右侧额顶网络在空间注意认知过程中的作用机制

目的:探讨右侧额顶网络(FPN)与视空间注意认知功能的关联性和作用机制.方法:选取志愿受试者60人参加本实验,随机分为顶叶组和额叶组.采用持续短阵快速脉冲(cTBS)经颅磁刺激(rTMS)右侧背外侧前额叶(DLPFC)和后顶叶皮质(DPC)后进行注意网络测试(ANT),所有受试者均按照随机顺序进行真/假刺激.结果:持续短阵快速脉冲经颅磁刺激施加于前额叶和后顶叶,不同提示和刺激类型的平均反应时均无明显改变.右侧后顶叶抑制,警觉和定向功能受损(P＜0.05);右侧额叶抑制,执行功能受损(P＜0.05),而定向功能增强(P＜0.05).结论:在视空间注意过程中,右侧后顶叶是定向功能的关键区,右侧前额叶是执行功能的关键区,并且右侧额顶区之间存在竞争性抑制现象.     

持续短阵快速脉冲刺激前额叶皮质对视空间注意功能的调控机制

目的:探讨持续短阵快速脉冲刺激背外侧前额叶皮质对视空间注意功能的调控机制.方法:选取志愿受试者40人参加本实验,男女各半,全部为右利手.采用持续短阵快速脉冲经颅磁刺激(cTBS,TMS)背外侧前额叶皮质(DLPFC)后进行注意网络测试(ANT),所有受试者均按照随机顺序进行真/假刺激左佑侧背外侧前额叶脑区.结果:持续短阵快速脉冲经颅磁刺激施加于前额叶时,不同提示和刺激类型的平均反应时均无明显改变.右侧额叶抑制,警觉和执行功能受损(P＜0.05);左侧额叶抑制,反而出现警觉和执行功能增强(P＜005).结论:背外侧前额叶皮质主要与警觉和执行功能有关,具有明显的右侧半球优势.在双侧大脑半球同源脑区间,视空间注意认知过程存在竞争性抑制.     

后顶叶皮质调控视空间注意功能的经颅磁刺激研究

目的探讨后顶叶皮质与视空间注意功能的关联性及其调控机制。 方法选取志愿受试者40例参加本实验，所有受试者均按照随机顺序对左、右侧后顶叶进行真、假刺激。于刺激前和每次刺激后(刺激后)对40例受试者进行神经行为学评价和注意网络测试，并对所获得的数据进行分析。 结果刺激前、后，受试者各项行为学评价差异均无统计学意义（P&rt;0.05）。右侧真刺激与假刺激比较，空间提示状态下平均RT明显延长，差异具有统计学意义（t=2.648,P<0.05）；且右侧真刺激时与左侧真刺激时空间提示状态下的平均RT比较，差异有统计学意义（t=3.689,P<0.01）。右侧PPC真刺激后，警觉网络效率（t=2.843,P<0.01）及其比率（t=2.841,P<0.01）明显降低，而左侧PPC真刺激后，警觉网络效率（t=2.324,P<0.05）及其比率（t=2.225,P<0.05）明显增强，且左侧与右侧真刺激后警觉网络效率及其比率比较，差异均也有统计学意义（P<0.05）；定向网络——右侧PPC真刺激后，定向网络效率（t=5.535,P<0.01）及其比率（t=5.245,P<0.01）明显降低，左侧与右侧真刺激后定向网络效率及其比率比较，差异均也有统计学意义（P<0.05）。 结论后顶叶皮质主要与定向和警觉功能有关，具有明显的右侧半球优势。在双侧大脑半球同源脑区间，视空间注意认知过程存在竞争性抑制。     

经颅磁刺激对健康受试者舌骨上肌群运动诱发电位的影响

目的研究短阵快速脉冲经颅磁刺激（TBS）对舌骨上肌群运动皮质兴奋性的影响,进一步探讨双侧大脑半球运动皮质对舌骨上肌群的调控机制。 方法选取健康受试者24例,采用持续短阵快速脉冲经颅磁刺激（cTBS）刺激受试者左侧舌骨上肌群运动皮质,采用间隔短阵快速脉冲经颅磁刺激(iTBS)刺激受试者右侧舌骨上肌群运动皮质,记录刺激前及刺激后即刻、15min、30min双侧舌骨上肌群的运动诱发电位（MEP）,用重复测量方差分析方法分析刺激前、后不同时间点双侧舌骨上肌群MEP波幅的变化。 结果刺激前,左右两侧舌骨上肌群MEP波幅分别为（375.29±176.09）μV和（368.17±149.02）μV,分别与同侧刺激后即刻、刺激后15min和刺激后30min舌骨上肌群MEP波幅比较,差异均有统计学意义（P<0.05）。 结论iTBS可兴奋右侧舌骨上肌群运动皮质,并能逆转左侧相应皮质被cTBS预处理的抑制效应。TBS可以影响两侧大脑半球舌骨上肌群运动皮质的兴奋性,对脑卒中后吞咽障碍患者的康复具有重要指导意义。     

