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Results for “Motor Cortex”

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PubMedDate not supplied

Effect of elaboration of a local motor-food conditioned reflex and reconditioning its effector component on the protein content in neurons of the motor cortex of rats.

Elaboration in rats of a local motor-food conditioned reflex in the form of pressing a lever by a preferred foot was accompanied by an increase of the protein content in interneurons in the absence of a change of this index in large and medium pyramidal neurons in the V layer of the motor cortex in the projection of the preferred foot in comparison with the symmetric point of the opposite hemisphere. Reconditioning of the conditioned reflex, i.e., its accomplishment by the nonpreferred foot, was accompanied by a decrease of the protein content in large pyramidal neurons of the V layer of the motor cortex in the absence of changes in the dry mass of interneurons in the projection of the nonpreferred foot in comparison with the projection of the preferred foot. Pyramidal neurons of the III layer reacted by an insignificant change in the protein content both in the case of elaborating the conditioned reflex and reconditioning of its effector component. It is suggested that the pyramidal neurons of the III layer, large pyramidal neurons and interneurons of the V layer of the motor cortex are involved in metabolic provision of elaboration of the local motor-food conditioned reflex and in the formation of new motor coordination at different stages of these processes.

Animals↗

PubMed2006

A novel site of synaptic relay for climbing fibre pathways relaying signals from the motor cortex to the cerebellar cortical C1 zone.

The climbing fibre projection from the motor cortex to the cerebellar cortical C1 zone in the posterior lobe of the rat cerebellum was investigated using a combination of physiological, anatomical and neuropharmacological techniques. Electrical stimulation of the ipsilateral fore- or hindimbs or somatotopically corresponding parts of the contralateral motor cortex evoked climbing fibre field potentials at the same cerebellar recording sites. Forelimb-related responses were located in the C1 zone in the paramedian lobule or lobulus simplex and hindlimb-related responses were located in the C1 zone in the copula pyramidis. Microinjections of anterograde axonal tracer (Fluoro-Ruby or Fluoro-Emerald) were made into the fore- or hindlimb parts of the motor cortex where stimulation evoked the largest cerebellar responses. After a survival period of 7-10 days, the neuraxis was examined for anterograde labelling. No terminal labelling was ever found in the inferior olive, but labelled terminals were consistently found in a well-localized site in the dorso-medial medulla, ventral to the gracile nucleus, termed the matrix region. Pharmacological inactivation of the matrix region (2 mm caudal to the obex) selectively reduced transmission in descending (cerebro-olivocerebellar) but not ascending (spino-olivocerebellar) paths targeting fore- or hindlimb-receiving parts of the C1 zone. Transmission in spino-olivocerebellar paths was either unaffected, or in some cases increased. The identification of a novel pre-olivary relay in cerebro-olivocerebellar paths originating from fore- and hindlimb motor cortex has implications for the regulation of transmission in climbing fibre pathways during voluntary movements and motor learning.

Action Potentials↗

PubMed2004

The physiological basis of transcranial motor cortex stimulation in conscious humans.

Transcranial stimulation of the human motor cortex can evoke several different kinds of descending activity depending on the type of stimulation, the intensity of stimulation and the area of the cortex being stimulated. Thus, transcranial magnetic stimulation preferentially activates different structures than transcranial electrical stimulation. In addition, the response to magnetic stimulation depends on the direction of the induced current in the brain, the waveform of the stimulating current, and the shape of the coil. Stimulation of the lower limb area of motor cortex recruits different elements than stimulation of the upper limb area. These differences occur because different structures in the motor cortex have a differential threshold to the different techniques of stimulation. We have had the opportunity to perform a series of direct recordings of the corticospinal volley evoked by the different techniques of transcranial stimulation from the epidural space of conscious patients with chronically implanted spinal electrodes. These recordings provide insights about the physiological basis of the excitatory and inhibitory phenomena produced by transcranial stimulation.

Efferent Pathways↗

PubMed2004

Motor cortex hyperexcitability to transcranial magnetic stimulation in Alzheimer's disease.

