工作记忆与情景记忆的相互作用

虽然Baddeley的工作记忆模型得到大量实验研究的支持,但是有关工作记忆和长时记忆之间的关系未能得到详细阐述。来自神经心理学的证据表明,工作记忆与情景长时记忆任务均诱发了前额区的激活,但同时发现前额区存在不同的功能分区,可能在工作记忆与情景记忆过程中具有独立的执行功能。工作记忆与情景记忆的相互作用是当前记忆研究关注的问题。已有研究发现,在情景记忆对工作记忆的作用过程中,时间进程与头皮分布均显示了年龄效应与材料加工特点。而工作记忆对情景记忆的作用中,则发现工作记忆早期加工可能对情景记忆的成功形成有更大促进作用。今后的研究应在理论模型支持下,利用多种技术手段探讨两种记忆相互作用的神经加工机制     

提取学习有利于学习与记忆的认知神经基础

研究表明提取学习相比简单重复学习更加益于记忆的保持。近期的脑成像研究发现, 与简单重复学习相比, 提取学习时前额叶、顶下叶、颞叶及一些皮层下结构的脑激活更大, 这些脑区的激活也能预测随后的记忆成绩。这些研究表明, 在更多认知资源的投入和工作记忆系统的参与下, 提取学习是一个获得、加工、整合和巩固语义关系的过程。提取学习充分调用认知和情感、皮层与皮层下机能, 同时还发挥语义和情景记忆优势来促进学习与记忆。     

工作记忆训练对认知功能和大脑神经系统的影响

工作记忆训练成为近年来提升个体认知绩效的一种有效方式。工作记忆训练主要是指采用工作记忆广度任务、刷新任务以及各种复杂工作记忆任务在计算机上以循序渐进的方式进行训练。近年来的研究发现, 工作记忆训练能提升工作记忆、流体智力、抑制、注意、阅读和数学等认知功能。神经机制的研究发现：工作记忆训练引起大脑额-顶区域激活减弱, 而皮层下结构包括纹状体和尾状核区域的激活增强; 工作记忆训练减少了大脑灰质的数量, 增强了大脑白质的功能连通性; 工作记忆训练引起尾状核上多巴胺受体的变化。未来的研究需要在研究设计、被试人群、研究手段上进一步确认和扩展工作记忆训练的有效性和内在认知神经机制。     

情绪大脑机制研究的进展

文章综述情绪大脑机制研究的最新进展。情绪的脑机制——大脑回路,包括前额皮层、杏仁核、海马、前部扣带回、腹侧纹状体等。前额皮层中的不对称性与趋近和退缩系统有关,左前额皮层与趋近系统和积极感情有关,右前额皮层与消极感情和退缩有关。杏仁核易被消极的感情刺激所激活,尤其是恐惧。海马在情绪的背景调节中起着重要作用。前额皮层和杏仁核激活不对称性的个体差异是情绪个体差异的生理基础。情绪的中枢回路有可塑性。     

反应抑制的心理加工模型与神经机制

反应抑制是指抑制不符合当前需要的或不恰当行为反应的能力, 也是执行控制加工的重要成分。解释反应抑制的心理加工模型有两种: 反应与抑制相互独立的赛马模型和交互作用的赛马模型。近年来对反应抑制神经机制的研究表明: 额叶－基底神经节系统内的超直接通路和间接通路可能共同负责对优势反应的抑制, 而额下回、辅助运动区/辅助运动前区和前部扣带回皮层等脑区可能是抑制控制的关键脑区; 反应抑制与反应选择、工作记忆和注意的神经加工之间存在密切联系, 它们的激活脑区既相互重叠, 又相互区别; 右背外侧前额皮层的激活可能反映与抑制任务相关的注意和工作记忆的加工。未来的研究需要将脑损伤、神经功能成像和经颅磁刺激等多种技术结合起来, 进一步阐明上述脑区在反应抑制中的相互作用机制。     