小脑间歇性θ短阵脉冲刺激对健康人双侧大脑运动皮质兴奋性的调控

目的:研究小脑间歇性θ短阵脉冲刺激(iTBS)对双侧大脑运动皮质M1区兴奋性的影响及持续时间。方法:根据刺激部位的不同,按随机数字表法将纳入的20例青年健康受试者分为左侧小脑iTBS组和右侧小脑iTBS组,每组10例。所有受试者在进行所属组别的刺激模式干预前,先测量双侧大脑M1区静息运动阈值(RMT)及运动诱发电位(M...     

活体小鼠后顶叶皮质神经元双光子成像与空间定向机制

目的:结合双光子显微镜和Morris水迷宫探讨右侧顶叶皮质在空间认知功能中的作用机制.方法:选用C57BL/6J小鼠18只,随机分为正常对照组和右侧顶叶损毁组,用直流电损害小鼠的后顶叶皮质,正常对照组未做任何处理.在双光子显微镜下观测小鼠活体内右侧顶叶皮质神经元活动,Morris水迷宫评价小鼠的空间认知功能.结果:在双光子显微镜下,损毁组小鼠较正常组右侧顶叶皮质功能神经细胞明显减少,神经元跨膜电位明显减弱.在水迷宫空间任务中,损毁组小鼠空间学习能力及空间探索功能也均明显减弱.结论:双光子显微镜可在活体动物直接观察神经元活动;正常右侧后顶叶功能神经元活动是空间定向认知的关键.     

经颅直流电刺激对脑卒中视觉空间忽略患者视运动探查功能的影响

摘要 目的：观察阳极经颅直流电刺激作用于右侧后顶叶皮质对右侧脑卒中后左侧视觉空间忽略患者视运动探查功能表现的影响。 方法：研究纳入20例右侧脑卒中后左侧视觉空间忽略患者,分为治疗组和对照组：治疗组（n=10）行经颅直流电刺激联合常规康复治疗;对照组（n=10）行常规康复治疗。治疗前、治疗后予以不同注意需求的视运动探查任务评估：单纯搜索目标（线段删除）、对不同搜索目标进行不同标记（缺口探查）、从干扰刺激中搜索目标（星星删除）。 结果：治疗组线段删除得分较治疗前有改善,左侧缺口圆判断错误率、星星删除遗漏率有所减低,且差异均有显著性意义（P＜0.05）;而对照组较基线水平相比差异无显著性意义（P＞0.05）;治疗后两组间线段删除、缺口探查未标记目标百分比及左侧缺口率差异有显著性意义（P＜0.05）,但星星删除差异无显著性意义（P＞0.05）。 结论：阳极经颅直流电刺激作用于右侧后顶叶皮质对不同注意加工需求的视运动探查任务影响不同,经颅直流电刺激对单纯目标搜索功能的改善和以目标物自身为参考框架成分加工的改善有促进作用。     

间歇性θ短阵脉冲经颅磁刺激联合动作观察疗法对轻、中度阿尔茨海默病患者认知功能的影响

目的:研究间歇性θ短阵脉冲经颅磁刺激联合动作观察疗法对轻、中度阿尔茨海默病患者认知功能的影响。方法：选取轻、中度阿尔茨海默病患者52例随机分为观察组和对照组各26例。2组患者均接受常规药物治疗、认知功能训练、运动训练。对照组在此基础上采用动作观察疗法,观察组在对照组基础上联合间歇性θ短阵脉冲经颅磁刺激治疗。2组疗程均为4周。采用蒙特利尔认知评估（MoCA）、简易智能精神状态检查量表（MMSE）进行认知功能评估;采用改良Barthel指数、功能活动问卷FAQ进行日常生活活动能力的评估。结果:2组治疗后MMSE评分、MoCA评分均高于治疗前,观察组MMSE评分、MoCA评分改善幅度均高于对照组,差异有统计学意义（P＜0.05）。2组治疗后FAQ评分高于治疗前（P＜0.05）,观察组Barthel指数评分与FAQ评分改善幅度均高于对照组,差异有统计学意义（P＜0.05）。结论：间歇性θ短阵脉冲经颅磁刺激联合动作观察疗法可以改善轻、中度阿尔茨海默病患者的认知功能,提高患者的日常生活活动能力,有望在临床上推广使用。     

