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Results for “Motor Cortex”

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PubMed1998

Proton magnetic resonance spectroscopy of the primary motor cortex in patients with motor neuron disease: subgroup analysis and follow-up measurements.

OBJECTIVES: To determine the motor cortex degeneration in patients with amyotrophic lateral sclerosis (ALS) using proton magnetic resonance spectroscopy, and to prove that proton magnetic resonance spectroscopy is suited to monitor the course of disease with follow-up examinations. MATERIALS AND METHODS: We studied 33 patients with ALS whose conditions were diagnosed according to the El Escorial World Federation of Neurology criteria. Nine patients with ALS were followed up for up to 2 years. The control group included 20 healthy volunteers and 4 patients with multifocal motor neuropathy. Proton magnetic resonance spectroscopy determined levels of the brain metabolites N-acetylaspartate (NAA), choline, inositol-containing compounds, glutamate/glutamine, and phosphocreatine. RESULTS: Patients with ALS showed a significant reduction in the NAA-choline (P <.001) and NAA-phosphocreatine (P <.005) metabolite ratios and significantly elevated choline-phosphocreatine (P <.005) ratios compared with controls. Inositol-phosphocreatine ratios were also elevated in case patients, but the increase was less pronounced (P <.05). No differences in glutamate/glutamine-phosphocreatine ratios were detected between case patients and controls. An analysis of subgroups demonstrated less significant differences in NAA-choline metabolite ratios (P<.05), even in patients with pure lower motor neuron syndrome (suspected ALS). No changes in metabolite T1 and T2 relaxation times were observed. Patients with multifocal motor neuropathy showed normal metabolic ratios. Progressive alterations in affected metabolite ratios could be documented in the follow-up examinations. CONCLUSIONS: Spectroscopic changes in the motor cortices of patients with ALS correspond with a reduction in levels of NAA and an elevation in levels of choline and inositol compounds. Since NAA is exclusively expressed in neurons, the observed decrease of NAA reflects neuronal loss or dysfunction. Inositol and choline are associated with plasma membrane metabolism, so the release of these compounds may be related to membrane disorders.

Adult↗

PubMed1997

Early morphological changes in the thalamocortical projection onto the parietal cortex following ablation of the motor cortex in the cat.

Following a previous report that the cerebellar-induced cerebral response in the parietal cortex changes acutely after ablation of the frontal motor cortex, the present experiments tested whether morphological changes of the thalamo-parietal projection occur after ablation of the motor cortex. Anterograde and retrograde tracing with wheat germ agglutinin conjugated with horseradish peroxidase was used in intact and lesioned cats. The thalamocortical projection was labeled anterogradely by tracer injection into the thalamic ventral anterior and ventral lateral (VA-VL) nuclear complex that mainly relays the cerebello-cerebral projection, and thalamic neurons were labeled retrogradely by injection of the tracer into the parietal cortex. The labeled terminals in the parietal cortex of the intact animals were distributed densely in layer I and sparsely in layers III-IV, whereas those of the lesioned animals were distributed densely in layers I and III-IV. The distribution of the retrogradely labeled neurons after multiple tracer injections in layers III-IV of the parietal cortex was different in the intact and lesioned cats. In the intact animals, the labeled neurons were distributed sparsely in the central lateral nucleus and in the lateral posterior and pulvinar nuclear complex. In contrast, after ablation of the frontal cortex, the labeled neurons were also observed in the VA-VL nuclear complex. These differences between the intact and lesioned animals were detectable within 48 h after the lesion.

Animals↗

PubMed2006

Reduced size of the pre-supplementary motor cortex and impaired motor sequence learning in first-episode schizophrenia.

Increasing evidence suggests that schizophrenia is associated with various morphological and functional abnormalities of the frontal cortex. So far research has concentrated on the dorsolateral and orbitofrontal cortex. Behavioral evidence suggests however that regions responsible for higher motor control are compromised in schizophrenia as well. The current study assessed volumes of the anterior supplementary motor area (pre-SMA) and implicit motor sequence learning in 15 subjects with first-episode schizophrenia and 15 healthy matched controls. Pre-SMA volumes were assessed by three-dimensional structural magnetic resonance imaging (3D-MRI) and manual parcellation according to an established protocol. Implicit motor sequence learning was assessed using the Serial Reaction-Time Task (SRTT). Compared with control subjects, schizophrenia subjects had significantly smaller volumes of the left pre-SMA (16%). Subjects with schizophrenia were severely impaired on sequence-specific implicit motor learning. Size of the left pre-SMA of schizophrenia subjects was significantly related to impaired implicit learning. We conclude that subjects with first-episode schizophrenia have a morphological abnormality of the left pre-SMA that might predispose them to develop disturbances of higher motor control during acute episodes of psychosis. These structural and behavioral abnormalities might be conceptualized within a broader model that views schizophrenia as a disorder of disturbed coordination of thought and action.

