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Results for “Motor Cortex”

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PubMed1994

Efferents of frontal or occipital cortex grafted into adult rat's motor cortex.

Phaseolus vulgaris leucoagglutinin (PHA-L) was used to examine the efferent connectivity of embryonic (E16) frontal (homotopic) or occipital (heterotopic) neocortical transplants placed into--or in the vicinity of--lesion cavities made in the frontal cortex of adult recipients. Homotopic transplants projected towards the host sensorimotor cortex and, in most cases, into the lateral caudate-putamen (CPu). Heterotopic transplants projected into the anterior cingulate cortex and, in most cases, distributed terminals into the medial CPu. It is suggested that embryonic neocortical tissue placed into a damaged cortical site of an adult recipient develops a pattern of efferents corresponding to its cortical origin.

Animals↗

PubMed2004

Recovery of pain control by intensive reprogramming after loss of benefit from motor cortex stimulation for neuropathic pain.

INTRODUCTION: Motor cortex stimulation (MCS) may serve as an adjunct in managing neuropathic pain after other conservative and interventional methods have failed. However, the magnitude and duration of the benefit are highly variable, with a significant percentage of patients losing pain relief over time. We investigated whether intensive reprogramming could recapture the beneficial effects of MCS. METHODS: Six patients who had previously undergone MCS implantation for neuropathic pain but had lost benefit were brought back for 1-5 days of intensive reprogramming. Four patients were evaluated as inpatients while the others were seen as outpatients during multiple visits over several days. Several hours a day were spent with each patient. Patients completed visual analog scale (VAS) ratings at intervals throughout the reprogramming period to judge effectiveness of stimulation. Pre- and postadjustment VAS were compared using a paired t test. RESULTS: The patients' average age was 50 years (range 26-71). The diagnoses were trigeminal neuropathic pain (2 patients), complex regional pain syndrome I (2), phantom limb pain (1) and poststroke pain (1). The mean duration of pain was 6 years. The MCS benefit had initially lasted for a mean of 7.16 months (range 2-18 months). After reprogramming, 5 of 6 patients experienced improvement in pain. Average VAS scores decreased from 7.44 to 2.28 (p < 0.001) in those patients who responded to reprogramming. The average stimulation parameters in these patients were 5 V amplitude (range 1.7-10), 313 micros pulse width (range 240-390) and frequency of 84 Hz (range 55-130). Three patients experienced seizures during reprogramming. The mean seizure threshold was 8.9 V. No patient experienced seizures at their therapeutic settings. Pain control has been maintained after discharge. CONCLUSION: Intensive reprogramming can recapture the benefit of MCS in patients who have lost pain control. The use of broad dipoles using two contacts rather than one contact of the 1 x 4 electrode array improved the ability to recapture beneficial stimulation. There is a significant risk of seizures during aggressive reprogramming.

Adult↗

PubMed1997

The existence of a layer IV in the rat motor cortex.

We have reconstructed the laminar pattern of rat primary motor cortex (Fr1) using a computerized analysis system based on the so-called 'optical dissector'. Data were visualized on a graphics terminal. In contrast to current views, which state that there is no prominent layer IV in the motor cortex of the rat, our method of analysis revealed a genuine layer IV consisting of densely packed small neurons.

Animals↗

PubMed2002

Motor cortex activation is preserved in patients with chronic hemiplegic stroke.

Many central nervous system conditions that cause weakness, including many strokes, injure corticospinal tract but leave motor cortex intact. Little is known about the functional properties of surviving cortical regions in this setting, in part because many studies have used probes reliant on the corticospinal tract. We hypothesized that many features of motor cortex function would be preserved when assessed independent of the stroke-affected corticospinal tract. Functional MRI was used to study 11 patients with chronic hemiplegia after unilateral stroke that spared regions of motor cortex. Activation in stroke-affected hemisphere was evaluated using 3 probes independent of affected corticospinal tract: passive finger movement, a hand-related visuomotor stimulus, and tapping by the nonstroke index finger. The site and magnitude of cortical activation were similar when comparing the stroke hemisphere to findings in 19 control subjects. Patients activated each of 8 cortical regions with similar frequency as compared to controls, generally with a smaller activation volume. In some cases, clinical measures correlated with the size or the site of stroke hemisphere activation. The results suggest that, despite stroke producing contralateral hemiplegia, surviving regions of motor cortex actively participate in the same proprioceptive, visuomotor, and bilateral movement control processes seen in control subjects.

