重复经颅磁刺激改善帕金森病运动症状的脑功能网络分析

目的 重复经颅磁刺激（rTMS）技术已广泛应用在临床中，实现对神经、精神类疾病的治疗，特别在抑郁症、强迫症中取得较好的临床治疗效果。近年来越来越多的研究将其应用于帕金森病（PD）的辅助、康复治疗，以期缓解患者的运动症状改善运动功能。目前临床中多以PD统一量表、运动任务评估rTMS对运动症状的辅助治疗效果，缺乏对高频rTMS刺激调控作用机制的探究。方法 本研究采用10 Hz rTMS刺激肢体症状始发侧对侧初级运动皮层（M1），对比分析刺激前后各脑区神经元活动及其连接性的变化，研究高频rTMS刺激初级运动皮层对PD患者大脑神经元活动的调节作用。结果 运动皮层beta振荡增加、gamma振荡降低（P<0.05），额、顶叶脑区间连接性减弱（P<0.05）。结论 10 Hz rTMS主要改变了PD患者beta、gamma振荡，其中运动皮层beta、gamma神经振荡的变化可能与磁刺激对运动功能的改善作用有关，而前额叶gamma振荡的变化可能是磁刺激抑制神经元异常放电活动调节患者运动控制功能。     

γ节律振荡机制在视觉研究中的新进展

γ节律振荡是大脑皮质中常见的,频率在30～80 Hz之间的神经振荡模式,在初级视觉通道中能观察到多种起源的γ节律振荡.在小鼠、猫与猴V1的视觉诱发的γ节律振荡主要起源于L2/3和L4B,并对刺激参数敏感.猫与小鼠初级视觉通道(视网膜、LGN与V1)中观察到起源于视网膜由亮度诱发的高频γ节律振荡;在猴LGN却没有观察到γ节律振荡,而在V1上记录到亮度诱发的γ活动.γ节律振荡的产生与抑制性中间神经元网络有重要的关系,其中抑制性中间神经元中PV细胞被认为与自发γ节律振荡的产生相关. SOM细胞的参与对低频γ节律振荡(20～40 Hz)的产生起到关键作用;而光栅诱发的高频γ节律振荡(65～80 Hz)主要与PV细胞有关.动物在不同生理状态、发育阶段与脑疾病状态下光栅诱发的γ节律振荡存在较大差异,反映大脑对视觉信息加工的变化.     

额叶冲突加工机制及年老化改变的事件相关电位研究

目的：探讨大脑额叶对冲突信息的加工处理机制及其年老化改变,探索敏感的事件相关电位（ERPs）指标。方法：研究对象为15例正常老年人（老年组）和15例青年成人（青年组）,ERPs检查采用改良的Eriksenflanker视觉刺激范式,记录32导脑电、正确率及反应时。结果：与青年组相比,老年组反应时明显延长,反应阶段干扰效应尤其明显。老年组N380出现时间窗延迟,平均波幅两组无差异,源定位分析（IDRETA）显示青年组可见双颞叶、双前额背外侧区域激活,以右侧明显;老年组主要见左颞叶、左前额背外侧、左前额内侧面区域激活。结论：在反应阶段出现冲突信息时,老年人额叶干扰控制功能减退,差异负波N380与老年人左前额背外侧、左侧颞叶等区域在反应选择、执行控制中的活动有关,且增龄改变明显。     

视听跨通道干扰抑制:儿童ERP研究

为探查视听跨通道干扰抑制的认知神经机制的横断年龄特性,记录分析了14名10岁儿童视听词汇干扰任务时的事件相关电位.在不一致条件下,被试需要对同范畴听觉干扰词进行抑制,一致条件则没有干扰抑制.结果发现,不一致条件的反应时显著长于一致条件.不一致条件下P200的波幅显著大于一致条件,可能揭示了对探测刺激和干扰刺激在知觉上的差异.N300和N550主要分布于额叶区域,不一致条件的波幅均显著大于一致条件.N300可能反映了认知冲突监测,N550可能反映了对干扰刺激的抑制,这为儿童抑制发展脑机制提供了童年期特定阶段的初步证据.     

