脑内乙酰胆碱与认知活动的关系

脑内细胞外乙酰胆碱（ACh）的变化主要反映胆碱能神经元的活动,皮层和海马等脑区的ACh主要来源于基底前脑胆碱能神经元的纤维投射。应用微透析等技术在体检测清醒、自由活动动物认知过程中脑内乙酰胆碱的含量,可以研究ACh与特定行为反应和认知活动之间的关系。研究发现当机体需要对新刺激进行分析时,在学习与记忆、空间工作记忆、注意、自发运动和探究行为等认知活动中,基底前脑胆碱能神经元被激活,脑内ACh的释放也随之改变。结果提示脑内胆碱能递质系统活动与认知过程密切相关     

自我和他人的协调与心理理论的神经机制

有关心理理论神经机制的研究远未达到共识。从自我与他人协调的角度看,可认为它是一个由多脑区有机组织而成的系统。自我中心化偏差是人类认知的一种默认选择,要正确理解他人的心理状态,需要抑制自我中心偏差。因此,心理理论的加工至少包括以下几个不同的过程：通过模拟自我理解他人,相应的加工脑区为镜像神经元系统;从他人与客体形成的二元关系中表征心理状态的内容,相应脑区是颞顶联合区;对模拟自我进行抑制,相应脑区为背外侧额叶;以及整合协调以上几个过程,其脑区可能是内侧前额叶     

高压氧对小鼠学习记忆及脑细胞形态结构的影响

实验用两种行为模型（旷场行为模型和Ｙ－迷宫分辨学习模型）观察了幼龄小鼠在不同压力的高压氧处理后,对新异环境的探究行为和自发活动情况,以及学习记忆能力的变化;并用ＸＹ－生物医学电脑图像分析仪分析了与学习记忆相关的脑区（大脑皮层、海马）神经元密度,细胞核面积,胞核／胞浆比值的变化。结果表明：（１）与对照组相比,吸０.１ＭＰａ高压氧的幼鼠学习记忆能力明显提高,相关脑区的神经元密度、细胞核面积、胞核／浆比均显著增加。（２）吸０.２５ＭＰａ高压氧的幼鼠学习记忆能力与对照组相比无明显变化,但其在新异环境中的自发行为明显减少。提示：慢性吸入０.１ＭＰａ高压氧有利于促进幼鼠脑的生长发育,增强脑功能活动。     

序列学习下内隐记忆意识性的动态发展特征

该研究采用事件相关电位方法(ERP),通过算式符号判别任务研究大学生序列学习下内隐记忆意识性动态发展的时空分布特征。研究采用算式符号判别任务探讨在不同反应-刺激时间间隔条件下,序列学习过程中伴随的对整个算式刺激的内隐记忆意识性的影响及时空分布特征。实验结果表明:1)在对序列规则进行内隐学习的过程中同时可以伴随内隐记忆的发生,RSI的增加导致内隐记忆意识性增加;2)不同意识性程度的内隐记忆激活脑区的头皮分布存在差异。意识性程度高激活脑区范围更广泛和弥散,意识性程度低激活脑区范围较小和集中。意识性由大到小激活脑区有由后(枕区)向前(额区)连续变化的趋势。     

糖皮质激素与记忆

对近年来有关糖皮质激素对记忆的作用的研究进行了小结。由于糖皮质激素的受体广泛分布在与记忆行为相关的脑区,而且对相应的神经元可塑性进行调节,因此糖皮质激素对个体的记忆的形成有着重要的影响。     

复杂系统控制内隐学习范式的特点研究

在人工语法学习、序列学习以及复杂系统控制这三大内隐学习研究范式中,复杂系统控制范式尝试模拟出入们在实际问题解决过程中可能出现的内隐学习,具有更高的生态效度。对城市交通系统、英国经济学模型、糖生产任务以及人际交互任务等复杂系统控制任务进行研究后,我们得出复杂系统控制范式的特点：任务情境的自然性、学习过程的互动性、系统变化的连续性、系统规则的隐蔽性及内隐-外显学习的混合性等。     