Aged↗

PubMed1997

[Surgery of the rolandic region guided by the peroperative localization of the primary motor cortex and neuro-navigation].

Surgery close to the central motor area carries the risk of a new or increased postoperative motor deficit. One reason is the difficulty of localizing the motor cortex when it is displaced by the tumor. Neurosurgeons have long recognised the need for anatomical and functional localisations during any procedure and nowhere is this more important than in and around the central region. For ten years, we have used modern imaging techniques which provide a wealth of information concerning anatomy and pathophysiology and a new method of intraoperative localization of the primary motor cortex based on the application of single anodal electric pulses to the brain surface. In fifty patients, lesions within or adjacent to the motor area were microsurgically resected using a minimally invasive surgical technique.

Adolescent↗

PubMed2004

Amphetamine enhances training-induced motor cortex plasticity.

OBJECTIVES: Repetitive synchronized movements lead to short-term plastic changes in the primary motor cortex, which can be assessed by transcranial magnetic stimulation (TMS). Drugs which enhance such plastic changes could be of therapeutical interest, e.g. in patients with cerebral lesions. MATERIAL AND METHODS: We studied the effect of amphetamine on motor performance and plastic changes in the motor cortex as revealed by TMS mapping in healthy humans, who had to train a repetitive synchronized movement over 1 h. RESULTS: Cortical plastic changes observed after 1 h of training were more pronounced with amphetamine, whereas motor performance did not differ between training sessions with and without amphetamine. CONCLUSION: We conclude that amphetamine is able to enhance training-induced motor cortex plasticity. This effect could be due to its known influence on the GABAergic and glutamatergic system, but might also result from its role as an indirect catecholaminergic agonist.

Adult↗

PubMed2003

Modulation of excitability of human motor cortex (M1) by 1 Hz transcranial magnetic stimulation of the contralateral M1.

OBJECTIVE: Previous studies demonstrated that single-pulse transcranial magnetic stimulation (TMS) of one motor cortex (M1) exerts a brief inhibitory effect on the contralateral M1. The purpose of this study was to test the hypothesis that 30min of 1Hz TMS of M1 will result in a lasting increase in excitability in the contralateral M1. METHODS: Healthy volunteers were tested on 2 separate days, before (baseline) and after one of two interventions: (a) stimulation of M1 with 1Hz TMS for 30min at 115% of resting motor threshold, and (b) sham stimulation. Recruitment curves to TMS, pinch force, and simple reaction time were assessed in the hand contralateral to the unstimulated motor cortex. RESULTS: The main finding of this study was that 30min of 1Hz significantly increased recruitment curves in the contralateral motor cortex in the real stimulation condition relative to sham (P<0.005, factorial analysis of variance (ANOVA)). This change outlasted the stimulation period for at least 15min and occurred in the absence of changes in pinch force or reaction time. CONCLUSIONS: These results raise the potential for inducing lasting modulation of excitability in M1 by 1Hz TMS of the other M1, a phenomenon possibly reflecting modulation of interhemispheric interactions. SIGNIFICANCE: It is conceivable that 1Hz TMS applied to M1 may be used to modulate excitability in the opposite motor cortex for therapeutic purposes.

Aged↗

PubMed2001

Proton magnetic resonance spectroscopy (1H-MRS) of motor cortex and basal ganglia in de novo Parkinson's disease patients.