OBJECTIVES: Recent transcranial magnetic stimulation (TMS) studies demonstrate that motor cortex excitability is increased in Alzheimer's disease (AD) and that intracortical inhibitory phenomena are impaired. The aim of the present study was to determine whether hyperexcitability is due to the impairment of intracortical inhibitory circuits or to an independent abnormality of excitatory circuits. METHODS: We assessed the excitability of the motor cortex with TMS in 28 patients with AD using several TMS paradigms and compared the data of cortical excitability (evaluated by measuring resting motor threshold) with the amount of motor cortex disinhibition as evaluated using the test for motor cortex cholinergic inhibition (short latency afferent inhibition) and GABAergic inhibition (short latency intracortical inhibition). The data in AD patients were also compared with that from 12 age matched healthy individuals. RESULTS: The mean resting motor threshold was significantly lower in AD patients than in controls. The amount of short latency afferent inhibition was significantly smaller in AD patients than in normal controls. There was also a tendency for AD patients to have less pronounced short latency intracortical inhibition than controls, but this difference was not significant. There was no correlation between resting motor threshold and measures of either short latency afferent or intracortical inhibition (r = -0.19 and 0.18 respectively, NS). In 14 AD patients the electrophysiological study was repeated after a single oral dose of the cholinesterase inhibitor rivastigmine. Resting motor threshold was not significantly modified by the administration of rivastigmine. In contrast, short latency afferent inhibition from the median nerve was significantly increased by the administration of rivastigmine. CONCLUSIONS: The change in threshold did not seem to correlate with dysfunction of inhibitory intracortical cholinergic and GABAergic circuits, nor with the central cholinergic activity. We propose that the hyperexcitability of the motor cortex is caused by an abnormality of intracortical excitatory circuits.

Afferent Pathways↗

PubMed1984

Fetal frontal cortex transplant (14C) 2-deoxyglucose uptake and histology: survival in cavities of host rat brain motor cortex.

Fetal frontal neocortex from 18-day-old rat embryonic brain was transplanted into cavities in 30-day-old host motor cortex. Sixty days after transplantation, 5 of 15 transplanted rats had surviving fetal transplants. The fetal cortex transplants were physically attached to the host brain, completely filled the original cavity, and had numerous surviving cells including pyramidal neurons. Cell lamination within the fetal transplant was abnormal. The (14C) 2-deoxyglucose uptake of all five of the fetal neocortex transplants was less than adjacent cortex and contralateral host motor-sensory cortex, but more than adjacent corpus callosum white matter. The results indicate that fetal frontal neocortex can be transplanted into damaged rat motor cortex. The metabolic rate of the transplants suggests they could be partially functional.

Animals↗

PubMed1997

Functional magnetic resonance imaging in schizophrenia: initial methodology and evaluation of the motor cortex.

The purpose of the present study was to evaluate the differential activation of the motor cortex during finger tapping in patients with schizophrenia using the newly available imaging method of functional magnetic resonance imaging (fMRI). Nine patients with DSMIII-R schizophrenia and 9 well-matched healthy volunteer subjects underwent fMRI examination on a conventional MR unit; activation of the primary motor cortex was evaluated during performance of a finger motion task. Localized activation of the motor cortex was observed in 17 of 18 subjects during fMRI. Patients and controls were, however, indistinguishable with respect to signal intensity or area thereof within the motor cortex. fMRI did not reveal motor cortical dysfunction in schizophrenia. Despite its infancy, fMRI holds considerable promise to advance understanding of the neurodynamics of psychiatric disorders, particularly schizophrenia.

Adult↗

PubMedDate not supplied

[Involvement of rabbit motor cortex neurons in the instrumental behavior before and after chronic ethanol consumption: a comparison with the limbic cortex].

The effect of acute administration is significantly more prominent in the limbic (cingulate) than in the motor cortex [9]. We proposed that the limbic cortex is more sensitive also to chronic ethanol treatment (CET). It was shown that morphology as well as neuronal activity of the limbic cortex changed greatly after the CET [7]. The missing link of testing the above proposition was a comparison of the obtained data with the results of the experimental study of CET influence on the motor cortex. Morphology of the anterolateral motor cortex and activity of its neurons in the instrumental food-acquisition behavior were studied in 6 male rabbits after CET (9 months). It was found that the limbic cortex was modified morphologically and functionally to a significantly greater extent than the motor cortex. We consider the fact that in the limbic cortex of a healthy individual there are many neurons, which for a while cease their discharges after the acute ethanol administration, to be among the most important reasons for this difference. Such-like repeated activity interruptions in the course of CET impair the performance of the systems incorporating these neurons. In such a way ethanol prevents all neurons, especially the mentioned ones, from receiving adequate metabolic supply that is necessary for their survival and functioning.