图形形状与空间位置知觉诱发脑电的相干性分析

利用128道高分辨率脑电测量技术及脑电相干处理技术,通过测量大脑对图形形状知觉（任务1）、图形形状和空间位置知觉（任务2）两种任务的事件相关电位,并基于电极数大致相同的原则,从枕叶至额叶把头表分成7个区,然后分析了枕叶与其它各区在不同频段的相干性.结果发现：在γ1频段（28～39Hz）,任务2时的平均相干系数值显著大于任务1时的相应值;同时还发现在枕叶与额叶间,任务2的相干系数更显著地大于任务1的相干系数.结合视觉的两条通路的理论,这一结果从相干性角度表明,背侧通道的参与强化了枕叶与额叶之间的信息沟通,而这种沟通主要在γ1频段.     

不同频率的电针对大鼠神经源性痛的治疗作用

目的：探讨不同频率的电针能否减轻大鼠神经源性痛。方法：将大鼠右侧L5／L6脊神经结扎,用引起50％抬足的机械刺激阈值评价机械性痛觉超敏,用大鼠5min内从5℃冷权上的抬足次数反映冷诱发的持续性疼痛。用韩氏穴位神经刺激仪给与2Hz或100Hz电刺激。结果：①2Hz和100Hz电针均一轻痛觉超敏,2Hz起效较早。②两种频率电针均能减轻冷诱发的持续性疼痛,但2Hz持续的时间长,多次电针后2Hz的镇痛效果可持续长达48h。③针刺而不通电也能显著减轻冷诱发的持续性痛。结论：电针能减轻神经源性痛,且低频（2Hz）电针的镇痛效果优于高频（100Hz）电针。     

刺激兔下丘脑室旁核诱发的心律失常与增压反应

在60只局麻与肌松剂制动的家兔,观察到用0.1—0.4mA,50Hz,1ms 的方波电刺激下丘脑室旁核(PV)能诱发频发性心律失常(包括室性与室上性期前收缩)及显著的动脉血压升高。与同侧的下丘脑外侧区(LHA)及腹内侧核(VMH)相比,刺激PV诱发期前收缩的次数更为频繁,增压反应幅度较大,且所需阈值亦较低。较低强度刺激LHA 在部分兔能引起血压下降与心率减慢,而PV 则一致地诱发增压反应。电刺激腓深神经能抑制刺激PV诱发的期前收缩,但在中脑中央灰质微量注射吗啡或电解毁损只能完全阻断刺激VMH诱发的期前收缩,而不能完全阻断PV诱发的期前收缩。这些结果提示,PV是下丘脑中诱发心律失常与血压增高的高反应区之一,并且可能具有不同于LHA或VMH的神经机制或下行神经通路。     

视觉注意与神经振荡

人脑每时每刻都要接收大量视觉信息，由于人脑加工信息的能力有限，所以在较大视野内将注意分配给相关信息，同时抑制引起注意分散的不相关信息，对执行目标导向的行为至关重要。这种对视觉信息的选择性和主动性加工以适应当前目标的过程被称作视觉注意（visual attention），且视觉注意可分为自上而下的注意与自下而上的注意两种不同功能。由于来自大脑电信号的神经振荡活动在认知加工中发挥重要作用，已有研究综述了视觉注意与神经振荡（neural oscillation）的密切关系，但并未涉及不同的注意功能与神经振荡的关系。本文系统性调查了不同注意功能与神经振荡的关系，发现额-顶区域的theta频带振荡活动反映了自上而下的认知控制，而后部脑区的theta振荡与自下而上的注意相关。顶-枕区域alpha振荡的偏侧化有助于注意分配，而alpha频带的大规模同步促成了注意对视皮层自上而下的影响。Beta振荡介导了自上而下的信息与自下而上的信息之间的互动，作为信息载体促进了视觉信息处理。Gamma振荡则可能与自上而下和自下而上的注意间整合相关。本文就视觉注意功能与神经振荡关系的研究现状展开综述，旨在揭示不同的神经振荡活动在特定的视觉注意功能中的作用。     

