Initial motor impairment influences activation pattern of motor recovery

OBJECTIVES: We investigated the functional magnetic resonance imaging (fMRI) activation pattern of a motor task in patients with acute subcortical lesions to examine the relationship between activation pattern and recovery of motor impairment. METHODS: Five patients (one with subcortical infarction and four with thalamic hemorrhage) were examined using fMRI 1 month after the insult. Impairment was assessed by the Medical Research Council motor strength classification (MRC). One patient with severe motor deficits was also studied at 4 months when her motor deficits improved up to MRC grade 4. RESULTS: Three patients with relatively mild deficits (MRC grade 3 or 4) at their onsets, improved fully up to grade 5 within 1 month. FMRI performed at 1 month showed activation in the contralateral primary motor cortex and supplementary motor area (SMA), but no significant activation was seen on the ipsilateral unaffected side. Two patients with severe motor impairment (MRC grade 1) improved up to 3 and 4 of MRC at 1 month or later. They showed activation of the ipsilateral premotor area as well as contralateral primary motor cortex and SMA. One of them, whose severe motor deficit improved at 4 month, also showed activation of the ipsilateral postcentral gyrus and the activated area expanded longitudinally corresponding with her functional recovery. DISCUSSION: Our study demonstrates that the fMRI pattern varies according to functional recovery, suggesting the importance of the ipsilateral premotor area and postcentral gyrus especially for those patients with severe motor impairment initially.     

A tug of war: antagonistic effective connectivity patterns over the motor cortex and the severity of motor symptoms in Gilles de la Tourette syndrome

We tested the hypothesis that Gilles de la Tourette syndrome (GTS) is characterized by perturbed connectivity within cortico–subcortical motor networks. To this end, we performed a dynamic causal modelling (DCM) analysis of fMRI data collected during a finger opposition task in 24 normal controls and 24 GTS patients. The DCM analysis allowed us to assess whether any GTS‐specific patterns of brain activity were related to intrinsic and/or to task‐dependent connectivity. While no abnormalities were found for task‐dependent connectivity, intrinsic connectivity was abnormally increased in the premotor network, with stronger connections from the supplementary motor area (SMA), from the dorsolateral premotor cortex and from the putamen to the right superior frontal gyrus, an area where GTS showed over‐activation in a previous univariate analysis. We also found a positive correlation between the connectivity strength from the right basal ganglia to the right primary motor cortex (M1) and disease severity measured by the Yale Global Tic Severity Scale (YGTSS). This pattern was mirrored by a negative correlation between the connection strength from the right SMA to the right area M1 and the YGTSS score. These two reverse correlation effects showed a specific relationship with individual disease severity: the greater the imbalance between subcortical and premotor connectivity towards area M1, the higher the YGTSS score. These results reveal the existence of perturbed intrinsic connectivity patterns in the motor networks of GTS patients with two competing forces operating in a tug of war‐like mechanism: aberrant subcortical afferents to M1, compensated for by inputs from the premotor cortex.     

Functional neuroimaging at different disease stages reveals distinct phases of neuroplastic changes in amyotrophic lateral sclerosis

Some previous functional magnetic resonance imaging (fMRI) studies have revealed increased activation in amyotrophic lateral sclerosis (ALS) patients but longitudinal data on such activation changes are lacking. To assess the time course of changes in fMRI patterns and their potential contribution to the understanding of ALS pathophysiology, we, therefore, investigated a total of 22 patients with ALS and matched control participants while they performed a blocked motor task. Patients were assigned to three groups according to whether they had no (MRC grade 5), mild (MRC 4), or marked (MRC 3) weakness of the examined right hand. Significant activations were seen in primary motor and premotor cortex, somatosensory cortex, supplementary motor area and subcortical areas in all groups. The size of the activated area in the contralateral sensorimotor cortex was increased to a similar degree in all three ALS groups compared to control participants irrespective of weakness on clinical examination. Whereas movement related signal change and beta weights extracted from the activated cluster were unchanged relative to controls in ALS patients with no weakness, a marked decrease of these parameters was seen in patients with weakness. Two distinct stages of neuroplastic changes could be identified in ALS (first: increase of the activated area in contralateral sensorimotor cortex; second: reduction of signal change and beta weights with increasing weakness). We interpret the increase of the activated area as a result of decreased intracortical inhibition and the reduction of movement related signal change and beta weights as a consequence of loss of upper motor neurons. Hum Brain Mapp, 2011. © 2010 Wiley‐Liss, Inc.     