Adult↗

PubMed1987

Some aspects of the organization of the output of the motor cortex.

The precentral motor cortex in the macaque is defined here as that portion of the precentral motor-sensory areas which projects to the intermediate zone and motor neuronal cell groups in the spinal cord and their bulbar counterparts, i.e. the lateral reticular formation and motor nuclei of the lower brainstem. In this respect the precentral motor cortical areas differ from postcentral areas such that the descending projections from the latter are focused on the spinal dorsal horn and the spinal V complex. Differences in the distribution of the corticospinal fibres in different species are mentioned and differences in findings obtained by means of different tracing techniques are discussed. The projections from the precentral motor cortex to various brain-stem cell groups are also discussed and the areas of origin of these projections are delineated. The presence of branching neurons distributing collaterals to several of these areas is considered.

Animals↗

PubMed2003

Task-dependent modulation of excitatory and inhibitory functions within the human primary motor cortex.

We evaluated motor evoked potentials (MEPs) and duration of the cortical silent period (CSP) from the right first dorsal interosseous (FDI) muscle to transcranial magnetic stimulation (TMS) of the left motor cortex in ten healthy subjects performing different manual tasks. They abducted the index finger alone, pressed a strain gauge with the thumb and index finger in a pincer grip, and squeezed a 4-cm brass cylinder with all digits in a power grip. The level of FDI EMG activity across tasks was kept constant by providing subjects with acoustic-visual feedback of their muscle activity. The TMS elicited larger amplitude FDI MEPs during pincer and power grip than during the index finger abduction task, and larger amplitude MEPs during pincer gripping than during power gripping. The CSP was shorter during pincer and power grip than during the index finger abduction task and shorter during power gripping than during pincer gripping. These results suggest excitatory and inhibitory task-dependent changes in the motor cortex. Complex manual tasks (pincer and power gripping) elicit greater motor cortical excitation than a simple task (index finger abduction) presumably because they activate multiple synergistic muscles thus facilitating corticomotoneurons. The finger abduction task probably yielded greater motor cortical inhibition than the pincer and power tasks because muscles uninvolved in the task activated the cortical inhibitory circuit. Increased cortical excitatory and inhibitory functions during precision tasks (pincer gripping) probably explain why MEPs have larger amplitudes and CSPs have longer durations during pincer gripping than during power gripping.

Adult↗

PubMed1987

Importance of the projection from the sensory to the motor cortex for recovery of motor function following partial thalamic lesion in the monkey.

Motor deficits produced by thalamic lesions were studied using adult cynomolgus monkeys. Lesioned areas included n. ventralis anterior (VA), ventralis lateralis (VL), n. ventralis posterolateralis pars oralis (VPLo), pars caudalis (VPLc) n. subthalamus (STN) and n. centrum medianum (CM). When the lesion included VA, VL and VPLo, there was a cerebellar syndrome, i.e., ataxia and dysmetria. When the lesion included VPLo and VPLc, the animal was paralyzed. When the lesion included VPLo and rostral part of VPLc, there was loss of orientation in hand movement and clumsiness of finger manipulation. These motor deficits gradually disappeared within 1-2 weeks and the function recovered near to normal except for when VPLo and VPLc were totally destroyed. After recovery of motor function, the somatic sensory cortex (areas 1, 2, 3b) ipsilateral to the thalamic lesion was removed. Removal of the sensory cortex resulted in abolition of the recovered function, but when the border area between VPLo and VPLc was intact, the function recovered again. On the other hand, when the thalamic lesion included this border area, succeeding cortical lesion permanently abolished the recovered function or the reappeared function was substantially worse than that before the cortical lesion. Neuronal mechanisms subserving these differences are discussed and it is concluded that when direct sensory input to the motor cortex was interrupted by lesion of the border area between VPLo and VPLc, the lost function was compensated by reorganization of the projection from the sensory cortex to the motor cortex.

Animals↗

PubMedDate not supplied

[Long-term changes in the efficiency of the excitatory and inhibitory connections in the neuronal micronetworks of the motor cortex induced by tetanization of the thalamic nuclei and the sensory cortex].

