1秒以上时距判断的ERP研究

以视觉呈现时距信号,采用时间泛化范式要求被试判断5种探测时距(1～4秒)与标准时距(2秒)之间的长度关系,并记录11名大学生在时距判断过程中的事件相关电位(ERP),继而探讨不同探测时距条件下CNV波幅特征变化以及左、右侧额叶在时距判断中的功能。结果发现:1秒、1.42秒以及2秒条件下,CNV波幅峰出现在探测时距结束点,2.84秒、4秒条件下,CNV波幅峰出现在大约2秒处(标准时距);CNV负性翻转至基线位置在1秒、1.42秒、2秒条件下随探测时距的增长而延后,而在2.84秒、4秒两种条件下无显著差异;左、右侧额叶处诱发的CNV波幅峰潜时在2.84秒、4秒探测时距条件下无显著差异,且均在2秒附近。这说明在1秒以上视时距判断中CNV波幅峰反映了基于记忆中标准时距的时距判断的决策过程;CNV负性翻转至基线位置与时距判断的决策阶段存在共变关系,CNV负性翻转至基线位置相当于负荷解脱过程中的一个由负翻正的转折点;左、右侧额叶均参与了时距脉冲累加过程。     

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。     

Neuronal effects of auditory distraction on visual attention

Selective attention in the presence of distraction is a key aspect of healthy cognition. The underlying neurobiological processes, have not, however, been functionally well characterized. In the present study, we used functional magnetic resonance imaging to determine how ecologically relevant distracting noise affects cortical activity in 27 healthy adults during two versions of the visual Sustained Attention To Response Task (SART) that differ in difficulty (and thus attentional load). A significant condition (noise or silence) by task (easy or difficult) interaction was observed in several areas, including dorsolateral prefrontal cortex (DLPFC), fusiform gyrus (FG), posterior cingulate (PCC), and pre-supplementary motor area (PreSMA). Post hoc analyses of interaction effects revealed deactivation of DLPFC, PCC, and PreSMA during distracting noise under conditions of low attentional load, and activation of FG and PCC during distracting noise under conditions of high attentional load. These results suggest that distracting noise may help alert subjects to task goals and reduce demands on cortical resources during tasks of low difficulty and attentional load. Under conditions of higher load, however, additional cognitive resources may be required in the presence of noise.     

fMRI responses to Jung's Word Association Test: implications for theory,treatment and research

Jung's Word Association Test was performed under fMRI conditions by 12 normal subjects. Pooled complexed responses were contrasted against pooled neutral ones. The fMRI activation pattern of this generic ‘complexed response’ was very strong (corrected Z scores ranging from 4.90 to 5.69). The activation pattern in each hemisphere includes mirror neurone areas that track ‘otherness’ (perspectival empathy), anterior insula (both self‐awareness and emotional empathy), and cingulated gyrus (self‐awareness and conflict‐monitoring). These are the sites described by Siegel and colleagues as the ‘resonance circuitry’ in the brain which is central to mindfulness (awareness of self) and empathy (sense of the other), negotiations between self awareness and the ‘internal other’. But there is also an interhemispheric dialogue. Within 3 seconds, the left hemisphere over‐rides the right (at least in our normal subjects). Mindfulness and empathy are central to good psychotherapy, and complexes can be windows of opportunity if left‐brain hegemony is resisted. This study sets foundations for further research: (i) QEEG studies (with their finer temporal resolution) of complexed responses in normal subjects (ii) QEEG and fMRI studies of complexed responses in other conditions, like schizophrenia, PTSD, disorders of self organization.     

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。     

Cognitive control of a simple mental image in patients with obsessive--compulsive disorder

The nature of obsessions has led researchers to try to determine if the main problem in obsessive-compulsive disorder (OCD) is impaired inhibitory control. Previous studies report that the effort to suppress is one of the factors that increase the frequency of obsessive thoughts. Based on these results and those of the present study that suggest inferior parietal lobe (IPL) abnormality in OCD and findings of a recent study that reported the importance of the right posterior parietal cortex in cognitive control of a simple mental image, the present cognitive control paradigm study aimed to determine whether there is a difference in brain dynamics between OCD patients and non-obsessive controls while performing tasks that necessitate cognitive control of a simple mental image, and whether the right posterior parietal region is one of the regions in which a difference in activity between the OCD patients and controls would be observed. Functional brain imaging was performed while the participants attempted to suppress, imagine, or manipulate a mental image. The general linear model showed that there was a main effect of group and main effect of task. Accordingly, in all contrasts (suppression minus free-imagination, erasing minus free-imagination, and imagination minus free-imagination), the right IPL, right posterior cingulate cortex, and right superior frontal gyrus activity were lower in the OCD patients than in the healthy controls. These results and the observed correlations between activity levels, and symptom and subjective performance scores are discussed. In conclusion, the results of the present study and those of previous studies suggest that the main problem in OCD might be difficulty activating the right frontoparietal networks during tasks that require cognitive control, which might result in the intrusiveness of obsessive thoughts.     