听觉诱发脑电小波分量的混沌研究——婴儿痉挛症认知功能障碍的机制探讨

通过对婴幼儿期难治性癫痫———婴儿痉挛症(infantile spasms, IS)听觉诱发脑电细貌混沌特性的研究,探讨与IS相伴的认知功能障碍的发生机制。研究方法是分别记录IS组及正常对照组对象的听觉诱发脑电,经Mexihat连续小波变换后,分别计算信号各尺度小波分量的相关维数。结果表明IS组与正常对照组的各小波分量相关维数的差别主要表现在小波的第3尺度分量上(频带范围是32~64 Hz,主要为γ频带范围),在这个尺度上正常组相关维数明显低于IS组(P<0.05)。相关维数的降低意味着大脑活动自由度的减少,表明大脑的各单元耦合加强。因为正常组脑干内信息传递通道完好,使得大脑各个单元之间的信息耦合较强; IS组则由于脑干功能的异常,存在神经信息传递障碍,进而影响到脑干及其与大脑各个局部之间的信息耦合。小波第3尺度处于较高频率范围(γ频带范围),而在大脑皮层上的基频信号与听觉调频信号经加工后所产生的神经信号正在这一频率范围,且这一信号与大脑高级认知功能密切相关。因此,IS患者γ频带细貌信号的相关维数高于正常值,能够解释IS认知功能发生障碍的原因。     

大鼠尾壳核-海马癫痫电网络的神经信息编码特征

目的：观察强直电刺激大鼠右侧尾壳核（CPu）时,CPu-海马（HPC）网络癫痫的神经信息编码特征。方法：雄性SD大鼠59只。急性或慢性强直电刺激CPu（acute tetanization of the right CPu or chronic tetanization of the right CPu,ATRC or CTRC）（60Hz．0．4～0．6mA,2s）诱导大鼠癫痫模型。结果：①ATRC可以诱导双侧HPC神经元出现非对称性癫痫相关性单位电活动．增加对侧HPC单位放电时间间隔（Interspike interval,ISI）点分布的分岔角度。②CTRC可以诱导双侧CPu网络出现尖波样连续发放,同侧振荡样网络发作具有明显的相位移动特征;频率变化顺序为70Hz、110Hz、35Hz以及30Hz．与时间呈显著的负相关;振荡波波峰间隔（Interpeak interval,IPI）和波峰振幅逐渐增大,与时间呈显著正相关。③CTRC后加ATRC可以分别诱导双侧CPu网络出现原发性后放电。结论：激活CPu可以跨大脑半球重建双侧CPu—HPC癫痫电网络．其神经信息编码特征可能成为癫痫发生的神经信息学基础。     

EEG Source Reconstruction Reveals Frontal-Parietal Dynamics of Spatial Conflict Processing

Cognitive control requires the suppression of distracting information in order to focus on task-relevant information. We applied EEG source reconstruction via time-frequency linear constrained minimum variance beamforming to help elucidate the neural mechanisms involved in spatial conflict processing. Human subjects performed a Simon task, in which conflict was induced by incongruence between spatial location and response hand. We found an early (∼200 ms post-stimulus) conflict modulation in stimulus-contralateral parietal gamma (30–50 Hz), followed by a later alpha-band (8–12 Hz) conflict modulation, suggesting an early detection of spatial conflict and inhibition of spatial location processing. Inter-regional connectivity analyses assessed via cross-frequency coupling of theta (4–8 Hz), alpha, and gamma power revealed conflict-induced shifts in cortical network interactions: Congruent trials (relative to incongruent trials) had stronger coupling between frontal theta and stimulus-contrahemifield parietal alpha/gamma power, whereas incongruent trials had increased theta coupling between medial frontal and lateral frontal regions. These findings shed new light into the large-scale network dynamics of spatial conflict processing, and how those networks are shaped by oscillatory interactions.     