Assumption was verified that tetanization which produces long-term potentiation (LTP) and long-term depression (LTD) in the efficacy of thalamo-cortical inputs and the inputs from the sensory cortex to motor cortex results also in long-term modifications of the efficacy of interneuronal interactions in the motor-cortical networks. It was shown that monosynaptic excitation of one of the neighbouring neurons in the motor cortex by rhythmical stimulation of some thalamic nuclei or the sensory cortex resulted in LTP or LTD in the efficacy of excitatory and inhibitory transmission between the neurons of the network. The efficacy of the synapses formed by the terminals of one axon on the neighbouring cells could be variously modified. If the network contained the neurons with multiple convergent inputs the tetanization resulted in the LTP of most of them. In the neuronal networks which contained local feed-forward inhibitory circuits, LTP (LTD) of the inhibitory input to the target cell was accompanied by LTD (LTP) of the excitatory input to the same target cell. Different patterns of modified interneuronal connections were caused by tetanization of different brain structures (thalamic nuclei or sensory cortex).

Animals↗

PubMed2001

Increased excitability in the primary motor cortex and supplementary motor area in patients with phantom limb pain after upper limb amputation.

Using functional magnetic resonance imaging and single slice FLASH technique, we investigated reorganization of the hand representation of the primary sensorimotor cortex (SMC) in 16 patients with upper extremity amputation. Patients were asked to perform finger tapping with the intact hand, repetitive eye closing and anteflexion of the amputation stump or intact shoulder. Six normal volunteers served as control. In the normal volunteers activations during shoulder anteflexion, finger tapping and eye closure were located within the central sulcus in a medio-lateral fashion. Patients demonstrated invasion of the face or shoulder representation into the hand representation of the amputated limb. Eight phantom limb pain patients showed significantly greater activation in SMC and supplementary motor area (SMA) in contrast to eight patients without phantom limb pain. We conclude, that different parts of the motor system are affected in patients with phantom limb pain--possibly in the sense of an up-regulation of excitability.

Adolescent↗

PubMed1990

Changes in the cerebello-cerebral response in the parietal cortex following ablation of the motor cortex in the cat: early occurrence and persistence.

To elucidate the compensatory mechanism which begins to work soon after damage to the brain, changes in the cerebellar-induced cerebral cortical response in the parietal association cortex after ablation of the frontal motor cortex were studied in the cat. Stimulation of the interpositus or the lateral nucleus of the cerebellum before decortication, as reported in intact animals, induced two distinct types of response in the frontal motor and parietal association cortices respectively. The response in the frontal cortex was a sequential occurrence of a surface positive-depth negative (sP-dN) wave and a surface negative-depth positive (sN-dP) wave, and the response in the parietal cortex was mainly an sN-dP wave. In a small proportion of animals, the latter wave was preceded by a small sP-dN wave or a small dN wave without an sP wave. Ablation of the frontal motor cortex induced in the majority of animals a marked change in the cerebello-parietal cortical response, i.e. the occurrence of a new sP-dN wave preceding the sN-dP wave or enhancement of the pre-existing small dN wave, resulting in the parietal cortical response similar to the frontal cortical response of intact animals. The earliest post-lesion time observed for the occurrence of change was less than 1 hour, whereas its persistence was confirmed up to 213 days post-lesion.

Action Potentials↗

PubMed1989

Influence of somatosensory cortex on different classes of cat motor cortex output neuron.

1. Multiple output pathways originate from motor cortex. In this study on cats, six classes of corticofugal neurons were identified by antidromic activation. Corticocallosal neurons of layer III were activated antidromically by stimulation of contralateral motor cortex. Layer V neurons were identified by antidromic activation from cerebral peduncle, red nucleus, lateral reticular nucleus of medulla, or spinal cord. Corticothalamic neurons were identified in layer VI. All the identified neurons were tested for input from primary somatosensory cortex. 2. Neurons of all corticofugal groups received excitatory inputs from primary somatosensory cortex. The shortest latency corticocortical effects of 1.2-2.5 ms were found for corticocallosal neurons of layer III, and for layer V neurons which projected axons through the cerebral peduncle, to red nucleus, and to spinal cord. 3. Nearby neurons, projecting to the same of different targets, were affected nonuniformly by corticocortical inputs. This finding supports the conclusion that specificity of afferent connections within cerebral cortex is not determined by anatomic segregation of cell bodies nor by projection target of efferent neurons. 4. These selectively distributed input connectivities suggest that even a small region of motor cortex could send different signals to its diverse targets.

Animals↗

PubMedDate not supplied

[The effect of a microinjection of atropine into the rat motor cortex on the acquisition of a motor skill].

