Contralateral Primary Sensorimotor Cortex Research Articles

Differences of cortical activation pattern between cortical and corona radiata infarct

The aim of this study was to elucidate the differences of cortical activation pattern between patients with cortex (CO) infarct and those with corona radiata (CR) infarct. Twenty chronic patients with cerebral infarct and 11 normal subjects were recruited. The patients were classified into two groups according to infarct location: CO and CR group. After functional MRI was performed during the motor task of hand grasp-release movements, the hand motor function was assessed. The CO group tended to be activated on the contralateral primary sensori-motor cortex, whereas the CR group largely showed activation of the bilateral primary sensori-motor cortex. Namely, there was significantly more lateralized activation pattern of primary sensori-motor cortex in the CO group than in the CR group. Additionally, the CO group had better hand motor function than the CR group. Our results suggest that the motor recovery mechanism vary according to the lesion location between CO and CR infarct, indicating that the adaptive cortical reorganization proceeds under different patterns according to the lesion location.

Peri-infarct reorganization of motor function in patients with pontine infarct

Combined functional MRI (fMRI) and diffusion tensor tractography (DTT) imaging provides a powerful vehicle for the investigation of motor recovery mechanisms. Using this combined method, we investigated the motor recovery mechanism in patients with pontine infarct. We evaluated six healthy control subjects and two patients with pontine infarct at 6 months from onset. fMRI was performed at 1.5 T with timed hand grasp-release movements. For DTT, we used each of the 32 noncollinear diffusion-sensitizing gradients. Three-dimensional reconstructions of the fiber tracts were obtained with FA <0.3, angle >45 degrees as termination criteria. fMRI data revealed activation only in the contralateral primary sensorimotor cortex during movement of either hand. DTI findings from controls and the unaffected hemisphere of the patients showed that the corticospinal tract descended through the known corticospinal tract pathway. However, the tracts of the affected hemisphere in the patients were observed to pass along peri-infarct areas (patient 1: lateral, patient 2: posterior) in the pons. It seems that the peri-infarct areas compensate for corticospinal tract damage at the pons; this may be one mechanism of motor recovery for patients with pontine infarct.

Imaging correlates of motor recovery from cerebral infarction and their physiological significance in well-recovered patients

We studied motor representation in well-recovered stroke patients. Eighteen right-handed stroke patients and eleven age-matched control subjects underwent functional Magnetic Resonance Imaging (fMRI) while performing unimanual index finger (abduction–adduction) and wrist movements (flexion–extension) using their recovered and non-affected hand. A subset of these patients underwent Transcranial Magnetic Stimulation (TMS) to elicit motor evoked potentials (MEP) in the first dorsal interosseous muscle of both hands. Imaging results suggest that good recovery utilizes both ipsi- and contralesional resources, although results differ for wrist and index finger movements. Wrist movements of the recovered arm resulted in significantly greater activation of the contralateral (lesional) and ipsilateral (contralesional) primary sensorimotor cortex (SM1), while comparing patients to control subjects performing the same task. In contrast, recovered index finger movements recruited a larger motor network, including the contralateral SM1, Supplementary Motor Area (SMA) and cerebellum when patients were compared to control subjects. TMS of the lesional hemisphere but not of the contralesional hemisphere induced MEPs in the recovered hand. TMS parameters also revealed greater transcallosal inhibition, from the contralesional to the lesional hemisphere than in the reverse direction. Disinhibition of the contralesional hemisphere observed in a subgroup of our patients suggests persistent alterations in intracortical and transcallosal (interhemispheric) interactions, despite complete functional recovery.

