Neural substrates of impaired categorical perception of phonemes in adult dyslexics: an fMRI study

Phonological developmental dyslexics remain impaired in phonetic categorical perception (CP) even in adulthood. We studied the brain correlates of CP in dyslexics and controls using a block design fMRI protocol and stimuli from an phonetic continuum between natural /Pa/ and /Ta/ syllables. Subjects performed a pseudo-passive listening task which does not imply voluntary categorical judgment. In the control group, categorical deviant stimuli elicited specific activations in the left angular gyrus, the right inferior frontal gyrus and the right superior cingulate cortex. These regions were not activated in the dyslexic group in which activation was observed for acoustic but not phonetic changes in stimuli. Failures to activate key regions for language perception and auditory attention in dyslexic might account for persistent deficits in phonological awareness and reading tasks.     

选择注意神经机制:前扣带皮层对躯体感觉输入的丘脑-皮层调制

本文阐述了认知神经科学关于选择注意发生在感知觉中枢信息流加工较早阶段以及前扣带皮层（ACC）在丘脑和初级感觉皮层水平调制躯体感觉输入的研究证据,揭示了ACC在感知觉信息加工早期的选择注意控制执行机能,以及实行该机能的神经途径。     

Disentangling the neural mechanisms involved in Hinduism- and Buddhism-related meditations

The most diffuse forms of meditation derive from Hinduism and Buddhism spiritual traditions. Different cognitive processes are set in place to reach these meditation states. According to an historical-philological hypothesis (Wynne, 2009) the two forms of meditation could be disentangled. While mindfulness is the focus of Buddhist meditation reached by focusing sustained attention on the body, on breathing and on the content of the thoughts, reaching an ineffable state of nothigness accompanied by a loss of sense of self and duality (Samadhi) is the main focus of Hinduism-inspired meditation. It is possible that these different practices activate separate brain networks. We tested this hypothesis by conducting an activation likelihood estimation (ALE) meta-analysis of functional magnetic resonance imaging (fMRI) studies. The network related to Buddhism-inspired meditation (16 experiments, 263 subjects, and 96 activation foci) included activations in some frontal lobe structures associated with executive attention, possibly confirming the fundamental role of mindfulness shared by many Buddhist meditations. By contrast, the network related to Hinduism-inspired meditation (8 experiments, 54 activation foci and 66 subjects) triggered a left lateralized network of areas including the postcentral gyrus, the superior parietal lobe, the hippocampus and the right middle cingulate cortex. The dissociation between anterior and posterior networks support the notion that different meditation styles and traditions are characterized by different patterns of neural activation.     

The neural basis of insight problem solving: an event-related potential study

The electrophysiological correlates of successful insight problem solving (Chinese logogriphs) were studied in 18 healthy subjects using high-density event-related potentials (ERPs). A new experimental paradigm (learning-testing model) was adopted in order to make subjects find a solution on their own initiative rather than receive an answer passively. Results showed that Successful guessed logogriphs elicited a more positive ERP deflection (P200-600) than did Unsuccessful guessed logogriphs in the time window from 200 to 600 ms after onset of the stimuli. Subsequently Successful logogriphs elicited a more negative ERP deflection than did Unsuccessful logogriphs in the time windows of 1500-2000 ms (N1500-2000) and 2000-2500 ms (N2000-2500). Maps of the P200-600 showed strong activity in the midline parieto-occipital scalp regions. Dipole analysis localized the generator of P200-600 in the left superior temporal gyrus and parietotemporo-occipital cortex areas. The N1500-2000 and N2000-2500 had a distinct activation over left frontal scalp regions. Dipole analysis localized the generator of the N1500-2000 in the anterior cingulate cortex (ACC) and the N2000-2500 in the posterior cingulate cortex (PCC). This result indicates that the parietotemporo-occipital cortex areas might be involved in forming rich associations in the early stage of successful logogriph solving. Then, the ACC might play an important role in the breaking mental set and the forming of novel associations. At last, "Aha" feeling might activate the PCC.     