Atropine is known to impede the acquisition of conditioned responses by neurons of the motor cortex. Does atropine exert influence (and of what kind) on acquisition of local movements controlled by neurons of the motor cortex? In the present study we examined the influence of atropine microinjections on acquisition of reaching movement in freely moving rats. The intracortical pressure injections of atropine (5 mcg and 15 mcg/0,6 mcl/40 s) were made unilaterally into the forearm area of the motor cortex in adult mongrel rats. Hungry rats learned to reach sunflower seeds form a horizontal tube by using the forelimb contralateral to the injected site. Atropine exerted dose-dependent influence of the acquisition of the motor skill. All the tested doses depressed the inhibition of concurrent movements during learning. In addition, the higher dose of atropine inhibited the initiation of the reaching movements. A hypothesis was proposed to explain these differences.

Animals↗

PubMed1995

Input-output organization in the hand area of the human motor cortex.

The primate motor cortex consists of efferent zones which receive sensory information from a portion of limb in close anatomical relation to the muscle to which they project. To investigate a similar input-output relation in humans, we studied the effect of tactile stimuli on the size of motor evoked potentials (MEPs) elicited by transcranial magnetic and electrical stimulation. For tactile stimuli we applied air to the skin. The sizes of MEP of 3 finger muscles (flexor pollicis brevis, first dorsal interosseous, and abductor digiti minimi) with and without air stimuli were compared. Air stimuli applied to the tip of one finger facilitated mainly the magnetically evoked MEP of a muscle attached to that finger. A less obvious facilitatory effect was observed when giving stimuli on the dorsal aspect of the hand. Air stimuli had no facilitatory effect on electrically evoked MEPs. In one subject, there was no facilitatory effect even to magnetically evoked MEPs. In this subject, D-waves had the lowest threshold for magnetic and electrical stimulation. These results suggested that the effect was produced at the cortical level. This effect may correspond to the input-output relation found in the primate motor cortex.

Electric Stimulation↗

PubMed1991

A loss of short-latency excitatory caudate unitary responses to motor cortex but not to motor thalamic nuclei stimulation in MPTP-treated cats.

The effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 5 mg/kg i.m. for 5 days) on the evoked activity of caudate neurones were studied extracellularly in ketamine-anaesthetized and myorelaxant-immobilized cats. Two days after the last MPTP injection the latency of caudate neurone responses to the motor cortex stimulation increased as compared to intact animals, due to a 10-fold decrease in the number of neurones with short-latency responses (from 1.8 up to 8.0 ms). At the same time, no essential changes were observed under the influence of MPTP in the distribution pattern of the latency of caudate neurone responses to the stimulation of the ventral anterior and ventral lateral nuclei of the thalamus. The suggestion that dopamine protects monosynaptic transmission of impulses from the cerebral cortex to neostriatum neurones is discussed.

Action Potentials↗

PubMed1983

Focal increases of white matter glucose utilization produced by electrical stimulation of rat motor cortex.

The right motor cortex was electrically stimulated in adult, awake rats for 45 min. Local cerebral glucose utilization (LCGU) was measured in white matter pathways with the (14C)-2-deoxyglucose method. Stimulation increased LCGU in focal regions of the right internal capsule to 51.3 mumol/100 g/min, compared to 39.8 on the control left side. Stimulation also increased LCGU in the right, medial pontine pyramidal tract to 36.2 mumol/100 g/min, compared with 27.3 on the control left side. The data demonstrate that electrical stimulation of motor cortex neurons increases LCGU 30 to 40% in the efferent myelinated axons of those neurons.

Animals↗

PubMed2002

Visual and motor cortex excitability: a transcranial magnetic stimulation study.

OBJECTIVES: Phosphene thresholds (PTs) to transcranial magnetic stimulation over the occipital cortex and motor thresholds (MTs) have been used increasingly as measures of the excitability of the visual and motor cortex. MT has been utilized as a guide to the excitability of other, non-motor cortical areas such as dorsolateral prefrontal cortex. The aims of this study were to compare the PTs to MTs; to assess their stability across sessions; and to investigate their relation to MTs. METHODS: PTs and MTs were determined using focal transcranial magnetic stimulation over the visual and motor cortex. RESULTS: PTs were shown to be significantly higher than MTs. Both PTs and MTs were stable across sessions. No correlation between PTs and MTs could be established. CONCLUSIONS: Phosphene threshold is a stable parameter of the visual cortex excitability. MTs were not related to the excitability of non-motor cortical areas.

