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At least 343 records · Page 19Linked to original sources
PubMed2001

Assessment of reorganization in the sensorimotor cortex after upper limb amputation.

OBJECTIVE: We wanted to investigate plastic changes occurring in the motor and somatosensory cortex after upper limb amputation, and their possible relationship to phantom pain. METHOD: To assess these plastic changes, we used transcranial magnetic stimulation (TMS) and source localization of somatosensory evoked potentials (SEP). Eleven patients with upper limb amputation were investigated. The phantom pain intensity was assessed by visual analogue scaling (VAS). RESULTS: Using TMS mapping, we found a significant lateralization of the amplitude-weighted centre of gravity (P<0.01) and an enlargement of the excitable area (P<0.05) on the hemisphere contralateral to the amputation. SEP mapping showed a significant medialization of the N20 dipole (P<0.05) on this side. None of these changes correlated with the phantom pain intensity. CONCLUSIONS: We conclude that after limb amputation, the relationship between plastic changes occurring in the sensorimotor cortex and phantom pain seems to be more complex than previously believed.

Adult↗
PubMed1998

Intraoperative localization of functional regions in the sensorimotor cortex by neuronavigation and cortical mapping.

Surgery of lesions within the central region requires exact intraoperative anatomical orientation and knowledge of the position of functional cortical regions to minimize the surgical trauma and to avoid postoperative neurological deficits. We combined somatosensory evoked potential (SSEP) phase reversal and/or cortical electrical stimulation with neuronavigation in 26 patients for localization and visualization of functional cortical areas and their anatomical site in relation to the lesion. After location of the central sulcus by means of SSEP phase reversal, the precentral gyrus was electrically stimulated to detect functional motor regions. Electrode position was documented, and the functional regions were related to the site of the lesion using a specially developed neuronavigation system. In 11 of 15 patients the central fissure was located with SSEP phase reversal. Electrical stimulation yielded motor evoked potentials in 23 of the total 26 patients. The anatomical site of these functional regions and their relation to the lesion were evaluated with the neuronavigation system. The precentral gyrus, central sulcus, and postcentral gyrus could be identified in all 23 cases. The combination of intraoperative electrophysiological mapping and neuronavigation provides safe and reliable localization of the sensorimotor cortex. This technique is a promising tool to minimize the risk of surgically caused sensory and motor deficits.

Adult↗
PubMedDate not supplied

Age-related changes in the cytoarchitectonics of the human sensorimotor cortex.

The projection zones of the movement analyzer show a level of maturity which is required for maintaining the self-regulatory processes in children from the first days of life [4, 8]. The cytoarchitectonics of the motor zone of the cerebral cortex have been studied in a small number of people and at limited ages [1, 2, 4, 10]. One of the leading age-related changes consists of changes in neuronal and interneuronal connections, which have significant influences on the systems organization of the brain and its function as an integral organ. Pyramidal neurons are regarded as the main universal type of cortical neuron, in which the structure of the receptive surface supports transmission of a wide range of polymodal signals [1]. Large pyramidal neurons in layers III and IV can establish connections with all the neurons in a column of cells, which apparently leads to complete and reliable functional interactions between neurons [1, 6]. The aim of the present work was to study the quantitative changes in pyramidal neurons in layers III and IV in various fields of the human sensorimotor cortex from birth to the age of 20 years.

Adolescent↗
PubMed2004

Modulatory effects on human sensorimotor cortex by whole-hand afferent electrical stimulation.

OBJECTIVE: To investigate the effect of electrical stimulation of the nerve afferents of the hand on cortical activity elicited by whole-hand subthreshold stimulation for sensation in healthy human subjects. METHODS: Ten healthy volunteers were studied using BOLD-fMRI with 1) a test motor-task with finger-to-thumb tapping of the left hand, 2) a whole-hand afferent electrical stimulation of the left hand below the sensory level for sensation for 30 minutes, 3) a second fMRI run with the same paradigm as in the test motor-task immediately after electrical stimulation, and 4) a final identical fMRI run 2 hours post-stimulation to test the cortical changes induced by electrical stimulation. Experiments were carried out on a 1.5 T MR scanner and for fMRI echoplanar sequences were used. Data analysis was performed with SPM99. RESULTS: An increase of movement-related responses was seen within the primary motor and primary somatosensory areas of both hemispheres when comparing the test motor-task with the motor-task after electrical stimulation relative to the baseline or sham stimulation. Two hours post-stimulation the modulatory effects of mesh-glove stimulation diminished to baseline level except within the contralateral primary motor region. CONCLUSIONS: The increased BOLD response spatially localized within the sensorimotor cortex reflects an increase in neuronal activity that may provide augmented neuronal excitability.

