老化对来源记忆编码的影响——一项fMRI研究

为探讨HAROLD模型在来源记忆中的适用性以及对"补偿说"进行检验,本研究以汉语双字词为材料,采用高低两种难度水平的位置回忆任务对13名老年被试和15名年轻被试的来源记忆编码过程进行fMRI扫描,考察在编码阶段大脑额叶激活模式的年龄差异。行为研究结果发现:年龄的主效应和难度的主效应均显著;神经成像研究结果发现:在高难度条件下,老年人仅激活左侧额叶,而在低难度条件下老年人的额叶呈现出双侧激活.且无论难度高低,老年人都在右侧额下回显示出比年轻人更强的激活,但这种激活的增强和行为成绩的相关并不显著。因此,HAROLD模型具有任务特异性,并非通用模型,且本研究结果不支持补偿说。     

"心理理论"的神经机制:来自脑成像的证据

"心理理论"是认知发展领域的研究热点之一,迄今已积累了大量行为研究的证据.心理理论具有领域特异的模块化认知机制,脑成像研究中也发现心理理论任务激活前额叶皮质等多个模块区域.论文阐述了真实表征与错误信念、心智互动等心理理论推理的神经机制,总结了该领域存在的问题并对今后研究的发展趋势进行了展望.     

“心理理论”的神经机制：来自脑成像的证据

“心理理论”是认知发展领域的研究热点之一,迄今已积累了大量行为研究的证据。心理理论具有领域特异的模块化认知机制,脑成像研究中也发现心理理论任务激活前额叶皮质等多个模块区域。论文阐述了真实表征与错误信念、心智互动等心理理论推理的神经机制,总结了该领域存在的问题并对今后研究的发展趋势进行了展望。     

抑郁症人群的心境一致性认知偏向

心境一致性认知偏向指的是抑郁病人的认知加工偏向负性情绪效价, 简称认知偏向。大量行为学、电生理学以及脑成像学的研究显示该认知偏向主要包括知觉偏向、注意偏向、记忆偏向以及解释偏向。该认知偏向以加工偏向负性、积极偏向缺失以及认知控制受损为特点, 且是杏仁核等边缘系统对负性信息过度激活、纹状体对正性信息激活不足以及额区激活模式异常三个相应脑机制协同作用的产物。目前此领域存在各认知偏向之间联系不清楚、认知偏向和抑郁症的因果关系难以确定以及各研究结果不一致等有待回答的问题, 这些重要问题值得引起该领域未来研究者的注意。     

适于自然情境脑成像研究的分析方法:被试间相关及其应用

被试间相关分析是一种基于大脑活动的时间模式的数据分析方法。该方法通过计算接收相同刺激时被试间脑区活动的一致性,探讨认知加工与脑区功能的关系。与传统的基于激活水平的数据分析方法相比,该方法不需要设置严格的实验条件,能更好地应用于自然情境下的脑成像研究。文章介绍了被试间相关分析的基本原理和方法,分析了该方法如何识别认知功能脑区及其可靠性,并结合其在自然情境脑成像以及特定研究领域的应用,阐明被试间相关在自然情境脑成像研究中的优势,以及该方法在多个研究领域的广泛应用扩展了认知神经科学研究的深度和广度。     

自我情绪一致性效应及其可逆性:探究负荷理论

认知资源系统是单一的,还是多重的?根据不同脑区调节自我积极、消极信息加工这一脑成像研究结果,本研究通过验证自我情绪一致性效应(自我积极、消极工作记忆负荷干扰同类认知任务,而不干扰不同类认知任务)及其可逆性,考察这一争议。两个实验采用改编的阅读广度范式,通过操纵工作记忆负荷类型,证实了该效应的存在;通过控制认知任务的加工速度,发现了该效应的可逆性。研究结果支持了多重资源的观点。     

心理旋转中的性别差异

性别差异是认知心理学中一个重要的研究领域。男性在执行空间认知任务时的表现往往好于女性,在心理旋转任务中,这种现象更为普遍。近年来,人们在行为和脑成像等层面对心理旋转中的性别差异进行了大量的研究,该文通过对其中一部分研究的回顾描述了心理旋转的性别差异在行为及脑成像实验中的表现,总结了可能导致这种性别差异的生理及策略等因素     