Anticipatory Electroencephalography Alpha Rhythm Predicts Subjective Perception of Pain Intensity

This high-resolution electroencephalography (EEG) study tested the hypothesis that the suppression of rolandic alpha power before predictable painful stimulation affects the subject’s subsequent evaluation of pain intensity, as a reflection of the influence of expectancy processes on painful stimulus processing. High-resolution EEG data were recorded (126 channels) from 10 healthy adult volunteers during the expectancy of a painful CO 2-laser stimulation at the right wrist. Surface laplacian estimation enhanced the EEG spatial information content over 6 scalp regions of interest (left frontal, right frontal, left central, right central, left parietal, and right parietal areas). Spectral power was computed for 3 alpha sub-bands with reference to the individual alpha frequency peak (about 5-7 Hz for alpha 1, 7-9 Hz for alpha 2, and 9-11 Hz for alpha 3). The suppression of the alpha power before the painful stimulation [as reflected by the event-related desynchronization (ERD)] indexed the anticipatory cortical processes. Results showed maximum (negative) correlations between the alpha 2 and alpha 3 ERD amplitude at the left central area and the subjective evaluation of pain intensity ( P < .001). The stronger the anticipatory alpha 2 and alpha 3 ERD, the higher the subjective evaluation of pain intensity. For alpha 3, that correlation was confirmed even when the effect of habituation across the recording session was taken into account. These results suggest that the anticipatory suppression of the alpha rhythms over the contralateral primary sensorimotor cortex predicts subsequent subjects’ evaluation of pain intensity, in line with its crucial role for the discrimination of that intensity. Perspective This electroencephalographic study showed that anticipatory activation/deactivation of sensorimotor cortex roughly predicts subjective evaluation of pain. This motivates further investigation on possible implications for the understanding of central chronic pain. Chronic pain patients might exaggerate the anticipatory activation of sensorimotor cortex to negligible pain stimuli.

Loss of interhemispheric inhibition in patients with multiple sclerosis is related to corpus callosum atrophy

Axonal injury and loss in the corpus callosum (CC) is characteristic of the pathology of multiple sclerosis (MS). Functional magnetic resonance imaging (fMRI) potentially allows neurophysiological consequences of this interhemispheric axonal loss to be defined quantitatively. Here we have used 3T fMRI to study the activation in the contralateral primary sensorimotor cortex and deactivation (mediated by transcallosal tracts) in the homologous ipsilateral region in 14 patients with MS and in 14 matched healthy controls during a simple hand-tapping task. Both healthy controls and MS patients showed similar activation in the motor cortex contralateral to the hand moved, but the patients showed a significantly smaller relative deactivation in the ipsilateral motor cortex (P = 0.002). The difference was accounted for by the sub-group of MS patients who previously had impairment of motor function of the hand tested (MS-phd). The CC of the whole patient group was significantly thinner than for the controls (P = 0.001). Atrophy of the CC was correlated with loss of deactivation for the whole patient group (r = -0.50, P = 0.035), but particularly for MS-phd (r = -0.914, P = 0.004). Interhemispheric physiological inhibition thus is impaired in patients with MS, potentially contributing to impairment of motor control. This work suggests one way in which FMRI monitoring of the transcallosal interactions in motor cortex could become a tool for evaluation of therapies that may enhance function in reversibly impaired pathways.

An fMRI study of the motor system in patients with neuropsychiatric systemic lupus erythematosus

Functional cortical changes have been demonstrated in patients with several neurological conditions, including stroke, tumors and MS. The correlation found between the extent of fMRI activations and the extent and severity of brain structural damage suggests an adaptive role of these functional changes. In this study, we assess, using fMRI, the brain pattern of movement-associated cortical activations in neuropsychiatric systemic lupus erythematosus (NPSLE) patients and investigate whether the extent of cortical reorganization is associated with the extent of brain pathology, measured on dual-echo and diffusion tensor (DT) MR images. From 14 right-handed NPSLE patients and 14 matched controls, we obtained: (a) fMRI during the performance of repetitive flexion–extension of the last four fingers of the right hand; (b) dual-echo and (c) pulsed-gradient spin-echo echo-planar sequence to calculate DT MRI maps of the normal-appearing white (NAWM) and gray (NAGM) matter. Brain T2-visible abnormalities were detected in 11 NPSLE patients. Compared with controls, NPSLE patients had significantly higher NAWM fractional anisotropy histogram peak height ( P = 0.005), and more significant activations of the contralateral primary sensorimotor cortex, putamen and dentate nucleus. They also had more significant activations of several regions located in the frontal and parietal lobes as well as of MT/V5 and the middle occipital gyrus, bilaterally. Strong correlations (r values ranging from 0.79 to 0.87) were found between relative activations of sensorimotor areas and the extent and severity of brain damage. Movement-associated functional cortical changes do occur in patients with NPSLE and might contribute to the maintenance of their normal functional capacities.