Effects of pulsed and continuous wave 902 MHz mobile phone exposure on brain oscillatory activity during cognitive processing

The aim of the current double-blind studies was to partially replicate the studies by Krause et al. [2000ab, 2004] and to further investigate the possible effects of electromagnetic fields (EMF) emitted by mobile phones (MP) on the event-related desynchronisation/synchronisation (ERD/ERS) EEG (electroencephalogram) responses during cognitive processing. Two groups, both consisting of 36 male participants, were recruited. One group performed an auditory memory task and the other performed a visual working memory task in six exposure conditions: SHAM (no EMF), CW (continuous wave EMF) and PM (pulse modulated EMF) during both left- and right-side exposure, while the EEG was recorded. In line with our previous studies, we observed that the exposure to EMF had modest effects on brain oscillatory responses in the alpha frequency range ( approximately 8-12 Hz) and had no effects on the behavioural measures. The effects on the EEG were, however, varying, unsystematic and inconsistent with previous reports. We conclude that the effects of EMF on brain oscillatory responses may be subtle, variable and difficult to replicate for unknown reasons.     

Visual working memory load-related changes in neural activity and functional connectivity

Background

Visual working memory (VWM) helps us store visual information to prepare for subsequent behavior. The neuronal mechanisms for sustaining coherent visual information and the mechanisms for limited VWM capacity have remained uncharacterized. Although numerous studies have utilized behavioral accuracy, neural activity, and connectivity to explore the mechanism of VWM retention, little is known about the load-related changes in functional connectivity for hemi-field VWM retention.

Methodology/Principal Findings

In this study, we recorded electroencephalography (EEG) from 14 normal young adults while they performed a bilateral visual field memory task. Subjects had more rapid and accurate responses to the left visual field (LVF) memory condition. The difference in mean amplitude between the ipsilateral and contralateral event-related potential (ERP) at parietal-occipital electrodes in retention interval period was obtained with six different memory loads. Functional connectivity between 128 scalp regions was measured by EEG phase synchronization in the theta- (4–8 Hz), alpha- (8–12 Hz), beta- (12–32 Hz), and gamma- (32–40 Hz) frequency bands. The resulting matrices were converted to graphs, and mean degree, clustering coefficient and shortest path length was computed as a function of memory load. The results showed that brain networks of theta-, alpha-, beta-, and gamma- frequency bands were load-dependent and visual-field dependent. The networks of theta- and alpha- bands phase synchrony were most predominant in retention period for right visual field (RVF) WM than for LVF WM. Furthermore, only for RVF memory condition, brain network density of theta-band during the retention interval were linked to the delay of behavior reaction time, and the topological property of alpha-band network was negative correlation with behavior accuracy.

Conclusions/Significance

We suggest that the differences in theta- and alpha- bands between LVF and RVF conditions in functional connectivity and topological properties during retention period may result in the decline of behavioral performance in RVF task.     

Frequency Band-Specific Electrical Brain Stimulation Modulates Cognitive Control Processes

A large body of findings has tied midfrontal theta-band (4–8 Hz) oscillatory activity to adaptive control mechanisms during response conflict. Thus far, this evidence has been correlational. To evaluate whether theta oscillations are causally involved in conflict processing, we applied transcranial alternating current stimulation (tACS) in the theta band to a midfrontal scalp region, while human subjects performed a spatial response conflict task. Conflict was introduced by incongruency between the location of the target stimulus and the required response hand. As a control condition, we used alpha-band (8–12 Hz) tACS over the same location. The exact stimulation frequencies were determined empirically for each subject based on a pre-stimulation EEG session. Behavioral results showed general conflict effects of slower response times (RT) and lower accuracy for high conflict trials compared to low conflict trials. Importantly, this conflict effect was reduced specifically during theta tACS, which was driven by slower response times on low conflict trials. These results show how theta tACS can modulate adaptive cognitive control processes, which is in accordance with the view of midfrontal theta oscillations as an active mechanism for cognitive control.     

