视觉反馈增益对力量输出影响的fMRI研究

目的 运用全脑fMRI技术研究视觉反馈增益在运动功能执行中的调节作用.方法 设计快、慢两种变化速度的力量跟踪任务,在高低不同的两种视觉反馈增益下令15名正常受试者做右手握力运动,同时接受BOLD-fMRI扫描;采用t检验分析获得不同运动状态与静息状态信号对比的脑功能图,对比观察脑皮层兴奋区的异同.结果 四种模式握力运动均可激活初级躯体感觉运动区(SMC)、双侧前运动区(PMC)、辅助运动区(SMA)、小脑、基底节(BG)和对侧后顶叶(PPC)等.随着反馈增益的提高:S1、PPC、PMC、小脑等激活强度、范围均降低,BG恰好相反;SMA激活强度提高但范围缩小,M1表现不明显.结论 视觉反馈增益对力量输出有显著影响,不同增益所激活的脑区不同.PPC、PMC、小脑、基底节等参与调节过程.     

运动准备和运动执行活动空间分布的功能磁共振成像研究

目的:利用功能磁共振成像技术(fMRI),研究大脑皮质运动系统运动准备和执行活动的空间分布。方法:采用组块设计,分别对受试者执行实际运动和想象运动时的脑活动进行fMRI扫描,并运用多重回归分析和一般线性检验相结合的方法对运动准备和执行成分的空间分布进行分析。结果:大脑皮质运动系统各运动相关区均不是单一功能区,而是同时参与运动准备和执行两种成分;这两种成分各脑区的分布也不是均一的或者杂乱无章的,而是呈特征性梯度分布:其中辅助运动区(SMA)和运动前区(PMC)自前至后、后顶叶皮质(PPC)自后至前,其参与运动准备的程度越来越低,参与运动执行的程度越来越高。结论:组成大脑皮质运动系统的各随意运动脑区都不是孤立的功能单元,而是一个个同时包含运动执行和准备成分、并具有一定层次的功能子系统;大脑皮质运动系统实际上就是由这些功能上紧密相连的并行加工的子系统组成。     

运动准备和运动执行活动空间分布的功能磁共振成像研究

目的：利用功能磁共振成像技术(fMRI)，研究大脑皮质运动系统运动准备和执行活动的空间分布。方法：采用组块设计，分别对受试者执行实际运动和想象运动时的脑活动进行fMRI扫描，并运用多重回归分析和一般线性检验相结合的方法对运动准备和执行成分的空间分布进行分析。结果：大脑皮质运动系统各运动相关区均不是单一功能区，而是同时参与运动准备和执行两种成分；这两种成分各脑区的分布也不是均一的或者杂乱无章的，而是呈特征性梯度分布：其中辅助运动区(SMA)和运动前区(PMC)自前至后、后顶叶皮质(PPC)自后至前，其参与运动准备的程度越来越低，参与运动执行的程度越来越高。结论：组成大脑皮质运动系统的各随意运动脑区都不是孤立的功能单元，而是一个个同时包含运动执行和准备成分、并具有一定层次的功能子系统；大脑皮质运动系统实际上就是由这些功能上紧密相连的并行加工的子系统组成。     

正常人手指简单运动时脑功能区被激活的SPECT脑血流研究

目的运用单光子发射断层扫描仪(SPECT)对比观察不同年龄组正常人执行手指简单运动时脑内不同感兴趣区(ROI)的血流量变化,以期探讨运动功能区的作用。方法健康的志愿者18例,按照年龄划分为青年组和中老年组。每一受试对象分别安静和执行手指简单运动状态下进行99mTcECDSPECT扫描脑血流量测定。结果两组间的运动频率无明显差异,但中老年组的错误率显著高于青年组。运动激活后各脑叶的局部血流量无明显变化,而对侧初级运动区(M1)、同侧小脑、双侧辅助运动区(SMA)血流量显著变化。两组间相比,中老年组的对侧M1、同侧小脑的血流量增加低于年轻组,而双侧SMA则大于青年组(P<0.05)。结论手指的简单运动主要激活对侧M1、同侧小脑、双侧SMA;中老年组的SMA激活比青年组明显,显示中、老年人通过自身代偿机制调动更多的SMA参与运动的启动与执行。     