Cortical adaptation in patients with MS: a cross-sectional functional MRI study of disease phenotypes

Movement-associated cortical reorganisation is known to occur in multiple sclerosis (MS). We aimed to define the development of such cortical reorganisation by comparing data from patients with different disease phenotypes. We studied patients with different phenotypes of MS: 16 patients with a clinically isolated syndrome (CIS), 14 patients with relapsing-remitting MS (RRMS) and no disability, 15 patients with RRMS and mild clinical disability, and 12 patients with secondary progressive MS (SPMS). Patients did a simple motor task with their unimpaired dominant hand during MRI, which was compared across the phenotype groups. Patients with a CIS activated more of the contralateral primary sensorimotor cortex than those with RRMS and no disability, whereas patients with RRMS and no disability activated more of the supplementary motor area than those with a CIS. Patients with RRMS and no disability activated more of the primary sensorimotor cortex, bilaterally, and more of the ipsilateral supplementary motor area than patients with RRMS and mild clinical disability. Conversely, patients with RRMS and mild clinical disability activated more of the contralateral secondary somatosensory cortex and inferior frontal gyrus, and the ipsilateral precuneus. Patients with RRMS and mild clinical disability activated more of the contralateral thalamus and of the ipsilateral secondary somatosensory cortex than those with SPMS. However, patients with SPMS activated more of the inferior frontal gyrus, bilaterally, the middle frontal gyrus, bilaterally, the contralateral precuneus, and the ipsilateral cingulate motor area and inferior parietal lobule. Movement-associated cortical reorganisation in patients with MS seems to vary across individuals at different stages of disease. Our study suggests that early in the disease course more areas typically devoted to motor tasks are recruited. Then bilateral activation of these regions is seen, and late in the disease course, areas that healthy people recruit to do novel or complex tasks are activated.

Somatotopy and movement representation sites following cortical stroke

Stroke has been associated with many changes in motor system function, but there has been limited study of changes in somatotopic organization. This was examined in a group of patients with cortical stroke affecting primary sensorimotor cortex. In 17 patients with good outcome after cortical stroke involving precentral and/or postcentral gyri, plus 14 controls, four functional MRI evaluations of brain activity were obtained: finger, shoulder, and face motor tasks plus a sensory task, passive finger motion. For each, coordinates for contralateral primary sensorimotor cortex activation site were determined, as was a measure of inter-hemispheric balance. The normal motor somatotopy measured in controls was largely preserved after stroke. The main difference found between controls and patients was that the face was lateral to finger motor activation in all controls, but face was centered medial to finger in 43% of patients. Among patients, smaller infarct volume was associated with more ventral, and larger infarct with more dorsal, contralateral primary sensorimotor cortex activation. On the other hand, better behavioral outcome was associated with a more posterior, and poorer outcome with more anterior, activation. Larger infarct and poorer behavioral outcome were each associated with a change in inter-hemispheric balance towards the non-stroke hemisphere. Shifts in contralateral movement representation site did not correlate with changes in inter-hemispheric balance. Motor somatotopy is generally preserved after injury to primary sensorimotor cortex. Greater injury and larger behavioral deficits are associated with distinct effects on movement representation sites. Changes in motor organization within and between hemispheres arise independently after stroke.

Cortical Reorganization of Hand Motor Function to Primary Sensory Cortex in Hemiparetic Patients With a Primary Motor Cortex Infarct

