工作记忆的神经振荡调控：基于神经振荡夹带现象

工作记忆的神经振荡机制研究是当前记忆领域的研究热点之一。那么, 神经振荡仅仅是工作记忆过程的伴随现象, 还是直接参与并调控了工作记忆的加工过程?已有研究发现, 大脑内部的神经振荡活动在外界节律性刺激的驱动下, 逐步与外界刺激节律相位同步化, 这一现象被称为“神经振荡夹带”。重复经颅磁刺激(repetitive Transcranial Magnetic Stimulation, rTMS)和经颅交流电刺激(transcranial Alternating Current Stimulation, tACS)干预研究基于此现象, 对大脑局部脑区施加节律性磁、电刺激, 进而调控工作记忆过程中特定频段的神经振荡活动、跨频段的神经振荡耦合或跨脑区的神经振荡相位同步, 为神经振荡参与工作记忆加工提供较为直接的因果证据。未来研究需考虑从脑网络的角度出发, 调控多个脑区之间的神经振荡活动, 进一步考察神经振荡对工作记忆的影响。此外, 还需注意探索和优化rTMS/tACS调控工作记忆的刺激方案, 并辅以客观的脑电记录, 提高该类研究的有效性和可重复性, 最终达到提高工作记忆能力的目的。     

Neural correlates of three cognitive processes involved in theory of mind and discourse comprehension

Neuroimaging studies have found that theory of mind (ToM) and discourse comprehension involve similar brain regions. These brain regions may be associated with three cognitive components that are necessarily or frequently involved in ToM and discourse comprehension, including social concept representation and retrieval, domain-general semantic integration, and domain-specific integration of social semantic contents. Using fMRI, we investigated the neural correlates of these three cognitive components by exploring how discourse topic (social/nonsocial) and discourse processing period (ending/beginning) modulate brain activation in a discourse comprehension (and also ToM) task. Different sets of brain areas showed sensitivity to discourse topic, discourse processing period, and the interaction between them, respectively. The most novel finding was that the right temporoparietal junction and middle temporal gyrus showed sensitivity to discourse processing period only during social discourse comprehension, indicating that they selectively contribute to domain-specific semantic integration. Our finding indicates how different domains of semantic information are processed and integrated in the brain and provides new insights into the neural correlates of ToM and discourse comprehension.     

Bi-hemispheric engagement in the retrieval of autobiographical episodes

Functional magnetic resonance imaging (fMRI) was used to study the neural correlates of neutral, stressful, negative and positive autobiographical memories. The brain activity produced by these different kinds of episodic memory did not differ significantly, but a common pattern of activation for different kinds of autobiographical memory was revealed that included (1) largely bilateral portions of the medial and superior temporal lobes, hippocampus and parahippocampus, (2) portions of the ventral, medial, superior and dorsolateral prefrontal cortex, (3) the anterior and posterior cingulate, including the retrosplenial, cortex, (4) the parietal cortex, and (5) portions of the cerebellum. The brain regions that were mainly activated constituted an interactive network of temporal and prefrontal areas associated with structures of the extended limbic system. The main bilateral activations with left-sided preponderance probably reflected reactivation of complex semantic and episodic self-related information representations that included previously experienced contexts. In conclusion, the earlier view of a strict left versus right prefrontal laterality in the retrieval of semantic as opposed to episodic autobiographical memory, may have to be modified by considering contextual variables such as task demands and subject variables. Consequently, autobiographical memory integration should be viewed as based on distributed bi-hemispheric neural networks supporting multi-modal, emotionally coloured components of personal episodes.     