风险决策的神经机制:基于啮齿类动物研究

风险决策是在不同选项的结果确定、并且结果出现的概率已知情况下的决策。啮齿类风险决策模型研究发现前额皮层-杏仁核-伏隔核神经环路联系是决定风险决策的选择倾向的关键。前额皮层中的眶额皮层和内侧前额皮层参与风险决策的策略形成和策略转换有关;而皮层下核团中的杏仁核、腹侧纹状体的伏隔核等结构参与策略保持、价值判断,影响决策偏向和行动强度;眶额皮层、伏隔核神经元和多巴胺神经元编码风险决策过程中的概率、风险等因素;此外,多巴胺等单胺类神经递质及受体在风险决策中有复杂的作用。     

比喻性语言加工的脑机制

早期观点认为比喻性语言加工主要依赖右脑, 随着研究的深入, 右脑假说受到许多研究结果的挑战, 左脑参与比喻性语言的加工。同时, 左右脑语言区发挥各自不同的作用, 新的研究证实, 前额前部皮层同样参与比喻性语言的加工。比喻性语言的理解需要左右半球及前额皮层的共同激活, 同时对其加工还依赖左右半球的联合作用, 比喻性语言理解神经网络的建立需要新证据。     

客体与空间工作记忆的分离：来自皮层慢电位的证据

利用128导事件相关电位技术,采用延迟匹配任务的实验范式,测查了16名正常被试在完成客体任务和空间任务时的皮层慢电位（slow cortical potentials,简称sp成分）,实验发现：在后部脑区,客体工作记忆与空间工作记忆在慢波活动的时间上存在分离,空间任务更早的诱发出负sp成分,并且空间任务激活更多的后部脑区;左下前额叶在客体工作记忆任务与空间工作记忆任务中都有激活,并且激活强度不存在显著差异;背侧前额叶主要负责客体信息的保持与复述,但左右背侧前额叶的激活强度存在不对称性。     

负启动效应的认知神经科学研究

近几年,对负启动效应的神经机制研究发现,干扰项抑制与情节提取都是引起负启动的原因,究竟哪种机制起主要作用与实验任务有很大的关系。从现有的研究结果来看,位置负启动与前额皮层有关,EPR上表现为P1和N1波幅减小或N2波幅的增大,支持抑制机制。特性负启动P3成分仍存在不一致的结果,脑区的广泛激活模式使得研究者越来越倾向采取整合的观点。     

序数表征及其脑机制

人类天生就具有一些初级的数概念。研究表明,顶内沟是基数表征的脑基础,这一区域受损或发展受阻将导致计算失能等与数有关的认知障碍。尽管序数与基数存在相似的行为效应,但与序数相联系的皮层通路不同于基数,序数表征主要激活前额皮层与颞叶皮层区域。序数是否也存在符号效应以及跨文化差异等问题有待进一步研究     

Remembering the time: a continuous clock

The neural mechanisms for time measurement are currently a subject of much debate. This article argues that our brains can measure time using the same dorsolateral prefrontal cells that are known to be involved in working memory. Evidence for this is: (1) the dorsolateral prefrontal cortex is integral to both cognitive timing and working memory; (2) both behavioural processes are modulated by dopamine and disrupted by manipulation of dopaminergic projections to the dorsolateral prefrontal cortex; (3) the neurons in question ramp their activity in a temporally predictable way during both types of processing; and (4) this ramping activity is modulated by dopamine. The dual involvement of these prefrontal neurons in working memory and cognitive timing supports a view of the prefrontal cortex as a multipurpose processor recruited by a wide variety of tasks.     

Updating working memory in aircraft noise and speech noise causes different fMRI activations

The present study used fMRI/BOLD neuroimaging to investigate how visual‐verbal working memory is updated when exposed to three different background‐noise conditions: speech noise, aircraft noise and silence. The number‐updating task that was used can distinguish between “substitution processes,” which involve adding new items to the working memory representation and suppressing old items, and “exclusion processes,” which involve rejecting new items and maintaining an intact memory set. The current findings supported the findings of a previous study by showing that substitution activated the dorsolateral prefrontal cortex, the posterior medial frontal cortex and the parietal lobes, whereas exclusion activated the anterior medial frontal cortex. Moreover, the prefrontal cortex was activated more by substitution processes when exposed to background speech than when exposed to aircraft noise. These results indicate that (a) the prefrontal cortex plays a special role when task‐irrelevant materials should be denied access to working memory and (b) that, when compensating for different types of noise, either different cognitive mechanisms are involved or those cognitive mechanisms that are involved are involved to different degrees.     