Jang SH, Ahn SH, Yang DS, Lee DK, Kim DK, Son SM. Cortical reorganization of hand motor function to primary sensory cortex in hemiparetic patients with a primary motor cortex infarct. Objective To show cortical reorganization in hemiparetic patients with a primary motor cortex (M1) infarct including the precentral knob by using functional magnetic resonance imaging (fMRI). Design Case-control. Setting Outpatient clinics in the rehabilitation department of a university hospital. Participants Two stroke patients and 20 control subjects. Interventions By using fMRI, we evaluated the hand motor function of 2 hemiparetic stroke patients, who had made some recovery from complete paralysis of the affected hand, and 20 control subjects. Main Outcome Measures fMRI was performed by using the blood oxygen level-dependent technique at 1.5T with a standard head coil. The motor task paradigm consisted of hand grasp-release movements. Results The contralateral primary sensorimotor cortex was activated by the hand movements of the control subjects and of the unaffected side of the 2 patients. Only the contralateral (infarct side) primary sensory cortex (S1) was activated by the movements of the affected hand of the 2 patients, a result that was not observed in the control subjects or with the unaffected hand in the stroke patients. Conclusions The hand motor function associated with the infarcted M1 in our patients was reorganized into the S1. These results suggest cortical reorganization in patients with an M1 infarct.

Spatiotemporal brain dynamics in response to muscle stimulation

The objective of the present study was to assess the spatiotemporal scenario of brain activity associated with sensory stimulation of the abductor pollicis brevis muscle. Spatiotemporal dipole models, using realistic individual boundary element head models, were built from somatosensory evoked potentials (SEPs; 64 Ch. EEG) to nonpainful and painful intramuscular electrostimulation (IMES) as well as to cutaneous electrostimulation delivered to the distal phalanx of the thumb. Nonpainful and painful muscle stimuli resulted in activation of the same brain regions. In temporal order, these were: the contralateral primary sensorimotor cortex, contralateral dorso-lateral premotor area (PM), bilateral operculo-insular cortices, caudal cingulate motor area (CMA), and posterior cingulate cortex/precuneus. Brain processing induced by muscle sensory input showed a characteristic pattern in contrast to cutaneous sensory input, namely: (1) no early SEP components to IMES; (2) an initial IMES component likely generated by proprioceptive input is not present for digit stimulation; (3) one source was located in the PM only for IMES. This source was unmasked by the lower stimulus intensity; (4) a source for IMES was located in the contralateral caudal CMA rather than being located in the cingulate gyrus. Cerebral sensory processing of input from the muscle involved several sensory and motor areas and likely occurs in two parallel streams subserving higher order somatosensory processing as well as sensory–motor integration. The two streams might on one hand involve sensory discrimination via SI and SII and on the other hand integration of sensory feedback for further motor processing via MI, lateral PM area, and caudal CMA.

Postural tremor in Wilson's disease: a magnetoencephalographic study.

The following study included 5 Wilson's disease (WD) patients showing a right-sided postural forearm tremor (4-6 Hz) and addressed the question of whether the primary motor cortex (M1) is involved in tremor generation. Using a 122-channel whole-head neuromagnetometer and surface electromyogram (EMG), we investigated cerebromuscular coupling. Postural tremor was observed in a sustained 45-degree posture of the right-sided forearm. Data were analyzed using dynamic imaging of coherent sources (DICS), revealing cerebromuscular coupling between EMG and cerebral activity. Coherent sources were superimposed on individual high-resolution T1-weighted magnetic resonance images (MRI). Phase lags between EMG and cerebral areas showing strongest coherence were determined by means of a Hilbert transform of both signals. In all patients, postural tremor was associated with strong coherence between tremor EMG and activity in contralateral primary sensorimotor cortex (S1/M1) at tremor or double tremor frequency. Phase lag values between S1/M1 activity and EMG revealed efferent and afferent components in the corticomuscular coupling. Taken together, our results indicate that postural tremor in WD is mediated through a pathological oscillatory drive from the primary motor cortex.

Pyramidal tract lesions and movement-associated cortical recruitment in patients with MS