Individual differences in the functional neuroanatomy of verbal discrimination learning revealed by positron emission tomography

Why do some people have better memory abilities than others? This issue has been of long-standing interest to scientists and lay people. However, using purely behavioral methods, psychologists have made little progress in illuminating it. Now that functional brain imaging techniques have become available to study mind/brain relations, there is a new promise of understanding individual differences in learning and memory in terms of corresponding differences in brain activity. In this paper, we will present a positron emission tomography (PET) study designed to examine individual differences in learning and memory abilities. The basic assumption is that different patterns of brain activity serve as strong predictors of memory performance. Two specific questions were addressed in this study: (i) Can PET illuminate the relations between memory processes and their neuroanatomical correlates among individual learners and rememberers? and (ii) if so, how are these relations affected by the stage of practice on a given memory task? Our PET study examined individual differences in the neuroanatomical correlates of multi-trial verbal discrimination learning in 16 young healthy subjects. The results identified patterns of brain regions in which blood flow correlated with subjects' retrieval performance. However, these regions did not correlate with performance during all learning trials. Instead, a gradual shift was observed from one pattern of brain regions to another over the course of learning. These results suggest that individual differences in memory performance are related to differences in neural activity within specific brain circuits.     

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.     

Coordination of multiple memory systems

On the basis of lesions of different brain areas, several neural systems appear to be important for processing information regarding different types of learning and memory. This paper examines the development of pharmacological and neurochemical approaches to multiple memory systems from past studies of modulation of memory formation. The findings suggest that peripheral neuroendocrine mechanisms that regulate memory processing may target their actions toward those neural systems most engaged in the processing of learning and memory. In addition, measurements of acetylcholine release in different memory systems reveals extensive interactions between memory systems, some cooperative and some competitive. These results imply that many neural systems, often characterized as relatively independent, may in fact interact extensively, blurring the dependencies of different memory tasks on specific neural systems.     

Distinguishing the neural correlates of episodic memory encoding and semantic memory retrieval

Episodic memory and semantic memory interact very closely. In particular, episodic memory encoding (EE) tends to elicit semantic memory retrieval (SR), and vice versa. Thus, similar activations for EE and SR in functional neuroimaging studies may reflect shared memory processes, or they may reflect the fact that EE and SR are usually confounded. To address this issue, we used a factorial functional magnetic resonance imaging approach to disentangle the neural correlates of EE and SR. Within the left temporal lobe, the hippocampus was associated with successful EE, whereas a posterior lateral region was associated with successful SR. Within the left inferior prefrontal cortex, a posterior region was involved in SR, a mid region was involved in both SR and EE, and an anterior region was involved in EE, but only when SR was also high. Thus, the neural correlates of EE and SR are dissociable but interact in specific brain regions.     

Mapping Cognition to the Brain Through Neural Interactions

Brain imaging methods, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), provide a unique opportunity to study the neurobiology of human memory. As these methods can measure most of the brain, it is possible to examine the operations of large-scale neural systems and their relation to cognition. Two neuroimaging studies, one concerning working memory and the other episodic memory retrieval, serve as examples of application of two analytic methods that are optimised for the quantification of neural systems, structural equation modelling, and partial least squares. Structural equation modelling was used to explore shifting prefrontal and limbic interactions from the right to the left hemisphere in a delayed match-to-sample task for faces. A feature of the functional network for short delays was strong right hemisphere interactions between hippocampus, inferior prefrontal, and anterior cingulate cortices. At longer delays, these same three areas were strongly linked, but in the left hemisphere, which was interpreted as reflecting change in task strategy from perceptual to elaborate encoding with increasing delay. The primary manipulation in the memory retrieval study was different levels of retrieval success. The partial least squares method was used to determine whether the image-wide pattern of covariances of Brodmann areas 10 and 45/47 in right prefrontal cortex (RPFC) and the left hippocampus (LGH) could be mapped on to retrieval levels. Area 10 and LGH showed an opposite pattern of functional connectivity with a large expanse of bilateral limbic cortices that was equivalent for all levels of retrieval as well as the baseline task. However, only during high retrieval was area 45/47 included in this pattern. The results suggest that activity in portions of the RPFC can reflect either memory retrieval mode or retrieval success depending on other brain regions to which it is functionally linked, and imply that regional activity must be evaluated within the neural context in which it occurs. The general hypothesis that learning and memory are emergent properties of large-scale neural network interactions is discussed, emphasising that a region can play a different role across many functions and that role is governed by its interactions with anatomically related regions.     

