Effective connectivity during haptic perception: a study using Granger causality analysis of functional magnetic resonance imaging data

Although it is accepted that visual cortical areas are recruited during touch, it remains uncertain whether this depends on top-down inputs mediating visual imagery or engagement of modality-independent representations by bottom-up somatosensory inputs. Here we addressed this by examining effective connectivity in humans during haptic perception of shape and texture with the right hand. Multivariate Granger causality analysis of functional magnetic resonance imaging (fMRI) data was conducted on a network of regions that were shape- or texture-selective. A novel network reduction procedure was employed to eliminate connections that did not contribute significantly to overall connectivity. Effective connectivity during haptic perception was found to involve a variety of interactions between areas generally regarded as somatosensory, multisensory, visual and motor, emphasizing flexible cooperation between different brain regions rather than rigid functional separation. The left postcentral sulcus (PCS), left precentral gyrus and right posterior insula were important sources of connections in the network. Bottom-up somatosensory inputs from the left PCS and right posterior insula fed into visual cortical areas, both the shape-selective right lateral occipital complex (LOC) and the texture-selective right medial occipital cortex (probable V2). In addition, top-down inputs from left postero-supero-medial parietal cortex influenced the right LOC. Thus, there is strong evidence for the bottom-up somatosensory inputs predicted by models of visual cortical areas as multisensory processors and suggestive evidence for top-down parietal (but not prefrontal) inputs that could mediate visual imagery. This is consistent with modality-independent representations accessible through both bottom-up sensory inputs and top-down processes such as visual imagery.     

Changes in hippocampal connectivity in the early stages of Alzheimer's disease: evidence from resting state fMRI

A selective distribution of Alzheimer's disease (AD) pathological lesions in specific cortical layers isolates the hippocampus from the rest of the brain. However, functional connectivity between the hippocampus and other brain regions remains unclear in AD. Here, we employ a resting state functional MRI (fMRI) to examine changes in hippocampal connectivity comparing 13 patients with mild AD versus 13 healthy age-matched controls. Hippocampal connectivity was investigated by examination of the correlation between low frequency fMRI signal fluctuations in the hippocampus and those in all other brain regions. We found that functional connectivity between the right hippocampus and a set of regions was disrupted in AD; these regions are: medial prefrontal cortex (MPFC), ventral anterior cingulate cortex (vACC), right inferotemporal cortex, right cuneus extending into precuneus, left cuneus, right superior and middle temporal gyrus and posterior cingulate cortex (PCC). We also found increased functional connectivity between the left hippocampus and the right lateral prefrontal cortex in AD. In addition, rightward asymmetry of hippocampal connectivity observed in elderly controls was diminished in AD patients. The disrupted hippocampal connectivity to the MPFC, vACC and PCC provides further support for decreased activity in "default mode network" previously shown in AD. The decreased connectivity between the hippocampus and the visual cortices might indicate reduced integrity of hippocampus-related cortical networks in AD. Moreover, these findings suggest that resting-state fMRI might be an appropriate approach for studying pathophysiological changes in early AD.     

fMRI during natural sleep as a method to study brain function during early childhood

Many techniques to study early functional brain development lack the whole-brain spatial resolution that is available with fMRI. We utilized a relatively novel method in which fMRI data were collected from children during natural sleep. Stimulus-evoked responses to auditory and visual stimuli as well as stimulus-independent functional networks were examined in typically developing 2-4-year-old children. Reliable fMRI data were collected from 13 children during presentation of auditory stimuli (tones, vocal sounds, and nonvocal sounds) in a block design. Twelve children were presented with visual flashing lights at 2.5 Hz. When analyses combined all three types of auditory stimulus conditions as compared to rest, activation included bilateral superior temporal gyri/sulci (STG/S) and right cerebellum. Direct comparisons between conditions revealed significantly greater responses to nonvocal sounds and tones than to vocal sounds in a number of brain regions including superior temporal gyrus/sulcus, medial frontal cortex and right lateral cerebellum. The response to visual stimuli was localized to occipital cortex. Furthermore, stimulus-independent functional connectivity MRI analyses (fcMRI) revealed functional connectivity between STG and other temporal regions (including contralateral STG) and medial and lateral prefrontal regions. Functional connectivity with an occipital seed was localized to occipital and parietal cortex. In sum, 2-4 year olds showed a differential fMRI response both between stimulus modalities and between stimuli in the auditory modality. Furthermore, superior temporal regions showed functional connectivity with numerous higher-order regions during sleep. We conclude that the use of sleep fMRI may be a valuable tool for examining functional brain organization in young children.     