Cortical functional changes, with the potential to limit the functional consequences of tissue injury, have been shown in patients with multiple sclerosis (MS). In this study, we assessed the influence of MS-related tissue damage of the brain portion of the left pyramidal tract on the corresponding movement-associated patterns of cortical recruitment in a large sample of MS patients when performing a simple motor task with their fully normal functioning right upper limbs. We investigated 76 right-handed patients with definite MS. In each subject, functional magnetic resonance imaging (fMRI) was acquired during the performance of a simple motor task with the dominant, right upper limb. During the same session, dual-echo, magnetization transfer (MT) and diffusion tensor (DT) MRI sequences were also obtained to quantify the extent and the severity of pyramidal tract damage. Lesions along the left pyramidal tract were identified in 43 patients. Compared to patients without pyramidal tract lesions, patients with such lesions had more significant activations of the contralateral primary sensorimotor cortex (SMC), secondary sensorimotor cortex (SII), inferior central sulcus, and cingulate motor area (CMA). They also showed more significant activations of several regions of the ipsilateral hemisphere, including the primary SMC and the precuneus. In these patients, T2 lesion load of left pyramidal tract was correlated with the extent of activation of the contralateral primary SMC ( r 2 = 0.25, P < 0.0001), whereas no correlations were found between the extent of fMRI activations and the severity of intrinsic lesion damage, as well as with left pyramidal tract normal-appearing white matter damage. This study shows that, in patients with MS, following injury of the motor pathways, there is an increased recruitment of a widespread sensorimotor network, which is likely to contribute to limit the appearance of overt clinical deficits.

Ankle dorsiflexion as an fMRI paradigm to assay motor control for walking during rehabilitation

The ability to walk independently with the velocity and endurance that permit home and community activities is a highly regarded goal for neurological rehabilitation after stroke. This pilot study explored a functional magnetic resonance imaging (fMRI) activation paradigm for its ability to reflect phases of motor learning over the course of locomotor rehabilitation-mediated functional gains. Ankle dorsiflexion is an important kinematic aspect of the swing and initial stance phase of the gait cycle. The motor control of dorsiflexion depends in part on descending input from primary motor cortex. Thus, an fMRI activation paradigm using voluntary ankle dorsiflexion has face validity for the serial study of walking-related interventions. Healthy control subjects consistently engaged contralateral primary sensorimotor cortex (S1M1), supplementary motor area (SMA), premotor (PM) and cingulate motor (CMA) cortices, and ipsilateral cerebellum. Four adults with chronic hemiparetic stroke evolved practice-induced representational plasticity associated with gains in speed, endurance, motor control, and kinematics for walking. For example, an initial increase in activation within the thoracolumbar muscle representation of S1M1 in these subjects was followed by more focused activity toward the foot representation with additional pulses of training. Contralateral CMA and the secondary sensory area also reflected change with practice and gains. We demonstrate that the supraspinal sensorimotor network for the neural control of walking can be assessed indirectly by ankle dorsiflexion. The ankle paradigm may serve as an ongoing physiological assay of the optimal type, duration, and intensity of rehabilitative gait training.

Cerebral motor control in patients with gliomas around the central sulcus studied with spatially filtered magnetoencephalography

Objective: Application of spatially filtered magnetoencephalography (MEG) to investigate changes in the mechanism of cerebral motor control in patients with tumours around the central sulcus. Methods: MEG records were made...

Subthalamic nucleus stimulation modulates motor cortex oscillatory activity in Parkinson's disease.

In Parkinson's disease, impaired motor preparation has been related to an increased latency in the appearance of movement-related desynchronization (MRD) throughout the contralateral primary sensorimotor (PSM) cortex. Internal globus pallidus (GPi) stimulation improved movement desynchronization over the PSM cortex during movement execution but failed to improve impaired motor preparation. PET studies indicate that subthalamic nucleus (STN) stimulation partly reverses the abnormal premotor pattern of brain activation during movement. By monitoring MRD, we aimed to assess changes in premotor and PSM cortex oscillatory activity induced by bilateral STN stimulation and to compare these changes with those induced by l-dopa. Ten Parkinson's disease patients and a group of healthy, age-matched controls performed self-paced wrist flexions in each of four conditions: without either stimulation or l-dopa (the 'off' condition), with stimulation and without l-dopa (On Stim), with l-dopa and without stimulation ('on drug'), and with both stimulation and l-dopa (On Both). Compared with the Off condition, in both the On Stim and the On Drug condition the Unified Parkinson's Disease Rating Scale (UPDRS) III score decreased by about 60% and in the On Both condition it decreased by 80%. The desynchronization latency over central regions contralateral to movement and the movement desynchronization over bilateral central regions were significantly increased by stimulation and by l-dopa, with a maximal effect when the two were associated. Furthermore, desynchronization latency significantly decreased over bilateral frontocentral regions in the three treatment conditions compared with the Off condition. In Parkinson's disease, STN stimulation may induce a change in abnormal cortical oscillatory activity patterns (similar to that produced by l-dopa) by decreasing the abnormal spreading of desynchronization over frontocentral regions and increasing PSM cortex activity during movement preparation and execution, with a correlated improvement in bradykinesia. Parkinsonians under treatment displayed a desynchronization pattern close to that seen in healthy, age-matched controls, although central latencies remained shorter. The study indicates that it is possible to influence cortical reactivity related to the planning and execution of voluntary movement through the basal ganglia, and furthermore that the oscillatory activity of the PSM cortex (in addition to that of premotor areas) could be of major importance in the control of movement-associated, neural activity in Parkinson's disease.

