刺激前alpha振荡对视知觉的影响

人类对感觉阈限附近的视觉刺激的知觉不总是一致的。为探究这种视知觉不一致的现象及其神经机制, 一些研究者关注刺激前脑内自发alpha神经振荡(8~13 Hz)对视知觉的影响。近年来的研究发现, 刺激前alpha振荡能量的降低能提高被试的探测击中率, 但不能提高知觉精确度; 而刺激前alpha振荡的相位能预测被试能否成功探测刺激。刺激前alpha能量被认为调控了视皮层的基础活动强度; alpha能量的降低反映了皮层基础活动的增强, 进而提高了对较弱刺激的探测率。刺激前alpha相位则被认为调控了皮层兴奋和抑制的时间; 大脑在刺激呈现时的不同状态(兴奋/抑制)决定了最终的知觉结果。     

工作记忆的神经振荡调控：基于神经振荡夹带现象

工作记忆的神经振荡机制研究是当前记忆领域的研究热点之一。那么, 神经振荡仅仅是工作记忆过程的伴随现象, 还是直接参与并调控了工作记忆的加工过程?已有研究发现, 大脑内部的神经振荡活动在外界节律性刺激的驱动下, 逐步与外界刺激节律相位同步化, 这一现象被称为“神经振荡夹带”。重复经颅磁刺激(repetitive Transcranial Magnetic Stimulation, rTMS)和经颅交流电刺激(transcranial Alternating Current Stimulation, tACS)干预研究基于此现象, 对大脑局部脑区施加节律性磁、电刺激, 进而调控工作记忆过程中特定频段的神经振荡活动、跨频段的神经振荡耦合或跨脑区的神经振荡相位同步, 为神经振荡参与工作记忆加工提供较为直接的因果证据。未来研究需考虑从脑网络的角度出发, 调控多个脑区之间的神经振荡活动, 进一步考察神经振荡对工作记忆的影响。此外, 还需注意探索和优化rTMS/tACS调控工作记忆的刺激方案, 并辅以客观的脑电记录, 提高该类研究的有效性和可重复性, 最终达到提高工作记忆能力的目的。     

前额叶的无创神经干预对饮食控制的影响:基于rTMS和tDCS研究的综述

饮食控制缺陷可导致超重、肥胖和饮食失调。已有研究表明,肥胖和饮食失调者在前额叶认知控制神经环路上存在缺陷。无创神经干预-经颅直流电刺激(t DCS)和重复经颅磁刺激(r TMS)-通过调节前额叶皮层兴奋性来提高饮食控制能力,改善饮食失调症状。未来的研究应考虑不同刺激参数和刺激位点下的干预效应,融合其他神经生理技术考察无创神经干预改善饮食控制的作用机制,考虑个体差异性并结合客观的行为范式进行探究。     

多巴胺D2受体参与调节感觉门控的机制

精神分裂症是一种常见的病因不明的精神疾病。大量文献表明精神分裂症患者所表现出来的认知紊乱和思维异常等症状与感觉门控功能的缺失有密切的关系, 感觉门控是指在充满刺激的环境中, 从外界的感觉信息中过滤无关的感觉信息然后执行与注意力相关的认知过程, 以对显著的刺激做出反应。研究感觉门控的经典范式是震惊反射的前脉冲抑制。研究发现多巴胺D₂受体可以参与调控前脉冲抑制的过程, 但是多巴胺D₂受体参与调控前脉冲抑制的机制仍不清楚。探讨多巴胺D₂受体参与调控感觉门控即前脉冲抑制的关键脑区、神经环路及分子机制, 有利于促进对精神分裂症感觉门控功能的深入研究。     

冲突解决过程中认知控制的注意调节机制

认知控制在冲突解决过程中起到重要的调节作用。相关理论大多结合任务相关刺激的加工增强和任务无关刺激的加工抑制进行解释,但近年来受到实证研究的挑战。综述了冲突解决中增强和抑制两种调节机制的争论和相应的实证证据,同时指出认知控制的调节机制可能受到冲突情境和个体自身等因素的影响。未来的研究应更多关注认知控制调节机制的影响因素,加强认知加工策略和认知训练的探究,为认知功能受损群体的干预提供依据。     