Age-Related Changes in Neural Activation During Working Memory Performance

Changes in frontal lobe functions are a typical part of aging of the brain. There are age-related declines in working memory performance, a skill requiring frontal lobe activation. This study examined neural activation, using [15 O] water positron emission tomography (PET) methodology, during performance on two verbal working memory tasks in younger and older participants. The results demonstrated the typical areas of activation associated with working memory performance (e.g., dorsolateral prefrontal cortex and inferior parietal cortex) in both groups. However, the younger participants utilized the right dorsolateral prefrontal cortex and anterior cingulate gyrus significantly more than the older participants. In turn, the older participants used the left dorsolateral prefrontal cortex significantly more than the younger participants and maintained material-specific lateralization in their pattern of activation. These findings are consistent with a previous report of different age-related patterns of frontal activation during working memory.     

Attention and cognitive control as emergent properties of information representation in working memory

A hallmark of primate, and particularly human, behavior is cognitive control, the ability to integrate information from a multitude of sources and use that information to flexibly guide behavior in order to achieve an infinite number of goals. The neural mechanisms of cognitive control have yet to be fully elucidated, although the prefrontal cortex is known to play a critical role. Here, I review evidence suggesting that a unifying principle regarding the role of various portions of the prefrontal cortex in a wide range of cognitive tasks is the active maintenance in working memory of different types of currently relevant information-from specific stimulus features, to instructional cues, to motivational goals and contexts. I argue that the key to demonstrating the existence of this domain-dependent organization lies in a better understanding of the nature of the representation of this information and the ways in which this information itself controls cognition and behavior.     

Working memory retention systems: a state of activated long-term memory

High temporal resolution event-related brain potential and electroencephalographic coherence studies of the neural substrate of short-term storage in working memory indicate that the sustained coactivation of both prefrontal cortex and the posterior cortical systems that participate in the initial perception and comprehension of the retained information are involved in its storage. These studies further show that short-term storage mechanisms involve an increase in neural synchrony between prefrontal cortex and posterior cortex and the enhanced activation of long-term memory representations of material held in short-term memory. This activation begins during the encoding/comprehension phase and evidently is prolonged into the retention phase by attentional drive from prefrontal cortex control systems. A parsimonious interpretation of these findings is that the long-term memory systems associated with the posterior cortical processors provide the necessary representational basis for working memory, with the property of short-term memory decay being primarily due to the posterior system. In this view, there is no reason to posit specialized neural systems whose functions are limited to those of short-term storage buffers. Prefrontal cortex provides the attentional pointer system for maintaining activation in the appropriate posterior processing systems. Short-term memory capacity and phenomena such as displacement of information in short-term memory are determined by limitations on the number of pointers that can be sustained by the prefrontal control systems.     

Integrating orbitofrontal cortex into prefrontal theory: common processing themes across species and subdivisions

Currently, many theories highlight either representational memory or rule representation as the hallmark of prefrontal function. Neurophysiological findings in the primate dorsolateral prefrontal cortex indicate that both features may characterize prefrontal processing. Neurons in the dorsolateral prefrontal cortex encode information in working memory, and this information is represented when relevant to the rules governing performance in a task. In this review, we discuss recent reports of encoding in primate and rat orbitofrontal regions indicating that these features also characterize activity in the orbitofrontal subdivision of the prefrontal cortex. These data indicate that (1) neural activity in the orbitofrontal cortex links the current incentive value of reinforcers to cues, rather than representing the physical features of cues or associated reinforcers; (2) this incentive-based information is represented in the orbitofrontal cortex when it is relevant to the rules guiding performance in a task; and (3) incentive information is also represented in the orbitofrontal cortex in working memory during delays when neither the cues nor reinforcers are present. Therefore, although the orbitofrontal cortex appears to be uniquely specialized to process incentive or motivational information, it may be integrated into a more global framework of prefrontal function characterized by representational encoding of performance-relevant information.     