Attentional processes and cognitive performance during expectancy of painful galvanic stimulations: a high-resolution EEG study

In the present high-resolution electroencephalographic (EEG) study, an omitted-stimulus paradigm induced a strong expectancy for a predictable painful stimulation (nonpainful in the control condition). During the expectancy of pain, concurrent cognitive demands were superimposed. The aim was to investigate the effects on primary sensorimotor and central midline areas of the competition among concurrent attentional processes related to cognition and pain expectancy, as indexed by behavioral performance and EEG data. A main issue was whether cognitive performance decreases, due to a re-allocation of attentional resources on primary sensorimotor and midline areas for the anticipation of pain. Behavioral results showed no differences in the cognitive (working memory) performance during the expectancy of nonpainful versus painful stimulations. In parallel, anticipatory event-related potentials (ERPs) were negligible in line with a low emotional reactivity/alertness as revealed by heart rate deceleration (HRD), skin conductance response (SCR), and low-band (6–10 Hz) alpha EEG oscillations. In contrast, high-band alpha EEG oscillations (10–12 Hz) over the contralateral primary sensorimotor cortex decreased more during the expectancy of painful compared to nonpainful stimuli, in line with an increased anticipatory preparation of the somatosensory channel. These findings provide further evidence on the fact that attentional processes at the basis of cognition can be defended by the anticipation of pain, at least when the incoming painful stimuli are repetitive and predictable. This happens even if the brain increases preparatory processes of the specific sensory channel to be targeted by the painful stimulus.

The musician's brain: functional imaging of amateurs and professionals during performance and imagery

We compared activation maps of professional and amateur violinists during actual and imagined performance of Mozart's violin concerto in G major (KV216). Execution and imagination of (left hand) fingering movements of the first 16 bars of the concerto were performed. Electromyography (EMG) feedback was used during imagery training to avoid actual movement execution and EMG recording was employed during the scanning of both executed and imagined musical performances. We observed that professional musicians generated higher EMG amplitudes during movement execution and showed focused cerebral activations in the contralateral primary sensorimotor cortex, the bilateral superior parietal lobes, and the ipsilateral anterior cerebellar hemisphere. The finding that professionals exhibited higher activity of the right primary auditory cortex during execution may reflect an increased strength of audio–motor associative connectivity. It appears that during execution of musical sequences in professionals, a higher economy of motor areas frees resources for increased connectivity between the finger sequences and auditory as well as somatosensory loops, which may account for the superior musical performance. Professionals also demonstrated more focused activation patterns during imagined musical performance. However, the auditory–motor loop was not involved during imagined performances in either musician group. It seems that the motor and auditory systems are coactivated as a consequence of musical training but only if one system (motor or auditory) becomes activated by actual movement execution or live musical auditory stimuli.

Abstract 19: Cortical reorganization of hand motor function to primary sensory cortex in hemiparetic patients with a primary motor cortex infarct.