Adult↗

PubMed1994

Information processing within the motor cortex. I. Responses of morphologically identified motor cortical cells to stimulation of the somatosensory cortex.

Inputs from the somatosensory cortex to the motor cortex have been proposed to function in learning of motor skills. In an attempt to analyze how these somatosensory inputs were processed in the motor cortex, neurons in the superficial layer of the cat motor cortex were classified into three groups on the basis of synaptic responses elicited by intracortical microstimulation (ICMS) of area 2. ICMS was delivered through seven electrodes implanted in area 2. When ICMS through one of the seven sites produced a response that was greater than 50% of the response produced by stimulating the seven sites at a time, the site was called a "dominant" site. Type I cells were those that had a dominant stimulation site and showed a constant response latency when examined by a double shock test. Type II cells were those that had a dominant site but displayed a variable latency. Type III cells had no dominant site and showed a variable latency. Latency of type I responses was 1.2-2.6 milliseconds, which was much shorter than that of type II and type III responses. Seventy-nine neurons in layers II/III of the motor cortex, which responded to ICMS in area 2, were stained by intracellular injection of biocytin. From the presence of an apical dendrite and rich spines on the dendrites, 23 type I, 21 type II, and 15 type III cells were classified as pyramidal cells. Type II pyramidal cells were located more superficially than type I and type III pyramidal cells. On the basis of the absence or sparseness of dendritic spines, three type I and four type II cells in layers II/III were classified as nonpyramidal cells. These cells consisted of five small multipolar cells in layer II and a large multipolar cell and a small bitufted cell in layer III. The remaining 11 cells were not classified because of insufficient staining. Since type I and type II cells are considered to represent monosynaptic and polysynaptic responses to stimulation of area 2, respectively, information flow from type I cells to more superficially located type II cells is presumed in layers II/III of the motor cortex. Type III responses suggest the presence of a convergent flow of impulses inside of and/or between areas 2 and 4.

Animals↗

PubMed1989

Inclusion bodies in motor cortex and brainstem of patients with motor neurone disease are detected by immunocytochemical localisation of ubiquitin.

Histological sections of cerebral motor cortex, brainstem, and spinal cord from 10 cases of clinically diagnosed motor neurone disease (MND) and 10 control cases were examined by conventional histology and immunocytochemical methods to localise ubiquitin. Intracytoplasmic inclusion bodies were identified in motor neurones of hypoglossal nuclei and appeared specific for MND. Similar inclusions were found in both large pyramidal cells and small neurones in the motor cortex, and were restricted to 4 cases having the amyotrophic lateral sclerosis form of MND with severe degeneration of corticospinal tracts. As reported in earlier studies, cellular inclusion bodies were identified in motor neurones of spinal cord from cases of MND but not in control material. Ubiquitin inclusions in motor neurones appear to be markers for the degenerative process causing neuronal loss in MND and there appears to be a close association between the anatomical location of inclusions and clinical manifestations of disease.

Aged↗

PubMed2006

Partial reconstruction of muscle activity from a pruned network of diverse motor cortex neurons.

Primary motor cortex (M1) neurons traditionally have been viewed as "upper motor neurons" that directly drive spinal motoneuron pools, particularly during finger movements. We used spike-triggered averages (SpikeTAs) of electromyographic (EMG) activity to select M1 neurons whose spikes signaled the arrival of input in motoneuron pools, and examined the degree of similarity between the activity patterns of these M1 neurons and their target muscles during 12 individuated finger and wrist movements. Neuron-EMG similarity generally was low. Similarity was unrelated to the strength of the SpikeTA effect, to whether the effect was pure versus synchrony, or to the number of muscles influenced by the neuron. Nevertheless, the sum of M1 neuron activity patterns, each weighted by the sign and strength of its SpikeTA effect, could be more similar to the EMG than the average similarity of individual neurons. Significant correlations between the weighted sum of M1 neuron activity patterns and EMG were obtained in six of 17 muscles, but showed R(2) values ranging from only 0.26 to 0.42. These observations suggest that additional factors-including inputs from sources other than M1 and nonlinear summation of inputs to motoneuron pools-also contributed substantially to EMG activity patterns. Furthermore, although each of these M1 neurons produced SpikeTA effects with a significant peak or trough 6-16 ms after the triggering spike, shifting the weighted sum of neuron activity to lead the EMG by 40-60 ms increased their similarity, suggesting that the influence of M1 neurons that produce SpikeTA effects includes substantial synaptic integration that in part may reach the motoneuron pools over less-direct pathways.

Action Potentials↗