缺血性脑卒中患者患手主动运动及被动运动时的功能性磁共振研究

目的观察缺血性脑卒中患者患手执行主动及被动运动时的脑激活模式,探讨主动运动和被动运动治疗脑卒中后手功能障碍的中枢机制。 方法对5例左侧大脑皮质下脑卒中患者患手执行主动及被动抓握-释放动作,执行动作期间采用血氧水平依赖性功能性磁共振（BOLD-fMRI）进行脑扫描,利用SPM5软件对上述患者试验数据进行分析,使用XJVIEW toolbox 8.11版软件得出入选患者在上述两种运动状态下的脑激活区分布图,并对其在不同运动状态下的脑激活模式特点进行分析比较。 结果入选患者患手在执行主动运动时其脑激活部位主要位于对侧感觉运动区(SMC)、运动前区(PMC)、双侧小脑及双侧辅助运动区(SMA),另外同侧SMC及PMC区也有轻度激活;激活脑区主要位于对侧大脑及小脑半球。患手执行被动运动时的脑激活部位主要位于双侧SMC、PMC区、双侧小脑、SMA区;激活脑区平均分布于两侧大脑及小脑半球。与患手主动运动比较,患手被动运动时的脑区激活范围较广泛,激活强度也较高。 结论患手执行主动运动和被动运动均可激活脑卒中患者运动相关脑区,提示对脑卒中患者进行主动运动及被动运动均可促进其脑功能重组。     

基于fMRI功能连接度分析正常人相关脑区在运动过程中的参与程度

目的 在运动及静息两种状态下,观察初级运动区(M1)与其他运动相关区域之间功能连接程度,分析特定功能区在运动执行过程中的作用.方法 选取6名正常人作为研究对象,进行血氧水平依赖功能磁共振成像(BOLD-fMRI)检查.功能成像分为静息功能、右手运动功能、左手运动功能三部分.运动功能采用Block设计,采取手指顺序对指任务.扫描结果 采用统计参数图 (SPM2)进行数据分析和脑功能区定位.功能连接度采用时间相关算法,选取运动任务时对应的最强激活点(均为一侧M1区)作为种子点,分别在静息功能数据和运动功能数据中将该种子区与相应全脑做相关分析,计算不同脑区与种子区之间的相关性,以Z值反映其功能连接程度,并观察同一脑区在运动及静息两种状态下与种子点之间Z值的变化.结果 在静息状态下,与种子点相关联的区域为双侧躯体感觉运动区(SMC)、辅助运动区(SMA)及同侧顶上小叶(SPL);在运动状态下,与种子点相关联的区域为双侧SMC、SMA、同侧SPL及小脑前叶(ALC);在运动状态下双侧SMC及SMA之间功能联系的Z值较静息状态下普遍增大.结论 静息状态下双侧SMC、SMA及同侧SPL之间存在比较稳定的功能联系;运动状态下双侧SMC及SMA之间功能联系增强.运动肢体同侧ALC参与运动任务的执行,但不参与静息状态下运动区之间的功能连接.     

完全性脊髓损伤亚急性期脑运动控制功能变化的功能磁共振研究

目的 探讨完全性脊髓损伤患者脑运动控制功能的变化情况。方法 2017年1月至2019年1月,病程3~6个月完全性脊髓损伤患者11例与健康人12例,在试图/实际运动、意象运动(MI)任务下行功能磁共振成像(fMRI)扫描,观察不同运动任务引发激活效应的空间分布和信号强度。结果 患者试图运动时的脑激活区域显著多于健康人实际运动时的激活区域,包括双侧初级感觉/运动皮质(S1/M1)、辅助运动区(SMA)、外侧苍白球(PA)、小脑、左侧丘脑和壳核等。健康人意象运动的比较,患者激活簇主要存在于右M1、SMA、背侧运动前区(PMd)、左SMA、岛叶和基底核。患者试图运动比意象运动在左M1、双SMA、扣带回运动区和右小脑诱发更多的兴奋。结论 亚急性期完全性脊髓损伤患者执行运动任务时,M1、SMA的兴奋模式基本正常,顶叶和小脑等感觉运动整合区域激活增加,提示发生适应性重组。     

