Functional magnetic resonance imaging of brain activity during chewing and occlusion by natural teeth and occlusal splints

Brain imaging based on functional magnetic resonance (fMRI) is a useful tool for examination of neuronal networks and cerebral structures subserving visiospatial function. The purpose of this study was to compare the brain activity during chewing and occlusal function in centric occlusion on natural teeth or on occlusal splints. Four tasks were performed by 13 healthy, fully dentate subjects (21-32 years old, 6 female and 7 male): occlusal tap-tap movements in centric occlusion by natural teeth, after application of a maxillary occlusal splint and chewing movements on left and right sided rubberdam strips. In order to reveal which areas of the brain were more strongly activated, conjunction analyses between the different tasks were performed for each subject and for the average values of brain signal activity of all subjects. Whilst several known foci of activity were subtracted, differences of significant activity rested in areas of the sensorimotor cortex. Mainly ipsitaterality of hemispheres concerned the left and right sided chewing, whereas the conjunction between tap-tap movements on natural teeth and splint occlusion indicated only one weak, but significant activation foci. The study confirms fMRT as one of the most useful developing methods to clear up neuro-cortical effectiveness of occlusion and occlusal therapy.     

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.     

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。     

健康成人吞咽活动脑功能区的功能磁共振成像研究

目的 利用脑功能磁共振成像(fMRI)技术研究健康成人不同吞咽任务时激活脑区的特点.方法 8名健康志愿者参与实验性自主和反射性吞咽任务的fMRI研究.采用SPM2软件对功能成像数据进行处理及图像显示.配对t检验用于比较2种吞咽任务激活脑区的容积及信号值大小.结果 自主吞咽任务激活脑区有双侧初级感觉运动皮质、运动前区、前扣带回等.反射性吞咽任务相关脑区有双侧初级感觉皮层、双侧额盖、双侧顶后区.自主性吞咽激活双侧半球容积(体素)分别为1213±110(左)、1969±133(右).反射吞咽激活双侧半球容积(体素)分别为488±45(左)、398±35(右).自主性咽水双侧感觉运动区信号增加值分别为4.4±0.4(左)、4.1±0.2(右);双侧岛叶容积为1.2±0.5(左)、1.5±0.6(右).反射性咽水双侧感觉运动区信号增加值分别为2.6±0.3(左)、2.5±1.2(右);双侧岛叶信号增加值为0.6±0.4(左)、0.2±0.1(右).自主吞咽激活双侧半球容积、感觉运动区及岛叶信号值均大于反射性吞咽(均为P<0.05).两种吞咽任务的偏侧性指数(LI)值分别为(-16±9)%和(11±5)%.结论 自主吞咽任务激活脑区数量及容积大于反射性吞咽任务.两种吞咽任务激活脑区的不同与自主吞咽过程中计划、发动、情感等多种高级脑活动有关.     

An event-related fMRI study of self-paced alphabetically ordered writing of single letters

The spatial location of activation for writing individual letters and for writing simple dots was studied using event-related functional MRI. Ten healthy right-handed subjects were scanned while performing two different protocols with self-paced repetitive movement. In the first protocol with self-paced dot writing, we observed significant activation in regions known to participate in motor control: contralateral to the movement in the primary sensorimotor and supramarginal cortices, the supplementary motor area (SMA) with the underlying cingulate, in the thalamus and, to a lesser extent, in the ipsilateral inferior parietal and occipital cortices. In the second protocol, we investigated an elemental writing feature—writing single letters. We observed statistically significant changes in the premotor, sensorimotor and supramarginal cortices, the SMA and the thalamus with left predominance, and in the bilateral premotor and inferior/superior parietal cortices. The parietal region that was active during the writing of single letters spanned the border between the parietal superior and inferior lobuli Brodmann area (BA 2, 40), deep in the intraparietal sulcus, with a surprising right-sided dominance. The direct comparison of the results of the two protocols was not significant with a confidence level of P<0.05 corrected for whole brain volume. Thus, the ROI approach was used, and we tried to find significant differences within the two predefined regions of interest (ROI) (BA 7, BA 37). The differences were found with a confidence level of P<0.05 corrected for the volume of these predicted areas. The ROI were located in the posterior parts of hemispheres, in the ventral and in the dorsal visual pathway. The right-sided posterior cortices may play a role in the elemental mechanisms of writing. It is possible that activation of this region is linked with the spatial dimension of the writing.An erratum to this article can be found at     