演绎推理是基于规则还是模型?——来自空间推理的证据

对空间推理的研究有助于探明其加工机制以及验证心理逻辑理论和心理模型理论。行为研究通过考察多种影响空间推理的因素(如心理模型数量、前提的对象顺序等)证实了心理模型理论的预测。脑成像的研究表明,空间推理活动主要激活枕-顶-额脑区网络,顶区可能是推理的特异性脑区。研究的结果同样支持心理模型理论。未来的研究应该整合演绎推理的不同理论,加强对不同演绎推理任务的研究,并将脑成像技术与EEG或ERP结合起来,进一步探明人类空间推理的机制。     

认知风格分型的神经基础:静息态fMRI研究

认知风格是个体习惯性的加工偏好。行为研究和任务态的功能成像研究已为认知风格分型理论提供了丰富的依据,但关于个体安静无任务状态下的脑活动是否也能表现出认知风格上的差异仍知之甚少。本研究使用静息态功能磁共振(f MRI)技术,以在校大学生为研究对象,以较为严格的标准使用认知风格分型任务分离出整体型和分析型认知风格被试,通过分析两组被试局部脑活动的一致性和整体脑活动的功能连接性,考察了静息条件下认知风格分型的神经基础。结果发现,不同认知风格群体的脑局部和整体活动均可能存在差异。个体越偏向分析型认知风格,左侧小脑的激活越强;左侧小脑与双侧大脑的功能区有更强、更广泛的连接。结果提示,安静无任务下个体的脑活动也可能表现出认知风格上的差异。     

中文音素言语流畅性任务的近红外脑功能成像研究

本文使用近红外脑功能成像技术探测正常被试在中文音素言语流畅性任务时的脑激活模式,34名右利手大学生被试参加了实验,实验任务为音素言语流畅性任务,采用近红外脑功能成像仪检测被试额颞区在任务时的激活情况,结果发现该任务激活了大脑双侧的额颞区,双侧缘上回的激活可能为中文音素言语流畅性任务的语言特异性激活脑区,该研究为临床诊断提供了参考价值,并说明了近红外脑功能成像仪可用于中文言语流畅性任务的研究     

Cognitive neuroscience of aging: contributions of functional neuroimaging

By revealing how brain activity during cognitive performance changes as a function of aging, studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) are contributing to the development of a new discipline of Cognitive Neuroscience of Aging. This article reviews functional neuroimaging studies of cognitive aging in the domains of visual perception, episodic memory encoding and semantic memory retrieval, episodic memory retrieval, implicit memory, and working memory. The most consistent finding of these studies was that brain activity tends to be less lateralized in older adults than in younger adults. This finding is conceptualized in terms of a model called Hemispheric Asymmetry Reduction in Old Adults (HAROLD). According to a compensation hypothesis, bihemispheric involvement could help counteract age-related neurocognitive decline, whereas, according to a dedifferentiation hypothesis, it reflects a difficulty in recruiting specialized neural mechanisms.     

Hemispheric asymmetry reduction in older adults: the HAROLD model

A model of the effects of aging on brain activity during cognitive performance is introduced. The model is called HAROLD (hemispheric asymmetry reduction in older adults), and it states that, under similar circumstances, prefrontal activity during cognitive performances tends to be less lateralized in older adults than in younger adults. The model is supported by functional neuroimaging and other evidence in the domains of episodic memory, semantic memory, working memory, perception, and inhibitory control. Age-related hemispheric asymmetry reductions may have a compensatory function or they may reflect a dedifferentiation process. They may have a cognitive or neural origin, and they may reflect regional or network mechanisms. The HAROLD model is a cognitive neuroscience model that integrates ideas and findings from psychology and neuroscience of aging.     