基于fMRI的力量调节速度相关神经兴奋模式的初步研究

目的研究视觉引导的握力运动力量调节速度快慢所激活脑功能区的异同。方法15例正常受试者右手进行四种模式（由视觉反馈增益和力量变化速度两个因素组合而成）握力运动，同时进行BOLD fMRI扫描，比较四种模式脑激活的异同。结果四种模式握力运动均可激活初级躯体感觉运动区（SMC），双侧前运动区（PMC）、辅助运动区（SMA）、小脑、基底节（BG），对侧后顶叶（PPC），Brodmann 40等。其中，随着力量调节速度的提高，SMC激活强度、范围都提高，而BG恰好相反，SMA激活强度提高但范围缩小，小脑表现不明显。结论SMC对力量输出的快速调节作用明显；PPC，PMC参与了将视觉信息转化成力量输出这一过程；BG在快速运动时受到SMC、SMA的制约。     

fMRI评价正常老年人腕关节被动运动下脑激活区

目的 用功能磁共振技术观察正常老年人双侧腕关节被动运动时脑区激活情况.方法 对30例正常的右利手老年受试者分别进行双侧腕关节被动运动的功能MR扫描,采用SPM2软件进行数据分析和脑功能区定位.结果 利手(右手)运动主要激活对侧感觉运动皮质、运动前区,双侧辅助运动区、后顶叶及同侧小脑;非利手运动时除激活上述脑区外,还激活了同侧运动感觉区和对侧小脑,且对侧运动前区、双侧辅助运动区和同侧小脑的激活体积明显大于利手腕关节运动.结论 被动运动依赖于大脑皮质和小脑等许多与运动相关的脑功能区的参与;与利手腕关节运动相比,非利手腕关节运动更依赖于对侧PMC、双侧SMA和同侧小脑等运动区.     

脑梗死患者脑功能重组的功能性磁共振成像研究

目的利用血氧水平依赖功能性磁共振成像（fMRI）技术研究恢复期脑梗死患者运动相关皮质的激活代偿情况，探讨脑梗死后脑功能重组的规律。 方法选取16例初发单侧放射冠和/或基底核区脑梗死患者作为研究对象，其中男12例，女4例；年龄37～80岁，平均（61.0±11.3）岁；病程1～3月，平均 1.7个月。每位患者依次进行患侧、健侧腕关节被动屈伸运动，同时对患者进行fMRI检查。所得数据采用SPM2软件包进行离线后处理，比较所有患者健侧及患侧腕关节被动运动时大脑皮质激活情况。 结果脑梗死患者患侧腕关节被动运动时较健侧运动时激活大脑皮质区域更多、范围更广，其中患侧腕关节被动运动时激活脑区特点如下：①主要运动皮质区（M1）激活缺失，仅4例出现对侧M1区激活，有5例出现同侧M1区激活；②非主要运动区明显激活，包括运动前区（PMC）、补充运动区（SMA）、扣带回运动区(CMA)、顶下小叶(IPL)、前额叶皮质(PFC)及小脑（CRB）等，并呈现双侧激活现象。健侧腕关节被动运动时主要激活对侧第一运动区（M1）、第一感觉区（S1）以及同侧CRB，有少数出现PMC、SMA、CMA及IPL激活，但均以对侧脑区激活为主。 结论脑梗死后大脑皮质功能发生代偿性改变，包括主要运动区激活缺失，非主要运动区激活增加，并且运动区发生移位，有向周围扩展的趋势，另外还可见非运动区激活。     