Comparable fMRI activity with differential behavioural performance on mental rotation and overt verbal fluency tasks in healthy men and women

To explicate the neural correlates of sex differences in visuospatial and verbal fluency tasks, we examined behavioural performance and blood-oxygenation-level-dependent (BOLD) regional brain activity, using functional magnetic resonance imaging, during a three-dimensional (3D) mental rotation task and a compressed sequence overt verbal fluency task in a group of healthy men (n=9) and women (n=10; tested during the low-oestrogen phase of the menstrual cycle). Men outperformed women on the mental rotation task, and women outperformed men on the verbal fluency task. For the mental rotation task, men and women activated areas in the right superior parietal lobe and the bilateral middle occipital gyrus in association with the rotation condition. In addition, men activated the left middle temporal gyrus and the right angular gyrus. For verbal fluency, men activated areas in the bilateral superior frontal gyrus, right cingulate gyrus, left precentral gyrus, left medial frontal gyrus, left inferior frontal gyrus, thalamus, left parahippocampal gyrus and bilateral lingual gyrus, and women activated areas in the bilateral inferior frontal gyrus and left caudate. Despite observing task related activation in the hypothesised areas in men and women, no areas significantly differentiated the two sexes. Our results demonstrate comparable brain activation in men and women in association with mental rotation and verbal fluency function with differential performance, and provide support for sex differences in brain–behaviour relationships.     

Functional connectivity reveals load dependent neural systems underlying encoding and maintenance in verbal working memory

One of the main challenges in working memory research has been to understand the degree of separation and overlap between the neural systems involved in encoding and maintenance. In the current study we used a variable load version of the Sternberg item recognition test (two, four, six, or eight letters) and a functional connectivity method based on constrained principal component analysis to extract load-dependent neural systems underlying encoding and maintenance, and to characterize their anatomical overlap and functional interaction. Based on the pattern of functional connectivity, constrained principal component analysis identified a load-dependent encoding system comprising bilateral occipital (Brodmann's area (BA) 17, 18), bilateral superior parietal (BA 7), bilateral dorsolateral prefrontal (BA 46), and dorsal anterior cingulate (BA 24, 32) regions. For maintenance, in contrast, constrained principal component analysis identified a system that was characterized by both load-dependent increases and decreases in activation. The structures in this system jointly activated by maintenance load involved left posterior parietal (BA 40), left inferior prefrontal (BA 44), left premotor and supplementary motor areas (BA 6), and dorsal cingulate regions (BA 24, 32), while the regions displaying maintenance-load-dependent activity decreases involved bilateral occipital (BA 17, 18), posterior cingulate (BA 23) and rostral anterior cingulate/orbitofrontal (BA 10, 11, 32) regions. The correlation between the encoding and maintenance systems was strong and negative (Pearson's r = -.55), indicting that some regions important for visual processing during encoding displayed reduced activity during maintenance, while subvocal rehearsal and phonological storage regions important for maintenance showed a reduction in activity during encoding. In summary, our analyses suggest that separable and complementary subsystems underlie encoding and maintenance in verbal working memory, and they demonstrate how constrained principal component analysis can be employed to characterize neuronal systems and their functional contributions to higher-level cognition.     

脑结构形态学改变是精神分裂症的遗传内表型

目的 通过对首发精神分裂症患者及其未患病同胞的磁共振成像脑结构分析,探讨遗传因素对脑结构改变的影响程度,为发现精神分裂症的遗传内表型提供实验依据.方法 采用优化的基于体素的形态学研究方法对15例首发精神分裂症患者、19名首发精神分裂症患者未患病同胞及38名正常对照的大脑磁共振图像进行处理,采用一般线性模型进行统计分析.结果 与正常对照组相比,患者组在双侧颢叶、双侧枕叶、左侧岛叶、左侧额叶额上回及右豆状核苍白球灰质有明显减少;在双侧顶叶及双侧边缘叶扣带回灰质增加;未患病同胞组在右侧颞叶、双侧枕叶、左侧岛叶及左侧额叶中央前回等区域灰质明显减少;在左侧顶叶及双侧小脑后叶灰质增加.患者较同胞左侧顶叶楔前叶灰质有增加,未发现两者其他区域存在明显差异.结论 精神分裂症患者及其同胞存在相似的脑结构异常,遗传因素可能是导致精神分裂症脑结构异常的重要因素,提示脑结构形态学改变是精神分裂症的遗传内表型.     