Functional brain activation differences in stuttering identified with a rapid fMRI sequence

The purpose of this study was to investigate whether brain activity related to the presence of stuttering can be identified with rapid functional MRI (fMRI) sequences that involved overt and covert speech processing tasks. The long-term goal is to develop sensitive fMRI approaches with developmentally appropriate tasks to identify deviant speech motor and auditory brain activity in children who stutter closer to the age at which recovery from stuttering is documented. Rapid sequences may be preferred for individuals or populations who do not tolerate long scanning sessions. In this report, we document the application of a picture naming and phoneme monitoring task in 3 min fMRI sequences with adults who stutter (AWS). If relevant brain differences are found in AWS with these approaches that conform to previous reports, then these approaches can be extended to younger populations. Pairwise contrasts of brain BOLD activity between AWS and normally fluent adults indicated the AWS showed higher BOLD activity in the right inferior frontal gyrus (IFG), right temporal lobe and sensorimotor cortices during picture naming and higher activity in the right IFG during phoneme monitoring. The right lateralized pattern of BOLD activity together with higher activity in sensorimotor cortices is consistent with previous reports, which indicates rapid fMRI sequences can be considered for investigating stuttering in younger participants.Educational objectives: The reader will learn about and be able to describe the: (1) use of functional MRI to study persistent developmental stuttering; (2) differences in brain activation between persons who stutter and normally fluent speakers; and (3) potential benefit of time efficient fMRI sequences combined with a range of speech processing tasks for investigating stuttering in younger populations.     

Afferent dysgraphia after right cerebral stroke: an autonomous syndrome?

Afferent dysgraphia is an acquired writing deficit characterized by deletions and duplications of letters and strokes. The commonly accepted interpretation states that afferent dysgraphia is associated with three main clinical features: production of spatial writing errors; the presence of left unilateral neglect; and no deterioration in performance when writing blindfolded. In order to test whether these symptoms necessarily co-occur with afferent dysgraphia, we studied the writing performances of a series of eight right brain-damaged patients. In sentence copying, spontaneous handwriting, and writing to dictation they showed afferent dysgraphia. However, signs of left neglect and spatial dysgraphia were evident only in some cases. Furthermore, the frequency of afferent errors increased when patients were required to write without vision. The present study demonstrates that afferent dysgraphia is an autonomous clinical entity and that it results from a selective impairment of a mechanism whose function is that of comparing the information about the number of letters and strokes specified at the level of letter motor programs and the actual number of movements already realized.     

Turing redux: Enculturation and computation

Many of our cognitive capacities are shaped by enculturation. Enculturation is the acquisition of cognitive practices such as symbol-based mathematical practices, reading, and writing during ontogeny. Enculturation is associated with significant changes to the organization and connectivity of the brain and to the functional profiles of embodied actions and motor programs. Furthermore, it relies on scaffolded cultural learning in the cognitive niche. The purpose of this paper is to explore the components of symbol-based mathematical practices. Phylogenetically, these practices are the result of concerted organism-niche interactions that have led from approximate number estimations to the emergence of discrete, symbol-based mathematical operations. Ontogenetically, symbol-based mathematical practices are associated with plastic changes to neural circuitry, action schemata, and motor programs. It will be suggested that these practices rely on previously acquired capacities such as subitizing and counting. With these considerations in place, I will argue that computations, understood in the sense of Turing (1936), are a specific kind of symbol-based mathematical practices that can be realized by human organisms, machines, or by hybrid organism-machine systems. In sum, this paper suggests a new way to think about mathematical cognition and computation.     

‘Language of the past’ – Exploring past tense disruption during autobiographical narration in neurodegenerative disorders

Compromised retrieval of autobiographical memory (ABM) is well established in neurodegenerative disorders. The recounting of autobiographical events is inextricably linked to linguistic knowledge, yet no study to date has investigated whether tense use during autobiographical narration is disrupted in dementia syndromes. This study investigated the incidence of correct past tense use during ABM narration in patients with Alzheimer's disease (AD, n = 10) and semantic dementia (SD, n = 10) in comparison with healthy older Controls (n = 10). Autobiographical narratives were analysed for episodic content (internal/external) and classified according to tense use (past/present). Across both patient groups, use of the past tense was significantly compromised relative to Controls, with increased levels of off‐target present tense verbs observed. Voxel‐based morphometry analyses based on structural MRI revealed differential associations between past tense use and regions of grey matter intensity in the brain. Bilateral temporal cortices were implicated in the SD group, whereas frontal, lateral, and medial temporal regions including the right hippocampus emerged in AD. This preliminary study provides the first demonstration of the disruption of specific linguistic constructs during autobiographical narration in AD and SD. Future studies are warranted to clarify at what point in the disease trajectory such deficits in tense use emerge, and whether these deficits are a product or contributing factor in memory disruption in these syndromes.