Proton MR spectroscopy (1H-MRS) has been previously performed in Parkinson's disease (PD) and parkinsonian syndromes to evaluate in vivo concentrations of basal ganglia and cerebral cortex metabolites such as N-acetylaspartate (NAA), choline (Cho), and creatine (Cr). However, this technique has never been used to evaluate motor cortex in untreated PD patients. In this study, single-voxel 1H-MRS of basal ganglia and motor cortex was carried out in 10 de novo patients with PD and 10 age-matched healthy controls. A significant reduction in the NAA/Cr ratio was observed in the motor cortex of PD patients compared with controls (p)<(0.01). Basal ganglia spectra did not allow any evaluation due to the presence of artefacts related to inorganic paramagnetic substances. The motor cortex reduction of the NAA/Cr ratio in de novo PD patients may reflect an altered neuronal functioning due to a loss of thalamocortical excitatory inputs and may represent an in vivo marker for the diagnosis of PD.

Aged↗

PubMed1999

Functional MR imaging of the motor cortex in healthy volunteers and patients with brain tumours: qualitative and quantitative results.

The purpose of this study was to compare functional magnetic resonance (MR) imaging of the motor cortex in healthy volunteers and patients with brain tumours. Functional MR imaging was performed in 14 healthy volunteers and 14 patients with tumours in or near the primary motor cortex with groups being matched for age, sex, and handedness. Functional images were acquired during motion of the right and left hand. Time courses of signal intensity within the contralateral, ipsilateral, and supplementary motor cortex as well as z-maps were calculated, their quality being assessed visually. Mean signal increase between activation and rest were evaluated within the contralateral, ipsilateral, and supplementary motor cortex, the activated area in those regions of interest was measured using z-maps. The quality of functional MR experiments was generally lower in patients than in volunteers. The quantitative results showed a trend towards increased ipsilateral activation in volunteers during left hand compared to right hand motion and in patients during motion of the affected compared to the non-affected hand. Considering quantitative and qualitative results, significantly increased ipsilateral activation was found in patients compared to healthy volunteers. In conclusion, functional MR imaging quality was significantly reduced in patient studies compared to healthy volunteers, even if influences of age, sex, and handedness were excluded. Increased ipsilateral activation was found in patients with brain tumours which can be interpreted by an improved connectivity between both hemispheres.

Adult↗

PubMed1999

Quantitative analyses of neurons projecting to primary motor cortex zones controlling limb movements in the rat.

The objective was to determine if projections of single neurons to primary motor cortex preferentially terminate in several efferent zones that could form synergies for the execution of limb movements. Intracortical microstimulation was used to identify zones evoking hip flexion (HF), elbow flexion (EF), and both plantarflexion (PF) and dorsiflexion (DF) about the ankle. Histological examination showed that the zones from which some movements were evoked extended beyond the agranular cortex into granular cortex. Fluorogold, Fast blue, and propridium iodide or rhodamine-labeled dextran were injected into three of these four efferent zones in each rat. There was a virtual absence of multiple-labeled cells despite having an intermingling of different-colored cells of which 15% in frontal cortex were less than 1.2 mm away from a neighboring neuron that projected to a different efferent zone. This suggests that single neurons projecting to the motor cortex do not hard-wire specific synergies but rather project to single efferent zones in order to offer the greatest degree of freedom for the generation of movements. The distribution of ventral posterolateral and ventrolateral thalamic nucleus labeling depended on whether the injections were in granular or agranular cortex. Conversely, frontal cortex projections to motor efferent zones were made irrespective of their location in either granular or agranular cortex and thereby supporting their presumed role in the control of movements. Hindlimb motor cortex injections yielded retrograde labeling that extended into the more localised distribution of frontal cortex neurons retrogradely labeled from forelimb injections. This may allow hindlimb movements to be synchronized by forelimb movements during walking on challenging terrain.

Animals↗

PubMed2001

Sensory disturbances after focal extirpations of the human "motor" cortex.