The neural basis of motor sequencing: an fMRI study of healthy subjects

The present study used functional MRI to clarify the brain regions activated during a series of motor sequencing tasks in healthy volunteers. Ten subjects were scanned while performing three soft signs tasks ranging from simple (PT: palm tapping), moderate (PS: pronation/supination) to complex movements (FEP: fist-edge-palm). The FEP task induced significant activations within the cortical networks including bilateral sensorimotor, SMA, left parietal, and right cerebellum, but no activation in the prefrontal area. Moreover, the percentage signal changes within the left sensorimotor, left thalamus and right cerebellum showed an increase in activation with task complexity. The present findings challenge the traditional belief that FEP was a task for frontal lobe function but suggest that successful performance of more complex neurological soft sign tasks like FEP requires the participation of more brain areas than simple motor sequencing and coordination task like PS and PT. These also provide the empirical data on the neural basis of neurological soft signs for further study in other clinical group like schizophrenia in the near future.     

Functional MRI activation in children with and without dyslexia during pseudoword aural repeat and visual decode: before and after treatment

Children without dyslexia (n=10) received nonphonological treatment, and those with dyslexia received phonological (n=11) or nonphonological (n=9) treatment. Before and after treatment they performed aural repeat, visual decode, and aural match pseudoword tasks during functional MRI scanning that separated stimulus input from response production. Group map analysis indicated that children with dyslexia overactivated compared with good readers during the aural-repeat/aural-match contrast in bilateral frontal (Brodmann's area [BA] 3, 4, 5, 6, 9), left parietal (BA 2, 3), left temporal (BA 38), and right temporal (BA 20, 21, 37) regions (stimulus input) and underactivated in right frontal (BA 24, 32) and right insula (BA 48) regions (response production); they underactivated in BA 19/V5 during the visual-decode/aural-match contrast (response production). Individual brain analysis for children with dyslexia revealed that during the aural-repeat/aural-match contrast (stimulus input), phonological treatment decreased and normalized activation in left supramarginal gyrus and postcentral gyrus. Nonphonological treatment increased and normalized activation during the visual-decode/aural-match contrast (response production) in BA19/V5 and changed activation in the same direction as good readers during aural-repeat/aural-match contrast (stimulus input) in left postcentral gyrus. The significance of the findings for competing theories of dyslexia is discussed.     

An fMRI study of brain activation in a visual adaptation task: activation limited to sensory guidance

Previous neuroimaging studies yielded different patterns of brain areas activated during sensorimotor adaptation, when sensory conflicts are introduced, e.g. by manipulating visual information. We propose that possible reasons might be the lack to control for adaptation or the change in motor performance. In consequence, it was not possible to distinguish between adaptation-related and error-related brain activations. We have developed a sensorimotor adaptation task which controls for these errors using two types of visual distortion and thus is suited to disambiguate sensorimotor adaptation from the related activation patterns. Twenty healthy subjects were scanned by fMRI during a tracking task, while adapting to a visual distortion, which depended either on hand position or on hand velocity. In either case, adaptation was interleaved with a control condition, designed such that the time-course of tracking errors approximated that under visual distortion. We found that adaptation-related neural activation was limited to the left supramarginal and angular gyrus under the position-dependent distortion, but extended bilaterally in the supramarginal gyrus, as well as in the left middle and right superior frontal gyrus under the velocity-dependent distortion. Our findings confirm that equating the errors under both conditions will yield an anatomically more restricted activation pattern compared with other studies. The additional recruitment in right parietal and bilateral frontal areas under the velocity-dependent distortion might reflect a higher computational demand, or the involvement of different adaptive mechanisms.