Cortical motor activation in akinetic schizophrenic patients: a pilot functional MRI study.

Akinesia is associated with supplementary motor area (SMA) dysfunction in Parkinson's disease. We looked for a similar association in patients with schizophrenia. Using functional magnetic resonance imaging (fMRI), we compared motor activation in 6 akinetic neuroleptic-treated schizophrenic patients and 6 normal subjects. Schizophrenic patients had a defective activation in the SMA, left primary sensorimotor cortex, bilateral lateral premotor and inferior parietal cortices, whereas the right primary sensorimotor cortex and a mesial frontal area were hyperactive. SMA was hypoactive in akinetic schizophrenic patients, emphasizing the role of this area in motor slowness. Other abnormal signals likely reflect schizophrenia-related abnormal intracortical connections.     

Neural correlates of motor recovery after robot-assisted stroke rehabilitation: a case series study

ABSTRACT

Robot-assisted bilateral arm therapy (RBAT) has shown promising results in stroke rehabilitation; however, connectivity mapping of the sensorimotor networks after RBAT remains unclear. We used fMRI before and after RBAT and a dose-matched control intervention (DMCI) to explore the connectivity changes in 6 subacute stroke patients. Sensorimotor functions improved in the RBAT and DMCI groups after treatment. Enhanced activation changes were observed in bilateral primary motor cortex (M1) and bilateral supplementary motor area (SMA) after RBAT. Dynamic causal model analysis revealed that interhemispheric connections were enhanced in RBAT patients. These preliminary findings suggest that intracortical and intercortical coupling might underlie poststroke RBAT.     

The role of the unaffected hemisphere in motor recovery after stroke

The contribution of the ipsilateral (nonaffected) hemisphere to recovery of motor function after stroke is controversial. Under the assumption that functionally relevant areas within the ipsilateral motor system should be tightly coupled to the demand we used fMRI and acoustically paced movements of the right index finger at six different frequencies to define the role of these regions for recovery after stroke. Eight well‐recovered patients with a chronic striatocapsular infarction of the left hemisphere were compared with eight age‐matched participants. As expected the hemodynamic response increased linearly with the frequency of the finger movements at the level of the left supplementary motor cortex (SMA) and the left primary sensorimotor cortex (SMC) in both groups. In contrast, a linear increase of the hemodynamic response with higher tapping frequencies in the right premotor cortex (PMC) and the right SMC was only seen in the patient group. These results support the model of an enhanced bihemispheric recruitment of preexisting motor representations in patients after subcortical stroke. Since all patients had excellent motor recovery contralesional SMC activation appears to be efficient and resembles the widespread, bilateral activation observed in healthy participants performing complex movements, instead of reflecting maladaptive plasticity. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.     

脑血管畸形患者运动皮质可塑性的功能MRI研究

目的 :探讨应用功能MRI(fMRI)研究位于或邻近初级运动中枢脑血管畸形患者运动皮质功能的可塑性。方法 :8例患者采集双手对掌运动激发后功能图像 ,观察功能区的分布特征 :计算活动指数 (AI)值 ;测量不同活动区信号强度 (SI)上升百分率。结果 :8例患者运动激发后在手运动区 (HRA)、辅助运动区 (SMA)、中央后回、额前区、顶叶等区域见活动。 5例有功能区移位的患者正常侧HRA活动区扩大 ,AI值为 0 3 9± 0 0 7,3例功能区无移位患者的AI值为 0 87± 0 12 (P <0 0 5 )。正常侧不同部位SI上升百分率均较病灶侧相应部位高 (P >0 0 5 )。结论 :脑血管畸形患者运动皮质可塑性改变表现为正常侧初级运动中枢的功能加强以及非特定手运动皮质的激活     

Ictal SPECT in supplementary motor area seizures

Abstract

Objectives: We used ictal single photon emission computed tomography (SPECT) to clarify the propagation pathways of epileptic discharges in patients with supplementary motor area (SMA) seizure.