From the late 1800s until approximately the middle of the 20th century, neurosurgeons made discrete motor cortex lesions in humans in attempts to reduce or eliminate a variety of involuntary movements, resulting mainly from epilepsy. In some cases, the neurosurgeons tested and recorded their patients' ability to perform various movements and to perceive various types of sensory stimuli after the operation. Although these studies have been largely forgotten, they have an immense advantage over primate lesion studies for understanding the function of the motor cortex because the patients were able to attempt to perform complex movements upon request, and to describe their perceptions of cutaneous stimuli, including integrated sensations (e.g., recognition of objects by palpation alone). We provide here a table containing the results of these studies pertaining to sensory deficits. The most consistent and persistent sensory deficits reported relate to object recognition and position sense. This finding is in keeping with recent electrophysiological studies in primates. Our analysis suggests that the "motor" cortex serves important sensory functions; hence, the term sensorimotor cortex, remains appropriate for the primate precentral (and postcentral) cortex.

Epilepsies, Partial↗

PubMed2002

Effects of acute stimulation through contacts placed on the motor cortex for chronic stimulation.

OBJECTIVES: We tried to determine which neural elements were activated in awake subjects by stimulation through contacts placed chronically on the motor cortex. METHODS: We recorded the motor effects of stimulation through 4 disc contacts placed in the subdural space over the motor cortex in 9 patients undergoing chronic stimulation for the control of pain or for the control of the rigidity of multiple system atrophy. RESULTS: Single stimuli could elicit short latency motor evoked potentials or facilitate active motoneurons in the contralateral limbs. The responsible neural elements had a short chronaxie (the pulse duration necessary to reach threshold with a stimulus intensity twice that required to reach threshold at the longest pulse duration used) and refractory period implying that they were myelinated axons. The facilitation was larger with cathodal than with anodal monopolar stimulation. The short latency facilitation in response to the second of two stimuli was greater at condition test intervals of 2-5 ms. This enhancement could be demonstrated with conditioning stimuli subthreshold for the excitation of active motoneurons suggesting that it arose, in part, at the level of the cortex. Single cortical stimuli could result in inhibition of voluntarily activated motoneurons. The inhibition was larger with cathodal than anodal monopolar stimulation. The responsible neural elements also had a short chronaxie and refractory period. CONCLUSIONS: Stimulation in awake subjects through contacts placed chronically over the motor cortex appears to activate axons in the cortex, which excite both corticospinal neurons and inhibitory neurons.

Adult↗

PubMed1983

Afferent and efferent pathways of the vibrissal region of primary motor cortex in the mouse.

The afferent and efferent connections of the vibrissal representation within the mouse primary motor cortex (MsI) were identified by using the retrograde transport of horseradish peroxidase (HRP) and the anterograde transport of tritiated amino acids injected into MsI. Following aldehyde perfusion brains were frozen-sectioned at 40 microns and reacted for HRP using the 3-3' diaminobenzidine-cobalt chloride technique of Adams ('77). Alternate HRP reacted sections were processed for autoradiography. HRP-filled pyramidal cell somata and concentrations of developed silver grains above background levels were observed in both the vibrissal area of primary somatosensory cortex (SmI) cortex (i.e., the posteromedial barrel subfield; PMBSF cortex) and in the face region of SmII (area 40). In both regions labeled somata occurred predominantly in cortical layers II-III and V. Autoradiographic label was superimposed over the regions containing labeled somata but exhibited a less distinct laminar organization. A dense reciprocal projection connected the injection site with the homotopic area in contralateral MsI; somata occurred for the most part in layers III and V. Developed silver grains were uniformly dispersed over the area containing labeled cell bodies. HRP-labeled pyramidal somata were noted in contralateral PMBSF cortex, but no silver grains occurred in this region. Reciprocal projections linked MsI cortex with the ipsilateral thalamic nuclei: ventralis pars lateralis (VL) and centralis pars lateralis (CL) and with the zona incerta (ZI). Labeled cell bodies and developed silver grains were more dense in VL than in CL. The ipsilateral striatum and thalamic reticular nucleus (NRT) received afferents from the motor cortex but did not project to it. Thus, the vibrissal area of primary motor cortex is connected with a number of cortical and subcortical structures, each of which has been shown to play a role in motor performance. Identification of the afferent and efferent pathways of MsI cortex will now enable further investigation of the ultrastructural and synaptic organization of the vibrissal area of MsI.