经颅磁刺激抑制健康人初级运动皮质后双侧中央前回精细分区的脑有效连接变化

目的观察经颅磁刺激抑制右侧初级运动皮质(M1)后双侧中央前回精细分区有效连接变化情况。方法选取21例健康志愿者纳入本研究,于持续短阵脉冲刺激(cTBS)干预前、后分别行静息态功能磁共振(rs-fMRI)检查,参照中科院自动化研究所制订的脑图谱对受试者双侧中央前回进行精细分区,选用Granger因果分析观察受试者双侧中央前回有效连接变化情况。结果经cTBS抑制右侧M1区后受试者双侧中央前回各亚区有效连接呈显著变化,右上肢功能区对左上肢、左头面部功能区的有效连接减弱,左上肢功能区对右侧头面部及右上肢功能区的有效连接增强。结论经cTBS抑制右侧M1区后,受试者双侧M1区上肢功能区的有效连接变化反映了半球间交互抑制,同时M1躯干功能区也发生了与上肢功能区方向相反的有效连接改变。     

右侧正中神经电刺激促醒疗法对健康人脑功能影响的fMRI研究

目的 探讨右侧正中神经电刺激（RMNS）促醒疗法对健康人脑功能的影响。 方法 选取28例健康志愿者作为受试者，将RMNS促醒治疗模式作为任务刺激，采用Block实验设计，给予受试者30 s刺激-30 s休息共重复6次，并同步采用大脑功能磁共振成像(fMRI)技术进行成像扫描。使用SPM 12软件进行统计处理时将同一受试者刺激状态与静息状态的脑功能成像互为对照，分析其脑区激活情况。 结果 fMRI检查显示，RMNS促醒治疗模式下健康人脑正激活区主要集中在左侧初级运动皮质(M1)、皮质运动前区(PMC)，双侧初级体感皮质(S1）、双侧次级体感皮质(S2)及左侧岛叶。与静息态相比，RMNS促醒刺激模式下上述激活脑区BOLD信号强度变化较大，T>5.84，P<0.05（FWE校正）。 结论 右侧正中神经电刺激促醒治疗能通过激活右手运动及感觉功能相关脑区，兴奋局部大脑皮质，产生一定促醒效应。     

The activation of attentional networks

Alerting, orienting, and executive control are widely thought to be relatively independent aspects of attention that are linked to separable brain regions. However, neuroimaging studies have yet to examine evidence for the anatomical separability of these three aspects of attention in the same subjects performing the same task. The attention network test (ANT) examines the effects of cues and targets within a single reaction time task to provide a means of exploring the efficiency of the alerting, orienting, and executive control networks involved in attention. It also provides an opportunity to examine the brain activity of these three networks as they operate in a single integrated task. We used event-related functional magnetic resonance imaging (fMRI) to explore the brain areas involved in the three attention systems targeted by the ANT. The alerting contrast showed strong thalamic involvement and activation of anterior and posterior cortical sites. As expected, the orienting contrast activated parietal sites and frontal eye fields. The executive control network contrast showed activation of the anterior cingulate along with several other brain areas. With some exceptions, activation patterns of these three networks within this single task are consistent with previous fMRI studies that have been studied in separate tasks. Overall, the fMRI results suggest that the functional contrasts within this single task differentially activate three separable anatomical networks related to the components of attention.     

Cerebral correlates of alerting, orienting and reorienting of visuospatial attention: an event-related fMRI study

The identification of brain systems contributing to different aspects of visuospatial attention is of both clinical and theoretical interest. Cued target detection tasks provide a simple means to dissociate attentional subcomponents, such as alerting, orienting or reorienting of attention. Event-related functional magnetic resonance imaging (fMRI) was used to study neural correlates of these distinct attentional processes. Volunteers were scanned while performing a centrally cued target detection task. Four different types of trials (no cue, neutral cue, valid cue and invalid cue trials) with targets appearing either in the right or left hemifield were randomly intermixed. Behaviourally, the data provided evidence for alerting, spatial orienting and reorienting of attention. Neurally, the alerting effect was seen in bilaterally increased extrastriatal blood oxygenation level-dependent (BOLD) activity in neutral as compared to no cue trials. Neural correlates of spatial orienting were seen in anterior cingulate cortex, which was more active during valid as compared to neutral cue trials. Neural correlates of reorienting of attention, that is, higher BOLD activity to invalid as compared to validly cued trials were evident in several brain regions including left and right intraparietal sulcus, right temporo-parietal junction and middle frontal gyrus bilaterally. The data suggest that frontal and parietal regions are specifically involved in reorienting rather than orienting attention to a spatial position. Alerting effects were seen in extrastriate regions which suggest that increased phasic alertness results in a top-down modulation of neural activity in visual processing areas.     