Evaluation of the effective connectivity of supplementary motor areas during motor imagery using Granger causality mapping

Brain activation during motor imagery has been studied extensively for years, but only a few of these studies focused on investigating the effective connectivity in the brain. The existence of interactions or closed loop circuits between the SMA and other brain regions during motor imagery still remains unclear. In the present study, selecting the SMA as the region of interest, we used the Granger causality mapping (GCM) method to explore the effective connectivity in the brain during motor imagery. Our results demonstrated that more brain regions showed effective connections to the SMA during the right-hand motor imagery than during the left-hand motor imagery, but the strength of the casual influence during the left-hand motor imagery was stronger than that of the right-hand motor imagery. We further found forward and backward effective connectivity between the SMA and three regions, including the bilateral dorsal premotor area (PMd), the contralateral primary and secondary somatosensory cortex (S1), and the primary motor cortex (M1). these results might indicate how the brain regions were inter-activated during motor imagery.     

Cortical activity in multiple motor areas during sequential finger movements: an application of independent component analysis

Multiple cortical regions such as the supplementary motor area (SMA), premotor cortex (PM), and primary motor cortex (M1) are involved in the sequential execution of hand movements, but it is unclear how these areas collaborate in the preparation and execution of ipsilateral and contralateral hand movements. In this study, we used right-handed subjects to examine the spatial distribution and temporal profiles of motor-related activity during visually cued sequential finger movements by applying independent component analysis (ICA) to event-related functional magnetic resonance imaging (fMRI) signals. The particular merit of the ICA method is that it allows brain activity in individual subjects to be elucidated without making a priori assumptions about the anatomical areas that are activated or the temporal profile of activity. By applying ICA, we found that (1) the SMA contributed to both the preparation and execution of movements of the right and left hand; (2) the left M1 and dorsal premotor cortex (PMd) contributed to both the preparation and execution of movements of the right and left hand, whereas the right M1 and PMd contributed mainly to the execution of movements of the left hand; (3) pre-SMA areas were activated in some subjects in concert with the posterior parietal and prefrontal cortex; and (4) fMRI signals over superficial cortical draining veins could be distinguished from cortical activation. We suggest that ICA is useful for categorizing distributed task-related activities in individual subjects into several spatially independent activities that represent functional units in motor control.     

The role of higher-order motor areas in voluntary movement as revealed by high-resolution EEG and fMRI

In the human motor cortex structural and functional differences separate motor areas related to motor output from areas essentially involved in higher-order motor control. Little is known about the function of these higher-order motor areas during simple voluntary movement. We examined a simple finger flexion movement in six healthy subjects using a novel brain-imaging approach, integrating high-resolution EEG with the individual structural and functional MRI. Electrical source reconstruction was performed in respect to the individual brain morphology from MRI. Highly converging results from EEG and fMRI were obtained for both executive and higher-order motor areas. All subjects showed activation of the primary motor area (MI) and of the frontal medial wall motor areas. Two different types of medial wall activation were observed with both methods: Four of the subjects showed an anterior type of activation, and two of the subjects a posterior type of activation. In the former, activity started in the anterior cingulate motor area (CMA) and subsequently shifted its focus to the intermediate supplementary motor area (SMA). Approximately 120 ms before the movement started, the intermediate SMA showed a drop of source strength, and simultaneously MI showed an increase of source strength. In the posterior type, activation was restricted to the posterior SMA. Further, three of the subjects investigated showed activation in the inferior parietal lobe (IPL) starting during early movement preparation. In all subjects showing activation of higher-order motor areas (anterior CMA, intermediate SMA, IPL) these areas became active before the executive motor areas (MI and posterior SMA). We suggest that the early activation of the anterior CMA and the IPL may be related to attentional functions of these areas. Further, we argue that the intermediate part of the SMA triggers the actual motor act via the release of inhibition of the primary motor area. Our results demonstrate that a noninvasive, multimodal brain imaging technique can reveal individual cortical brain activity with high temporal and spatial resolution, independent of a priori physiological assumptions.     