The Neural Dynamics of Conflict Adaptation within a Look-to-Do Transition

Background

For optimal performance in conflict situations, conflict adaptation (conflict detection and adjustment) is necessary. However, the neural dynamics of conflict adaptation is still unclear.

Methods

In the present study, behavioral and electroencephalography (EEG) data were recorded from seventeen healthy participants during performance of a color-word Stroop task with a novel look-to-do transition. Within this transition, participants looked at the Stroop stimuli but no responses were required in the ‘look’ trials; or made manual responses to the Stroop stimuli in the ‘do’ trials.

Results

In the ‘look’ trials, the amplitude modulation of N450 occurred exclusively in the right-frontal region. Subsequently, the amplitude modulation of sustained potential (SP) emerged in the posterior parietal and right-frontal regions. A significantly positive correlation between the modulation of reconfiguration in the ‘look’ trials and the behavioral conflict adaptation in the ‘do’ trials was observed. Specially, a stronger information flow from right-frontal region to posterior parietal region in the beta band was observed for incongruent condition than for congruent condition. In the ‘do’ trials, the conflict of ‘look’ trials enhanced the amplitude modulations of N450 in the right-frontal and posterior parietal regions, but decreased the amplitude modulations of SP in these regions. Uniquely, a stronger information flow from centro-parietal region to right-frontal region in the theta band was observed for iI condition than for cI condition.

Conclusion

All these findings showed that top-down conflict adaptation is implemented by: (1) enhancing the sensitivity to conflict detection and the adaptation to conflict resolution; (2) modulating the effective connectivity between parietal region and right-frontal region.     

Effect of alexithymia on the event-related theta-synchronization of human EEG during reception of emotional visual stimuli

The 62-channel EEG was recorded while control non-alexithymic (n = 21) and alexithymic (n = 20) participants viewed sequentially presented neutral, pleasant and unpleasant pictures and subjectively rated them after each presentation. The event-related synchronization (ERS) to these stimuli was assessed in the theta-1 (4-6 Hr) and theta-2 (6-8 Hz) frequency bands. The obtained findings indicate that alexithymia influences perception of only emotional stimuli. In the upper theta over anterior cortical regions alexithymia vs control individuals in response to both pleasant and unpleasant stimuli manifested decreased left hemisphere ERS in the early test period of 0-200 ms along with enhanced ERS in response to negative vs positive and neutral stimuli in the right hemisphere at 200-600 ms after stimulus onset. The findings provide the first EEG evidence that alexithymia construct, associated with a cognitive deficit in initial evaluation of emotion, is indexed by disrupted early frontal synchronization in the upper theta band that can be best interpreted to reflect disregulation during appraisal of emotional stimuli.     

Peculiarities of changes of EEG reactivity during performance of dual tasks in healthy subjects (voluntary postural control and calculation)

Complex EEG and stabilography investigation with separate and simultaneous performance of motor (voluntary postural control) and cognitive (calculation) tasks has been performed in 20 healthy subjects (22 +/- 0.7 yo.). Specific spatial and frequency reactive changes have been revealed during motor task performance. These included increase of coherence in alpha-band for long pair of channels in right hemisphere as well as in symmetric parietal-occipital regions in both hemispheres. Cognitive task performance has been accompanied by coherence increase for low bands (delta- and theta-) with higher activation in left hemisphere and frontal regions. In dual tasks where both components were performed worse comparing to control, performance led to reactive spatial and frequency changes of both--motor and cognitive--tasks, though these changes were less than during separate task performance. Decrease of coherence in alphal-band in frontal areas appeared as a zone of "conflict of interest - interferention". In dual tasks with better performance of each component comparing to control EEG coherence increased in each specific area as well as in areas of "conflict of interest".     

