Representations in the Human Prefrontal Cortex

ABSTRACT— The prefrontal cortex (PFC) in humans has been studied for more than a century, but many crucial questions about its functions remain unanswered. This paper will highlight a few key differences between human and animal PFCs, and between the human PFC (HPFC) and other parts of the human brain. We then make a case that the HPFC is critically important for executing behaviors over time and integrating disparate information from throughout the brain. Finally, we will focus on our position in the current debate regarding how the HPFC performs its functions and discuss future directions for research.     

Infant Expressions in an Approach/Withdrawal Framework

Since the introduction of empirical methods for studying facial expression, the interpretation of infant facial expressions has generated much debate. The premise of this article is that action tendencies of approach and withdrawal constitute a core organizational feature of emotion in humans, promoting coherence of behavior, facial signaling, and physiological responses. The approach/withdrawal framework can provide a taxonomy of contexts and the neurobehavioral framework for the systematic, empirical study of individual differences in expression, physiology, and behavior within individuals as well as across contexts over time. By adopting this framework in developmental work on basic emotion processes, it may be possible to better understand the behavioral principles governing facial displays, and how individual differences in them are related to physiology and behavioral function in context.     

前额叶皮质损伤患者的情绪异常

人类前额叶皮质与情绪之间有着密切的关系,文章在相关的临床和神经成像研究结果基础上,分析了前额叶皮质损伤对情绪行为造成的影响,分别概述了精神分裂症、重性抑郁和焦虑患者的情绪变化、前额叶切除对情绪的影响以及左右前额叶皮质与情绪的关系,重点阐述了前额叶功能异常的神经生理学特点,认为情绪的改变会随着前额叶皮质不同部位的结构缺损或功能变化而有所不同,此有利于对前额叶皮质损伤患者情绪异常的评价与防治。     

A System for Relational Reasoning in Human Prefrontal Cortex

The integration of multiple relations between mental representations is critical for higher level cognition. For both deductive- and inductive-reasoning tasks, patients with prefrontal damage exhibited a selective and catastrophic deficit in the integration of relations, whereas patients with anterior temporal lobe damage, matched for overall IQ but with intact prefrontal cortex, exhibited normal relational integration. In contrast, prefrontal patients performed more accurately than temporal patients on tests of both episodic memory and semantic knowledge. These double dissociations suggest that integration of relations is a specific source of cognitive complexity for which intact prefrontal cortex is essential. The integration of relations may be the fundamental common factor linking the diverse abilities that depend on prefrontal function, such as planning, problem solving, and fluid intelligence.     

内侧前额叶皮质—— “自我”的神经基础

自我神经基础的探讨常基于自我相关加工的研究, 涉及皮质中线结构各个脑区甚至全脑协同作用。内侧前额叶皮质及其次成分在自我相关加工中发挥重要作用：腹内侧前额叶皮质较多支持默认模式下的自我加工、自我信息的觉察和“在线”自我加工, 背内侧前额叶皮质主要参与有意识的自我参照加工、自我信息的评价和“主导的”自我加工。在自我-他人表征中, 自我-他人表征的情感性、认知性和文化性因素均调节内侧前额叶皮质及次成分的活动。未来在动态的时间和人际背景中解析自我加工的神经机制是重要的研究方向。     

