静息态脑功能技术对平衡针治疗中枢机制的分析应用

背景：平衡针治疗疾病疗效显著,但缺乏相关现代科学理论机制。 目的：利用静息态脑功能成像技术探讨平衡针疗法的中枢作用机制。 方法：纳入10例腰椎间盘突出腰腿痛患者及10例正常受试者,于平衡针针刺前后进行功能磁共振扫描,通过AFNI软件对与双侧杏仁核表现为显著联系的脑区进行功能连接分析,并对平衡针刺后腰椎间盘突出患者及正常受试者的脑功能连接的差异进行探讨。 结果与结论：经平衡针治疗后10例腰椎间盘突出患者疼痛均有好转。脑功能连接分析显示腰椎间盘突出患者丘脑、脑干、腹前核、腹外侧核、额内侧回、额上回、额叶眶上回、额下回、颞上回、颞中回、海马回、扣带回、岛叶等脑区功能连接增强。正常受试者双侧颞中回、双侧眶上回、双侧尾状核头、双侧岛叶、左侧腹背侧核、双侧额上回、左侧额中回、前扣带回、右侧顶下小叶与杏仁核连接增强;双侧小脑齿状核、小脑蚓、左侧小脑坡、双侧舌回、左侧枕中回、右侧额上回、右侧中央前回、双侧顶下小叶、右侧顶上小叶、右侧中央后回与杏仁核连接下降。提示通过静息脑功能成像技术对杏仁核的研究有助于更深入理解平衡针灸治疗腰腿痛的中枢机制。     

Involvement of classical anterior and posterior language areas in sign language production, as investigated by 4 T functional magnetic resonance imaging

To investigate the cerebral organization for language production across the particular channels supporting linguistic behavior, a functional magnetic resonance (fMRI) study was conducted in deaf native users of American Sign Language (ASL) and age-matched hearing controls. Seven native ASL speakers and 15 vocal English speaking subjects covertly performed an object naming task inside the 4 T scanner using their native languages ASL or English, respectively. In subjects of both groups, classical language areas were found to be activated, including posterior Broca's area, the anterior insula, premotor cortex, and the posterior parts of the superior temporal cortex. Activations showed a predominance of the left hemisphere for both groups. In the deaf group, however, there was markedly larger involvement of the cerebellum, the inferior frontal gyrus, and the posterior insula and more robust activation in occipito-temporal and superior parietal cortices. In summary, it could be demonstrated by fMRI that native language production using ASL is associated with activation of classical language areas, although the neural organization for language processing is not identical in the two language modalities ASL and English language.     

健康人大脑和小脑空间记忆认知功能的fMRI研究

本研究应用功能磁共振成像(functional magnetic resonance imaging,fMRI)技术,检测了健康人大脑和小脑参与空间记忆的认知过程。通过对10名右利手健康志愿者进行一项短时空间记忆任务作业的同时进行脑功能磁共振扫描,实验采用组块设计,任务与对照任务交替进行,数据采用SPM99软件进行数据分析和脑功能区定位。结果显示:当统计阈值设定为P<0.0001时,大脑皮层和右侧小脑一起被显著激活;大脑皮层所激活的脑区有双侧顶叶的楔前叶、顶上小叶、缘上回(BA7/40,BA:Brodma-nn Area),双侧前额上、中、下回(BA6/9/47),双侧枕叶和枕颞交界处(BA18/19/37),右侧海马回;左侧中脑黑质及被盖部也被激活。上述结果提示:小脑和大脑皮层一起参与了空间记忆的认知过程。     