Afferent Pathways↗

PubMed2005

Selective excision of metastatic brain tumors originating in the motor cortex with preservation of function.

PURPOSE: Brain metastases are common in patients with cancer and can cause considerable morbidity or death. Metastasis in eloquent areas of the brain, particularly the primary motor cortex, may present significant treatment challenges. PATIENTS AND METHODS: Seventeen consecutive patients with metastasis within the primary motor cortex underwent selective microsurgical tumor resection. Operative, hospital, neuroimaging, and follow-up information was reviewed. RESULTS: There were 10 women and seven men (mean age, 54.3 years) who underwent 17 operations for symptomatic brain metastases. Motor cortex was identified and tumor (mean volume, 10.2 cm(3)) was completely resected in all patients. Three patients had transient or reversible complications. Karnofsky performance scores improved in 16 of 17 patients at 4 weeks postoperatively, with a mean improvement of 1.8 grades compared with preoperative scores (P < .05). Overall survival of 16 patients with distant follow-up (> 6 months or until death) averaged 10.6 +/- 4.4 months, with nine of 16 (56%) assessable patients surviving 1 year or longer. Survival of these 16 patients, by recursive partitioning analysis (RPA), was 11.2, 13.3, and 6.7 months for RPA classes I, II, and III, respectively. The cause of death in 14 of 15 patients who have died was progressive systemic disease; in one patient it was a combination of systemic and distant CNS disease progression. There were no local CNS recurrences. CONCLUSION: Complete microsurgical resection of metastatic tumors in the primary motor cortex is feasible and efficacious, results in a sustained improvement in performance outcomes, and permits satisfactory long-term survival.

Adult↗

PubMed1992

Spontaneous forelimb grasping in free feeding by rats: motor cortex aids limb and digit positioning.

Forelimb use in grasping food during free feeding was studied in control and motor cortex damaged rats using videoanalysis and Eshkol-Wachmann Movement Notation (EWMN). Rats detected food using olfaction, grasped it by mouth, and then sat and reached for it with their paws. Once held in the paws, the food was eaten. A reach consists of: (1) lifting the forelimbs from the ground, (2) positioning them elbows-in, so that the paws were adjacent to the mouth, and (3) clasping the food in the digits. These movements were executed mainly with the upper arm. Limb movements were usually bilaterally symmetrical but when asymmetrical movements occurred, the forelimb least involved in weight support initiated the movement. As the limb was positioned for grasping, the aperture of the digits was adjusted to anticipate the size of the food and the food was grasped and manipulated with the tips of the digits. Following unilateral motor cortex lesions to the forelimb area: (1) the ipsilateral limb (good limb) initiated lifting, positioning, and grasping movements, (2) appropriate adjustment of the digits of the contralateral limb (bad limb) and grasping were impaired, and (3) when contact with food was lost, the bad limb adopted an extended, closed-fist spastic posture and could not be repositioned independently. The gross impairments cleared within 2 weeks, and after a few months impairments were infrequently observed. These findings show that: (1) spontaneous food grasping uses both proximal movements of the limb and distal movements of the digits, (2) digit aperture anticipates food size in reaching, and (3) motor cortex damage impairs both proximal and distal movements more profoundly when the limb is used independently than when it is used in conjunction with the good limb. The results are discussed in relation to kinematic studies on primates and humans.

Animals↗

PubMed2001

Decreased sensory cortical excitability after 1 Hz rTMS over the ipsilateral primary motor cortex.