Methods: In four patients (four males, age range, 18–27 years) with SMA seizures, SPECT studies by radioisotope 99mTc-ECD were performed as a preoperative evaluation. Two of the patients remained seizure-free after complete resection of the focal cortical dysplasia on magnetic resonance (MR) images including epileptic foci. In the other two patients, MR images were normal, but subdural electrode monitoring allowed for verifying the ictal onset in the left SMA. After partial resection of the SMA including epileptic foci, these patients experienced a significant (>90%) reduction of seizure frequency. Regional cerebral blood flow (rCBF) measurements obtained under ictal and interictal conditions were compared on a voxel-by-voxel basis by means of the SPM99 paired t-test option (uncorrected p<0.001).

Results: Significant increases in rCBF under ictal conditions were identified in the bilateral anterior cingulate cortex (ACC), the globus pallidus ipsilateral to epileptic foci and the contralateral cerebellar hemisphere. The right ACC included a cluster with a submaximum in the right primary sensorimotor area.

Discussion: In patients with SMA seizures, the hyperperfusion areas of ictal SPECT did not localize within the SMA but spread to the adjacent cortex such as the ACC and sensorimotor cortex ipsilateral to epileptic foci. Additionally, the epileptic discharges propagated to the remote areas such as the globus pallidus and cerebellum. We caution that ictal SPECT localization in patients with SMA seizures is not always concordant to epileptic focus but reveals already spread seizure activities.     

Modulation of interhemispheric activation balance in motor-related areas of stroke patients with motor recovery: Systematic review and meta-analysis of fMRI studies

BackgroundFunctional magnetic resonance imaging (fMRI) studies suggest that stroke-induced motor deficits are associated with an interhemispheric imbalance of motor activation. This meta-analysis aims to determine the changes of interhemispheric activation balance (IHAB) in motor-related cortices along with post-stroke motor recovery.MethodsWe searched PubMed for fMRI studies that investigated IHAB in stroke patients with motor recovery. Laterality indexes (LIs, (ipsilesional activation − contralesional activation)/(ipsilesional activation + contralesional activation)) before and after motor improvement were extracted as the outcome measures of IHAB. Data were synthesized by calculating standardized mean difference (SMD, Hedges’ adjusted g) with 95% confidence intervals (CI).ResultsAfter the rejection of 459 studies, 22 trials fulfilled the inclusion criteria and were included in the systematic review and meta-analysis. The LIs of sensorimotor cortex (SMC, 22 trials, 195 subjects), premotor cortex (PMC, 12 trials, 93 subjects), supplementary motor area (SMA, 12 trials, 92 subjects), and cerebellum (CB, 4 trials, 31 subjects) were assessed. Studies sampling from stroke patients with motor improvement showed positive changes of LI in SMC (SMD, 0.71; 95% CI, 0.41–1.01; P < 0.00001) and PMC (SMD, 0.68; 95% CI, 0.36–1.00; P < 0.0001), but not in SMA (SMD, 0.07; 95% CI, −0.62 to 0.75; P = 0.85) and CB (SMD, −0.17; 95% CI, −1.52 to 1.19, P = 0.81). Studies involving stroke patients with poor motor recovery showed non-significant changes in all of the four motor-related cortices (P > 0.05).ConclusionsThis meta-analysis suggests that along with good motor recovery of stroke patients, the IHAB is up-regulated in SMC and PMC, but not significantly changed in SMA and CB. Because of the limited data, further studies are needed to verify the findings.     