The left parietal and premotor cortices: motor attention and selection

It is well established that the premotor cortex has a central role in the selection of movements. The role of parts of the parietal cortex in movement control has proved more difficult to describe but appears to be related to the preparation and the redirection of movements and movement intentions. We have referred to some of these processes as motor attention. It has been known since the time of William James that covert motor attention can be directed to an upcoming movement just as visuospatial attention can be directed to a location in space. While some parietal regions, particularly in the right hemisphere, are concerned with covert orienting and the redirecting of covert orienting it may be useful to consider other parietal regions, in the anterior inferior parietal lobule and in the posterior superior parietal lobule, particularly in the left hemisphere, as contributing to motor attention. Such parts of the parietal lobe are activated in neuroimaging experiments when subjects covertly prepare movements or switch intended movements. Lesions or transcranial magnetic stimulation (TMS) affect the redirecting of motor attention. The difficulties apraxic patients experience when sequencing movements may partly be due to an inability to redirect motor attention from one movement to another. The role of the premotor cortex in selecting movements is also lateralized to the left hemisphere. Damage to left hemisphere movement selection mechanisms may also contribute to apraxia. If, however, it remains intact after a stroke then the premotor cortex may contribute to the recovery of arm movements. A group of patients with unilateral left hemisphere lesions and impaired movements in the contralateral right hand was studied. Functional magnetic resonance imaging showed that in some cases the premotor cortex in the intact hemisphere was more active when the stroke-affected hand was used. TMS in the same area in the same patients had the most disruptive effect on movements. In summary, patterns of motor impairment and recovery seen after strokes can partly be explained with reference to the roles of the parietal and premotor cortices in motor attention and selection.     

rTMS evidence of different delay and decision processes in a fronto-parietal neuronal network activated during spatial working memory

The existence of a specific and widely distributed network for spatial working memory (WM) in humans, involving the posterior parietal cortex and the prefrontal cortex, is supported by a number of neuroimaging studies. We used a repetitive transcranial magnetic stimulation (rTMS) approach to investigate the temporal dynamics and the reciprocal interactions of the different areas of the parieto-frontal network in normal subjects performing a spatial WM task, with the aim to compare neural activity of the different areas in the delay and decision phases of the task. Trains of rTMS at 25 Hz were delivered over the posterior parietal cortex (PPC), the premotor cortex (SFG) and the dorsolateral prefrontal cortex (DLPFC) of the right hemisphere alternatively during the two phases. We found a pattern of interference of TMS during the delay phase for both parietal and DLPFC sites of stimulation, with no effect observed for the SFG site. When rTMS trains were applied during the decision phase, an interference was observed selectively for DLPFC. The present study shows the existence of a parallel processing in the parieto-frontal network of spatial WM during the delay phase. Furthermore, it provides new evidence of the critical role of the DLPFC during both the delay and the decision phases. We suggest that in DLPFC, two different networks coexist: A local neural network subserving the decisional processes and a second neural population functionally interconnected with the PPC and activated when a certain spatial information has to be kept in memory, available to use.     

Motor and parietal cortex stimulation for phantom limb pain and sensations

Limb amputation may lead to chronic painful sensations referred to the absent limb, ie phantom limb pain (PLP), which is likely subtended by maladaptive plasticity. The present study investigated whether transcranial direct current stimulation (tDCS), a noninvasive technique of brain stimulation that can modulate neuroplasticity, can reduce PLP. In 2 double-blind, sham-controlled experiments in subjects with unilateral lower or upper limb amputation, we measured the effects of a single session of tDCS (2 mA, 15 min) of the primary motor cortex (M1) and of the posterior parietal cortex (PPC) on PLP, stump pain, nonpainful phantom limb sensations and telescoping. Anodal tDCS of M1 induced a selective short-lasting decrease of PLP, whereas cathodal tDCS of PPC induced a selective short-lasting decrease of nonpainful phantom sensations; stump pain and telescoping were not affected by parietal or by motor tDCS. These findings demonstrate that painful and nonpainful phantom limb sensations are dissociable phenomena. PLP is associated primarily with cortical excitability shifts in the sensorimotor network; increasing excitability in this system by anodal tDCS has an antalgic effect on PLP. Conversely, nonpainful phantom sensations are associated to a hyperexcitation of PPC that can be normalized by cathodal tDCS. This evidence highlights the relationship between the level of excitability of different cortical areas, which underpins maladaptive plasticity following limb amputation and the phenomenology of phantom limb, and it opens up new opportunities for the use of tDCS in the treatment of PLP.     