Parallel cortical networks for volitional control of swallowing in humans

A number of studies have demonstrated the involvement of parallel networks in the control of voluntary sequential motor procedures. We sought to determine whether a parallel network organization may be found for complex, sequentially based motor systems that are the product of both voluntary and automatic control processes. Specifically, we sought to determine whether the cortical organizational scheme for voluntary repetitive swallowing in adult humans is characterized by a hierarchical dual-projection model or by modules organized into parallel systems. We utilized functional magnetic resonance imaging (fMRI) to investigate cortical function during normal swallowing tasks in eight healthy human adults. Subjects performed both dry (saliva) and bolus (3 ml/bolus of water) swallows. Activation during swallowing tasks localized to sensorimotor areas (M1, S1, and SMA), S2, premotor cortex, posterior parietal cortex, cingulate gyrus, inferior frontal gyrus, the cerebellum, the insular cortex, auditory cortex, corpus callosum, and the basal ganglia and thalamus. Principal components analysis (PCA) of these regions revealed five functional clusters or modules: (1) sensorimotor areas and cingulate gyrus; (2) inferior frontal gyrus, S2, corpus callosum, basal ganglia and thalamus; (3) premotor cortex and posterior parietal cortex; (4) cerebellum; and (5) insula. Analysis of the functional relationship between these areas demonstrated two parallel loops defined by connections to either the cerebellum or insula and connected through the sensorimotor-cingulate module. Path analysis was performed to test the hypothesis of modules organized into parallel loops versus a hierarchical dual-projection model consisting of two separate, singular hierarchical serial pathways from the sensorimotor cortex or insula to the thalamus. These results support the model of modules organized into parallel loops (P=0.8), but not the hierarchical dual-projection model (P<0.0001). Organization of the control of voluntary repetitive swallowing into two parallel systems may confer the ability to effectively coordinate and integrate this highly complex sequentially based motor behavior. Electronic Publication     

正常中老年人词语联想任务功能磁共振成像研究

目的 采用功能磁共振成像(fMRI)技术对正常中老年人进行研究,检测与词语联想功能相关脑区的激活特点.方法 采用GE 1.5 T磁共振扫描仪对23例(男12例,女11例)正常中老年人行组块设计的词语联想任务fMRI研究.采用SPM 2软件进行数据处理和统计分析,通过组分析获得平均脑激活图,观察脑激活区的部位和激活强度.结果 12例符合入组条件,激活脑区为运动前区(PMC)、双侧额下回后部(Broca区及Broca镜像区)、双侧辅助运动区(SMA)、左侧顶后皮层、双侧岛叶、双侧扣带回前部、双侧基底节、左侧丘脑以及右侧小脑半球.全脑以左侧PMC激活强度最大.激活强度左侧大于右侧的脑区为额下回后部、背侧PMC及SMA;右侧大于左侧的脑区为腹侧PMC、岛叶、扣带回前部、基底节.结论 中老年人参与运动性语言表达的脑区,由包括Broca区在内的多个脑区组成复杂的神经网络,且相关脑区存在偏侧化现象,以左侧大脑半球和右侧小脑半球激活为主.     

Cerebral areas processing swallowing and tongue movement are overlapping but distinct: a functional magnetic resonance imaging study

Although multiple regions of the cerebral cortex have been implicated in swallowing, the functional contributions of each brain area remain unclear. The present study sought to clarify the roles of these cortical foci in swallowing by comparing brain activation associated with voluntary saliva swallowing and voluntary tongue elevation. Fourteen healthy right-handed subjects were examined with single-event-related functional magnetic resonance imaging (fMRI) while laryngeal movements associated with swallowing and tongue movement were simultaneously recorded. Both swallowing and tongue elevation activated 1) the left lateral pericentral and anterior parietal cortex, and 2) the anterior cingulate cortex (ACC) and adjacent supplementary motor area (SMA), suggesting that these brain regions mediate processes shared by swallowing and tongue movement. Tongue elevation activated a larger total volume of cortex than swallowing, with significantly greater activation within the ACC, SMA, right precentral and postcentral gyri, premotor cortex, right putamen, and thalamus. Although a contrast analysis failed to identify activation foci specific to swallowing, superimposed activation maps suggested that the most lateral extent of the left pericentral and anterior parietal cortex, rostral ACC, precuneus, and right parietal operculum/insula were preferentially activated by swallowing. This finding suggests that these brain areas may mediate processes specific to swallowing. Approximately 60% of the subjects showed a strong functional lateralization of the postcentral gyrus toward the left hemisphere for swallowing, whereas 40% showed a similar activation bias for the tongue elevation task. This finding supports the view that the oral sensorimotor cortices within the left and right hemispheres are functionally nonequivalent.     