Induced cortical electrical activity during different time-spans between warning and target stimuli

A certain alpha-band EEG dynamics was revealed in healthy adults (n = 16) at the interval between a warning and a target stimulus in a simple visuospatial task (subjects were instructed to locate a specific letter in the table of letters). Two series of experiment--either with a 2-sec or a 9-sec inter-stimulus interval were conducted, each consisting of 60 trials. In both series, we observed an induced desynchronization of low alpha (8-10 Hz) at the first second after the warning stimulus and its desynchronization just before the target stimulus. In series with a 9-sec inter-stimulus interval at the 4-6 s of it we observed an alpha-band synchronization, especially distinct in high alpha (10.5-13 Hz). This synchronization gradually reduced towards the end of the inter-stimulus interval. We consider the above changes in alpha-band spectral power during the inter-stimulus interval to be induced by "inner impulsations" caused by an internal representation (set) of the stimuli time-sequence. Changes in the level of cognitive control during the inter-stimulus interval cause increases and decreases in fronto-thalamic system activity, which are manifested in changes of alpha-band spectral power. Analysis of theta-band dynamics suggests that cortico-hippocampal system doesn't participate in this process.     

Long lasting modulation of cortical oscillations after continuous theta burst transcranial magnetic stimulation

Transcranial magnetic theta burst stimulation (TBS) differs from other high-frequency rTMS protocols because it induces plastic changes up to an hour despite lower stimulus intensity and shorter duration of stimulation. However, the effects of TBS on neuronal oscillations remain unclear. In this study, we used electroencephalography (EEG) to investigate changes of neuronal oscillations after continuous TBS (cTBS), the protocol that emulates long-term depression (LTD) form of synaptic plasticity. We randomly divided 26 healthy humans into two groups receiving either Active or Sham cTBS as control over the left primary motor cortex (M1). Post-cTBS aftereffects were assessed with behavioural measurements at rest using motor evoked potentials (MEPs) and at active state during the execution of a choice reaction time (RT) task in combination with continuous electrophysiological recordings. The cTBS-induced EEG oscillations were assessed using event-related power (ERPow), which reflected regional oscillatory activity of neural assemblies of θ (4-7.5 Hz), low α (8-9.5 Hz), μ (10-12.5 Hz), low β (13-19.5 Hz), and high β (20-30 Hz) brain rhythms. Results revealed 20-min suppression of MEPs and at least 30-min increase of ERPow modulation, suggesting that besides MEPs, EEG has the potential to provide an accurate cortical readout to assess cortical excitability and to investigate the interference of cortical oscillations in the human brain post-cTBS. We also observed a predominant modulation of β frequency band, supporting the hypothesis that cTBS acts more on cortical level. Theta oscillations were also modulated during rest implying the involvement of independent cortical theta generators over the motor network post cTBS. This work provided more insights into the underlying mechanisms of cTBS, providing a possible link between synchronised neural oscillations and LTD in humans.     

Alpha-Band Rhythms in Visual Task Performance: Phase-Locking by Rhythmic Sensory Stimulation

Oscillations are an important aspect of neuronal activity. Interestingly, oscillatory patterns are also observed in behaviour, such as in visual performance measures after the presentation of a brief sensory event in the visual or another modality. These oscillations in visual performance cycle at the typical frequencies of brain rhythms, suggesting that perception may be closely linked to brain oscillations. We here investigated this link for a prominent rhythm of the visual system (the alpha-rhythm, 8–12 Hz) by applying rhythmic visual stimulation at alpha-frequency (10.6 Hz), known to lead to a resonance response in visual areas, and testing its effects on subsequent visual target discrimination. Our data show that rhythmic visual stimulation at 10.6 Hz: 1) has specific behavioral consequences, relative to stimulation at control frequencies (3.9 Hz, 7.1 Hz, 14.2 Hz), and 2) leads to alpha-band oscillations in visual performance measures, that 3) correlate in precise frequency across individuals with resting alpha-rhythms recorded over parieto-occipital areas. The most parsimonious explanation for these three findings is entrainment (phase-locking) of ongoing perceptually relevant alpha-band brain oscillations by rhythmic sensory events. These findings are in line with occipital alpha-oscillations underlying periodicity in visual performance, and suggest that rhythmic stimulation at frequencies of intrinsic brain-rhythms can be used to reveal influences of these rhythms on task performance to study their functional roles.