Functional magnetic resonance imaging in schizophrenia: cortical response to motor stimulation

Previous functional magnetic resonance imaging (fMRI) studies suggest that motor system abnormalities are present in schizophrenia. However, these studies have often produced conflicting or ambiguous findings. The purpose of this study was to ascertain whether activation differences could be identified in stable schizophrenic patients on the basis of BOLD measures in two motor regions, the primary motor cortex, Brodmann area 4 (BA4) and the premotor and supplementary motor area, Brodmann area 6 (BA6). Twenty-one schizophrenic patients and 21 healthy control subjects were studied with BOLD fMRI methods during a sequential finger tapping task. Statistical parametric maps were generated for each subject, and anatomic regions were automatically defined using an anatomic atlas. Compared with controls, the schizophrenic patients showed a significant reduction in contralateral activation for both BA4 and BA6 (P<0.001), and in ipsilateral activation in BA4 (P=0.007) and BA6 (P=0.002). In healthy controls, the coactivation in the ipsilateral cortex is reduced in comparison with the contralateral cortex for right and left handed tasks. In BA4, this reduction is significant for right (P=0.007) and left (P=0.003) finger tapping. Similar results were obtained for BA6. Further analyses are necessary to evaluate the activation in other motor system regions.     

Effect of intensive motor training with repetitive transcranial magnetic stimulation on upper limb motor function in chronic post-stroke patients with severe upper limb motor impairment

Background Intensive motor training with low-frequency repetitive transcranial magnetic stimulation (rTMS) has efficacy as a therapeutic method for motor dysfunction of the affected upper limb in patients with mild to moderate stroke. However, it is not clear whether this combination therapy has the same effect in chronic post-stroke patients with severe upper limb motor impairment.

Objectives The aim of this study was to test the treatment effects of intensive motor training with low-frequency rTMS in chronic post-stroke patients with severe upper limb motor impairment.

Methods A convenience sample of 26 chronic post-stroke patients with severe upper limb motor impairment participated in this study with the non-randomized, non-controlled clinical trial. All subjects were hospitalized to receive intensive motor training with low-frequency rTMS. During 2 weeks in which Sundays were excluded, a total of 24 sessions (2 sessions per day) of the intervention were conducted. The Fugl–Meyer Assessment (FMA) and Wolf Motor Function Test (WMFT) were used to assess motor impairment and function of the affected upper limb, respectively, before and after intervention. Paired t-test was used to analyze the effects of the intervention.

Results The FMA total score and WMFT log performance time significantly improved from before to after intervention (FMA: 12.6–18.0; WMFT: 3.6–3.3, p < 0.001).

Conclusions The present results suggest that intensive motor training with low-frequency rTMS could improve motor impairment in chronic post-stroke patients with severe upper limb motor impairment and contribute to the expansion of the application range of this combination therapy.     

Functional magnetic resonance imaging in schizophrenia: cortical response to motor stimulation

Previous functional magnetic resonance imaging (fMRI) studies suggest that motor system abnormalities are present in schizophrenia. However, these studies have often produced conflicting or ambiguous findings. The purpose of this study was to ascertain whether activation differences could be identified in stable schizophrenic patients on the basis of BOLD measures in two motor regions, the primary motor cortex, Brodmann area 4 (BA4) and the premotor and supplementary motor area, Brodmann area 6 (BA6). Twenty-one schizophrenic patients and 21 healthy control subjects were studied with BOLD fMRI methods during a sequential finger tapping task. Statistical parametric maps were generated for each subject, and anatomic regions were automatically defined using an anatomic atlas. Compared with controls, the schizophrenic patients showed a significant reduction in contralateral activation for both BA4 and BA6 (P<0.001), and in ipsilateral activation in BA4 (P=0.007) and BA6 (P=0.002). In healthy controls, the coactivation in the ipsilateral cortex is reduced in comparison with the contralateral cortex for right and left handed tasks. In BA4, this reduction is significant for right (P=0.007) and left (P=0.003) finger tapping. Similar results were obtained for BA6. Further analyses are necessary to evaluate the activation in other motor system regions.     