遭受多重侵害高职高专女生静息态脑功能局部一致性的研究

目的:探讨遭受多重侵害的高职高专女生静息态脑功能磁共振特点。方法:15名遭受多重侵害无创伤后应激症状被试(PV无PTSS组)、15名多重侵害有创伤后应激症状被试(PV有PTSS组)和15名正常对照接受静息态脑功能扫描。采用SPM8和静息态功能磁共振数据处理工具包分别进行数据预处理和ReHo分析。结果:静息状态下,与对照组相比,PV无PTSS组左侧额下回、左右额内侧回、右侧中央后回、左侧梭状回、左右海马旁回、右侧扣带回、左右豆状核和右侧岛叶的ReHo值降低;左右额上回、左右额中回、左右额下回、左右顶下小叶、左右楔前叶、左右颞上回、左侧颞横回、左右颞中回、右侧舌回和右侧扣带后回的ReHo值升高。与PV有PTSS组相比,PV无PTSS组在右侧额中回和额下回、左侧楔前叶、左侧舌回、左右海马旁回、左侧扣带回和左侧豆状核ReHo值降低;在左右额上回、左右额中回、左侧额内侧回、右侧中央后回、左侧缘上回、左右顶下小叶、左侧梭状回和左侧尾状核ReHo值升高。结论:遭受多重侵害但无创伤后应激症状的高职高专女生在静息状态下脑默认网络以及岛叶、基底神经节、海马旁回存在局部一致性信号异常,这些脑区异常可能为遭受多重侵害导致精神障碍的发病机制提供重要线索。     

Identification of the cerebral loci processing human swallowing with H2(15)O PET activation

Lesional and electrophysiological data implicate a role for the cerebral cortex in the initiation and modulation of human swallowing, and yet its functional neuroanatomy remains undefined. We therefore conducted a functional study of the cerebral loci processing human volitional swallowing with 15O-labeled water positron emission tomography (PET) activation imaging. Regional cerebral activation was investigated in 8 healthy right handed male volunteers with a randomized 12-scan paradigm of rest and water swallows (5 ml/bolus, continuous infusion) at increasing frequencies of 0.1, 0.2, and 0.3 Hz, which were visually cued and monitored with submental electromyogram (EMG). Group and individual linear covariate analyses were performed with SPM96. In five of eight subjects, the cortical motor representation of pharynx was subsequently mapped with transcranial magnetic stimulation (TMS) in a posthoc manner to substantiate findings of hemispheric differences in sensorimotor cortex activation seen with PET. During swallowing, group PET analysis identified increased regional cerebral blood flow (rCBF) (P < 0.001) within bilateral caudolateral sensorimotor cortex [Brodmann's area (BA) 3, 4, and 6], right anterior insula (BA 16), right orbitofrontal and temporopolar cortex (BA 11 and 38), left mesial premotor cortex (BA 6 and 24), left temporopolar cortex and amygdala (BA 38 and 34), left superiomedial cerebellum, and dorsal brain stem. Decreased rCBF (P < 0.001) was also observed within bilateral posterior parietal cortex (BA 7), right anterior occipital cortex (BA 19), left superior frontal cortex (BA 8), right prefrontal cortex (BA 9), and bilateral superiomedial temporal cortex (BA 41 and 42). Individual PET analysis revealed asymmetric representation within sensorimotor cortex in six of eight subjects, four lateralizing to right hemisphere and two to left hemisphere. TMS mapping in the five subjects identified condordant interhemisphere asymmetries in the motor representation for pharynx, consistent with the PET findings. We conclude that volitional swallowing recruits multiple cerebral regions, in particular sensorimotor cortex, insula, temporopolar cortex, cerebellum, and brain stem, the sensorimotor cortex displaying strong degrees of interhemispheric asymmetry, further substantiated with TMS. Such findings may help explain the variable nature of swallowing disorders after stroke and other focal lesions to the cerebral cortex.     