Objective: To demonstrate cortical reorganization in hemiparetic patients with a primary motor cortex (M1) infarct using functional magnetic resonance imaging (fMRI). Design: The hand motor function of 2 hemiparetic stroke patients and 20 control subjects was evaluated by fMRI. Setting: Academic medical center. Participants: 2 hemiparetic patients and 20 control subjects with no history of neurologic disease. Interventions: fMRI was performed using the blood oxygen level-dependent technique at 1.5T. For the motor task paradigm, hand grasp-release movements were performed at a frequency of 1Hz for stimulation, guided with a metronome, over a repeated cycle of 15 seconds of control and 15 seconds of stimulus. Each task paradigm of alternating control-stimulus (30s) was repeated 3 times. Main Outcome Measures: fMRI data were analyzed using SPM-99 software running under the Matlab environment. The images were then smoothed with an 8mm isotropic gaussian kernel. Statistical parametric maps were obtained and voxels were considered significant at P<.001, uncorrected, with the additional requirement of a cluster size of 5 voxels. Results: The contralateral primary sensorimotor cortex was activated by the hand movements of control subjects and of the unaffected side of the 2 patients. Only the contralateral (infarct side) primary sensory cortex (S1) was activated by the affected hand movements of the 2 patients, a result that was not observed in control subjects or the unaffected hand of stroke patients. Conclusions: We believe that the hand motor function of the infarcted M1 of these patients was reorganized into S1. It seems that cortical reorganization took place in patients with an M1 infarct.

A functional magnetic resonance imaging study of patients with secondary progressive multiple sclerosis

Although several functional magnetic resonance imaging (fMRI) studies have shown adaptive cortical changes in patients with early multiple sclerosis (MS), the presence of brain plasticity and its role in limiting the functional consequences of brain tissue damage in patients with secondary progressive (SP) MS have not been fully investigated yet. In this study, we assessed the movement-associated brain pattern of cortical activations in patients with SPMS and investigated whether the extent of cortical brain activations is correlated with the extent of brain structural changes. From 13 right-handed SPMS patients and 15 sex- and age-matched healthy volunteers, we obtained: (a) brain dual-echo scans; (b) brain mean diffusivity and fractional anisotropy maps of the normal-appearing white (NAWM) and gray matter (NAGM); (c) fMRI during the performance of simple motor tasks [flexion–extension of the last four fingers of the right hand (task 1) and flexion–extension of the right foot (task 2)]. Compared to healthy volunteers, during task 1 performance, SPMS patients showed more significant activations of the ipsilateral inferior frontal gyrus, middle frontal gyrus, bilaterally, and contralateral intraparietal sulcus. During task 2 performance, SPMS patients had more significant activations of the contralateral primary sensorimotor cortex and thalamus and of the ipsilateral upper bank of sylvian fessure. For both tasks, strong correlations ( r values ranging from −0.83 to 0.88) were found between relative activations of cortical areas of the motor network and the severity of structural changes of the NAWM and NAGM. This study demonstrates that cortical plasticity does occur in patients with SPMS and that it might have a role in limiting the clinical impact of MS-related damage. It also suggests that, in these patients, functional abilities are sustained by increased recruitment of highly specialized cortical areas.

Cortical activations associated with auditorily paced finger tapping

We investigated neuromagnetic responses during an auditorily paced synchronization task using a 122-channel whole-head neuromagnetometer. Eight healthy right handed subjects were asked to synchronize left and right unilateral finger taps to a regular binaural pacing signal. Synchronization of the right hand with an auditory pacing signal is known to be associated with three tap-related neuromagnetic sources localized in the contralateral primary sensorimotor cortex. While the first source represents the neuromagnetic correlate of the motor command the second one reflects somatosensory feedback due to the finger movement. The functional meaning of the third source, which is also localized in the primary somatosensory cortex is still unclear. On the one hand this source represents a neuromagnetic correlate of somatosensory feedback due to the finger tap. On the other hand it has been suggested that the function of this source could additionally represent a cognitive process, which enables the subject to monitor the time distance between taps and clicks. The aim of the present study was to elucidate the function of this source, which would fundamentally reform the meaning of the primary somatosensory cortex in the timing of movements with respect to external events. The data of the present study demonstrate that the three sources in the contralateral sensorimotor cortex are stronger related to the tap than to the click. This result contradicts the assumption of a cognitive process localized in the primary somatosensory cortex. Thus, activation in the primary somatosensory cortex most likely represents exclusively somatosensory feedback and no further cognitive processes.