情景记忆成功年老化的神经机制

随着年龄的增长, 大部分老年人的情景记忆会出现衰退, 但也会有一部分老年人的情景记忆表现出成功的年老化, 即记忆成绩较好或随增龄的衰退程度较小。脑保持理论、神经去分化理论、认知储备理论以及神经补偿理论分别从不同角度解释了情景记忆成功年老化的神经机制。基于选择性优化与补偿模型对现有理论进行整合, 发现情景记忆成功年老化可能与个体的认知储备水平直接相关：高认知储备的老年人能够对情景记忆相关的脑区和脑网络进行优化且具备更强的神经补偿能力, 因而其脑功能(比如, 神经表征和神经加工通路的特异性)可能会保持地更好。未来研究需要更多地采用纵向设计来考察各理论之间的关系及其影响因素, 从而更好地解释记忆成功年老化的神经机制并为提升老年人的脑与认知健康提供支持。     

情绪加工老化效应的神经机制

行为学研究发现,老年人对消极情绪的辨别、注意和记忆都有所下降,而对积极情绪并未表现出类似的现象。情绪加工老化效应的神经影像学研究发现,老年人在情绪加工过程中边缘系统（尤其杏仁核）的激活强度低于年轻人,但额叶皮层区域的激活却有所增强。研究者对该结果提出了两种假说,一种是功能代偿假说,另一种是策略改变假说。功能代偿假说认为老年人额叶皮层区域的激活增强是为了弥补边缘系统功能的下降,反映了大脑功能的代偿;策略改变假说认为老年人主动使用了不同于年轻人的策略,情绪加工方式的不同导致了两组人群大脑活动的差异。未来这方面研究可以从研究层面、研究方法、研究问题等方面逐步完善     

Age-related changes in brain–behaviour relationships: Evidence from event-related functional MRI studies

A fundamental aim of studies in neurocognitive ageing is to understand age-related changes in brain–behaviour relationships. Neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) can be used for observation of these age-related changes only if the assumption of age-equivalent relations between neural activity and haemodynamic activity is valid. In one study, we characterised age-related differences in the coupling of the haemodynamic response to neural activity and found greater voxel-wise noise in older than in younger adults, but age-equivalent signal magnitude. These results suggested that alternative techniques may be necessary for analysing age-related differences in neuroimaging data. In a second study, we utilised one alternative method for comparing fMRI activation between younger and older adults performing a working memory (WM) task. Across three experiments, the results suggested that age-related functional changes in fMRI activation can be isolated to dorsolateral prefrontal cortex (PFC) during memory retrieval. These results suggest a plausible model for WM decline with normal ageing. In a third study we propose and test a model of age-related PFC dysfunction that may account for these and other age-related differences in cognitive performance.     

Contribution of NIRS to the study of prefrontal cortex for verbal fluency in aging

Healthy aging is characterized by a number of changes on brain structure and function. Several neuroimaging studies have shown an age-related reduction in hemispheric asymmetry on various cognitive tasks, a phenomenon captured by Cabeza (2002) in the Hemispheric Asymmetry Reduction in Older Adults (HAROLD) model. Although this phenomenon is supported by a range of neuroimaging data on memory and inhibitory processes, there is little evidence concerning changes in hemispheric asymmetry for language processing, and particularly word retrieval, which is assessed with verbal fluency task (VFT). This study aimed to investigate the age-related changes in cerebral oxygenation in the prefrontal cortex for both letter and category VFT, varying the complexity of the criteria (i.e., degree of productivity) and using near-infrared spectroscopy (NIRS). Sixteen younger and 16 older adults participated in this study. For both VF conditions, participants were instructed to pronounce as many nouns as possible as a function of high-productivity (e.g., “animals” or “L”) or low-productivity (e.g., “flowers” or “V”) criteria. Behavioral data (i.e., accuracy responses) showed comparable performance in younger and older adults for both VF conditions. However, NIRS data showed more reduced activation (i.e., significantly reduced increase in [O₂Hb] and reduced decrease in [HHb]) in older than younger adults for both VFT. In addition, a bilateral effect was found for both groups, suggesting that VFT requires both executive and language functions. The results are discussed in the context of the current theories of aging.     