认知风格影响归类过程中的神经活动-来自fMRI研究的证据

行为学研究表明归类过程中的反应具有认知风格上的不同,但未有研究明确探讨归类过程的神经活动是否也受认知风格的影响。本研究通过双重认知风格分型任务筛选出分析型和整体型被试,以探讨归类过程中二者之间是否表现出神经活动的差异。实验任务要求被试从两个待选物中选出与目标物属于同一类别的一个。同时,采用fMRI技术扫描并记录他们完成任务时的BOLD信号。结果发现,与基线任务相比,整体型和分析型个体均激活了额-枕网络的一些脑区,包括额下回、楔前叶、枕中回等,表明不同认知风格个体在任务中可能共享与工作记忆等相关的脑区。另外,与分析型个体相比,整体型个体在右额下回、右旁海马回呈现更广泛的特异性激活,提示,认知风格可以影响归类过程中的脑活动,而整体型个体大脑右半球更强烈的活动表明这一类型认知风格个体在归类时更依赖于远距离的语义联结。     

镜像神经元系统的研究回顾及展望

镜像神经元系统的发现使得研究者从一个较为统一的神经机制层面了解人类多个层次的社会认知活动。在猕猴大脑F5区发现的镜像神经元可以在抽象的层面上帮助猕猴理解他人行为的意图。利用脑成像技术,研究发现人类的镜像神经元系统能够匹配外界的知觉表征和内在的动作表征从而通过“居身模仿”这一过程来进行模仿、语言理解、理解他人的意图及情绪这些重要的社会认知活动。另外,镜像神经元系统在社会交往中也起着重要作用,最后,就镜像神经元系统在心理理论中的作用、了解自我-他人问题和镜像神经元系统的关系、动机、经验等因素对镜像神经元系统活动的调控等问题对未来的研究方向进行了展望     

记忆过程中海马CA1区神经元的集群放电特征

观察空间工作记忆过程中海马CA1区神经元群的放电特征。应用多通道神经元集群放电记录技术, 同步观察和记录清醒大鼠在执行延迟选择任务时的行为轨迹以及海马CA1区神经元的放电活动。发现：海马CA1区位置细胞的位置野是在学习过程中逐渐形成并可消退; 部分位置细胞的放电对未来目标定向性行为具有预测作用; 在空间工作记忆过程中, 神经元放电之间的相关性加强, 神经元之间以及神经元与局部场电位之间存在相位编码方式。结果提示海马CA1区神经元参与对空间信息的初级编码和加工, 并为未来行为决策提供有效信息, 而且海马对信息的加工是通过局部神经网络进行, 时间编码可能是海马信息加工的重要方式之一。     

额叶区域的经颅直流电刺激对抑制控制的影响

抑制控制是执行功能的重要组成部分之一, 研究表明抑制控制与额叶区域的活动有关。经颅直流电刺激(Transcranial Direct Current Stimulation, tDCS)是一种非侵入性的脑刺激技术, 可以调节脑区的激活程度。研究表明tDCS刺激额叶的部分区域可以有效干预参与者的抑制控制水平, 而这一干预作用会受到刺激位置、刺激类型以及实验任务等条件变化的影响。目前tDCS已应用于不同人群的抑制控制研究, 并能与其他研究技术较好的结合。     

言语学习引起的脑功能和结构变化

文章系统介绍了言语学习引起的脑功能和结构可塑性变化研究的最新进展,例如：第二语言的词汇——语义学习引起的脑功能变化主要受熟练程度的影响,而句法学习引起的脑功能变化主要受获得年龄的影响;实验室言语训练可以引起语言加工相关区域激活增强或减弱,以及出现新的激活区域;第二语言学习导致了左侧顶下皮层灰质密度增加。此外,文章还总结了言语学习的脑成像研究中常用的实验范式,并提出了有待于进一步解决的关键问题     

Centrally elicited aggressive behavior: A model system for the study of episodic neurobehavioral pathologies?

