Dissociating the representation of action- and sound-related concepts in middle temporal cortex

Modality-specific models of conceptual memory propose close links between concepts and the sensory-motor systems. Neuroimaging studies found, in different subject groups, that action-related and sound-related concepts activated different parts of posterior middle temporal gyrus (pMTG), suggesting a modality-specific representation of conceptual features. However, as these different parts of pMTG are close to each other, it is possible that the observed anatomical difference is merely related to interindividual variability. In the present functional magnetic resonance imaging study, we now investigated within the same participant group a possible conceptual feature-specific organization in pMTG. Participants performed lexical decisions on sound-related (e.g., telephone) and action-related (hammer) words. Sound words elicited higher activity in anterior pMTG adjacent to auditory association cortex, but action-related words did so in posterior pMTG close to motion sensitive areas. These results confirm distinct conceptual representations of sound and action in pMTG, just adjacent to the respective modality-specific cortices.     

Neural correlates of feigned memory impairment are distinguishable from answering randomly and answering incorrectly: an fMRI and behavioral study

Previous functional magnetic resonance imaging (fMRI) studies have identified activation in the prefrontal-parietal-sub-cortical circuit during feigned memory impairment when comparing with truthful telling. Here, we used fMRI to determine whether neural activity can differentiate between answering correctly, answering randomly, answering incorrectly, and feigned memory impairment. In this study, 12 healthy subjects underwent block-design fMRI while they performed digit task of forced-choice format under four conditions: answering correctly, answering randomly, answering incorrectly, and simulated feigned memory impairment. There were three main results. First, six areas, including the left prefrontal cortex, the left superior temporal lobe, the right postcentral gyrus, the right superior parietal cortex, the right superior occipital cortex, and the right putamen, were significantly modulated by condition type. Second, for some areas, including the right superior parietal cortex, the right postcentral gyrus, the right superior occipital cortex, and the right putamen, brain activity was significantly greater in feigned memory impairment than answering randomly. Third, for the areas including the left prefrontal cortex and the right putamen, brain activity was significantly greater in feigned memory impairment than answering incorrectly. In contrast, for the left superior temporal lobe, brain activity was significantly greater in answering incorrectly than feigned memory impairment. The results suggest that neural correlates of feigned memory impairment are distinguishable from answering randomly and answering incorrectly in healthy subjects.     

Conflicts as aversive signals

Theories of human action control deal with the question of how cognitive control is dynamically adjusted to task demands. The conflict monitoring theory of anterior cingulate (ACC) function suggests that the ACC monitors for response conflicts in the ongoing processing stream thereby triggering the mobilization of cognitive control. Alternatively, the outcome evaluation account of ACC function suggests that the ACC monitors for negative performance outcomes, an information that serves as an aversive learning signal for future action selection. Botvinick (2007) recently suggested that both theories might converge on the detection of aversive signals in general. Here, the authors provide first evidence that conflicts are registered as aversive signals. Congruent and incongruent Stroop color-words served as primes, and positive and negative stimuli as targets in an affective priming paradigm. Negative targets were evaluated faster after incongruent than after congruent Stroop primes, and positive targets were evaluated slower after incongruent than after congruent primes. The finding that conflicts are actually registered as aversive signals bridges the gap between competing theories of ACC function and has broad theoretical and behavioral implications as it makes the conflict monitoring theory applicable to a much wider range of situations and tasks.     

Conflict and Cognitive Control in the Brain

ABSTRACT— Recent research from cognitive psychology and cognitive neuroscience has suggested that the control mechanisms by which people are able to regulate task performance can be dissociated into evaluative and executive components. One process, implemented in the anterior cingulate cortex of the brain, monitors the amount of conflict that occurs during information processing; another process, implemented in the dorsolateral prefrontal cortex, is involved with maintaining the requirements of the task at hand and with biasing information processing in favor of appropriate responses. In the current article, we review this theory and some of the research that has supported it, including its implication for understanding cognitive disturbances in clinical disorders such as schizophrenia and obsessive-compulsive disorder. We conclude by addressing several interesting possibilities for future research.     