Asymmetric bilateral effect of the supplementary motor area proper in the human motor system

ObjectiveThis study aimed to clarify the function of human supplementary motor area proper (SMA) by the single-pulse electric stimulation method and its clinical usefulness for SMA mapping.MethodsWe studied five patients with epilepsy or brain tumour who underwent invasive functional mapping with subdural electrodes. Single-pulse electric stimulation of primary motor area (MI) and SMA was carried out through pairs of subdural electrodes, and motor-evoked potentials (MEPs) were recorded from surface electromyogram on both sides and also cortico-cortical-evoked potentials (CCEPs) from electrocorticogram.ResultsSMA stimulation elicited: (1) MEPs and following silent periods (SPs) in the contralateral upper and lower extremities, (2) SPs with or without minimal MEPs in the ipsilateral upper extremity and (3) CCEPs in the somatotopically corresponding region of the ipsilateral MI. Compared with MI stimulation, SMA stimulation required higher stimulus intensities (mean 14.2 mA (SMA) vs. 8.5 mA (MI)) to elicit MEPs and showed significantly longer onset latencies in upper extremity (range: 4–10 ms).ConclusionsThe results demonstrated an asymmetric bilateral effect of human SMA upon the corticospinal pathway.SignificanceSingle-pulse electric cortical stimulation would be clinically useful for distinguishing SMA from MI. The asymmetric bilateral effect of SMA might be conveyed through the direct descending pathway.     

Temporal dynamics of ipsilateral and contralateral motor activity during voluntary finger movement

The role of motor activity ipsilateral to movement remains a matter of debate, due in part to discrepancies among studies in the localization of this activity, when observed, and uncertainty about its time course. The present study used magnetoencephalography (MEG) to investigate the spatial localization and temporal dynamics of contralateral and ipsilateral motor activity during the preparation of unilateral finger movements. Eight right-handed normal subjects carried out self-paced finger-lifting movements with either their dominant or nondominant hand during MEG recordings. The Multi-Start Spatial Temporal multi-dipole method was used to analyze MEG responses recorded during the movement preparation and early execution stage (-800 msec to +30 msec) of movement. Three sources were localized consistently, including a source in the contralateral primary motor area (M1) and in the supplementary motor area (SMA). A third source ipsilateral to movement was located significantly anterior, inferior, and lateral to M1, in the premotor area (PMA) (Brodmann area [BA] 6). Peak latency of the SMA and the ipsilateral PMA sources significantly preceded the peak latency of the contralateral M1 source by 60 msec and 52 msec, respectively. Peak dipole strengths of both the SMA and ipsilateral PMA sources were significantly weaker than was the contralateral M1 source, but did not differ from each other. Altogether, the results indicated that the ipsilateral motor activity was associated with premotor function, rather than activity in M1. The time courses of activation in SMA and ipsilateral PMA were consistent with their purported roles in planning movements.     