Alcohol Drinking↗

PubMed1987

A quantitative study of the distribution of neurons projecting to the precentral motor cortex in the monkey (M. fascicularis).

The relative numbers and locations of neurons projecting to the "forelimb" region of the precentral motor cortex were studied in three monkeys by using the retrograde transport of horseradish peroxidase. Within the forelimb area of the motor cortex itself, there are extensive and profuse interconnections. However, regions within this area receive afferents from very few neurons in other parts of the motor cortex representing hindlimb or head movements. Most of the motor cortical representation of the forelimb in the anterior bank of the central sulcus is devoid of callosal connections. In both the ipsilateral and contralateral hemispheres, the premotor (lateral area 6) and supplementary motor (medial area 6) areas dominate quantitatively the inputs to the motor cortical representation of the forelimb. The afferents from the premotor area are restricted and come from a region immediately behind the arcuate spur and adjacent parts of the superior and inferior limbs of the arcuate sulcus in the floor, caudal bank, and caudal lip of that sulcus. From the supplementary motor area (SMA), afferents originate from its whole rostrocaudal extent. Thalamic nuclear regions projecting to a restricted zone in the anterior bank of the central sulcus are recipients of cerebellar and somatosensory outputs. Involvement of more anterior parts of the motor cortex by the tracer labels thalamocortical cells, which are targets of pallidal output also. Within the first somatosensory cortex, cytoarchitectonic areas 1, 2, and 3a project to area 4. The projection from area 3a may provide one pathway by which short-latency peripheral inputs, especially from muscles, reach the motor cortex.

Afferent Pathways↗

PubMed1993

Oscillations in local field potentials of the primate motor cortex during voluntary movement.

We investigated the occurrence and distribution of oscillatory activity in local field potentials (LFPs) recorded from the frontal motor cortex of behaving monkeys performing skilled voluntary movements. LFPs were recorded simultaneously from up to 12 sites distributed throughout motor cortex while monkeys performed a visually guided, instructed delay task using the wrist or digits. Oscillatory activity between 15 and 50 Hz was evident in the LFP recorded from both primary motor cortex and premotor areas. Oscillations occurred preferentially before the visual cue to initiate movement but were infrequent during movement. Oscillations typically stopped before movement initiation during the wrist task, although they often continued into the initial phases of movement during the digit task. The relationship of oscillations to task performance was consistent across trials over periods of many months, although the amplitude and duration of oscillations varied across trials and days. Interactions between pairs of LFP recordings, evaluated with cross-correlation analysis, revealed synchronous oscillations over long distances (> 7 mm) and across primary motor cortex and premotor recording sites. These studies demonstrate that oscillations recorded in the LFP in motor cortex during trained motor tasks are not related to the details of movement execution but may be related to aspects of movement preparation.

Animals↗

PubMed1999

The time course of changes in motor cortex excitability associated with voluntary movement.

The excitability of the motor cortex is modulated before and after voluntary movements. Transcranial magnetic stimulation studies showed increased corticospinal excitability from about 80 and 100 ms before EMG onset for simple reaction time and self-paced movements, respectively. Following voluntary movements, there are two phases of increased corticospinal excitability from 0 to approximately 100 ms and from approximately 100 to 160 ms after EMG offset. The first phase may correspond to the frontal peak of motor potential in movement-related cortical potentials studies and the movement-evoked magnetic field I (MEFI) in magnetoencephalographic (MEG) studies, and likely represents a time when decreasing output from the motor cortex falls below that required for activation of spinal motoneurons, but is still above resting levels. The second phase of increased corticospinal excitability may be due to peripheral proprioceptive inputs or may be centrally programmed representing a subthreshold, second agonist burst. This may correspond to the MEFII in MEG studies. Corticospinal excitability was reduced below baseline levels from about 500 to 1,000 ms after EMG offset, similar to the timing of increase in the power (event-related synchronization, ERS) of motor cortical rhythm. Similarly, motor cortex excitability is reduced at the time of ERS of motor cortical rhythm following median nerve stimulation. These findings support the hypothesis that ERS represents an inactive, idling state of the cortex. The time course of cortical activation is abnormal in movement disorders such as Parkinson's disease and dystonia, reflecting abnormalities in both movement preparation and in cortical excitability following movement.