Involvement of multiple functionally distinct cerebellar regions in visual discrimination: a human functional imaging study

We investigated the contribution of the human cerebellum to cerebral function during visual discrimination using PET and fMRI. The cognitive task was a successive discrimination of shades of brown with a parametric variation of the stimulus presentation rate and a constant task difficulty. The successive color discrimination task was contrasted to a dimming detection control task, with identical retinal input but with double the number of motor responses. Three sets of activated cerebellar and cerebral regions were observed: rate-dependent and rate-independent color discrimination networks and a motor-and-detection network. The rate-dependent color discrimination network included both an anterior and a posterior activation site in lobule-VI of the two lateral cerebellar hemispheres, whereas the rate-independent network involved a bilateral activation site in lateral Crus-I. Cerebellar sites of the motor-and-detection network were located in medial lobule-V bilaterally, in the vermis, and in posterior left Crus-I and right Crus-II. An additional fMRI study was performed to control for differences in motor output and response timing between the tasks. In this control study, the cerebellar activation sites of the rate-dependent and rate-independent color discrimination networks remained unaltered. The motor-and-detection network included cerebellar activations in posterior left Crus-I and right Crus-II, but none in lobule-V or the vermis. Thus, cerebellar activation sites of the motor-and-detection network could be subdivided into those related to a motor network and those belonging to a dimming detection network. We conclude that successive color discrimination activates multiple, functionally distinct cerebellar regions.     

Multisensory speech perception without the left superior temporal sulcus

Converging evidence suggests that the left superior temporal sulcus (STS) is a critical site for multisensory integration of auditory and visual information during speech perception. We report a patient, SJ, who suffered a stroke that damaged the left tempo-parietal area, resulting in mild anomic aphasia. Structural MRI showed complete destruction of the left middle and posterior STS, as well as damage to adjacent areas in the temporal and parietal lobes. Surprisingly, SJ demonstrated preserved multisensory integration measured with two independent tests. First, she perceived the McGurk effect, an illusion that requires integration of auditory and visual speech. Second, her perception of morphed audiovisual speech with ambiguous auditory or visual information was significantly influenced by the opposing modality. To understand the neural basis for this preserved multisensory integration, blood-oxygen level dependent functional magnetic resonance imaging (BOLD fMRI) was used to examine brain responses to audiovisual speech in SJ and 23 healthy age-matched controls. In controls, bilateral STS activity was observed. In SJ, no activity was observed in the damaged left STS but in the right STS, more cortex was active in SJ than in any of the normal controls. Further, the amplitude of the BOLD response in right STS response to McGurk stimuli was significantly greater in SJ than in controls. The simplest explanation of these results is a reorganization of SJ's cortical language networks such that the right STS now subserves multisensory integration of speech.     

Oscillatory MEG response to human locomotion is modulated by periventricular lesions

Veridical processing of biological movement is of immense value for adaptive behavior and social communication. Here we ask whether and, if so, how oscillatory cortical magnetoencephalographic (MEG) response to biological motion is modulated by early damage to periventricular regions that might affect the pathways interconnecting subcortical structures with cortex and cortico-cortical connectivity. The visual sensitivity to biological motion was lower in adolescents with periventricular leukomalacia (PVL). In controls, the evoked oscillatory MEG response (26.5 Hz) to biological motion peaked at a latency of 170 ms over the right temporo-parietal cortex. This increase was absent in PVL patients. By contrast, peaks in the oscillatory response to biological motion of lower frequency (23.5 Hz) were found in PVL patients later, at a latency of 290 ms over the left temporal region. The findings provide the first evidence for modulation of oscillatory cortical activity by periventricular lesions. The data suggest that PVL affects the brain connectivity with the right temporo-parietal cortex leading to disintegration of the neural network engaged in biological motion processing.     