Memory for Duration: Role of Hippocampus and Medial Prefrontal Cortex

In this task rats had to learn that a three-dimensional object stimulus (a rectangle) that was visible for 2 s would result in a positive (go) reinforcement for one object (a ball) and no reinforcement (no go) for a different object (a bottle). However, if the rectangle stimulus was visible for 8 s then there would be no reinforcement for the ball (no go), but a reinforcement for the bottle (go). After rats learned this conditional discrimination by responding differentially in terms of latency to approach the object, they received large (dorsal and ventral) lesions of the hippocampus, lesions of the medial prefrontal cortex (anterior cingulate and precentral cortex), lesions of the cortex dorsal to the dorsal hippocampus, or served as sham-operated controls. Following recovery from surgery they were retested. The results indicate that there were major impairments following hippocampal lesions, in contrast to cortical control and medial prefrontal cortex lesions, as indicated by smaller latency differences between positive and negative trials on postsurgery tests. In order to ensure that the deficits observed with hippocampal lesions were not due to a discrimination problem, new rats were trained in an object (gray cylinder) duration discrimination task. In this go/no go procedure, the rats were reinforced for a 2-s exposure (duration) of the gray cylinder, but not a 10-s duration, or vice versa. The results indicate that after hippocampal lesions, there was an initial deficit followed by complete recovery. There were no significant changes for the medial prefrontal, cortical control, or sham-operated animals. It appears that the hippocampus, but not the medial prefrontal cortex, is actively involved in representing in short-term memory temporal attribute information based on the use of markers for the beginning and end of the presence (duration) of a stimulus (object).     

前额皮层肾上腺素能受体在工作记忆中的作用

前额皮层去甲肾上腺素能神经支配主要来自脑干蓝斑核。前额皮层存在不同类型的肾上腺素能受体。其中突触后α2及β2肾上腺素能受体的激活提高工作记忆;α1及β1肾上腺素能受体的激活损害工作记忆。不同受体是通过激活不同的信号通路发挥对工作记忆的调节作用。来自人类被试的研究结果与对动物的研究结果之间尚存在不一致。了解前额皮层不同肾上腺素受体的作用为开发治疗与前额皮层功能失调相关疾病的药物提供了新的方向。     

双侧前额皮层的语言功能--用近红外技术研究语言功能的初步实验

本文报告一个用近红外技术进行的语言认知脑成像实验.实验通过脑f血流的变化情况考察了双侧前额皮层对由不同通道输入的,不同语言的各个层次的认知反应.实验结果表明,双侧前额皮层对高层语义加工,包括对篇章的归纳与抽象,具有特殊的功能,这种功能的神经学分布是对称的,这种功能及其对称性不随语言和输入通道的变化而变化.相比之下,前额皮层对读、听语言材料以及听音乐却显得不敏感.局部血流的变化只显示其对上述任务的一般性的注意力控制.     

用整合的观点看情绪

该文主要根据James R．Averill(1997)等人的观点，从整合的角度探讨了情绪问题，阐述了情绪分析的框架。此框架由6个情绪变量组成，分五个水平。在阐述了这五个水平及其关系之后，又从下向上论述了处于不同情绪组织水平上的成份反应、情绪状态、情绪症侯群和气质特征。     

情绪对成就动机与风险决策关系的调节效应

本研究在验证成就动机对风险决策倾向的预测作用的基础上,进一步探索情绪在成就动机和风险决策关系中的调节效应。通过对三所学校随机抽取的150名被试进行筛选,采用成就动机量表和自编风险决策任务问卷等对120名有效被试实施问卷调查。结果发现：情绪启动使大学生风险决策行为产生一致性效应,即心境一致性;情绪在成就动机和风险决策中起到了一定的调节作用,无论是高成就动机者还是低成就动机者,在愉悦情绪下都表现出更多的风险寻求倾向,并达到了极其显著的水平,而在悲伤情绪下,低成就动机者表现出更多的风险规避,高成就动机者的风险规避倾向虽有所增加,但并未达到显著水平。     

Right Prefrontal Cortex Responds to Item Familiarity During a Memory Encoding Task

In a previous word-pair encoding study (Dolan & Fletcher, 1997), we examined the effect of introducing novelty, either in studied words or in their mutual associations. A left medial temporal lobe (MTL) sensitivity to novel words and left prefrontal cortex (PFC) to novel associations was observed. In this further report on the data, we explored the extent to which the right PFC, more generally implicated in retrieval operations (Fletcher, Frith, & Rugg, 1997), was sensitive to these manipulations. Specifically, we characterised changes associated with increasing familiarity of study material. We demonstrate that the response in right ventrolateral PFC is preferentially sensitive to a condition in which all material was familiar (that is, in which all material had been presented prior to scanning). A more dorsal region in right PFC was found to be relatively more active in association with a condition in which one item in the pair was familiar but was paired with a novel associate. Our results suggest that sensitivity to stimulus familiarity is expressed in right PFC, even within the context of an encoding task. The data also provide further evidence for functional heterogeneity within right PFC, with a more ventral region responding to familiarity of complete word pairs and a more dorsal region responding to familiar single words occurring in the context of new associative relationships.     