经颅直流电刺激对健康人群反应抑制的影响

反应抑制是指抑制不恰当的或不符合当前需要的行为的能力, 研究表明反应抑制主要与额下回、背外侧前额叶和前辅助运动区的功能有关。经颅直流电刺激(tDCS)是一种非侵入式脑刺激技术, 近年来对健康人群使用tDCS刺激相应脑区从而影响反应抑制功能的研究日益增多, 但主要研究结果不一致。阐明tDCS影响反应抑制具体的神经机制、减少tDCS研究的异质性、探索更有效的tDCS刺激方式和确定tDCS效果的年龄依赖性差异已成为目前亟待解决的问题。     

大学生的三重自我建构与个人自主的关系

采用问卷法,以477名本科学生为被试,探讨大学生的三重自我建构与个人自主水平之间的关系。结果显示:(1)个体自我可显著负向预测外部调控,正向预测认同调控和整合调控。(2)关系自我可显著正向预测外部调控和投射调控,且可在个体自我与外部调控、认同调控的关系中起调节作用。(3)集体自我可显著负向预测外部调控,正向预测投射调控、认同调控和整合调控,且可在个体自我与投射调控的关系中起调节作用。研究支持了个体自我的积极作用,同时也揭示了关系自我和集体自我对个人自主产生积极作用的方式。     

对听感觉运动门控自上而下调节的动物模型和神经机制

对惊反射的前脉冲抑制是减少干扰影响、保护脑内信息加工的重要机制。它既是研究感觉运动门控的模型, 也是探究精神分裂症机制的模型。前脉冲抑制可被选择性注意和情绪等高级认知活动所调节。本论文工作围绕着恐惧条件化和知觉空间分离去掩蔽(空间选择性注意)对听觉前脉冲抑制多层次化的自上而下调节, 在大鼠行为模型、神经通路、神经电生理机制等几个层次上开展了系统性研究, 并引入了精神分裂症的神经发育模型, 证实早期社会隔离饲养对前脉冲抑制注意调节的破坏影响。本论文研究成果不仅对认识正常情况下脑在复杂刺激场景中的信息加工机制有重要意义, 以感觉运动门控认知调节功能缺失为基础的动物模型也将推动精神分裂症心理学和神经生物学机制的研究。     

大脑视知觉调控的神经机制

大脑的知觉加工并非单纯由外部刺激驱动,而是存在自上而下的知觉调控。尽管这一现象被大量实验研究证实,但其神经机制仍然是认知神经科学研究的重要问题。本研究系统介绍了知觉调控的神经基础、实现形式、研究范式,及其理论模型,分析指出了当前研究面临的主要问题,并对未来的研究进行了展望,以期促进该问题研究的进一步开展。     

奖赏学习对视觉注意的调控

经过学习获得的奖赏预测性可以改变相关刺激的显著性,进而影响个体对该刺激的知觉加工与注意选择。探究奖赏学习在注意调节中的神经机制有利于理解人类的适应性行为。近期研究发现,大脑不仅可以增强具有奖赏显著性刺激所在空间位置或相应特征的表征,还可以通过注意抑制机制减弱具有奖赏显著性的刺激在初级视觉皮层的神经表征,从而减少对它的注意分配。这些研究提示奖赏信号在调节认知控制、优化行为过程中的重要作用。     

Transcutaneous vagus nerve stimulation (tVNS) enhances conflict-triggered adjustment of cognitive control

Response conflicts play a prominent role in the flexible adaptation of behavior as they represent context-signals that indicate the necessity for the recruitment of cognitive control. Previous studies have highlighted the functional roles of the affectively aversive and arousing quality of the conflict signal in triggering the adaptation process. To further test this potential link with arousal, participants performed a response conflict task in two separate sessions with either transcutaneous vagus nerve stimulation (tVNS), which is assumed to activate the locus coeruleus-noradrenaline (LC-NE) system, or with neutral sham stimulation. In both sessions the N2 and P3 event-related potentials (ERP) were assessed. In line with previous findings, conflict interference, the N2 and P3 amplitude were reduced after conflict. Most importantly, this adaptation to conflict was enhanced under tVNS compared to sham stimulation for conflict interference and the N2 amplitude. No effect of tVNS on the P3 component was found. These findings suggest that tVNS increases behavioral and electrophysiological markers of adaptation to conflict. Results are discussed in the context of the potentially underlying LC-NE and other neuromodulatory (e.g., GABA) systems. The present findings add important pieces to the understanding of the neurophysiological mechanisms of conflict-triggered adjustment of cognitive control.     