静息态fMRI观察遗忘型轻度认知障碍患者长-短程功能连接

目的 分析遗忘型轻度认知障碍（aMCI）患者长、短程功能连接的变化。方法 采集37例aMCI患者（aMCI组）和40名认知功能正常志愿者（对照组）的静息态fMRI数据,以GRETNA软件自动计算完成全脑长程和短程功能连接,比较2组间差异。结果 与对照组比较,aMCI组长程功能连接减低的脑区主要位于双侧楔前叶/中后扣带回、右侧中央沟盖,长程功能连接增强的脑区主要分布于双侧中央前回、左侧颞极/颞中回、左侧直回、右侧眶内额上回、左侧眶内额下回;其短程功能连接减低脑区位于左侧岛叶,短程功能连接增强脑区主要包括左侧颞极/颞上回、左侧颞中回、左侧直回、左侧眶内额下回、右侧海马、右侧颞上回、右侧额中回、右侧辅助运动区及左侧中央后回/楔前叶。结论 aMCI组患者脑长、短程功能连接模式均有所改变,有助于理解aMCI患者脑网络改变的病理生理机制。     

单纯脊髓受累型多发性硬化患者视觉网络的脑功能及结构研究

目的 联合应用静息态功能MRI(RS-fMRI)及基于体素的形态学(VBM)方法探讨单纯脊髓受累型多发性硬化患者(MS-SSCI)脑功能与结构改变。方法 对19例MS-SSCI(MS-SSCI组)及18名年龄、性别相匹配志愿者(对照组)行3D T1WI及RS-fMRI,用独立成分分析法(ICA)提取并比较2组视觉网络功能成分的差异;再用VBM方法对比2组FC有差异脑区及全脑的体积,分析MS-SSCI功能、结构参数与临床扩展残疾状态量表评分及病程的相关性。结果 与对照组相比,MS-SSCI组左侧小脑6区功能连接值明显减低,左侧枕中回、右侧楔叶、左侧楔前叶、左侧额中回功能连接值明显升高;MS-SSCI组全脑体积无明显差异,右侧楔叶,左侧楔前叶体积明显萎缩(P<0.01)。MS-SSCI右侧楔叶的功能连接值与病程呈正相关(r=0.507,P=0.027)。结论 RS-fMRI和VBM方法显示MS-SSCI视觉网络存在功能和结构异常。     

阿尔茨海默病患者静息态下磁共振成像对小脑功能评估价值

【目的】应用静息态功能磁共振成像技术(fMRI)观察阿尔茨海默病(Alzheimer's disease,AD)患者,轻度认知功能障碍(mild cognition impairment,MCI)和正常人静息态下小脑齿状核功能连接改变的差异。【方法】对19例 AD 患者,16例 MCI 患者及19例正常对照者在静息态下行 fMRI 检查。以双侧齿状核为感兴趣区,对功能连接的相关系数进行双样本 t 检验,比较不同组别小脑功能连接改变的差异。【结果】AD 组小脑齿状核与左缘上回/顶下小叶、右豆状核、左顶下小叶、双侧前额叶功能连接低于正常对照组,而右颞下回、双侧枕下回、右小脑前叶、右颞中回、右中央前回、左中央后回功能连接高于正常对照组(P <0.05,AlphaSim校正)。【结论】静息态下 AD 及 MCI 患者小脑齿状核功能连接的改变提示小脑在 AD 及 MCI 发病过程中起重要作用。     

The responsiveness of biological motion processing areas to selective attention towards goals

A growing literature indicates that visual cortex areas viewed as primarily responsive to exogenous stimuli are susceptible to top-down modulation by selective attention. The present study examines whether brain areas involved in biological motion perception are among these areas-particularly with respect to selective attention towards human movement goals. Fifteen participants completed a point-light biological motion study following a two-by-two factorial design, with one factor representing an exogenous manipulation of human movement goals (goal-directed versus random movement), and the other an endogenous manipulation (a goal identification task versus an ancillary color-change task). Both manipulations yielded increased activation in the human homologue of motion-sensitive area MT+ (hMT+) as well as the extrastriate body area (EBA). The endogenous manipulation was associated with increased right posterior superior temporal sulcus (STS) activation, whereas the exogenous manipulation was associated with increased activation in left posterior STS. Selective attention towards goals activated a portion of left hMT+/EBA only during the perception of purposeful movement-consistent with emerging theories associating this area with the matching of visual motion input to known goal-directed actions. The overall pattern of results indicates that attention towards the goals of human movement activates biological motion areas. Ultimately, selective attention may explain why some studies examining biological motion show activation in hMT+ and EBA, even when using control stimuli with comparable motion properties.     