Mapping cognition to the brain through neural interactions

Brain imaging methods, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), provide a unique opportunity to study the neurobiology of human memory. As these methods can measure most of the brain, it is possible to examine the operations of large-scale neural systems and their relation to cognition. Two neuroimaging studies, one concerning working memory and the other episodic memory retrieval, serve as examples of application of two analytic methods that are optimised for the quantification of neural systems, structural equation modelling, and partial least squares. Structural equation modelling was used to explore shifting prefrontal and limbic interactions from the right to the left hemisphere in a delayed match-to-sample task for faces. A feature of the functional network for short delays was strong right hemisphere interactions between hippocampus, inferior prefrontal, and anterior cingulate cortices. At longer delays, these same three areas were strongly linked, but in the left hemisphere, which was interpreted as reflecting change in task strategy from perceptual to elaborate encoding with increasing delay. The primary manipulation in the memory retrieval study was different levels of retrieval success. The partial least squares method was used to determine whether the image-wide pattern of covariances of Brodmann areas 10 and 45/47 in right prefrontal cortex (RPFC) and the left hippocampus (LGH) could be mapped on to retrieval levels. Area 10 and LGH showed an opposite pattern of functional connectivity with a large expanse of bilateral limbic cortices that was equivalent for all levels of retrieval as well as the baseline task. However, only during high retrieval was area 45/47 included in this pattern. The results suggest that activity in portions of the RPFC can reflect either memory retrieval mode or retrieval success depending on other brain regions to which it is functionally linked, and imply that regional activity must be evaluated within the neural context in which it occurs. The general hypothesis that learning and memory are emergent properties of large-scale neural network interactions is discussed, emphasising that a region can play a different role across many functions and that role is governed by its interactions with anatomically related regions.     

语言系统对不同数量系统的影响机制

已有研究较一致地发现语言加工系统对不同的数量加工系统起到不同作用, 表现为语言不影响概略数量和小数加工系统, 主要影响大数的精确加工系统。然而, 其影响机制并不明确。新近几年采用跟踪测验、语言转换、同语言内语音长度操控、双任务等范式来探索数量加工对语言依赖性的行为和脑机制研究。但结论不完全一致。通过记忆中介的视角可以为这些不一致提供新的解释。未来相关研究的思路应包括跟踪语言关键期幼儿的数量系统发展轨迹, 注意区分在记忆不同层面(长时/短时)中介下语言系统对数量系统的影响, 关注语义句法等对数量系统的作用, 以及深入了解基础四则运算的认知神经机制。     

汉词和图画再认的ERP效应及脑机制

目的：比较汉词与图画材料再认过程中的事件相关电位（ERP）表现并探讨其脑机制。方法：使用经典“学习一再认”实验模式对21名大学生进行测验,同时记录EEG,离线处理后对汉词及图画再认诱发的ERP波形主要成分及新旧效应进行比较。结果：两种材料的再认均诱发出了明显的新旧效应。顶区新旧效应头皮分布基本一致,但图画再认该效应波幅大于汉词再认;两种材料诱发的额区新旧效应有所不同,图画再认该效应为正走向,而汉词再认此效应表现为负走向趋势。结论：汉词与图画再认既存在某种共同的神经加工机制,叉分别涉及一些特异性的神经活动模式。     

Psychogenic amnesia – A malady of the constricted self

Autobiographical–episodic memory is the conjunction of subjective time, autonoetic consciousness and the experiencing self. Understanding the neural correlates of autobiographical–episodic memory might therefore be essential for shedding light on the neurobiology underlying the experience of being an autonoetic self. In this contribution we illustrate the intimate relationship between autobiographical–episodic memory and self by reviewing the clinical and neuropsychological features and brain functional imaging correlates of psychogenic amnesia – a condition that is usually characterized by severely impaired retrograde memory functioning, in absence of structural brain damage as detected by standard imaging. We demonstrate that in this disorder the autobiographical–episodic memory deficits do not exist in isolation, but occur with impairments of the autonoetic self-consciousness, emotional processing, and theory of mind or executive functions. Furthermore functional and metabolic brain alterations involving regions that are agreed upon to exert crucial roles in memory processes were frequently found to accompany the psychogenic memory “loss”.     