Adult↗
PubMed2003

Role of primary sensorimotor cortex and supplementary motor area in volitional swallowing: a movement-related cortical potential study.

We investigated the role of the cerebral cortex, particularly the face/tongue area of the primary sensorimotor (SMI) cortex (face/tongue) and supplementary motor area (SMA), in volitional swallowing by recording movement-related cortical potentials (MRCPs). MRCPs with swallowing and tongue protrusion were recorded from scalp electrodes in eight normal right-handed subjects and from implanted subdural electrodes in six epilepsy patients. The experiment by scalp EEG in normal subjects revealed that premovement Bereitschaftspotentials (BP) activity for swallowing was largest at the vertex and lateralized to either hemisphere in the central area. The experiment by epicortical EEG in patients confirmed that face/tongue SMI and SMA were commonly involved in swallowing and tongue protrusion with overlapping distribution and interindividual variability. BP amplitude showed no difference between swallowing and tongue movements, either at face/tongue SMI or at SMA, whereas postmovement potential (PMP) was significantly larger in tongue protrusion than in swallowing only at face/tongue SMI. BP occurred earlier in swallowing than in tongue protrusion. Comparison between face/tongue SMI and SMA did not show any difference with regard to BP and PMP amplitude or BP onset time in either task. The preparatory role of the cerebral cortex in swallowing was similar to that in tongue movement, except for earlier activation in swallowing. Postmovement processing of swallowing was lesser than that of tongue movement in face/tongue SMI; probably suggesting that the cerebral cortex does not play a significant role in postmovement processing of swallowing. SMA plays a supplementary role to face/tongue SMI both in swallowing and tongue movements.

Adult↗
PubMedDate not supplied

The dependance of neuronal reactions of the sensorimotor cortex to a simultaneous complex stimulus upon the level of differentiation of its components.

The change in the neuronal activity of the sensorimotor area of the cerebral cortex of the cat was investigated in awake animals as a function of the level of differentiation of the components of a simultaneous heteromodal complex stimulus. Two groups of neurons in the sensorimotor cortex were distinguished on the basis of the character of this relationship and a number of other parameters. It was shown that the parameters of the reactions of all neurons recorded to the positive conditional stimulus following the consolidation of the conditioned motoric reaction are established first. Such parameters of the responses as degree of manifestation, intensity, duration, and the length of the latent period changed in the process of development. The reactions of neurons of both groups to inhibitory signals were stabilized only after the consolidation of the differentiation skill. In the process only the pattern of the discharge changed in the neurons of the first group, while in the neurons of the second group, the degree of manifestation of the response, its sign, duration, and length of the latent period could vary. Fluctuations in the level of differentiation following the development of the inhibitory conditioned reactions had an effect only on the responses of the neurons of the second group to the components of the complex.

Acoustic Stimulation↗
PubMed1984

[Changes in the arterial pressure and evoked potential in the sensorimotor cortex induced by nalorphine injected in the hypothalamus during painful electric shock in rabbits].

During the hypotensive phase of electronocuous shock in rabbits, injection of nalorphine to the hypothalamus provoked elevation in the blood pressure (BP), recovery of the evoked potential (EP) of the sensorimotor brain cortex in response to electrodermal stimulation (EDS) of the hind limb. Injection of the drug to the central gray of the midbrain resulted in an insignificant short-term elevation of the BP followed by its drop. It is concluded that the endogenous opioid system of the hypothalamus is of importance in the genesis of the hypotensive response and suppression of the EP of the rabbit sensorimotor brain cortex in response to EDS during electronocuous shock.

Animals↗
PubMed1978

Developing role of sensorimotor cortex and pyramidal tract neurons in contact placing in kittens.

Unilateral or bilateral removal of kitten sensorimotor (SM) cortex prior to the fourth postnatal week was followed by recovery of contact placing (CP) to stimulation of any of the four forepaw cutaneous fields. However, immediately after a removal under ethyl chloride, CP was depressed contralaterally, especially to lateral stimulation (lateral CP). When the operated kitten aged to 5--9 weeks, the likelihood of CP secondarily declined contralateral to the SM cortical extirpation, but was restored by administration of d-amphetamine. An initial extirpation after the fifth postnatal week was followed by a severe deficit in CP. 2. Cooling the SM cortex, internal capsule or bulbar pyramid during the 2nd and 3rd week was followed by reversible, contralateral loss of lateral CP, extension of the forelimb and, later, by reduced movements. Lateral CPs were often hypermetric prior to loss. By contrast, cooling SM cortex in the first week was usually ineffective. Thus, during the 2nd week, lateral CP developed a dependence on SM cortex, and in particular on PT neurons. 3. After a delay usually of 1 or more min, cooling the SM cortex reduced the resting discharge of individual neurons in buried motor cortex; the antidromic conduction time in PT neurons was significantly increased and the spike height was reduced.