美沙酮维持治疗的海洛因成瘾者左侧执行控制网络功能特征的fMRI研究

目的探讨美沙酮维持治疗的海洛因成瘾者左侧执行控制网络功能连接的特点。材料与方法纳入21例美沙酮维持治疗的海洛因成瘾者与20例年龄、性别、教育程度相匹配的健康者,采用3.0 T磁共振设备进行静息态磁共振成像。首先,基于左侧执行控制网络感兴趣区计算全脑功能连接,分析两组间左侧执行控制网络功能连接差异,并进一步分析差异区功能连接值与海洛因吸食史和美沙酮治疗史的相关性。结果与健康组相比,美沙酮维持治疗的海洛因成瘾者的左侧背外侧前额叶与双侧背外侧前额叶功能连接增强(P<0.05,GRF校正),左侧后顶叶与左侧中央后回的功能连接增强。(P<0.05,GRF校正)。上述区域的功能连接强度值与海洛因吸食史和美沙酮治疗史无相关性(P值均>0.05)。结论美沙酮维持治疗的海洛因成瘾者左侧背外侧前额叶与双侧背外侧前额叶功能连接增强可能提示美沙酮有助于改善海洛因成瘾者的大脑执行控制功能,从而降低复吸风险;大脑左后顶叶与中央后回功能连接增强,可能是长期服用海洛因导致的对毒品线索刺激异常适应的表现。     

Understanding the functional neuroanatomy of acquired prosopagnosia

One of the most remarkable disorders following brain damage is prosopagnosia, the inability to recognize faces. While a number of cases of prosopagnosia have been described at the behavioral level, the functional neuroanatomy of this face recognition impairment, and thus the brain regions critically involved in normal face recognition, has never been specified in great detail. Here, we used anatomical and functional magnetic resonance imaging (fMRI) to present the detailed functional neuroanatomy of a single case of acquired prosopagnosia (PS; Rossion, B., Caldara, R., Seghier, M., Schuller, A.-M., Lazeyras, F., Mayer, E., 2003a. A network of occipito-temporal face-sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing. Brain 126, 2381-95; Rossion, B., Joyce, C.A., Cottrell, G.W., Tarr, M.J., 2003b. Early lateralization and orientation tuning for face, word, and object processing in the visual cortex. Neuroimage 20, 1609-24) with normal object recognition. First, we clarify the exact anatomical location and extent of PS' lesions in relation to (a) retinotopic cortex, (b) face-preferring regions, and (c) other classical visual regions. PS' main lesion - most likely causing her prosopagnosia - is localized in the posterior part of the right ventral occipitotemporal cortex. This lesion causes a left superior paracentral scotoma, as frequently observed in cases of prosopagnosia. While the borders of the early visual areas in the left hemisphere could be delineated well, the extensive posterior right-sided lesion hampered a full specification of the cortical representation of the left visual field. Using multiple scanning runs, face-preferring activation was detected within the right middle fusiform gyrus (MFG) in the so-called 'fusiform face area' ('FFA'), but also in the left inferior occipital gyrus (left 'OFA'), and in the right posterior superior temporal sulcus (STS). The dorsal part of the lateral occipital complex (LOC) and the human middle temporal cortex (hMT+/V5) were localized bilaterally. The color-preferring region V4/V8 was localized only in the left hemisphere. In the right hemisphere, the posterior lesion spared the ventral part of LOC, a region that may be critical for the preserved object recognition abilities of the patient, and the restriction of her deficit to the category of faces. The presumptive functions of both structurally damaged and preserved regions are discussed and new hypotheses regarding the impaired and preserved abilities of the patient during face and non-face object processing are derived. Fine-grained neurofunctional analyses of brain-damaged single cases with isolated recognition deficits may considerably improve our knowledge of the brain regions critically involved in specific visual functions, such as face recognition.     