Spatiotemporal imaging of electrical activity related to attention to somatosensory stimulation

The aim of the present study was to localize the effects of spatial attention on somatosensory stimulation in EEG. Median and tibial nerve were stimulated at all four limbs in a random order. Subjects were instructed to count the events on either the right median or the right tibial nerve. Attention-induced changes in the somatosensory evoked potentials (SEP) were revealed by subtracting the median nerve SEPs recorded while subjects attended to stimuli applied to the tibial nerve from those obtained during attention to the stimulated hand. In a current density reconstruction approach source maxima in the time range from 30 to 260 ms after median nerve stimulation were localized and the time courses of activation were elaborated by dipole modeling. Six regions were identified which contribute significant source activity related to selective spatial attention: contralateral postcentral gyrus (Brodman area (BA) 3), contralateral mesial frontal gyrus (BA 6), right posterior parietal cortex (BA 7), anterior cingulate gyrus (BA 32), and bilateral middle temporal gyrus (BA 21). Activation started at the right posterior parietal cortex, followed by the contralateral middle temporal gyrus, probably representing SII activity, and the middle frontal and anterior cingulate gyrus. Similar regions of source activation were revealed by tibial nerve SEP, but the effect was less pronounced and restricted almost entirely to activation of the contralateral postcentral gyrus (BA 3), anterior cingulate gyrus (BA 32), and ipsilateral middle temporal gyrus (BA 21). Our data provide evidence for a spatially separated frontal generator within the anterior cingulum, dependent on selective attention in the somatosensory modality.     

Parietal magnetic stimulation delays visuomotor mental rotation at increased processing demands

Visuomotor rotation (VMR) is a variant of the classic mental rotation paradigm. Subjects perform a center-out arm reaching movement, with the instruction to point clockwise or anticlockwise away from the direction of a reaction signal by a prespecified amount. Like classic mental rotation (MR) tasks, there is a linear relationship between reaction time (RT) and required angle of rotation (angular disparity). Although functional imaging studies have consistently demonstrated parietal activations centered around the intraparietal sulcus during MR tasks, the involvement of parietal cortex in VMR has not been investigated. The aim of the present experiments was to test in human subjects whether VMR also involves activity in parietal areas. We used short trains of transcranial magnetic stimulation (TMS) to produce a temporary "virtual lesion" of the posterior parietal cortex (PPC) around the intraparietal sulcus during the reaction period of a VMR task. Four pulses of 20-Hz rTMS were applied to the left PPC, right PPC, or vertex (control condition) 100 ms after the presentation of an instruction cue. Reaction times (RTs) were evenly prolonged by right or left parietal TMS compared with vertex stimulation, but only for large angles of rotation, and without affecting the spatial accuracy of the final response. A control experiment showed that parietal rTMS did not impair visual perception or the ability to judge the size of visual angles. The data thus provide evidence for bilateral involvement of the PPC in VMR that increases with processing demands.     

Endogenous and exogenous attention shifts are mediated by the same large-scale neural network

Event-related fMRI was used to examine the neural basis of endogenous (top-down) and exogenous (bottom-up) spatial orienting. Shifts of attention were induced by central (endogenous) or peripheral (exogenous) cues. Reaction times on subsequently presented targets showed the expected pattern of facilitation and inhibition in both conditions. No difference in brain activity was observed when the two orienting conditions were contrasted with a liberal threshold, showing that both forms of orienting were mediated by the same neural network. Compared to within-block control trials, both endogenous and exogenous orienting activated a fronto-parietal network consisting of premotor cortex, posterior parietal cortex, medial frontal cortex and right inferior frontal cortex. Within these regions, equally strong activation was observed for both orienting conditions. It is concluded that endogenous and exogenous orienting are mediated by the same large-scale network of frontal and parietal brain areas.