains across adulthood. Such results provide essential information about the neurobiology of aging.     

Head size and cognitive ability in nondemented older adults are related

In a cross-sectional analysis of 818 healthy older individuals (aged 50 to 81 years), head size was found to be related to performance on tests measuring intelligence, global cognitive functioning, and speed of information processing, but not memory. These relations were not confounded by educational level, socioeconomic background, or height. Large head/brain size may protect elderly people against cognitive deterioration, supporting a reserve hypothesis of brain aging.     

Normal aging modulates prefrontoparietal networks underlying multiple memory processes

A functional decline of brain regions underlying memory processing represents a hallmark of cognitive aging. Although a rich literature documents age‐related differences in several memory domains, the effect of aging on networks that underlie multiple memory processes has been relatively unexplored. Here we used functional magnetic resonance imaging during working memory and incidental episodic encoding memory to investigate patterns of age‐related differences in activity and functional covariance patterns common across multiple memory domains. Relative to younger subjects, older subjects showed increased activation in left dorso‐lateral prefrontal cortex along with decreased deactivation in the posterior cingulate. Older subjects showed greater functional covariance during both memory tasks in a set of regions that included a positive prefronto‐parietal‐occipital network as well as a negative network that spanned the default mode regions. These findings suggest that the memory process‐invariant recruitment of brain regions within prefronto‐parietal‐occipital network increases with aging. Our results are in line with the dedifferentiation hypothesis of neurocognitive aging, thereby suggesting a decreased specialization of the brain networks supporting different memory networks.     

Reward-based decision-making and aging

Healthy aging is associated with a number of neuroanatomical and neurobiological alterations that result in various cognitive changes. Both, the dopaminergic as well as the serotonergic system are subject to change during aging. Receptor loss and severe structural changes in PFC and striatum have been reported. Aging is associated with a progressive decline in several cognitive functions, such as episodic memory, working memory, and processing speed. Furthermore, it is associated with deficits in tasks requiring adaptation to external feedback of right or wrong, or task-switching. Here, we develop the hypothesis that this loss of behavioral flexibility is caused by structural and functional alterations of the reward system leading to impairments in reward processing, learning stimulus reinforcement associations, and reward-based decision-making. We review (a) data on neural correlates and substrates of reward processing in young healthy animals and humans, (b) evidence for age related functional and structural alterations of the reward system, and (c) behavioral and neuroimaging data of age effects on reward-based decision-making processes. Implications for neuroeconomics and neurodegenerative diseases are discussed.