Measuring temporal dynamics of functional networks using phase spectrum of fMRI data

We present a novel method to measure relative latencies between functionally connected regions using phase-delay of functional magnetic resonance imaging data. Derived from the phase component of coherency, this quantity estimates the linear delay between two time-series. In conjunction with coherence, derived from the magnitude component of coherency, phase-delay can be used to examine the temporal properties of functional networks. In this paper, we apply coherence and phase-delay methods to fMRI data in order to investigate dynamics of the motor network during task and rest periods. Using the supplementary motor area (SMA) as a reference region, we calculated relative latencies between the SMA and other regions within the motor network including the dorsal premotor cortex (PMd), primary motor cortex (M1), and posterior parietal cortex (PPC). During both the task and rest periods, we measured significant delays that were consistent across subjects. Specifically, we found significant delays between the SMA and the bilateral PMd, bilateral M1, and bilateral PPC during the task condition. During the rest condition, we found that the temporal dynamics of the network changed relative to the task period. No significant delays were measured between the SMA and the left PM and left M1; however, the right PM, right M1, and bilateral PPC were significantly delayed with respect to the SMA. Additionally, we observed significant map-wise differences in the dynamics of the network at task compared to the network at rest. These differences were observed in the interaction between the SMA and the left M1, left superior frontal gyrus, and left middle frontal gyrus. These temporal measurements are important in determining how regions within a network interact and provide valuable information about the sequence of cognitive processes within a network.     

Reduction of intractable deafferentation pain by navigation-guided repetitive transcranial magnetic stimulation of the primary motor cortex

The precentral gyrus (M1) is a representative target for electrical stimulation therapy of pain. To date, few researchers have investigated whether pain relief is possible by stimulation of cortical areas other than M1. According to recent reports, repetitive transcranial magnetic stimulation (rTMS) can provide an effect similar to that of electrical stimulation. With this in mind, we therefore examined several cortical areas as stimulation targets using a navigation-guided rTMS and compared the effects of the different targets on pain. Twenty patients with intractable deafferentation pain received rTMS of M1, the postcentral gyrus (S1), premotor area (preM), and supplementary motor area (SMA). Each target was stimulated with ten trains of 10-s 5-Hz TMS pulses, with 50-s intervals in between trains. Intensities were adjusted to 90% of resting motor thresholds. Thus, a total of 500 stimuli were applied. Sham stimulations were undertaken at random. The effect of rTMS on pain was rated by patients using a visual analogue scale (VAS) and the short form of the McGill Pain Questionnaire (SF-MPQ). Ten of the 20 patients (50%) indicated that stimulation of M1, but not other areas, provided significant and beneficial pain relief (p<0.01). Results indicated a statistically significant effect lasting for 3 hours after the stimulation of M1 (p<0.05). Stimulation of other targets was not effective. The M1 was the sole target for treating intractable pain with rTMS, in spite of the fact that M1, S1, preM, and SMA are located adjacently.     

Dynamic causal modeling of cortical activity from the acute to the chronic stage after stroke