Electroencephalography↗

PubMed1995

Thalamic distribution of projection neurons to the primary motor cortex relative to afferent terminal fields from the globus pallidus in the macaque monkey.

To examine quantitatively the pathway from the internal segment of the globus pallidus to the primary motor cortex through the thalamus, we compared the distribution of thalamocortical neurons projecting to the motor cortex with the distribution of afferent terminal fields from the pallidum in the ventrolateral nuclear group of the thalamus in four Japanese monkeys by using the anterograde and retrograde double-labeling method. In each monkey, different fluorescent retrograde tracers (Fast Blue and Diamidino Yellow) were injected separately into the distal and proximal forelimb areas of the primary motor cortex after physiological mapping with intracortical microstimulation. In the same individual monkeys, an anterograde tracer, wheatgerm agglutinin conjugated to horseradish peroxidase, was injected into the internal segment of the globus pallidus after the forelimb part was identified physiologically. A small group of projection neurons to the distal and proximal representations of the motor cortex were found in the terminal fields from the pallidum, but a majority of the projection neurons were distributed outside the terminal area in the thalamus. These results confirm the existence of the pathway from the pallidum through the thalamus to the primary motor cortex, but also indicate that the primary motor cortex receives its major thalamic inputs from outside of the pallidal projection area, and that the pallidum sends its major outputs to nonprimary motor areas through the thalamus.

Afferent Pathways↗

PubMed1992

Localization of multiple dopamine receptor subtype mRNAs in human and monkey motor cortex and striatum.

Dopamine plays a critical role in motor and cognitive function through actions mediated by specific receptors, multiple subtypes of which have recently been identified. The distribution of mRNAs encoding D1, D2 and D5 receptors in the motor cortex of humans and in the motor cortex and striatum of macaque monkeys was examined using in situ hybridization. In motor cortices from both primate species, hybridization to each receptor probe resulted in numerous labeled cells throughout layers II-VI. In contrast to neocortex, in monkey striatum only the D1 and D2 receptor probes showed significant hybridization. Thus, not only does primate neocortex possess a broader representation of the dopamine receptor subtype mRNAs examined in comparison with striatum, but the unexpected presence and widespread distribution of D2 and D5 receptor mRNAs in cortex suggests that, along with D1 receptors, D2 and D5 receptors play a crucial role in the dopaminergic modulation of cognition and motor behavior, and in dopamine dysfunction associated with neuropsychiatric disorders.

Aged↗

PubMed2002

Control of post-stroke movement disorders using chronic motor cortex stimulation.

The effects of motor cortex (MC) stimulation on post-stroke movement disorders were analyzed in 50 patients. These individuals either underwent MC stimulation primarily for the purpose of controlling their post-stroke involuntary movements (n = 8) or underwent MC stimulation for the purpose of controlling their post-stroke central pain (n = 42). In the latter patients, the effects of MC stimulation on co-existent involuntary or voluntary movement disorders were analyzed retrospectively. Good control of involuntary movements was observed in 2 of 3 patients with hemichoreo-athetosis, 2 of 2 patients with distal resting or action tremor, and 1 of 3 patients with proximal postural tremor. Subjective improvements in motor performance were reported by 8 patients who had mild motor weakness, and the effects appeared to be attributable to attenuation of rigidity. We consider that these findings justify further clinical studies on MC stimulation for the control of post-stroke movement disorders.

Electric Stimulation Therapy↗

PubMed2001

Motor cortex stimulation for neuropathic pain.

Motor cortex stimulation is increasingly reported in the literature as a surgical option for the alleviation of neuropathic pain. The authors review the published literature and present their results including those demonstrated in a randomized controlled trial that confirmed the efficacy of the procedure. Patient selection and prediction of outcomes, however, remain difficult issues.

Adult↗

PubMed1980

Alumina cream-induced focal motor epilepsy in cats. IV. Thickness and cellularity of layers in the perilesional motor cortex.