Role for human posterior parietal cortex in visual processing of aversive objects in peripersonal space

The posterior parietal cortex of both human and non-human primates is known to play a crucial role in the early integration of visual information with somatosensory, proprioceptive and vestibular signals. However, it is not known whether in humans this region is further capable of discriminating if a stimulus poses a threat to the body. In this functional magnetic resonance imaging (fMRI) study, we tested the hypothesis that the posterior parietal cortex of humans is capable of modulating its response to the visual processing of noxious threat representation in the absence of tactile input. During fMRI, participants watched while we "stimulated" a visible rubber hand, placed over their real hand with either a sharp (painful) or a blunt (nonpainful) probe. We found that superior and inferior parietal regions (BA5/7 and BA40) increased their activity in response to observing a painful versus nonpainful stimulus. However, this effect was only evident when the rubber hand was in a spatially congruent (vs. incongruent) position with respect to the participants' own hand. In addition, areas involved in motivational-affective coding such as mid-cingulate (BA24) and anterior insula also showed such relevance-dependent modulation, whereas premotor areas known to receive multisensory information about limb position did not. We suggest these results reveal a human anatomical-functional homologue to monkey inferior parietal areas that respond to aversive stimuli by producing nocifensive muscle and limb movements.     

The role of inferior frontal gyrus and inferior parietal lobule in semantic processing of Chinese characters

Functional magnetic resonance imaging was used to explore the neural correlates of semantic judgments to Chinese characters. Adult participants were asked to indicate if character pairs were related in meaning that were arranged in a continuous variable according to association strength. This parametric manipulation allowed for a more precise determination of the role of the left inferior parietal lobule in processing meaning, which has not been reported in previous Chinese studies. Consistent with previous findings in English, participants showed activation in left inferior frontal gyrus (BA 47, 45) and left posterior middle temporal gyrus (BA 21). Characters with stronger semantic association elicited greater activation in left inferior parietal lobule (BA 39), suggesting stronger integration of highly related semantic features. By contrast, characters with weaker semantic association elicited greater activation in both an anterior ventral region (BA 47) and a mid-ventral region of left inferior frontal gyrus (BA 45), suggesting a controlled retrieval process and a selection process. Our findings of association strength are discussed in a proposed neuro-anatomical model of semantic processing.     

Multisensory cortical signal increases and decreases during vestibular galvanic stimulation (fMRI)

Functional magnetic resonance imaging blood-oxygenation-level-dependent (BOLD) signal increases (activations) and BOLD signal decreases ("deactivations") were compared in six healthy volunteers during galvanic vestibular (mastoid) and galvanic cutaneous (neck) stimulation in order to differentiate vestibular from ocular motor and nociceptive functions. By calculating the contrast for vestibular activation minus cutaneous activation for the group, we found activations in the anterior parts of the insula, the paramedian and dorsolateral thalamus, the putamen, the inferior parietal lobule [Brodmann area (BA) 40], the precentral gyrus (frontal eye field, BA 6), the middle frontal gyrus (prefrontal cortex, BA 46/9), the middle temporal gyrus (BA 37), the superior temporal gyrus (BA 22), and the anterior cingulate gyrus (BA 32) as well as in both cerebellar hemispheres. These activations can be attributed to multisensory vestibular and ocular motor functions. Single-subject analysis in addition showed distinctly nonoverlapping activations in the posterior insula, which corresponds to the parieto-insular vestibular cortex in the monkey. During vestibular stimulation, there was also a significant signal decrease in the visual cortex (BA 18, 19), which spared BA 17. A different "deactivation" was found during cutaneous stimulation; it included upper parieto-occipital areas in the middle temporal and occipital gyri (BA 19/39/18). Under both stimulation conditions, there were signal decreases in the somatosensory cortex (BA 2/3/4). Stimulus-dependent, inhibitory vestibular-visual, and nociceptive-somatosensory interactions may be functionally significant for processing perception and sensorimotor control.     