抑郁症情绪加工与认知控制的脑机制

抑郁症患者负性认知加工偏向是导致抑郁的一个主要认知因素, 是抑郁症的一个稳定特质。这种偏向与对负性情绪刺激自下而上的情绪加工增强有关, 表现为杏仁核和梭状回等脑区过度激活; 也与自上而下的认知控制功能不足有关, 表现为背外侧前额皮质、前扣带回等脑区活性不足。文章在前人研究基础上, 提出了关于抑郁症情绪加工与认知控制脑机制的一个理论假说, 即抑郁症的产生是由于抑郁症患者情绪加工脑区过度激活与认知控制脑区功能降低之间的相互作用而形成的恶性循环所介导。目前证明此理论假说在研究内容、研究材料、研究技术等方面还存在一些问题, 这些可能是未来研究的方向。     

触觉的情绪功能及其神经生理机制

触觉是个体探知外部世界的重要感觉通道, 其情绪功能在维系社会联结、促进人际沟通等方面具有重要作用。触觉的情绪功能一方面表现为通过触觉动作本身直接传递情绪信息, 另一方面则是通过增强注意和锐化社会评价的方式促进个体对跨通道情绪信息的加工。神经生理学研究发现, 触觉情绪信息由无髓鞘C纤维介导, 经脊髓丘脑束通路投射于岛叶(头面部触觉情绪信息的传导路径尚不明确), 并在杏仁核、内侧前额叶、后颞上沟等“社会脑”网络的核心区域被精细加工。未来还应对触觉情绪的人际依赖性、文化独特性、操作标准化, 及其在神经水平上与感觉-辨识系统间的关联性与独立性做深入探究。     

Perception of phosphenes and flashed alphabetical characters is enhanced by single-pulse transcranial magnetic stimulation of anterior frontal lobe: the thalamic gate hypothesis

Single pulses of transcranial magnetic stimulation (sTMS) restricted locally to the primary cortical areas for somatosensory and visual input, unlike the effects of repetitive stimulation, usually fail to elicit projected sensations. We tested the effect of sTMS over anterior frontal cortex in facilitating phosphenes from preceding sTMS over calcarine cortex, which alone was rarely effective in eliciting phosphenes. The combined sTMS elicited complex phosphenes, which changed with the site of frontal sTMS and the interstimulus interval. Our results show that sTMS over anterior frontal cortex also improved reporting of weakly illuminated, flashed four-letter stimuli, which permitted its statistical validation. We propose that the present demonstration of frontal cortical facilitation of visual awareness, when combined with the previous finding of projected paresthesias and sense of movement (Amassian et al, 1991 Brain 114 2505-2520), provide evidence of a general frontal opening effect on a thalamic gate. Opening this gate facilitates entry of information from primary cortical receiving areas to thalamus. Thereby, the reciprocal thalamocortical interrelations that subserve conscious awareness of sensory stimuli could be fostered.     

Meditation-specific prefrontal cortical activation during acem meditation: an fMRI study

Some of the most popular meditation practices emphasize a relaxed focus of attention in which thoughts, images, sensations, and emotions may emerge and pass freely without actively controlling or pursuing them. Several recent studies show that meditation activates frontal brain areas associated with attention focusing and physical relaxation. The objective of the present study was to assess whether brain activation during relaxed focusing on a meditation sound could be distinguished from similar, concentrative control tasks. Brain activation was measured with functional magnetic resonance imaging (fMRI) in experienced practitioners of Acem meditation. Bilateral areas of the inferior frontal gyrus (BA47) were significantly more activated during repetition of a meditation sound than during concentrative meditation-like cognitive tasks. Meditation-specific brain activation did not habituate over time, but increased in strength with continuous meditation bouts. These observations suggest that meditation with a relaxed focus of attention may activate distinct areas of the prefrontal cortex, with implications for the understanding of neurobiological correlates of meditation.     