Bilaterally recorded multiple-unit activity of the cingulate cortex during head turning conditioning with unilateral medial forebrain bundle stimulation

Cats were conditioned to turn their heads using a tone conditioned stimulus (CS) and medial forebrain bundle stimulation (MFB) unconditioned stimulus (US). The CS+ was delivered to one ear at a time, in random order, followed by the US. A tone of a different frequency was used as a CS-. The cats learned to respond differentially to the CSs showing head movements of greater acceleration to the CS+ than CS- over sessions. Bilateral recordings of cingulate cortex multiple-unit activity showed increased response amplitudes over sessions and larger responses in the hemisphere ipsilateral to the US. Since ipsilateral multiple-unit responses did not differ for the CSs, the asymmetry was probably due to the sensitizing effect of the unilateral US. Although increases in cingulate cortex neural activity coincided with increases in conditioned head movements, larger activation of the cingulate cortex ipsilateral to the US suggests that the neural changes were independent of these movements.     

左侧额下回在句子语义整合加工中的作用

语义整合帮助人们在阅读理解中将小信息块整合成一个完整、连贯的句子意义表达, 是阅读理解中非常重要的认知过程。通过对比40多篇句子加工相关的脑机制研究, 发现左侧额下回在fMRI研究中是参与语义整合加工激活概率最高的区域, 而颞叶及后部是MEG研究中激活概率最高的区域。另外, 左侧额下回是如何参与语义整合、它在内隐和外显语义整合中的机制是否相同、以及这种整合加工与一般的控制性加工、词汇启动的关系都是研究者广泛关注的问题。本文对上述问题进行了详细的综述和讨论。     

大脑视觉词形区及其在阅读神经网络中的作用

大脑梭状回中部被认为是视觉词形加工区(Visual Word Form Area, VWFA)。近年来的研究对VWFA的功能提出了质疑, 研究者开始关注VWFA作为复杂阅读网络的一部分与其它脑区的动态联结机制, 主要集中在三个方面：一是梭状回中部对于视觉词形选择性敏感的本质; 二是它在词汇阅读的神经网络中的作用; 最后是语言经验对于VWFA认知神经功能的塑造作用。结合以上研究的最新进展, 文中指明从动态神经网络的角度揭示大脑功能成为今后认知神经科学研究的最新取向。     

Attentional control in the aging brain: insights from an fMRI study of the stroop task

Several recent studies of aging and cognition have attributed decreases in the efficiency of working memory processes to possible declines in attentional control, the mechanism(s) by which the brain attempts to limit its processing to that of task-relevant information. Here we used fMRI measures of neural activity during performance of the color-word Stroop task to compare the neural substrates of attentional control in younger (ages: 21-27 years old) and older participants (ages: 60-75 years old) during conditions of both increased competition (incongruent and congruent neutral) and increased conflict (incongruent and congruent neutral). We found evidence of age-related decreases in the responsiveness of structures thought to support attentional control (e.g., dorsolateral prefrontal and parietal cortices), suggesting possible impairments in the implementation of attentional control in older participants. Consistent with this notion, older participants exhibited more extensive activation of ventral visual processing regions (i.e., temporal cortex) and anterior inferior prefrontal cortices, reflecting a decreased ability to inhibit the processing of task-irrelevant information. Also, the anterior cingulate cortex, a region involved in evaluatory processes at the level of response (e.g., detecting potential for error), showed age-related increases in its sensitivity to the presence of competing color information. These findings are discussed in terms of newly emerging models of attentional control in the human brain.     

努力控制及其神经基础

本文对努力控制的概念、发展及其神经基础进行了归纳和总结。我们发现努力控制涉及的脑区主要包括背外侧和腹外侧前额叶,前扣带回,顶上和顶下小叶以及辅助运动皮层等。此外,通过分析对比后发现努力控制与执行功能之间在行为表现和神经基础上有密切关系：两者都与个体的学业成绩、情绪状态和攻击行为等有关;努力控制涉及的脑区有很大部分处于具有执行功能的突显网络和额顶控制网络。这些证据表明两者之间可能有共同的脑结构基础。     

视觉词形加工：从脑区到神经通路

视觉词形加工是阅读机制中的重要环节。基于获得性阅读障碍的早期阅读“神经病学模型”对视觉词形加工的神经通路进行了描述。近年来,随着脑功能成像技术的发展和左梭状回中部视觉词形区的发现,研究者们对原有视觉词形加工的神经通路加以补充和修订,并提出了新的模型。该文对视觉词形加工障碍患者的神经心理学研究和正常人视觉词形加工的脑功能成像研究进行了总结,并讨论了研究的局限性,对今后该领域的发展方向进行展望