Right-lateralized pain processing in the human cortex: an FMRI study

Neuroimaging studies of human pain have revealed a widespread "pain matrix" distributed across both hemispheres of the brain. It is not resolved whether the pain matrix is biased toward one hemisphere, although behavioral and clinical data suggest that pain is perceived differently on the two sides of the body, and several neuroimaging studies suggest that pain processing in some regions of cortex may be lateralized toward the right hemisphere. The current study used fMRI in nine subjects to determine whether acute pain is preferentially processed in one cortical hemisphere. All cortical areas that were activated during the painful simulation were investigated, and several analytic approaches were used to directly compare activated regions to similar regions in the opposite hemisphere. Results indicated that four regions of the cortical pain matrix were activated either contralaterally (somatosensory cortex) or bilaterally (mid/posterior insula, anterior insula, and posterior cingulate). In addition, activation in five cortical regions during acute pain stimulation was localized either exclusively in the right hemisphere or was strongly lateralized to the right. These five areas were in the middle frontal gyrus, anterior cingulate, inferior frontal gyrus, medial/superior frontal gyri, and inferior parietal lobule. The location of some of these regions is consistent with the idea that there may be a right-lateralized attentional system to alert an organism to an infrequent, but behaviorally relevant, stimulus such as pain.     

Cerebral cortical representation of automatic and volitional swallowing in humans

Although the cerebral cortex has been implicated in the control of swallowing, the functional organization of the human cortical swallowing representation has not been fully documented. Therefore, the present study determined the cortical representation of swallowing in fourteen healthy right-handed female subjects using single-event-related functional magnetic resonance imaging (fMRI). Subjects were scanned during three swallowing activation tasks: a na?ve saliva swallow, a voluntary saliva swallow, and a water bolus swallow. Swallow-related laryngeal movement was recorded simultaneously from the output of a bellows positioned over the thyroid cartilage. Statistical maps were generated by computing the difference between the magnitude of the voxel time course during 1) a single swallowing trial and 2) the corresponding control period. Automatic and volitional swallowing produced activation within several common cortical regions, the most prominent and consistent being located within the lateral precentral gyrus, lateral postcentral gyrus, and right insula. Activation foci within the superior temporal gyrus, middle and inferior frontal gyri, and frontal operculum also were identified for all swallowing tasks. In contrast, activation of the caudal anterior cingulate cortex was significantly more likely in association with the voluntary saliva swallow and water bolus swallow than the na?ve swallow. These findings support the view that, in addition to known brain stem areas, human swallowing is represented within a number of spatially and functionally distinct cortical loci which may participate differentially in the regulation of swallowing. Activation of the insula was significantly lateralized to the right hemisphere for the voluntary saliva swallow, suggesting a functional hemispheric dominance of the insula for the processing of swallowing.     

Relationship Between Brain and Cognitive Processes in Down Syndrome

We investigated regional grey matter (GM) density in adolescents with Down syndrome (DS) compared to age-matched controls and correlated MRI data with neuropsychological measures in the DS group. Inter-group comparisons documented several GM concentration abnormalities in the participants with DS compared to controls. In the adolescents with DS, intra-group results also showed associations between regional GM density and the neuropsychological measures considered. In particular, GM density of the cerebellum and middle and inferior temporal gyrus was associated with linguistic measures. Short-term memory performances were correlated with the inferior parietal lobule, insula, superior temporal gyrus, medial occipital lobe, and cerebellum. Long-term memory abilities were correlated with GM density in the orbitofrontal cortex, lateral and medial temporal lobe regions, and anterior cingulum and visuo-perceptual abilities with GM density the left middle frontal gyrus. Results of this preliminary study are consistent with a not always efficient brain organization in DS.     

同一经络上穴位的脑功能磁共振成像研究

目的:手针针刺同一经络上但被同一神经阶段支配的不同穴位的核磁共振功能成像研究。方法:对33名志愿者进行手针针刺,每一位志愿者会随机地接受一个点的针刺:太冲穴,中都穴,太冲穴旁的非穴位点和中都穴旁的非穴位点,在针刺同时用1.5T核磁共振扫描仪进行扫描,得到针刺穴位相对于非穴位的激活脑区。结果:相对于刺激假穴组,刺激真穴组都激活了额内侧面、前扣带回(ACC,BA24/32/25);对侧中央后回、顶叶BA7/31、额中回;还有同侧的BA19和小脑。针刺太冲穴特异地激活了两侧额中回和颞下回,对侧颞中回、岛叶、小脑和同侧额中回、尾状核;针刺中都穴特异地激活了对侧颞上回、顶下小叶、同侧的中央前回和额上回。结论:针刺同一经络上的不同穴位会引起相似的大脑反应,而针刺同一经络上不同穴位所引起的特异性激活也表明了穴位特异性的存在。     

fMRI signal increases and decreases in cortical areas during small-field optokinetic stimulation and central fixation