复发性孤立性视神经炎患者初级视觉皮层功能连接的静息态fMRI

目的 采用静息态功能磁共振成像（rs-fMRI）技术,观察复发性孤立性视神经炎（RION）患者初级视觉皮层（V1）与全脑功能连接的改变。方法 收集45例RION患者（RION组）及45名年龄、性别相匹配的健康志愿者（正常对照组）的临床资料,并行常规头部MRI及rs-fMRI,选取V1为种子点,采用统计参数图5（SPM5）分析其与全脑的功能连接,比较两组数据的差异,并将RION组功能连接异常的脑区与其视力、病程及认知功能评分（PASAT）进行相关性分析。结果 与正常对照组相比,RION组左侧额中回、双侧枕叶舌回、右侧颞中回及右侧顶下小叶与V1的功能连接明显减低;双侧楔前叶、右侧额前回、左侧顶下小叶及右侧岛叶与V1的功能连接明显增强,且差异均有统计学意义（P均<0.01）。右侧顶下小叶及右侧额前回的功能连接异常与PASAT评分呈正相关;左侧额中回的功能连接异常与患者视力呈正相关。结论 rs-fMRI可检测出RION患者与V1区功能连接异常的脑区,并且显示与视力、病程及认知功能评分相关的脑区,可为临床探索RION功能连接异常提供客观依据。     

静息态磁共振功能连接方法的多模态应用

目的 探讨度中心度(DC)、镜像组织功能连接(VMHC)和基于感兴趣区的功能连接(ROI-FC)3种多模态静息态磁共振功能连接类数据处理方法在反映脑功能信息中的价值.方法 采集10名正常志愿者和10例亚急性期脑桥梗死患者的静息态fMRI数据.首先采用DC和VMHC对数据进行预分析,获得梗死患者脑功能显著改变的脑区作为ROI,然后采用ROI-FC分析梗死患者脑功能网络的改变.结果 采用DC未得到有意义的结果,VMHC发现患者左右顶下小叶/角回功能连接显著降低,以此为ROI,ROI-FC发现患者右楔前叶、左顶下小叶、左右颞中回、左右额中回功能连接降低,左额中回/中央前回、左额上回和右扣带回后部/楔前叶的功能连接增强.结论 综合应用DC、VMHC和ROI-FC 3种静息态fMRI功能连接类数据处理方法,可发现脑桥梗死患者相关的脑功能网络紊乱,为脑梗死的临床研究提供有价值的信息.     

Processing social aspects of human gaze: a combined fMRI-DTI study

Human gaze is a critical social cue that can reveal intentions and dispositions of others. The right posterior superior temporal sulcus (pSTS) is thought to be critically involved in processing eye gaze information. We combined diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) to identify direct neural connections of right pSTS and to determine how these connections are modulated by the social significance of perceived gaze shifts. Participants saw faces with direct or averted gaze during event-related fMRI. Half of these faces remained static, and half displayed a dynamic gaze shift either towards or away from the subject. Social attention (dynamic gaze shifts towards the observer) not only increased activity in right pSTS, but also its functional connectivity with the right anterior insula (aIns) and right fusiform gyrus (FG). However, direct fiber connections from pSTS were demonstrated by DTI for the right aIns, but not the right FG. Moreover, the right FG responded to eye motion irrespective of direction and social significance; whereas the right aIns was selectively sensitive to social significance (i.e. gaze shifts towards the observer), but not generally to eye motion. We conclude that the social aspects of mutual gaze contact are processed by direct fiber pathways between right pSTS and right aIns; whereas increased connectivity with FG could reflect an enhanced perceptual analysis of changing facial features in dynamic gaze conditions and involves indirect fiber pathways with pSTS, perhaps via motion-selective regions in middle temporal (MT) gyrus that exhibited strong white-matter connections with both pSTS and FG and could thus provide inputs to these two areas.     