Animals↗
PubMed2000

Long-term changes of GABAergic function in the sensorimotor cortex of amputees. A combined magnetic stimulation and 11C-flumazenil PET study.

Primary sensory and motor areas of the cerebral cortex contain organised maps of the body. These maps appear to reorganise after damage to the peripheral parts of the sensory or motor systems, so that the cortical representation of undamaged structures expands at the expense of the damaged parts. Several studies in animals have suggested that decreased activity of the inhibitory GABAergic neurones is responsible for driving these changes. However, whether similar mechanisms sustain the effects in the longer term in humans is unknown. The present study addressed this question by examining reorganisation of sensorimotor areas of cortex in six unilateral upper limb amputees several years after the initial injury. We measured two independent indices of GABAergic function. Volumes of distribution of GABA(A) receptors were determined from 11C-flumazenil binding measured with positron emission tomography (PET). The strength of inhibition in the motor cortex was measured with paired-pulse transcranial magnetic stimulation. In the six amputees taken as a whole and compared with 24 normal subjects, there was a highly significant increase in 11C-flumazenil binding in the upper limb region of primary sensorimotor cortex bilaterally and in medial frontal cortex of the hemisphere contralateral to the amputation. Surprisingly, however, there was no change in the time course or strength of intra-cortical inhibition in the motor cortex of the amputees compared with matched control subjects. The increased 11C-flumazenil binding may reflect up-regulation of GABA(A) receptors to compensate for a decrease in the GABA content or activity of inhibitory neurones. Up-regulation of GABA(A) receptors may also indicate that long-term changes require stabilisation of cortical organisation.

Adult↗
PubMed1991

Cortical microstimulation thresholds adjacent to sensorimotor cortex injury.

The initial severe contralateral impairment of motor function after unilateral damage to a portion of sensorimotor (SM) cortex lessens within a few weeks after injury. In this study, two hypotheses proposed to explain recovery of behavioral function after cortical injury were tested: (1) Intact cortex adjacent to the injury reorganizes to take over the function of the destroyed area. (2) Intact SM cortex adjacent or connected to the injured area undergoes a transient shock (diaschisis), and as this dissipates, some behavioral recovery occurs. Using microstimulation of the cortex of the adult rat, movements evoked from areas near cortical injuries were studied at various times after undercut laceration, contusion, or suction ablation of an area of SM cortex. Stimulation areas were compared to those obtained from uninjured control animals and to the contralateral uninjured hemisphere. No evidence was obtained for any reorganization of stimulated motor responses in the injured hemisphere even in animals followed for as long as 475 days postinjury, suggesting other mechanisms underlying functional recovery. In intact cortex at some distance from contusion and laceration injuries, there was a marked elevation of thresholds to evoke movements that returned to normal by 9-15 days postinjury. Some intact hindlimb responses were observed after contusion injury that were absent in animals after 15 days postinjury, indicating a slow-growing lesion after this type of trauma. Surprisingly, no elevation in thresholds was noted for ablation injuries up to the edge of the cavity at any time postinjury, indicating that threshold changes near the boundary may be uncorrelated with functional recovery.

Animals↗
PubMed1996

Activation PET scanning in pretreatment evaluation of patients with cerebral tumours or vascular lesions in or close to the sensorimotor cortex.

Treatment of tumours and vascular lesions in or close to eloquent cortex may inflict neurological deficits. Intra-operative mapping procedures have been used for many decades in efforts to minimize neurological sequelae. The possibility for non-invasive pre-operative brain mapping has emerged with the advent of positron emission tomography (PET). In this paper we report on 11 patients with a tumour or vascular lesion in or close to the sensorimotor (10 patients) or visual cortex (one patient). The patients were subjected to activation PET scanning by means of vibrotactile or visual stimulation. The results show that in most of the patients the important relation between the lesion and the sensorimotor cortex could be determined. The patient with a lesion in the occipital lobe had involvement of the entire visual cortex as judged by comparison with activated areas on the nonlesion side.

Adult↗
PubMed1993

Effects of nimodipine on two neurologic measures sensitive to sensorimotor cortex damage.

Seventeen rats with lesions involving the sensorimotor forepaw and hindpaw regions were tested for the ability to run along a narrow bridge without slipping and to hold on to a small-diameter dowel suspended above the ground. Nine of the animals received the calcium channel blocker, nimodipine, once per day for the first 2 weeks after surgery, while the remaining eight rats received vehicle alone. Repeated measurements over the first 3 postoperative weeks showed deficits among the rats with lesions on both tasks. The animals treated with nimodipine, however, showed much better recovery, especially after the initial testing sessions.

Analysis of Variance↗