Evidence for the Involvement of the Rat Prefrontal Cortex in Sustained Attention

Previous studies suggest that, in both humans and rats, the prefrontal cortex (PFC) is involved in both selective and divided attention. We have also shown that the PFC is involved in response selection and that its involvement is modulated by the cognitive effort required by the task. However, the role of the PFC is much less clear when no response selection is required. The purpose of the present experiments was to assess the role of the PFC in attentional functions with a low response-selection demand. We used two tasks in which information processing was effortful but where the demand on a response selection process is low. Moreover, we assessed two different types of visual attentional functions: selective attention (Experiment 1) and sustained attention (Experiment 2). The results showed a differential involvement of the PFC in the two tasks. Selective attention was not impaired by prefrontal lesions when the number of possible positions for the stimulus on which the subjects must focus was restricted to two (Experiment 1). In contrast, prefrontal rats were unable to sustain their attention long enough to detect, and react to, subtle variations in brightness (Experiment 2). This result suggests a dissociation between different types of attentional functions depending upon the integrity of the PFC. More specifically, results in Experiment 2 suggest an involvement of the PFC in sustained attention. Finally, the overall results show that even in tasks involving low demands on response selection the PFC is involved in attentional functions.     

Tonic Activity Level in the Right Prefrontal Cortex Predicts Individuals' Risk Taking

ABSTRACT— Human risk taking is characterized by a large amount of individual heterogeneity. In this study, we applied resting-state electroencephalography, which captures stable individual differences in neural activity, before subjects performed a risk-taking task. Using a source-localization technique, we found that the baseline cortical activity in the right prefrontal cortex predicts individual risk-taking behavior. Individuals with higher baseline cortical activity in this brain area display more risk aversion than do other individuals. This finding demonstrates that neural characteristics that are stable over time can predict a highly complex behavior such as risk-taking behavior and furthermore suggests that hypoactivity in the right prefrontal cortex might serve as a dispositional indicator of lower regulatory abilities, which is expressed in greater risk-taking behavior.     

Identity, Reasoning, and Emotion: An Empirical Comparison of Three Sources of Moral Motivation

Prior research on moral motivation has primarily emphasized moral reasoning and moral emotion; however, identity may also play an important role. Therefore, the purpose of the present study was to examine the relative importance of prosocial identity, prosocial moral reasoning, and empathy in predicting prosocial behavior. The sample included 91 university students, ages 19–35 years (M=21.89; SD=3.01; 80% European American; 65% female). Prosocial identity and empathy, but not prosocial moral reasoning, were positively associated with overall prosocial behavior. Exploratory analyses examined how these three sources of prosocial motivation differentially related to six forms of prosocial behavior. Results suggest the importance of considering the roles of all three sources of moral motivation.     

前额叶损害对个体一般智力、认知策略与自我监控能力影响的研究

本研究随机挑选了15名因外伤而造成的前额叶损害者和15名正常成人,采用韦氏成人智力量表和自编的图片分类作业,考查了他们在一般智力、认知策略与自我监控能力方面的差异,研究结果表明:(1)前额叶损害对个体的一般智力产生显著的影响,但是其智力仍然处于正常范围,可见智力的脑结构范围极为广泛,智力是一个具有多重性的系统。(2)前额叶损害者对无关刺激的抑制,对有效信息的提取与加工放大的心理活动受到极大影响,认知策略转换能力明显低于正常人,表现出了明显的认知不随意性,额叶可能更多的与个体的计划、认知策略选择、自我监控密切相关;(3)前额叶损害者对具体概念与抽象概念的自我监控能力表现出了不同的影响,对前者的损害显著大于后者,这表明个体依据具体概念进行的形象思维与凭借抽象概念进行的逻辑思维有不同的脑机制。