Small-field optokinetic nystagmus (OKN) was performed in seven healthy volunteers in order to analyze the activation and deactivation patterns of visual motion, ocular motor, and multisensory vestibular cortex areas by means of fMRI during coherent visual motion stimulation. BOLD signal decreases (deactivations) were found in the first and second long insular gyri and retroinsular areas (the human homologue of the parietoinsular vestibular cortex and the visual posterior sylvian area in the monkey) of both hemispheres, extending into the transverse temporal gyrus and inferior-anterior parts of the superior temporal gyrus (BA 22), and the precentral gyri at two separate sites (BA 4 and 6). Further deactivations were found in cranioposterior parts of the superior temporal gyrus (BA 22) and the adjacent inferior parietal lobule (BA 40), anterior cingulate gyrus, hippocampus, and corpus callosum. Most of these BOLD signal decreases involved parts of the "multisensory vestibular cortical circuit". These findings support the concept of a reciprocally inhibitory visual–vestibular interaction that has now been demonstrated not only for large-field visual motion stimulation that induces vection (without eye movements) but also for optokinetically induced eye movements (without vection). The functional significance of this concept may be related to the perception of self-motion, since both large-field visual motion stimulation and optokinetic nystagmus are linked to the visual control of self-motion. With respect to activation of the cortical ocular motor system two separate and distinct areas of activations were delineated in the precentral sulcus of both hemispheres, one ventrolaterally (in BA 9) and the other dorsomedially at the junction of the superior frontal sulcus with the precentral sulcus (in BA 6). Both probably correspond to different subregions of the frontal eye field and the premotor cortex for the ocular motor performance of OKN. Electronic Publication     

Visually cued motor synchronization: modulation of fMRI activation patterns by baseline condition

A well-known issue in functional neuroimaging studies, regarding motor synchronization, is to design suitable control tasks able to discriminate between the brain structures involved in primary time-keeper functions and those related to other processes such as attentional effort. The aim of this work was to investigate how the predictability of stimulus onsets in the baseline condition modulates the activity in brain structures related to processes involved in time-keeper functions during the performance of a visually cued motor synchronization task (VM). The rational behind this choice derives from the notion that using different stimulus predictability can vary the subject's attention and the consequently neural activity. For this purpose, baseline levels of BOLD activity were obtained from 12 subjects during a conventional-baseline condition: maintained fixation of the visual rhythmic stimuli presented in the VM task, and a random-baseline condition: maintained fixation of visual stimuli occurring randomly. fMRI analysis demonstrated that while brain areas with a documented role in basic time processing are detected independent of the baseline condition (right cerebellum, bilateral putamen, left thalamus, left superior temporal gyrus, left sensorimotor cortex, left dorsal premotor cortex and supplementary motor area), the ventral premotor cortex, caudate nucleus, insula and inferior frontal gyrus exhibited a baseline-dependent activation. We conclude that maintained fixation of unpredictable visual stimuli can be employed in order to reduce or eliminate neural activity related to attentional components present in the synchronization task.     