工作记忆训练诱发的神经可塑性——基于系列fMRI实验的脑区分布递减时空模型

工作记忆训练(Working Memory Training, WMT)诱发神经可塑性, 但其具体机制尚不明晰。为探索WMT改变正常人群大脑功能的时空特性, 以“扩展的智力顶额整合理论”和“神经效率假说”为依据, 采用逐层递进的5种方法, 分6个步骤来查究近20年来正常人群WMT的37篇fMRI文献。第一步, 用叙述性综述、频数分析和卡方检验法比较脑区激活模式和脑网络功能连接在WMT前后发生的改变, 发现WMT改变了大脑的5个联合区、7个宏观区和3个子区。其中, 额上回、顶下小叶和扣带回这3个子区各自激活减弱的报道文献数量多于其激活增强的, 且这种差异分别具有统计学意义。第二步, 采用激活似然估计法对其中26篇开展元分析, 发现大脑的3个子区激活减弱水平在WMT前后的差异具有统计学意义, 即额中回(BA6和8)、额上回(BA6)和前扣带回(BA24和32)。第三步, 综合定性和定量分析结果, 提出WMT脑区分布递减时空模型, 产生5个结果和讨论。第四步, 采用非参数检验进一步追踪WMT效应的调节因素, 发现训练的任务类型和时间分别对脑区激活的影响具有统计学意义。第五步, 针对正常人群WMT诱发神经可塑性的时空特性, 得出3个结论：第一, WMT改变了正常人群相应脑区的神经活动, 表现为减弱或增强, 但减弱更加突出, 且更新和较短时间的WMT倾向于诱发较多减弱; 第二, 这些神经活动变化主要发生在额顶叶联合区, 但也包括分别以颞叶、枕叶、扣带回及纹状体为主的联合区, 在一定范围内体现了整脑功能联合。这体现了WMT诱发神经可塑性的空间特性, 且符合“扩展的智力顶额整合理论”; 第三, 额中回、额上回、顶下小叶和扣带回(尤其前扣带回)这4个子区在激活减弱水平上重点展示了WMT神经可塑性的时间特性, 且符合“神经效率假说”, 恰好体现出“聪明的大脑更懒惰”。第六步, 指出WMT诱发神经可塑性的未来研究可能关注脑可塑性中的低活跃性、辨析额中回、额上回、顶下小叶和扣带回(尤其前扣带回)这4个子区在激活减弱水平上体现的时间特性、找寻训练减弱或增强大脑活动的综合性影响因素。     

疼痛共情的神经机制

疼痛是一种多维度的体验。情感成分和感觉成分是疼痛体验的主要成分,二者有着不同的神经机制。疼痛共情是痛觉"共鸣"的情绪反应,其神经机制的研究也围绕疼痛的情感成分和感觉成分展开。疼痛共情的情感成分的相关脑区主要有前扣带皮层和脑岛等脑区,与自身疼痛时相比,它们的激活位点及所处的神经网络存在差异;疼痛共情的感觉成分主要与初级感觉皮层以及一些其它的躯体感觉皮层有关,对它们的激活情况的研究受技术手段和实验范式的影响较大。未来的研究应从技术手段、分析方法及实验操作上予以关注。     

Self-referential processing of negative stimuli within the ventral anterior cingulate gyrus and right amygdala

Neural activity associated with self-referential processing of emotional stimuli was investigated using whole brain functional magnetic resonance imaging (fMRI). Fifteen healthy subjects underwent fMRI scanning while making judgments about positive and negative trait words in four conditions (self-reference, other-reference, semantic processing, and letter processing). Significant activity was observed in the right ventral anterior cingulate gyrus and the right amygdala in the negative-word/self-reference condition, and in the left amygdala in the positive-word/self-reference condition. Compared with the semantic-processing condition, the self-reference conditions showed significantly more activity in the medial prefrontal and temporal gyri, posterior cingulate gyrus, and precuneus. These results suggest that the medial prefrontal gyrus, posterior cingulate gyrus, and precuneus are associated with a self-referential processing, and the ventral anterior cingulate gyrus is involved in self-referential processing of negative emotional stimuli. The results also suggest that the amygdala is associated with self-referential processing of both positive and negative emotional stimuli.     