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Working memory of somatosensory stimuli: An fMRI study

In a previous study, we have shown that passive recognition of tactile geometrical shapes (i.e. no exploratory movement) engages prefrontal and premotor areas in addition to somatosensory regions (Savini et al., 2010). In the present study we tested the hypothesis that these regions are involved not only in the perception but also during working memory of such somatic information.We performed functional magnetic resonance imaging (fMRI) during the execution of N-BACK tasks, with 2D geometrical shapes blindly pressed on the subjects' right hand palm. Three conditions with increasing memory load (0-BACK, 1-BACK, 2-BACK) were used. Results showed that primary somatosensory area (SI), secondary somatosensory area (SII) and bilateral Insula were active in all conditions, confirming their importance in coding somatosensory stimuli. Activation of fronto-parietal circuit in supplementary motor area (SMA), right superior parietal lobe (rSPL), bilateral middle frontal gyrus, left inferior frontal gyrus, and right superior frontal sulcus was significantly larger during 1-BACK and 2-BACK than 0-BACK. Left superior parietal lobe and right frontal eye field showed a higher activation during the 2-BACK than 0-BACK. Finally, SMA and rSPL were characterized by a statistically significant higher activation during 2-BACK than 1-BACK, revealing their sensitivity to the memory load. These results suggest that working memory of tactile geometrical shapes (no exploratory movement) involves a complex circuit of modal and supramodal fronto-parietal areas.     

Virtual needle pain stimuli activates cortical representation of emotions in normal volunteers

Psychological factors are known to play an extremely important role in the maintenance and development of chronic pain conditions. However, it is unclear how such factors relate to the central neural processing of nociceptive transmission in healthy individuals. To investigate this issue, the activation of the brain was studied in 30 healthy volunteers responding to virtual pain stimuli by fMRI. In the first series of the study (non-preconditioned study), 15 participants were shown a digital video demonstrating an injection needle puncturing the right palm. In the second series of the study (pre-conditioned study), same-task paradigms were used for another 15 participants. Prior to the fMRI session, real needle punctuate stimuli were applied to the right palm of participants for pre-conditioning. fMRI analysis revealed that bilateral activations in anterior insula (BA45), parietal operculum (S2: BA40), premotor area, medial globus pallidus, inferior occipital gyrus (BA18), left temporal association cortex, right fusiform gyrus, right parietal association cortex and cerebellum occurred due to the task in the preconditioned group. On the other hand, right parietal operculum (S2: BA40), premotor area, parietal association cortex, left inferior frontal gyrus and bilateral temporal association cortex were activated in the non-preconditioned group. In addition, activation of anterior insula, inferior frontal gyrus, precentral gyrus and cerebellum significantly increased in the preconditioned group compared with the non-preconditioned group. These results suggest that the virtual needle puncture task caused memory retrieval of unpleasant experiences which is possibly related to empathy for pain, resulting in the activation of specific brain areas.     

Fronto-striatal hypoactivation during correct information retrieval in patients with schizophrenia: an fMRI study

Working memory (WM) deficits are core symptoms of schizophrenia. Differing behavioral performance is known to represent a potent moderating variable when investigating the neural correlates of working memory in patients with schizophrenia compared with healthy controls. The present functional magnetic resonance imaging study examined performance-matched cerebral activity during correct WM retrieval by balancing the mean number of correct responses as well as the mean response times between patients and controls and analyzing remaining correct trials. Forty-one schizophrenia patients and 41 healthy controls performed an event-related Sternberg task allowing for analysis of correctly remembered trials. Correct retrieval was associated with activation in a bilateral fronto-parieto-occipital network comprising mainly the dorsolateral prefrontal cortex, ventrolateral prefrontal cortex and superior parietal cortex in controls and, to a weaker degree, in patients. Direct group comparison revealed significantly decreased activations in patients in the posterior (Brodmann area (BA) 31) and anterior (BA 32) cingulate cortex (ACC) and the medial caudate bilaterally when matching for performance. When matching for performance and response speed there was additional hypoactivation in the insula. Mean response times were negatively correlated with cingulate and caudate activation only in controls. Present findings suggest that during efficient WM retrieval processing patients exhibit only slightly impaired activation in a task-specific network containing mainly prefrontal and superior parietal areas. However, hypoactivation of areas predominantly responsible for cognitive control and response execution seems to remain even under performance-matched conditions. Given the relevant role of the caudate and the ACC in dopaminergically mediated executive processing, the results bear crucial implications for the psychopathology of schizophrenia.     