Posttraining Electrical Stimulation of Vagal Afferents with Concomitant Vagal Efferent Inactivation Enhances Memory Storage Processes in the Rat

Peripherally administered or released substances that modulate memory storage, but do not freely enter the brain, may produce their effects on memory by activating peripheral receptors that send messages centrally through the vagus nerve. Indeed, vagus nerve stimulation enhances memory performance, although it is unclear whether this effect is due to the activation of vagal afferents or efferents. To eliminate the possible influence of descending fibers on memory storage processes, rats were implanted with cuff electrode/catheter systems along the left cervical vagus. Forty-eight hours following surgery, each animal received a 3.0-μl infusion (1.0 μl/min) of either lidocaine hydrochloride (75.0 mM) or isotonic saline below the point of stimulation. Animals were then trained 10 min later on an inhibitory-avoidance task with a 0.75-mA, 1.0-s foot shock. Sham stimulation or vagus nerve stimulation (0.5-ms biphasic pulses; 20.0 Hz; 30 s; 0.2, 0.4, or 0.8 mA) was administered immediately after training. Memory, tested 24 h later, was enhanced by stimulation whether descending vagus nerve fibers were inactivated or not. Both lidocaine- and saline-infused groups showed an intensity-dependent, inverted-U-shaped pattern of retention performance, with the greatest effect observed for 0.4 mA (U= 9,p< .05, andU= 7,p< .01, respectively). Additionally, animals that received lidocaine infusions, but no vagus nerve stimulation, showed impaired memory compared to the performance of saline-infused control animals (U= 11,p< .05). Together, these findings suggest that vagal afferents carry messages about peripheral states that lead to the modulation of memory storage and that the memory-enhancing effect produced by vagus nerve stimulation is not mediated via the activation of vagal efferents.     

Vagus nerve stimulation: a new form of therapeutic brain stimulation

Although the vagus nerve has traditionally been considered to perform efferent functions, in reality it performs significant afferent functions as well, carrying information from the body, head, and neck to the brain. Preliminary studies examining this afferent activity led to the theory that vagus nerve stimulation (VNS) could successfully control seizure activity in persons who are refractory to antiepileptic medications. Unlike other forms of brain stimulation, VNS is unable to directly stimulate multiple discrete areas of the brain; however, through several pathways, it is able to relay sensory information to higher brain regions. An implantable VNS device known as the VNSTM NeuroCybernetic Prosthesis (NCP) System has been used in approximately 9,000 epilepsy patients in Europe and the United States since 1994. The implant has reduced seizure frequency by an average of 25% to 30%, with minimal side effects. Studies underway are also showing some degree of success in the management of treatment-refractory depression. The future efficacy of the implantable system in other disorders may depend on whether the implant can be more precisely focused to affect different brain regions. Research in this area is underway.     

Possible involvement of the vagus nerve in monitoring plasma catecholamine levels

In their article Miyashita and Williams (Neurobiology of Learning and Memory 2006, 85, 116-124) describe the effect of peripheral administration of epinephrine on neural discharge in vagal afferent fibers. It seems that described data supports the hypothesis of the vagus nerve participation in monitoring plasma catecholamine levels and consequently modifying brain functions. However, do these results indicate indeed that afferent vagus nerve pathways are activated by circulating epinephrine? Catecholamines influence virtually all tissues and many functions. Vagus nerve participates significantly in monitoring of those effects. Therefore epinephrine-induced increases of afferent vagus nerve activity described by Miyashita and Williams may reflect not only exclusive activation of beta-adrenergic receptors but also an activation of other types of receptors on vagal sensory nerve endings, e.g., mechanosensors, chemoreceptors, and osmosensors. Discussion is focused on the possibility that the increase in afferent vagus nerve activity may reflect activation of mechanoreceptors of the vagus nerve endings in the epinephrine-activated heart.     

Mechanisms and the current state of transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) is unique among the current brain stimulation techniques because it is relatively non-invasive. TMS markedly differs from vagus nerve stimulation, deep brain stimulation and magnetic seizure therapy, all of which require either an implanted prosthesis or general anesthesia, or both. Since its rebirth in its modern form in 1985, TMS has already shown potential usefulness in at least three important domains-as a basic neuroscience research instrument, as a potential clinical diagnostic tool, and as a therapy for several different neuropsychiatric conditions. The TMS scientific literature has now expanded beyond what a single summary article can adequately cover. This review highlights several new developments in combining TMS with functional brain imaging, using TMS as a psychiatric therapy, potentially using TMS to enhance performance, and finally recent advances in the core technology of TMS. TMS' ability to non-invasively and focally stimulate the brain of an awake human is proving to be a most important development for neuroscience in general, and neuropsychiatry in particular.     