Studies in which the predatory-like attack of a cat upon a rat has been elicited by electrical brain stimulation have been briefly reviewed with an emphasis on the question of where within the central nervous system such brain stimulation is producing its behaviorally meaningful effects. Two opposing but by no means mutually exclusive views are considered. The first is that brain stimulation elicits this behavior pattern primarily because it affects a specific motivated behavior system that is organized discretely in the midbrain and pons. The second is that forebrain neural activity is modulated in behaviorally significant ways by brainstem stimulation, which elicits predatory-like aggressive behavior in the cat. The possibility that further research on the altered state of central nervous system activity, induced by brain stimulation which elicits aggressive behavior in the cat, may lead to a further understanding of the altered states of central nervous system activity that underlie the aggressive dyscontrol syndrome and other episodic state disorders is discussed.     

Neural correlates of learning and working memory in the primate posterior parietal cortex

The posterior parietal cortex has been traditionally associated with coordinate transformations necessary for interaction with the environment and with visual-spatial attention. More recently, involvement of posterior parietal cortex in other cognitive functions such as working memory and task learning has become evident. Neurophysiological experiments in non-human primates and human imaging studies have revealed neural correlates of memory and learning at the single neuron and at the brain network level. During working memory, posterior parietal neurons continue to discharge and to represent stimuli that are no longer present. This activation resembles the responses of prefrontal neurons, although important differences have been identified in terms of the ability to resist stimulation by distracting stimuli, which is more evident in the prefrontal than the posterior parietal cortex. Posterior parietal neurons also become active during tasks that require the organization of information into larger structured elements and their activity is modulated according to learned context-dependent rules. Neural correlates of learning can be observed in the mean discharge rate and spectral power of neuronal spike trains after training to perform new task sets or rules. These findings demonstrate the importance of posterior parietal cortex in brain networks mediating working memory and learning.     

Learning and adult neurogenesis: survival with or without proliferation?

Recent high quality papers have renewed interest in the phenomenon of neurogenesis within the adult mammalian brain. Many studies now show that neurogenesis can be modulated by environmental factors including physical activity, stress, and learning. These findings have considerable implications for neuroscience in general, including the study of learning and memory, neural network plasticity, aging, neurodegeneration, and the recovery from brain injury. Although new light has been shed on this field, many contradictory findings have been reported. Here we propose two principle issues which underlie these inconsistencies, with particular focus on the interaction between learning and neurogenesis. The first issue relates to the basic methodology of measuring the generation of new brain cells, i.e., proliferation, as compared to survival of the newly made cells. Mostly, measures of neurogenesis reported are a combination of proliferation and survival, making it impossible to distinguish between these separate processes. The second aspect is in regards to the role of environmental factors which can affect both proliferation and survival independently. Especially the interaction between stress and learning is of importance since these might counteract each other in some circumstances. Reviewing the literature while taking these issues into account indicates that, in contrast to some findings, cell proliferation in the dentate gyrus of the hippocampus as a result of learning cannot be ruled out yet. On the other hand, increased survival of granule cells in the dentate gyrus as a result of hippocampal-dependent learning has been clearly demonstrated. Moreover, this learning-induced survival of granule cells, which were born before the actual learning experience, might provide a molecular mechanism for the 'use it or lose it' principle.     

增塑剂DEHP的神经和行为发育毒性

增塑剂邻苯二甲酸二乙基己酯(Di-(2-ethylhexyl) phthalate,DEHP)是一种具有拟雌激素和抗雄激素活性的环境内分泌干扰物,人类和野生动物可通过不同途径终生暴露于DEHP.母体摄入的DEHP可通过胎盘和乳汁转入子代体内并进入脑组织.围生期DEHP暴露性别特异性地改变子代大鼠下丘脑视前区芳香酶活性而影响雌激素合成,并通过改变雌激素受体活性干扰雌激素对脑发育的调节作用.DEHP及其代谢产物可以影响神经细胞的增殖分化和突触形成,干扰性激素调控发育过程中的下丘脑氨基酸递质系统对促性腺激素释放激素分泌的刺激作用,影响中脑多巴胺递质系统发育而诱导自发性多动症.DEHP对脑发育的作用最终影响动物的早期行为、学习记忆和情感等行为发育.     