术中唤醒直接电刺激在运动区胶质瘤切除术中的应用

目的探讨术中唤醒直接电刺激在运动区胶质瘤切除术中的应用效果。方法回顾性分析2015年3月至2017年7月南部战区总医院神经外科收治的34例位于运动区胶质瘤患者的临床资料。其中肿瘤位于左侧16例,右侧18例;肿瘤位于辅助运动区或运动前区23例,中央叶9例,从辅助运动区或运动前区侵袭到中央叶2例。患者均采用全身麻醉术中唤醒技术,神经导航和(或)术中超声定位病变位置,直接电刺激定位皮质和皮质下重要功能区,按照功能边界切除胶质瘤。患者术后均行神经功能和肿瘤切除程度的评估。结果34例患者中,有24例术中直接皮质电刺激后出现运动反应,13例有异常感觉,10例定位出语言相关皮质。皮质下电刺激有24例出现运动反应,1例有异常感觉,8例语言紊乱。共有30例(88.2%)肿瘤切除达到功能边界,另外4例(11.8%)皮质下电刺激未发现功能纤维,均为高级别胶质瘤患者。34例患者术后48 h内复查头颅MRI显示,肿瘤全切除22例(64.7%),次全切除9例(26.5%),部分切除3例(8.8%)。34例患者的随访时间为(23.6±8.6)个月(11.3~39.3个月),其中29例(85.3%)术后早期新发神经功能障碍或原有神经功能障碍加重;发生晚期神经功能障碍较术前加重者3例(8.8%),其中轻度1例、中度1例、重度1例(2.9%)。术前存在神经功能障碍或颅内压增高的16例患者中,术后3个月有13例神经功能好转,2例维持在术前状态,1例为重度神经功能障碍。结论术中唤醒状态下直接电刺激定位和持续监测运动区皮质和皮质下白质纤维,可最大程度地安全切除运动区胶质瘤,其远期重度神经功能障碍的发生率较低,术后生命质量提高。     

Brain motor functional changes after somatosensory discrimination training

Somatosensory discrimination training may modulate cognitive processes, such as movement planning and monitoring, which can be useful during active movements. The aim of the study was to assess the effect of somatosensory discrimination training on brain functional activity using functional magnetic resonance imaging (fMRI) during motor and sensory tasks in healthy subjects. Thirty-nine healthy young subjects were randomized into two groups: the experimental group underwent somatosensory discrimination training consisting of shape, surface and two-point distance discrimination; and the control group performed a simple object manipulation. At baseline and after 2 weeks of training, subjects underwent sensorimotor evaluations and fMRI tasks consisting of right-hand tactile stimulation, manipulation of a simple object, and complex right-hand motor sequence execution. Right-hand dexterity improved in both groups, but only the experimental group showed improvements in all manual dexterity tests. After training, the experimental group showed: decreased activation of the ipsilateral sensorimotor areas during the tactile stimulation task; increased activation of the contralateral postcentral gyrus and thalamus bilaterally during the manipulation task; and a reduced recruitment of the ipsilateral pre/postcentral gyri and an increased activation of the basal ganglia and cerebellum contralaterally during the complex right-hand motor task. In healthy subjects, sensory discrimination training was associated with lateralization of brain activity in sensorimotor areas during sensory and motor tasks. Further studies are needed to investigate the usefulness of this training in motor rehabilitation of patients with focal lesions in the central nervous system.     

Neurophysiological correlates of age-related changes in human motor function

BACKGROUND: There are well-defined and characteristic age-related deficits in motor abilities that may reflect structural and chemical changes in the aging brain. OBJECTIVE: To delineate age-related changes in the physiology of brain systems subserving simple motor behavior. METHODS: Ten strongly right-handed young (<35 years of age) and 12 strongly right-handed elderly (>50 years of age) subjects with no evidence of cognitive or motor deficits participated in the study. Whole-brain functional imaging was performed on a 1.5-T MRI scanner using a spiral pulse sequence while the subjects performed a visually paced "button-press" motor task with their dominant right hand alternating with a rest state. RESULTS: Although the groups did not differ in accuracy, there was an increase in reaction time in the elderly subjects (mean score plus minus SD, young subjects = 547 +/- 97 ms, elderly subjects = 794 +/- 280 ms, p < 0.03). There was a greater extent of activation in the contralateral sensorimotor cortex, lateral premotor area, supplementary motor area, and ipsilateral cerebellum in the elderly subjects relative to the young subjects (p < 0.001). Additional areas of activation, absent in the young subjects, were seen in the ipsilateral sensorimotor cortex, putamen (left > right), and contralateral cerebellum of the elderly subjects. CONCLUSIONS: The results of this study show that elderly subjects recruit additional cortical and subcortical areas even for the performance of a simple motor task. These changes may represent compensatory mechanisms invoked by the aging brain, such as reorganization and redistribution of functional networks to compensate for age-related structural and neurochemical changes.     