Event-related brain potential correlates of the other-race effect: A review

People are better at remembering own-race relative to other-race faces. Here, we review event-related brain potential (ERP) correlates of this so-called other-‘race’ effect (ORE) by discussing three critical aspects that characterize the neural signature of this phenomenon. First, difficulties with other-race faces initially emerge during perceptual processing, which is indexed by an increased N170. Second, as evidenced by ‘difference due to subsequent memory’ effects, more effortful processing of other-race faces is needed for successful encoding into long-term memory. Third, ERP old/new effects reveal that a stronger engagement of processing resources is also required for successful retrieval of other-race faces from memory. The ERP evidence available to date thus suggests widespread ethnicity-related modulations during both perceptual and mnemonic processing stages. We further discuss how findings from the ORE compared with potentially related memory biases (e.g. other-gender or other-age effects) and how ERP findings inform the ongoing debate regarding the mechanisms underlying the ORE. Finally, we outline open questions and potential future directions with an emphasis on using multiple, ecologically more valid ‘ambient’ images for each face to assess the ORE in paradigms that capture identity rather than image recognition.     

Trial-to-trial dynamics of selective long-term-memory retrieval with continuously changing retrieval targets

How do we control the successive retrieval of behaviorally relevant information from long-term memory (LTM) without being distracted by other potential retrieval targets associated to the same retrieval cues? Here, we approach this question by investigating the nature of trial-by-trial dynamics of selective LTM retrieval, i.e., in how far retrieval in one trial has detrimental or facilitatory effects on selective retrieval in the following trial. Participants first learned associations between retrieval cues and targets, with one cue always being linked to three targets, forming small associative networks. In successive trials, participants had to access either the same or a different target belonging to either the same or a different cue. We found that retrieval times were faster for targets that had already been relevant in the previous trial, with this facilitatory effect being substantially weaker when the associative network changed in which the targets were embedded. Moreover, staying within the same network still had a facilitatory effect even if the target changed, which became evident in a relatively higher memory performance in comparison to a network change. Furthermore, event-related brain potentials (ERPs) showed topographically and temporally dissociable correlates of these effects, suggesting that they result from combined influences of distinct processes that aid memory retrieval when relevant and irrelevant targets change their status from trial to trial. Taken together, the present study provides insight into the different processing stages of memory retrieval when fast switches between retrieval targets are required.     

先苦后乐:英语乐学大学生在英语学习时情绪反应的脑认知特点

运用功能性磁共振成像(fMRI)技术探索了乐学英语的大学生在对中、英文材料的学习、记忆及成绩反馈过程中的情绪和脑活动特征。结果发现,被试学习英文较之学习中文积极情绪更少且伴随更强的前部脑岛的激活;但当他们获得关于英文成绩的正反馈时,中脑奖赏区的激活却明显高于获得中文成绩正反馈时的情形,且中脑激活与英语乐学呈正相关。这说明乐学是"苦中作乐",人们虽在学习时并未体验到更多快乐,但其成功却带来了更大的心理奖赏。     

Measuring recollection and familiarity: Improving the remember/know procedure

The remember/know (RK) procedure is the most widely used method to investigate recollection and familiarity. It uses trial-by-trial reports to determine how much recollection and familiarity contribute to different kinds of recognition. Few other methods provide information about individual memory judgements and no alternative allows such direct indications of recollection and familiarity influences. Here we review how the RK procedure has been and should be used to help resolve theoretical disagreements about the processing and neural bases of components of recognition memory. Emphasis is placed on procedural weaknesses and a possible confound of recollection and familiarity with recognition memory strength. Recommendations are made about how to minimise these problems including using modified versions of the procedure. The proposals here are important for improving behavioural and lesion research, and vital for brain imaging work.     