The effects of prefrontal lesions on working memory performance and theory

The effects of experimental lesions of the monkey prefrontal cortex have played a predominant role in current conceptualizations of the functional organization of the lateral prefrontal cortex, especially with regard to working memory. The loss or sparing of certain performance abilities has been shown to be attributable to differences in the specific requirements of behavioral testing (e.g., spatial vs. nonspatial memoranda) along with differences in the specific locations of applied ablations (e.g., dorsal vs. ventral prefrontal cortex). Such findings, which have accumulated now for over a century, have led to widespread acceptance that the dorsolateral and ventrolateral aspects of the prefrontal cortex may perform different, specialized roles in higher order cognition. Nonetheless, it remains unclear and controversial how the lateral prefrontal cortex is functionally organized. Two main views propose different types of functional specialization of the dorsal and ventral prefrontal cortex. The first contends that the lateral prefrontal cortex is segregated according to the processing of spatial and nonspatial domains of information. The second contends that domain specialization is not the key to the organization of the prefrontal cortex, but that instead, the dorsal and ventral prefrontal cortices perform qualitatively different operations. This report critically reviews all relevant monkey lesion studies that have served as the foundation for current theories regarding the functional organization of the prefrontal cortex. Our goals are to evaluate how well the existing lesion data support each theory and to enumerate caveats that must be considered when interpreting the relevant literature.     

Neurocognitive Contributions to Motor Skill Learning: The Role of Working Memory

ABSTRACT

Researchers have begun to delineate the precise nature and neural correlates of the cognitive processes that contribute to motor skill learning. The authors review recent work from their laboratory designed to further understand the neurocognitive mechanisms of skill acquisition. The authors have demonstrated an important role for spatial working memory in 2 different types of motor skill learning, sensorimotor adaptation and motor sequence learning. They have shown that individual differences in spatial working memory capacity predict the rate of motor learning for sensorimotor adaptation and motor sequence learning, and have also reported neural overlap between a spatial working memory task and the early, but not late, stages of adaptation, particularly in the right dorsolateral prefrontal cortex and bilateral inferior parietal lobules. The authors propose that spatial working memory is relied on for processing motor error information to update motor control for subsequent actions. Further, they suggest that working memory is relied on during learning new action sequences for chunking individual action elements together.     

Laminar cortical dynamics of cognitive and motor working memory, sequence learning and performance: toward a unified theory of how the cerebral cortex works

How does the brain carry out working memory storage, categorization, and voluntary performance of event sequences? The LIST PARSE neural model proposes an answer that unifies the explanation of cognitive, neurophysiological, and anatomical data. It quantitatively simulates human cognitive data about immediate serial recall and free recall, and monkey neurophysiological data from the prefrontal cortex obtained during sequential sensory-motor imitation and planned performance. The model clarifies why spatial and non-spatial working memories share the same type of circuit design. It proposes how laminar circuits of lateral prefrontal cortex carry out working memory storage of event sequences within layers 6 and 4, how these event sequences are unitized through learning into list chunks within layer 2/3, and how these stored sequences can be recalled at variable rates that are under volitional control by the basal ganglia. These laminar prefrontal circuits are variations of visual cortical circuits that explained data about how the brain sees. These examples from visual and prefrontal cortex illustrate how laminar neocortex can represent both spatial and temporal information, and open the way towards understanding how other behaviors derive from shared laminar neocortical designs.     

The primate working memory networks

Working memory has long been associated with the prefrontal cortex, since damage to this brain area can critically impair the ability to maintain and update mnemonic information. Anatomical and physiological evidence suggests, however, that the prefrontal cortex is part of a broader network of interconnected brain areas involved in working memory. These include the parietal and temporal association areas of the cerebral cortex, cingulate and limbic areas, and subcortical structures such as the mediodorsal thalamus and the basal ganglia. Neurophysiological studies in primates confirm the involvement of areas beyond the frontal lobe and illustrate that working memory involves parallel, distributed neuronal networks. In this article, we review the current understanding of the anatomical organization of networks mediating working memory and the neural correlates of memory manifested in each of their nodes. The neural mechanisms of memory maintenance and the integrative role of the prefrontal cortex are also discussed.