Thickness and cellularity of motor cortical layers adjacent to epileptogenic lesions produced by administration of alumina cream (AC) were measured in the brains of 18 cats that were at latent, convulsive, and remissive stages of an experimental model of epilepsy. Sham-operated animals were used as controls. Brains were fixed by perfusion and embedded in paraffin. Sections of motor cortex adjacent to the AC deposit were obtained at constant thickness to measure thickness and cellularity in each cortical layer. A statistically significant reduction in thickness and cellularity was detected in layers 2, 4, and 6, whereas reduction in these aspects was not significant in layers 3 and 5 in the initial stages of the model (latent and convulsive). It is suggested that AC may exert a cytotoxic effect on inhibitory neurons located at layers 2 and 4, to determine an imbalance of intracortical excitability.

Aluminum Hydroxide↗

PubMed1992

Synaptic proliferation in the motor cortex of adult cats after long-term thalamic stimulation.

1. One of the hypotheses for information storage in the CNS postulates the induction of structural changes in synaptic circuits. This postulate predicts that behavioral experiences produce changes in neural activity that subsequently induce synaptogenesis in the mature CNS. Available data indicate that the establishment of engrams for novel motor acts may involve alterations of synaptic interactions within the primary motor cortex. The present study examines the hypothesis that patterns of synaptic circuitry and of synaptic activation are rearranged after enhanced neural activity in pathways projecting to the motor cortex. 2. Electrodes implanted in the ventroposterolateral (VPL) nucleus of the thalamus were used for long-term stimulation (20 microA, 4 days) of afferents to the motor cortex in freely behaving, adult cats. This stimulation primarily affected corticocortical inputs from the somatosensory cortex (area 2) to area 4 gamma of the motor cortex. Electron microscopy and stereological procedures were used to compare the numerical density (Nv) of various types of synapses in layers II/III of the stimulated (experimental) motor cortex with the Nv of the corresponding synapses in the contralateral (control) hemisphere. 3. Long-term stimulation produced a significant increase (25.6%) in synaptic Nv in experimental motor cortex. This increase was due primarily to an increase in the Nv of asymmetrical synapses with dendritic spines. The numbers of symmetrical synapses, and of asymmetrical synapses with dendritic shafts, were not affected by long-term stimulation. 4. Synaptic active zones [calculated by measuring the lengths of postsynaptic densities (PSDs)] were significantly longer in experimental motor cortex. Lengthening of PSDs occurred selectively in asymmetrical synapses with dendritic shafts (28% increase). 5. The Nv of synapses having perforations in their PSDs (perforated synapses) was significantly higher in experimental hemispheres. Also increased was the incidence of synapse-associated polyribosomes, which are most commonly found at the base of dendritic spines. An increase in the number of perforated synapses and of polyribosomes are both morphological hallmarks of synaptogenesis. 6. The percentages of synapses having different curvatures (i.e., presynaptically concave, convex, or flat) were similar in experimental and in control motor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

How somatotopic is the motor cortex hand area?

The primary motor cortex (M1) is thought to control movements of different body parts from somatotopically organized cortical territories. Electrical stimulation suggests, however, that territories controlling different fingers overlap. Such overlap might be artifactual or else might indicate that activation of M1 to produce a finger movement occurs over a more widespread cortical area than usually assumed. These possibilities were distinguished in monkeys moving different fingers. Recordings showed that single M1 neurons were active with movements of different fingers. Neuronal populations active with movements of different fingers overlapped extensively. Control of any finger movement thus appears to utilize a population of neurons distributed throughout the M1 hand area rather than a somatotopically segregated population.

Animals↗

PubMed1988

Activation of neck muscles from the human motor cortex.

Percutaneous stimulation of the motor cortex has been used to assess directly the supranuclear projection to the sternomastoid, trapezius and splenius capitis muscles. The projection to sternomastoid had a mean latency of 6.5 ms for the contralateral electromyographic response. A smaller and more variable response, usually with a longer latency (mean 9.5 ms), occurred in the ipsilateral sternomastoid. Electromyographic responses on both sides were potentiated by voluntary contraction or strong inspiratory efforts. They were evoked at lower stimulus intensities in the contralateral sternomastoid. Short-latency responses were recorded from the contralateral but not the ipsilateral trapezius and splenius capitis muscles. These results indicate that weakness of head rotation towards the hemiplegic limb following a supranuclear lesion may reflect reduced power of dorsal neck muscles rather than of sternomastoid.

Electric Stimulation↗