Wernicke-Geschwind语言模型的fMRI初步检验

目的利用fMRI方法检验经典的Wernicke-Geschwind语言模型.方法以Block Design设计模式,对10名正常中国人的听觉性语言(词语水平)功能进行BOLD磁共振脑功能成像,并与经典的Wernicke-Geschwind语言模型进行比较与检验.结果所有受试者均完成了实验要求,且头动范围小于1个像素大小.语言任务激活的脑区包括:双侧颞上回、双侧运动区(前后运动区及辅助运动区)、双侧小脑半球及视皮层,左侧颞横回、左侧角回,右侧颞中回及以及扣带回后部.结论经典的语言模型存在较明显的不足与缺陷,需要进一步完善.     

膝骨性关节炎患者脑结构和功能变化的多模态MRI

目的 联合基于体素的形态学测量（VBM）技术和静息态功能磁共振成像（rs-fMRI）技术探究膝骨性关节炎（KOA）患者静息状态下脑灰质体积、脑神经元活动强度及基于种子点的功能连接强度改变,综合分析KOA相关异常脑网络。方法 前瞻性收集30例KOA患者（KOA组）及30例健康人（HC组）的3D高分辨率T1WI像和rs-fMRI图像,采用VBM、低频振幅、功能连接3种方法分析两组间脑灰质结构和功能数据差异。结果 与HC组相比,KOA组双侧梭状回、右侧颞中回低频振幅值增高,右侧楔前叶、右侧内侧前额叶皮质、左侧额中回低频振幅值减低（体素水平P<0.005,团块水平P<0.05）;右侧楔前叶、右侧顶下小叶、右侧初级视觉皮层、左侧颞中回、左侧中央后回灰质体积减小（体素水平P<0.002,团块水平P<0.05）;以右侧楔前叶为种子点,与右侧颞中回的功能连接增强,与左侧前扣带回、左侧背外侧前额叶皮质的功能连接降低（体素水平P<0.005,团块水平P<0.05）。结论KOA患者感知皮层系统及联合皮层系统阵营均存在血氧水平依赖信号及灰质微结构的改变且有重叠,主要涉及视觉...     

Neural networks for short-term memory for order differentiate high and low proficiency bilinguals

Short-term memory (STM) for order information, as compared to STM for item information, has been shown to be a critical determinant of language learning capacity. The present fMRI study asked whether the neural substrates of order STM can serve as markers for bilingual language achievement. Two groups of German–French bilinguals differing in second language proficiency were presented STM tasks probing serial order or item information. During order STM but not item STM tasks, the high proficiency group showed increased activation in the lateral orbito-frontal and the superior frontal gyri associated with updating and grouped rehearsal of serial order information. Functional connectivity analyses for order encoding showed a functional network involving the left IPS, the right IPS and the right superior cerebellum in the high proficiency group while the low proficiency group showed enhanced connectivity between the left IPS and bilateral superior temporal and temporo-parietal areas involved in item processing. The present data suggest that low proficiency bilinguals activate STM networks for order in a less efficient and differentiated way, and this may explain their poorer storage and learning capacity for verbal sequences.     

帕金森病静息状态下纹状体功能连接的fMRI研究

目的应用血氧水平依赖的功能性磁共振成像研究帕金森病(Parkinson's disease,PD)静息状态下功能连接的改变。材料与方法对35例符合PD诊断标准的患者及20名健康者行静息态脑功能性磁共振成像,选双侧纹状体(striaum,STR)为感兴趣区,采用双样本t检验分别比较左侧STR(L-STR)、右侧STR(R-STR)在两组间的脑功能连接的差异。结果 (1)以L-STR为种子点时,PD组右侧前额叶背外侧部、双侧后扣带回皮质、左侧中央前后回、顶下小叶、左侧楔前叶、左侧缘上回等脑区的正连接较正常组减弱(P0.05,Alpha Sim校正),额下回、海马旁回、左侧海马、左侧岛叶正连接增强(P0.05,Alpha Sim校正)。(2)以R-STR为种子点时,PD组右侧前额叶背外侧部、双侧后扣带回皮质等脑区正连接较正常组减弱(P0.05,Alpha Sim校正),右侧舌回、岛叶、海马旁回、双侧海马、左侧丘脑等脑区正连接增强(P0.05,Alpha Sim校正)。结论静息状态下PD患者的脑功能连接网络存在异常。