Functional neuroimaging studies frequently demonstrated that stroke patients show bilateral activity in motor and premotor areas during movements of the paretic hand in contrast to a more lateralized activation observed in healthy subjects. Moreover, a few studies modeling functional or effective connectivity reported performance-related changes in the motor network after stroke. Here, we investigated the temporal evolution of intra- and interhemispheric (dys-) connectivity during motor recovery from the acute to the early chronic phase post-stroke. Twelve patients performed hand movements in an fMRI task in the acute (≤72 hours) and subacute stage (2 weeks) post-stroke. A subgroup of 10 patients participated in a third assessment in the early chronic stage (3-6 months). Twelve healthy subjects served as reference for brain connectivity. Changes in effective connectivity within a bilateral network comprising M1, premotor cortex (PMC), and supplementary motor area (SMA) were estimated by dynamic causal modeling. Motor performance was assessed by the Action Research Arm Test and maximum grip force. Results showed reduced positive coupling of ipsilesional SMA and PMC with ipsilesional M1 in the acute stage. Coupling parameters among these areas increased with recovery and predicted a better outcome. Likewise, negative influences from ipsilesional areas to contralesional M1 were attenuated in the acute stage. In the subacute stage, contralesional M1 exerted a positive influence on ipsilesional M1. Negative influences from ipsilesional areas on contralesional M1 subsequently normalized, but patients with poorer outcome in the chronic stage now showed enhanced negative coupling from contralesional upon ipsilesional M1. These findings show that the reinstatement of effective connectivity in the ipsilesional hemisphere is an important feature of motor recovery after stroke. The shift of an early, supportive role of contralesional M1 into enhanced inhibitory coupling might indicate maladaptive processes which could be a target of non-invasive brain stimulation techniques.     

Effects of motor fatigue on human brain activity, an fMRI study

The main purpose of this study was to investigate effects of motor fatigue on brain activation in humans, using fMRI. First, we assessed brain activation that correlated with muscle activity during brief contractions at different force levels (force modulation). Second, a similar analysis was done for sustained contractions inducing motor fatigue. Third, we studied changes in brain activation due to motor fatigue over time. And fourth, we investigated cross-over effects of fatigue by comparing brain activation before and after the fatiguing condition during simple and high-order motor tasks (reaction time tasks). Several motor areas in the brain showed increased activity with increased muscle activity, both during force modulation and motor fatigue. Interestingly, the cerebellum showed a smaller increase in activation, during compensatory activation due to fatigue, while additional activation was found in the pre-supplementary motor area and in a frontal area. During motor fatigue, there was a decrease in force production, an increase in force variability, and an increase in muscle activity. Brain areas comparable with the aforementioned areas also showed stronger activation over time. After fatigue, reaction time task performance remained the same (compared to before fatigue), while increased activation in orbitofrontal areas was found. Furthermore, there was a reduction in subjects' maximal voluntary contraction force, accompanied by a decrease in activation of the supplementary motor area (SMA). These results suggest that especially the activity in the SMA and frontal areas is affected by motor fatigue.     

Transcranial direct current stimulation over the primary motor cortex during fMRI

Measurements of motor evoked potentials (MEPs) have shown that anodal and cathodal transcranial direct current stimulations (tDCS) have facilitatory or inhibitory effects on corticospinal excitability in the stimulated area of the primary motor cortex (M1). Here, we investigated the online effects of short periods of anodal and cathodal tDCS on human brain activity of healthy subjects and associated hemodynamics by concurrent blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) at 3T. Using a block design, 20s periods of tDCS at 1 mA intensity over the left M1 altered with 20s periods without tDCS. In different fMRI runs, the effect of anodal or cathodal tDCS was assessed at rest or during finger tapping. A control experiment was also performed, in which the electrodes were placed over the left and right occipito-temporo-parietal junction. Neither anodal nor cathodal tDCS over the M1 for 20s stimulation duration induced a detectable BOLD signal change. However, in comparison to a voluntary finger tapping task without stimulation, anodal tDCS during finger tapping resulted in a decrease in the BOLD response in the supplementary motor area (SMA). Cathodal stimulation did not result in significant change in BOLD response in the SMA, however, a tendency toward decreased activity could be seen. In the control experiment neither cathodal nor anodal stimulation resulted in a significant change of BOLD signal during finger tapping in any brain area including SMA, PM, and M1. These findings demonstrate that the well-known polarity-dependent shifts in corticospinal excitability that have previously been demonstrated using measurements of MEPs after M1 stimulation are not paralleled by analogous changes in regional BOLD signal. This difference implies that the BOLD signal and measurements of MEPs probe diverse physiological mechanisms. The MEP amplitude reflects changes in transsynaptic excitability of large pyramidal neurons while the BOLD signal is a measure of net synaptic activity of all cortical neurons.