原发性失眠患者大脑背外侧前额叶的异常静息态功能连接

目的:利用功能连接方法观察原发性失眠患者静息态下的背外侧前额叶的异常功能连接。方法:采集33 例原 发性失眠患者以及33 例年龄、性别和受教育程度相匹配的健康对照的功能磁共振图像,以背外侧前额叶为感兴趣区 域,与全脑其他体素进行功能连接分析,得到两组之间功能连接的差异脑区,再对异常功能连接脑区与临床的量表分 数做相关分析。结果:与对照组相比,发现失眠患者左侧背外侧前额叶与左侧枕下回、右侧枕下回、右侧枕中回、右侧 颞叶、左侧额中回,左侧额下回以及右侧梭状回之间的功能连接增强（P<0.05,体素簇个数≥100,FDR校正）,与左侧前 扣带皮层、右侧海马旁回、右侧脑岛、右侧背外侧额上回、右侧顶上回、右侧中央后回以及右侧中央前回之间的功能连 接减弱（P<0.05,体素簇个数≥100,FDR校正）。并且左侧背外侧前额叶与左侧枕叶下回的功能连接值与睡眠状况自评 量表分数成正相关（P=0.035）。结论:原发性失眠患者背外侧前额叶与大脑多个脑区出现异常的功能连接,可能为理 解原发性失眠患者的神经机制提供一些新的影像学依据。     

Intermittent visuomotor processing in the human cerebellum, parietal cortex, and premotor cortex

The cerebellum, parietal cortex, and premotor cortex are integral to visuomotor processing. The parameters of visual information that modulate their role in visuomotor control are less clear. From motor psychophysics, the relation between the frequency of visual feedback and force variability has been identified as nonlinear. Thus we hypothesized that visual feedback frequency will differentially modulate the neural activation in the cerebellum, parietal cortex, and premotor cortex related to visuomotor processing. We used functional magnetic resonance imaging at 3 Tesla to examine visually guided grip force control under frequent and infrequent visual feedback conditions. Control conditions with intermittent visual feedback alone and a control force condition without visual feedback were examined. As expected, force variability was reduced in the frequent compared with the infrequent condition. Three novel findings were identified. First, infrequent (0.4 Hz) visual feedback did not result in visuomotor activation in lateral cerebellum (lobule VI/Crus I), whereas frequent (25 Hz) intermittent visual feedback did. This is in contrast to the anterior intermediate cerebellum (lobule V/VI), which was consistently active across all force conditions compared with rest. Second, confirming previous observations, the parietal and premotor cortices were active during grip force with frequent visual feedback. The novel finding was that the parietal and premotor cortex were also active during grip force with infrequent visual feedback. Third, right inferior parietal lobule, dorsal premotor cortex, and ventral premotor cortex had greater activation in the frequent compared with the infrequent grip force condition. These findings demonstrate that the frequency of visual information reduces motor error and differentially modulates the neural activation related to visuomotor processing in the cerebellum, parietal cortex, and premotor cortex.     

Deriving angular displacement from optic flow: a fMRI study

Using fMRI we wished to identify brain areas subserving the conversion of velocity signals into estimates of self-displacement (velocity-to-displacement integration, VDI), a function which is a prerequisite for the ability to navigate without landmarks. As real self-motion is not feasible in an fMRI environment, we presented subjects with a ride along a circular path in virtual reality devoid of usable landmarks. We asked subjects to try and feel as if actually moving in the scene and to either detect and count changes in driving speed (V-task) or to estimate the angular displacement achieved during a ride (D-task). We examined the contrast between these two tasks with regard to two hypothesised key functions for VDI: (1) evoking an internal image of the self in space and (2) manipulating this image in proportion to perceived velocity at the pace of a time base. The BOLD-responses during both tasks were fairly similar showing activity with right hemispheric dominance in a large parieto-temporo-occipital area as well as in frontal and prefrontal areas. Contrast D–V revealed a mainly parieto-hippocampal network comprising precuneus and inferior parietal cortex, posterior parieto-occipital cortex, retrosplenial cortex and the hippocampal region, but also right superior frontal gyrus and right cerebellum. It can be viewed as a blend of networks known to be involved in mental rotation and in navigation, except for the lack of ventral premotor and prefrontal activity. A tentative interpretation proposes a scenario where precuneus, together perhaps with posterior parieto-occipital cortex, provides the postulated mental image of the self in space and uses it to interpret results computed in the hippocampal region. In the hippocampal region, VDI proper would take place based on a map of spatial orientation, with the appropriate time scale being an intrinsic property. In addition, a dedicated time keeping system in inferior parietal cortex appears to be involved.