Aggression in temporal lobe epilepsy and limbic psychotic trigger reaction implicating vagus kindling of hippocampus/amygdala (in sinus abnormalites on MRIs)

Five aspects associated with potentially aggressive partial limbic seizures are interrelated: (1) Five out of six unselected (consecutively referred) White, male out-of-character aggressive felons (mean age 33) had histories of recurrent nasopharyngeal infections, four with congruent MRIs, two of these MRIs also showed cortical atrophy, three men had histories of various seizures, and one scalp EEG was “congruent with seizures in the temporal regions.” All men had histories of head injuries. The diagnoses of their bizarre acts during a brief psychosis were partial limbic seizures in an “exhibitionist” with temporal lobe epilepsy (TLE) and proposed limbic psychotic trigger reaction (LPTR) in four “murderers”, based on 13 specific symptoms and signs. (2) The men's nasopharyngeal (medical) conditions are hypothesized to be associated with intermittent mild stimulation of the vagus nerve. Supportive evidence shows that (3) experimental vagus stimulation has the most excitatory impact on hippocampus and amygdala, which are also (4) the most susceptible to limbic seizure kindling (by intermittent subthreshold stimuli). (5) even by contrast, high-voltage energy level and frequently applied vagus nerve stimulation (VNS), which is used as an antiepileptic treatment; however, VNS has elicited seizures in some patients.     

Putative common pathways in therapeutic brain stimulation for affective disorders

Brain stimulation methods in the treatment of affective disorder are electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS). Clinically, ECT is considered the strongest remedy in the treatment of severe depression, especially depression with psychotic features, and in the elderly. TMS, despite positive reports, is somewhat more controversial. VNS has, so far, only been used in treatment-resistant depression with limited results. DBS may be of potential use in rare cases of treatment-resistant cases of affective disorder. This article highlights the similarities and differences between the four stimulation methods. The main difference is the seizures necessary in ECT. A stronger involvement of the hippocampus following experimental seizures compared with effects in that region induced by TMS and VNS might explain the consistent findings of the superiority of ECT in the most severe cases of affective disorder.     

心房颤动的病因、发病机制与射频导管消融治疗现状

随着人们研究的不断深入,对心房颤动的病因、发病机制有了更新的认识。后者从起搏点兴奋性增高,折返机制,发展到对心肌袖、电重构的认识;以及肺静脉、迷走神经在阵发性心房颤动中的作用,遗传物质异质性及基因突变等。同样,心房颤动的射频导管消融治疗也取得了突破性的进展。     

条件反射性免疫增强的研究进展

综述了国内外研究条件反射性免疫增强的主要成果;介绍了相关实验所使用的刺激物,观测的指标和实验程序;探讨了一些脑区如下丘脑、岛叶皮质,神经通道如交感和迷走神经,多种神经内分泌激素如β-内啡肽、干扰素以及白细胞介素如IL-1等在条件反射性免疫增强中的介导作用     

不同感觉功能对抑郁的影响及其神经机制

大脑通过视觉、听觉、嗅觉、味觉和触觉等感官通道接收来自外界的信息。不同感觉功能受损涉及抑郁发生的中枢机制,而基于不同感官通道进行适当刺激以及多感官联合干预也可能发挥显著的抑郁治疗作用。笔者以症状-脑区-机制-治疗为逻辑主线,首次系统梳理了五种主要感觉障碍人群的抑郁临床症状、抑郁神经机制以及基于感觉刺激的抗抑郁治疗。结果表明,不同感觉功能障碍对抑郁相关神经机制的影响可能表征了不同的抑郁病理,涉及神经元电活动(某些神经元放电和神经环路激活等)和神经生化改变(神经可塑性和神经发生、炎症免疫和HPA轴、神经激素和神经递质等),且主要发生在边缘系统及其附近脑区,涉及岛叶、颞叶、额叶等。因此,未来研究可聚焦于机体对不同感觉信息的提取,这将为人类抑郁的病因和治疗提供新的研究视角。