Hearing others’ pain: neural activity related to empathy

The human voice is one of the principal conveyers of social and affective communication. Recent neuroimaging studies have suggested that observing pain in others activates neural representations similar to those from the first-hand experience of pain; however, studies on pain expressions in the auditory channel are lacking. We conducted a functional magnetic resonance imaging study to examine brain responses to emotional exclamations of others’ pain. The control condition comprised positive (e.g., laughing) or negative (e.g., snoring) stimuli of the human voice that were not associated with pain and suffering. Compared to these control stimuli, pain-related exclamations elicited increased activation in the superior and middle temporal gyri, left insula, secondary somatosensory cortices, thalamus, and right cerebellum, as well as deactivation in the anterior cingulate cortex. The left anterior insular and thalamic activations correlated significantly with the Empathic Concern subscale of the Interpersonal Reactivity Index. Thus, the brain regions involved in hearing others’ pain are similar to those activated in the empathic processing of visual stimuli. Additionally, the findings emphasise the modulating role of interindividual differences in affective empathy.     

The functional anatomy of a hysterical paralysis

The concept of a conversion disorder (such as hysterical paralysis) has always been controversial (Ron, M.A. (1996). Somatization and conversion disorders. In: B.S. Fogel, R.S. Schiffer & S.M. Rao (Eds.), Neuropsychiatry. Williams and Wilkins, Baltimore, MD). Although the diagnosis is recognised by current psychiatric taxonomies, many physicians still regard such disorders either as feigned or as failure to find the responsible organic cause for the patient's symptoms. We report a woman with left sided paralysis (and without somatosensory loss) in whom no organic disease or structural lesion could be found. By contrast, psychological trauma was associated with the onset and recurrent exacerbation of her hemiparalysis. We recorded brain activity when the patient prepared to move and tried to move her paralysed (left) leg and when she prepared to move and did move her good (right) leg. Preparing to move or moving her good leg, and also preparing to move her paralysed leg, activated motor and/or premotor areas previously described with movement preparation and execution. The attempt to move the paralysed leg failed to activate right primary motor cortex. Instead, the right orbito-frontal and right anterior cingulate cortex were significantly activated. We suggest that these two areas inhibit prefrontal (willed) effects on the right primary motor cortex when the patient tries to move her left leg.     

Neural basis of individual differences in impulsivity: contributions of corticolimbic circuits for behavioral arousal and control

The objective of the current study was to analyze the neural correlates of behavioral arousal and inhibitory control as they relate to individual differences in impulsivity via well-established functional MRI amygdala reactivity and prefrontal inhibitory control paradigms in healthy adult subjects. Impulsivity correlated positively with activity of the bilateral ventral amygdala, parahippocampal gyrus, dorsal anterior cingulate gyrus (BA 32), and bilateral caudate. Conversely, impulsivity correlated negatively with activity of the dorsal amygdala and ventral prefrontal cortex (BA 47). Together, these findings suggest that dispositional impulsivity is influenced by the functional interplay of corticolimbic behavioral arousal and control circuits.     

Attention and cognitive control networks assessed in a dichotic listening fMRI study

A meaningful interaction with our environment relies on the ability to focus on relevant sensory input and to ignore irrelevant information, i.e. top-down control and attention processes are employed to select from competing stimuli following internal goals. In this, the demands for the recruitment of top-down control processes depend on the relative perceptual salience of the competing stimuli. In the present functional magnetic resonance imaging (fMRI) study, we investigated the recruitment of top-down control processes in response to varying degrees of control demands in the auditory modality. For this purpose, we tested 20 male and 20 female subjects with a dichotic listening paradigm, in which the relative perceptual salience of two simultaneously presented stimuli was systematically manipulated by varying the inter-aural intensity difference (IID) and asking the subjects to selectively attend to either ear. The analysis showed that the interaction between IID and attentional direction involves two networks in the brain. A fronto-parietal network, including the pre-supplementary motor area, anterior cingulate cortex, inferior frontal junction, insula and inferior parietal lobe, was recruited during cognitively demanding conditions and can thus be seen as a top-down cognitive control network. In contrast, a second network including the superior temporal and the post-central gyri was engaged under conditions with low cognitive control demands. These findings demonstrate how cognitive control is achieved through the interplay of distinct brain networks, with their differential engagement determined as a function of the level of competition between the sensory stimuli.     