Functional imaging of the semantic system: retrieval of sensory-experienced and verbally learned knowledge

This paper considers how functional neuro-imaging can be used to investigate the organization of the semantic system and the limitations associated with this technique. The majority of the functional imaging studies of the semantic system have looked for divisions by varying stimulus category. These studies have led to divergent results and no clear anatomical hypotheses have emerged to account for the dissociations seen in behavioral studies. Only a few functional imaging studies have used task as a variable to differentiate the neural correlates of semantic features more directly. We extend these findings by presenting a new study that contrasts tasks that differentially weight sensory (color and taste) and verbally learned (origin) semantic features. Irrespective of the type of semantic feature retrieved, a common semantic system was activated as demonstrated in many previous studies. In addition, the retrieval of verbally learned, but not sensory-experienced, features enhanced activation in medial and lateral posterior parietal areas. We attribute these "verbally learned" effects to differences in retrieval strategy and conclude that evidence for segregation of semantic features at an anatomical level remains weak. We believe that functional imaging has the potential to increase our understanding of the neuronal infrastructure that sustains semantic processing but progress may require multiple experiments until a consistent explanatory framework emerges.     

提取干扰对知觉和概念启动的影响

通过学习—测验范式,分别以词汇判断、语义分类任务为测验,探讨提取干扰对不同识别式记忆的影响差异。结果发现,实验1验证了识别式知觉内隐记忆的提取干扰效应,实验2发现识别式概念内隐记忆在提取干扰下也明显降低;两个实验启动量联合分析发现,相比无干扰条件,概念启动比知觉启动受到提取干扰的破坏更大。上述结果说明识别式内隐记忆的提取干扰具有普遍性,提取干扰产生了不同识别式内隐记忆之间的分离,识别式概念内隐记忆更容易受到提取干扰的影响。     

How does a child solve 7 + 8? Decoding brain activity patterns associated with counting and retrieval strategies

Cognitive development and learning are characterized by diminished reliance on effortful procedures and increased use of memory-based problem solving. Here we identify the neural correlates of this strategy shift in 7-9-year-old children at an important developmental period for arithmetic skill acquisition. Univariate and multivariate approaches were used to contrast brain responses between two groups of children who relied primarily on either retrieval or procedural counting strategies. Children who used retrieval strategies showed greater responses in the left ventrolateral prefrontal cortex; notably, this was the only brain region which showed univariate differences in signal intensity between the two groups. In contrast, multivariate analysis revealed distinct multivoxel activity patterns in bilateral hippocampus, posterior parietal cortex and left ventrolateral prefrontal cortex regions between the two groups. These results demonstrate that retrieval and counting strategies during early learning are characterized by distinct patterns of activity in a distributed network of brain regions involved in arithmetic problem solving and controlled retrieval of arithmetic facts. Our findings suggest that the reorganization and refinement of neural activity patterns in multiple brain regions plays a dominant role in the transition to memory-based arithmetic problem solving. Our findings further demonstrate how multivariate approaches can provide novel insights into fine-scale developmental changes in the brain. More generally, our study illustrates how brain imaging and developmental research can be integrated to investigate fundamental aspects of neurocognitive development.     

新颖性图像加工的时间进程

采用ERPs技术,考察了个体新颖性图像加工的时间进程。行为结果表明: 新颖性图像的判断时间更长。ERPs结果显示:新颖与非新颖图像在刺激呈现后190–340ms诱发出明显的前额区N190–340,但在波幅上无显著差异;在400–600ms以及600–1000ms,新颖性图像在顶区与额–中央区, 特别在右侧半球诱发出更大的正性偏移(P400–600和LPC)。研究表明: 图像新颖性属性的识别主要发生在涉及图像特征融合、图像记忆编码等多项认知活动参与的晚期加工阶段,并存在半球右侧化效应。