Cortical negative motor network in comparison with sensorimotor network: A cortico-cortical evoked potential study

The purpose of this study was to investigate the connectivity from the negative motor area and to elucidate the mechanism of negative motor phenomena. We report the results of cortico-cortical evoked potentials (CCEPs) by electrical stimulation of the primary motor area (MI), primary sensory area (SI), primary (PNMA) and supplementary negative motor area (SNMA) in eight epilepsy patients who underwent intracranial electrode placement. Alternating 1-Hz electrical stimuli were delivered to MI (six patients), SI (five), PNMA (six) and SNMA (two). CCEPs were recorded by averaging electrocorticograms time-locked to the stimuli. Stimulation of MI, SI and PNMA induced CCEP responses in the premotor area (PM), pre- and postcentral gyri, posterior parietal cortex and the temporo-parietal junction. Upon SNMA stimulation, CCEP responses were detected in the prefrontal cortex, PM, pre- and postcentral gyri, supplementary motor area (SMA) and preSMA. Compared with stimulation of SI and MI, PNMA stimulation revealed a broader distribution of CCEP responses in the frontal or parietal association cortex, indicating the importance of the fronto-parietal network associated with a higher level of motor control. We concluded that these connections are associated with motor control and that the negative motor phenomenon results from impairment of the organization of movements.     

How do the basal ganglia and cerebellum gain access to the cortical motor areas?

We have used retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase to examine the origin of the thalamic input to the two premotor areas with the densest projections to the motor cortex. These are: arcuate premotor area (APA) and the supplementary motor area (SMA). Retrograde transport demonstrated that the two premotor areas and the motor cortex each receive thalamic input from separate, cytoarchitectonically well-defined subdivisions of the ventrolateral thalamus. According to the nomenclature of Olszewski (1952), input to the APA originates largely from area X; input to the SMA originates largely from the pars oralis subdivision of the nucleus ventralis lateralis (VLo); and that to the motor cortex is largely from the pars oralis subdivision of the nucleus ventralis posterior lateralis (VPLo). These observations, when combined with prior studies on the termination of various subcortical efferents in the thalamus, lead to the following scheme of projections: rostral portions of the deep cerebellar nuclei project to motor cortex via VPLo, caudal portions of the deep cerebellar nuclei project to the APA via area X; and the globus pallidus projects to the SMA via VLo. Thus each thalamocortical pathway is associated with a distinct subcortical input.     

Altered sensorimotor integration in multiple sclerosis: A combined neurophysiological and functional MRI study

ObjectiveTo explore whether abnormal thalamic resting-state functional connectivity (rsFC) contributes to altered sensorimotor integration and hand dexterity impairment in multiple sclerosis (MS).MethodsTo evaluate sensorimotor integration, we recorded kinematic features of index finger abductions during somatosensory temporal discrimination threshold (STDT) testing in 36 patients with relapsing-remitting MS and 39 healthy controls (HC). Participants underwent a multimodal 3T structural and functional MRI protocol.ResultsPatients had lower index finger abduction velocity during STDT testing compared to HC. Thalamic rsFC with the precentral and postcentral gyri, supplementary motor area (SMA), insula, and basal ganglia was higher in patients than HC. Intrathalamic rsFC and thalamic rsFC with caudate and insula bilaterally was lower in patients than HC. Finger movement velocity positively correlated with intrathalamic rsFC and negatively correlated with thalamic rsFC with the precentral and postcentral gyri, SMA, and putamen.ConclusionsAbnormal thalamic rsFC is a possible substrate for altered sensorimotor integration in MS, with high intrathalamic rsFC facilitating finger movements and increased thalamic rsFC with the basal ganglia and sensorimotor cortex contributing to motor performance deterioration.SignificanceThe combined study of thalamic functional connectivity and upper limb sensorimotor integration may be useful in identifying patients who can benefit from early rehabilitation to prevent upper limb motor impairment.