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。     

Where language meets meaningful action: a combined behavior and lesion analysis of aphasia and apraxia

It is debated how language and praxis are co-represented in the left hemisphere (LH). As voxel-based lesion-symptom mapping in LH stroke patients with aphasia and/or apraxia may contribute to this debate, we here investigated the relationship between language and praxis deficits at the behavioral and lesion levels in 50 sub-acute stroke patients. We hypothesized that language and (meaningful) action are linked via semantic processing in Broca’s region. Behaviorally, half of the patients suffered from co-morbid aphasia and apraxia. While 24 % (n = 12) of all patients exhibited aphasia without apraxia, apraxia without aphasia was rare (n = 2, 4 %). Left inferior frontal, insular, inferior parietal, and superior temporal lesions were specifically associated with deficits in naming, reading, writing, or auditory comprehension. In contrast, lesions affecting the left inferior frontal gyrus, premotor cortex, and the central region as well as the inferior parietal lobe were associated with apraxic deficits (i.e., pantomime, imitation of meaningful and meaningless gestures). Thus, contrary to the predictions of the embodied cognition theory, lesions to sensorimotor and premotor areas were associated with the severity of praxis but not language deficits. Lesions of Brodmann area (BA) 44 led to combined apraxic and aphasic deficits. Data suggest that BA 44 acts as an interface between language and (meaningful) action thereby supporting parcellation schemes (based on connectivity and receptor mapping) which revealed a BA 44 sub-area involved in semantic processing.     

基于脑网络组图谱的首发-未服药抑郁症白质结构网络研究

使用图论的分析方法对首发-未服药抑郁症（MDD）的扩散磁共振数据进行分析,探讨其白质结构网络变化。结果显示相较于健康对照组,MDD患者的网络节点拓扑属性受到了破坏,主要位于双侧海马旁回、双侧基底节、双侧顶下小叶、左侧中央后回、左侧中央旁小叶、右侧颞中回、右侧顶上小叶、右侧岛叶、右侧枕叶皮层腹中部、右侧扣带回以及右侧丘脑。进一步的相关分析结果表明,MDD患者的右侧顶上小叶、右侧岛叶的节点介数与病程呈正相关,右侧丘脑、左侧海马旁回的节点介数,左侧海马旁回、右侧顶下小叶的节点度与汉密尔顿的抑郁得分呈显著正相关。     

Visual cortex activation in kinesthetic guidance of reaching

The purpose of this research was to determine the cortical circuit involved in encoding and controlling kinesthetically guided reaching movements. We used ¹⁵O-butanol positron emission tomography in ten blindfolded able-bodied volunteers in a factorial experiment in which arm (left/right) used to encode target location and to reach back to the remembered location and hemispace of target location (left/right side of midsagittal plane) varied systematically. During encoding of a target the experimenter guided the hand to touch the index fingertip to an external target and then returned the hand to the start location. After a short delay the subject voluntarily moved the same hand back to the remembered target location. SPM99 analysis of the PET data contrasting left versus right hand reaching showed increased (P < 0.05, corrected) neural activity in the sensorimotor cortex, premotor cortex and posterior parietal lobule (PPL) contralateral to the moving hand. Additional neural activation was observed in prefrontal cortex and visual association areas of occipital and parietal lobes contralateral and ipsilateral to the reaching hand. There was no statistically significant effect of target location in left versus right hemispace nor was there an interaction of hand and hemispace effects. Structural equation modeling showed that parietal lobe visual association areas contributed to kinesthetic processing by both hands but occipital lobe visual areas contributed only during dominant hand kinesthetic processing. This visual processing may also involve visualization of kinesthetically guided target location and use of the same network employed to guide reaches to visual targets when reaching to kinesthetic targets. The present work clearly demonstrates a network for kinesthetic processing that includes higher visual processing areas in the PPL for both upper limbs and processing in occipital lobe visual areas for the dominant limb.     

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.