Brain activity for visual judgment of lifted weight

It is well established that humans can recognize high-level aspects from point-light biological motion, such as gender and mood. If the task is to judge the manipulated weight we expected that sensorimotor regions should be recruited in the brain. Moreover, we have recently shown that chronic pain in a limb that is involved in the presented movement disturbs the weight judgment. We therefore hypothesized that some cortical regions usually activated during the processing of pain will also be activated while viewing point-light biological motion with the instruction to judge the manipulated weights. We investigated point-light biological motion of two types of movements performed with different weights in a blocked fMRI experiment in healthy subjects. In line with our a priori hypothesis, we found strong activity in the regions known as the neuromatrix of pain, such as the anterior cingulate (ACC), insula, as well as primary and secondary somatosensory regions. We also found activation in the occipital and temporal regions that are typical for biological motion, as well as regions in the cerebellum and prefrontal cortex. The activation of the somatosensory regions probably serves the judgment of the biological motion stimuli. Activation of the anterior cingulate and the insula might be explained by their role in the integration of behaviorally relevant information. Alternatively, these structures are known to be involved in the processing of nociceptive information and pain. So it seems possible that the interference between judgment of weights and perception of pain in chronic pain patients occurs in the somatosensory areas, anterior cingulate and/or insula. This finding provides important information as to the underlying mechanisms used for the weight judgment task, but also why chronic pain interferes with this task.     

顿悟的大脑机制

自从柯勒1917年提出顿悟的概念以来,这个问题一直吸引着心理学家的关注。但有关顿悟过程的精确的大脑机制却始终未被触及。从心理过程上看,顿悟是一个瞬间实现的、问题解决视角的“新旧交替”过程;它包含两个方面,一是新的有效的问题解决思路如何实现,二是旧的无效的思路如何被抛弃（即打破思维定势）。我们以谜语作为材料,利用功能性磁共振成像（fMRI）技术精确记录了人类的大脑在实现顿悟的一瞬间的活动状况。结果显示顿悟过程激活了包括额叶、颞叶、扣带前回、以及海马在内的广泛脑区。根据各方面的综合证据,本文认为：顿悟过程中,新异而有效的联系的形成依赖于海马,问题表征方式的有效转换依赖于一个“非语言的” 视觉空间信息加工网络,而思维定势的打破与转移则依赖于扣带前回与左腹侧额叶。     

Enhanced occipital and anterior cingulate activation in men but not in women during exposure to angry and fearful male faces

Blood-oxygenation-level-dependent signal was measured with functional magnetic resonance imaging in 24 healthy young subjects (12 men and 12 women) during viewing of angry, fearful, and neutral male and female face pictures. Exposure to angry male as opposed to angry female faces activated the visual cortex and the anterior cingulate gyrus significantly more in men than in women. A similar sex-differential brain activation pattern was present during exposure to fearful but not neutral faces. Previous behavioral studies indicate enhanced physiological arousal in men but not in women during exposure to angry male as opposed to female faces, and brain imaging studies have shown that the occipital cortex and the anterior cingulate gyrus are influenced by activity in the autonomic nervous system as well as by visual attention. Hence, we suggest that the elevated occipital and anterior cingulate activation in men during confrontation with other angry and fearful males may reflect enhanced vigilance in a potentially dangerous situation.     

Direct comparison of episodic encoding and retrieval of words: an event-related fMRI study

Functional magnetic resonance imaging (fMRI) was used to compare directly episodic encoding and retrieval. During encoding, subjects studied visually presented words and reported via keypress whether each word represented a pleasant or unpleasant concept (intentional, deep encoding). During the retrieval phase, subjects indicated (via keypress) whether visually presented words had previously been studied. No reliable differences were found during the recognition phase for words that had been previously studied and those that had not been studied. Areas preferentially active during encoding (relative to retrieval) included left superior frontal cortex, medial frontal cortex, left superior temporal cortex, posterior cingulate, left parahippocampal gyrus, and left inferior frontal gyrus. Regions more active in retrieval than encoding included bilateral inferior parietal cortex, bilateral precuneus, right frontal polar cortex, right dorsolateral prefrontal cortex, and right inferior frontal/insular cortex.