The time course of access to semantic information in high-performing older adults: behavioral evidence for the hemispheric asymmetry reduction in OLDer individuals

The possibility that the HAROLD phenomenon (i.e., Hemispheric Asymmetry Reduction in OLDer adults) is manifested in the course of access to semantic information, in particular the meaning of emotional words, was investigated using the visual half-field priming paradigm. The time course of priming was tracked in the cerebral hemispheres across three SOAs: 150, 300, and 750 ms. The results showed older and young adults had the same level of accuracy. While priming occurred unilaterally in young participants, the pattern of priming in older participants appeared to be bilateral whenever it was present, that is, at the 300- and 750-ms SOAs. The delay in the appearance of priming in older adults may be due to an increase in sensory thresholds that causes older adults to need more time to encode stimuli and fully activate their semantic network. It is concluded that the bilateral pattern of priming in the presence of an equivalent level of performance in older adults provides behavioral evidence supporting the compensatory role of the HAROLD phenomenon for this particular task.     

The time course of access to semantic information in high-performing older adults: Behavioral evidence for the hemispheric asymmetry reduction in OLDer individuals

ABSTRACT

The possibility that the HAROLD phenomenon (i.e., Hemispheric Asymmetry Reduction in OLDer adults) is manifested in the course of access to semantic information, in particular the meaning of emotional words, was investigated using the visual half-field priming paradigm. The time course of priming was tracked in the cerebral hemispheres across three SOAs: 150, 300, and 750 ms. The results showed older and young adults had the same level of accuracy. While priming occurred unilaterally in young participants, the pattern of priming in older participants appeared to be bilateral whenever it was present, that is, at the 300- and 750-ms SOAs. The delay in the appearance of priming in older adults may be due to an increase in sensory thresholds that causes older adults to need more time to encode stimuli and fully activate their semantic network. It is concluded that the bilateral pattern of priming in the presence of an equivalent level of performance in older adults provides behavioral evidence supporting the compensatory role of the HAROLD phenomenon for this particular task.     

Age differences in prefrontal cortical activity in working memory

Working memory (WM) declines with advancing age. Brain imaging studies indicate that ventral prefrontal cortex (PFC) is active when information is retained in WM and that dorsal PFC is further activated for retention of large amounts of information. The authors examined the effect of aging on activation in specific PFC regions during WM performance. Six younger and 6 older adults performed a task in which, on each trial, they (a) encoded a 1- or 6-letter memory set, (b) maintained these letters over 5-s. and (c) determined whether or not a probe letter was part of the memory set. Comparisons of activation between the 1- and 6-letter conditions indicated age-equivalent ventral PFC activation. Younger adults showed greater dorsal PFC activation than older adults. Older adults showed greater rostral PFC activation than younger adults. Aging may affect dorsal PFC brain regions that are important for WM executive components.     

Cortical plasticity associated with stuttering therapy

Neuroimaging studies have indicated that persistent developmental stuttering (PDS) may be associated both with an abnormality in white matter of left-hemispheric speech areas and a right-hemispheric hyperactivity. The latter may compensate for the deficient structural connectivity in the left hemisphere. To investigate the effects of stuttering therapy on brain activity nine male adults with PDS underwent functional magnetic resonance imaging (fMRI) before and within 12 weeks after fluency shaping therapy. Brain response differences during overt sentence reading before and after therapy were assessed by utilizing random effects analyses. After therapy, a more widespread activation was observed in frontal speech and language regions and temporal areas of both hemispheres, particularly and more pronounced on the left side. Interestingly, distinct posttreatment left-sided activation increases were located directly adjacent to a recently detected area of white matter anomaly [M. Sommer, M.A. Koch, W. Paulus, C. Weiller, C. Buchel (2002). Disconnection of speech-relevant brain areas in persistent developmental stuttering. The Lancet, 360, 380-383] suggesting that fluency shaping techniques reorganize neuronal communication between left-sided speech motor planning, motor execution, and temporal areas. Hence, a therapeutic mechanism can be assumed to remodel brain circuitry close to the source of the dysfunction instead of reinforcing compensation via homologous contralateral brain networks. EDUCATIONAL OBJECTIVES: The reader will learn about and be able to: (1) describe brain activation changes detected shortly after fluency-shaping therapy; (2) identify left-hemispheric regions where a (re)functionalization after fluency-shaping therapy seems to occur adjacent to a recently described abnormal white matter region in PDS subjects; and (3) discuss how an effective cerebral compensation mechanism for stuttering could work.