Functional specialization within the striatum along both the dorsal/ventral and anterior/posterior axes during associative learning via reward and punishment

The goal of the present study was to elucidate the role of the human striatum in learning via reward and punishment during an associative learning task. Previous studies have identified the striatum as a critical component in the neural circuitry of reward-related learning. It remains unclear, however, under what task conditions, and to what extent, the striatum is modulated by punishment during an instrumental learning task. Using high-resolution functional magnetic resonance imaging (fMRI) during a reward- and punishment-based probabilistic associative learning task, we observed activity in the ventral putamen for stimuli learned via reward regardless of whether participants were correct or incorrect (i.e., outcome). In contrast, activity in the dorsal caudate was modulated by trials that received feedback--either correct reward or incorrect punishment trials. We also identified an anterior/posterior dissociation reflecting reward and punishment prediction error estimates. Additionally, differences in patterns of activity that correlated with the amount of training were identified along the anterior/posterior axis of the striatum. We suggest that unique subregions of the striatum--separated along both a dorsal/ventral and anterior/posterior axis--differentially participate in the learning of associations through reward and punishment.     

Fearful expressions enhance recognition memory: electrophysiological evidence

Facial expressions play a key role in affective and social behavior. However, the temporal dynamics of the brain responses to emotional faces remain still unclear, in particular an open question is at what stage of face processing expressions might influence encoding and recognition memory. To try and answer this question we recorded the event-related potentials (ERPs) elicited in an old/new recognition task. A novel aspect of the present design was that whereas faces were presented during the study phase with either a happy, fearful or neutral expression, they were always neutral during the memory retrieval task. The ERP results showed three main findings: An enhanced early fronto-central positivity for faces encoded as fearful, both during the study and the retrieval phase. During encoding subsequent memory (Dm effect) was influenced by emotion. At retrieval the early components P100 and N170 were modulated by the emotional expression of the face at the encoding phase. Finally, the later ERP components related to recognition memory were modulated by the previously encoded facial expressions. Overall, these results suggest that face recognition is modulated by top-down influences from brain areas associated with emotional memory, enhancing encoding and retrieval in particular for fearful emotional expressions.     

c-Fos expression reveals aberrant neural network activity during cued fear conditioning in APPswe transgenic mice

The neural circuitry underlying emotional learning and memory is known to involve both the amygdala and hippocampus. Both of these structures undergo anatomical and functional changes during the course of Alzheimer's disease. The present study used expression of the immediate early gene c-Fos to examine the effect of amyloid-induced synaptic pathology on neural activity in the hippocampus and amygdala immediately following Pavlovian fear conditioning. Tg2576 mice underwent cued fear conditioning and the regional interdependencies of c-Fos expression in the hippocampus and the amygdala were assessed using structural equation modelling. Tg2576 mice displayed normal acquisition of conditioned freezing to a punctate auditory cue paired with shock. However, the analysis of c-Fos expression indicated abnormal regional activity in the hippocampal dentate gyrus of Tg2576 mice. Structural equation modelling also supported the view that activity within the amygdala was independent of hippocampal activity in Tg2576 mice (unlike control mice) and regional interaction between the dentate gyrus and CA3 region was disrupted. The results provide novel insight into the effects of excess amyloid production on brain region interdependencies underpinning emotional learning.     

Regional differences in brain volume predict the acquisition of skill in a complex real-time strategy videogame

Previous studies have found that differences in brain volume among older adults predict performance in laboratory tasks of executive control, memory, and motor learning. In the present study we asked whether regional differences in brain volume as assessed by the application of a voxel-based morphometry technique on high resolution MRI would also be useful in predicting the acquisition of skill in complex tasks, such as strategy-based video games. Twenty older adults were trained for over 20 h to play Rise of Nations, a complex real-time strategy game. These adults showed substantial improvements over the training period in game performance. MRI scans obtained prior to training revealed that the volume of a number of brain regions, which have been previously associated with subsets of the trained skills, predicted a substantial amount of variance in learning on the complex game. Thus, regional differences in brain volume can predict learning in complex tasks that entail the use of a variety of perceptual, cognitive and motor processes.