OBJECTIVES: To study changes in the excitability of the sensory cortex by repetitive transcranial magnetic stimulation (rTMS) in humans. METHODS: Somatosensory evoked potentials (SEPs) and antidromic sensory nerve action potentials (SNAPs) were elicited by right median nerve stimulation at the wrist before and after low frequency (1 Hz) rTMS over the left motor cortex, lateral premotor cortex, sensory cortex, and also after sham stimulation. The intensity of rTMS was fixed at 1.1 times the active motor threshold at the hand area of motor cortex. RESULTS: N20 peak (N20p)-P25 and P25-N33 amplitudes were suppressed after rTMS over the motor cortex, whereas the N20 onset (N20o)-N20p and SNAP amplitudes were not affected. They recovered to the baseline about 100 min after the rTMS. rTMS over the premotor cortex or sensory cortex or sham stimulation had no suppressive effect on SEPs. CONCLUSIONS: The reduction of N20p-P25 and P25-N33 components without any changes of N20o-N20p amplitude suggests that the suppression occurs in the sensory cortex. rTMS (1 Hz) of the motor cortex induces a long-lasting suppression of the ipsilateral sensory cortex even at an intensity as low as 1.1 times the active motor threshold, probably via cortico-cortical pathways between motor and sensory cortex.

Action Potentials↗

PubMed1998

Functional magnetic resonance mapping of sensory motor cortex for image-guided neurosurgical intervention.

PURPOSE: This paper describes the potentials of functional magnetic resonance imaging (fMRI) to map sensory motor cortex in patients with mass lesions near primary motor cortex and to guide neurosurgical procedures located close to eloquent brain regions. MATERIAL AND METHODS: 7 patients with mass lesions near the central sulcus and 10 healthy volunteers were studied using a blood oxygenation level dependent 2D multislice multishot T2* weighted gradient echo EPI sequence on a 1.5T Phillips Gyroscan during alternating epochs of rest and motor activation of hand, foot and tongue. Sites of neuronal activation were identified by statistical analysis of the signal time course using Kolmogorov Smirnov statistics. RESULTS: Neuronal activation following motor tasks consistently localised to the contralateral precentral gyrus and the supplementary motor area, even in the presence of local brain pathology. Additionally we could observe activation in primary sensory areas (post-central gyrus) and supplementary motor area (SMA) in some cases. CONCLUSION: fMRI is capable of mapping sensory motor cortex even in the presence of distorting brain lesions. Since this information will provide valuable information to the neurosurgeon during pre-operative planning, we consider this method for neurosurgical navigation a valuable tool in the routine diagnostic of intracerebral interventions.

Adult↗

PubMed2004

Comparison of descending volleys evoked by transcranial and epidural motor cortex stimulation in a conscious patient with bulbar pain.

OBJECTIVE: To compare the pattern of activation of motor cortex produced by transcranial magnetic stimulation and epidural electrical stimulation. METHODS: The spinal volleys evoked by transcranial magnetic stimulation and epidural electrical stimulation over the cerebral motor cortex were recorded from an electrode inserted into the cervical epidural space of one conscious subject who also had a cortical epidural electrode over the motor area. The volleys were termed D- and I-waves according to their latency. Magnetic stimulation was performed with a figure-of-eight coil and the induced current flowed either in a postero-anterior (PA) or in latero-medial (LM) direction. RESULTS: At active motor threshold intensity LM magnetic stimulation evoked a D wave whereas PA stimulation evoked an I(1) wave with later I waves being recruited at increasing stimulus intensities. Electrical epidural stimulation evoked both a D wave and I waves. However, the D wave evoked by electrical epidural stimulation had a longer latency than the LM D wave, suggesting either a more proximal site of activation of the pyramidal axon or activation of slightly faster conducting set of corticospinal fibres by LM stimulation. The I3 wave evoked by electrical epidural stimulation also had a longer latency than the PA I3-wave CONCLUSIONS: Epidural stimulation of the motor cortex can produce repetitive excitation of corticospinal neurones. The order of recruitment of the volleys, and the latency of the D and I3 waves may be slightly different to that seen after transcranial magnetic stimulation. SIGNIFICANCE: Our findings suggest that there may be subtle differences in the populations of neurones activated by the two forms of stimulation.

Consciousness↗