SEARCH · PubMed Health

Results for “Motor Cortex”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources

PubMed1984

[Functional aspects of the relation between the claustrum and motor cortex in the cat].

In order to study the relationships between the claustrum and motor cortex neurons both of area 4 and area 6 in the cat, an experiment was performed in which the effect of claustral stimulation on pyramidal tract neurons was investigated. Single shock electrical activation of the claustrum caused an inhibition of the spontaneous activity of the neurons, or an inhibition preceded by short activation, or no effect. These evidences lead to the conclusion that the claustrum exerts a role in movement organization.

Animals↗

PubMed1987

Acetylcholine reduces net outward currents measured in vivo with single electrode voltage clamp techniques in neurons of the motor cortex of cats.

Effects of acetylcholine (ACh) on membrane currents of cells of the motor cortex were measured directly, in vivo, in awake cats using single electrode voltage clamp (SEVC) techniques. Extracellular applications (90-95 nA) of 2 M ACh for periods of 30 s or less produced significant decreases in net outward currents elicited by depolarizing commands whereas applications of saline did not. Reductions of net outward currents were also obtained after intracellular pressure injections of cyclic guanosine monophosphate (GMP)-dependent protein kinase (cGPK) mixed with 10 microM cyclic GMP.

Acetylcholine↗

PubMed1975

Effect of succinylcholine on responses of neurons in the motor cortex to natural activation of muscle spindle primary endings.

In locally anesthetized cats, the effects of intravenous administration of succinylcholine (SCh) in sub-paralytic dosages on the responses of single neurons in motor cortex to small dynamic muscle stretches were studied. A large transient enhancement of these cortical responses with a time course corresponding to the peripheral action of SCh on muscle spindles was observed. This finding is discussed in terms of the hypothesis that muscle spindle primary endings may activate projections to motor cortex.

Animals↗

PubMed1998

Partial inactivation of the primary motor cortex hand area: effects on individuated finger movements.

After large lesions of the primary motor cortex (M1), voluntary movements of affected body parts are weak and slow. In addition, the relative independence of moving one body part without others is lost; attempts at individuated movements of a given body part are accompanied by excessive, unintended motion of contiguous body parts. The effects of partial inactivation of the M1 hand area are comparatively unknown, however. If the M1 hand area contains the somatotopically ordered finger representations implied by the classic homunculus or simiusculus, then partial inactivation might produce weakness, slowness, and loss of independence of one or two adjacent digits without affecting other digits. But if control of each finger movement is distributed in the M1 hand area as many studies suggest, then partial inactivation might produce dissociation of weakness, slowness, and relative independence of movement, and which fingers movements are impaired might be unrelated to the location of the inactivation along the central sulcus. To investigate the motoric deficits resulting from partial inactivation of the M1 hand area, we therefore made single intracortical injections of muscimol as trained monkeys performed visually cued, individuated flexion-extension movements of the fingers and wrist. We found little if any evidence that which finger movements were impaired after each injection was related to the injection location along the central sulcus. Unimpaired fingers could be flanked on both sides by impaired fingers, and the flexion movements of a given finger could be unaffected even though the extension movements were impaired, or vice versa. Partial inactivation also could produce dissociated weakness and slowness versus loss of independence in a given finger movement. These findings suggest that control of each individuated finger movement is distributed widely in the M1 hand area.

Animals↗

PubMed1982

Specificity of visual and motor cortex neurons activity in behavior.

The involvement of the units of visual (VC) and motor cortex (MC) in the systemic behavioral mechanisms is determined by the "environment" and "executive mechanisms of behavior". The unit activity in VC and MC, head and lower jaw movements, EMG of m. masseter and latency of touching the food were recorded. In experiment I the rabbits eyes were covered with occluders that were put on and taken off after every 4-5 repetitions of the behavioral act. It was found that the visual inflow was not necessary for the activations of both MC and VC neurons to appear. The pattern of neuronal activity changed when behavioral act was performed with the eyes closed. These changes following the "visual" influences were more pronounced in the VC. In experiment II the unit activity of both cortical areas was compared during the free head movement towards food and during the movement hampered with the rubber thread. The more pronounced susceptibility of VC neurons to activity changes was demonstrated again, this time after motor influences.

Animals↗

PubMed2006

Single-axon tracing study of corticostriatal projections arising from primary motor cortex in primates.

The axonal projections arising from the forelimb area of the primary motor cortex (M1) in cynomolgus monkeys (Macaca fascicularis) were studied following microiontophoretic injections of biotinylated dextran amine under electrophysiological guidance. The microinjections were centered on layer V, and 42 anterogradely labeled corticofugal axons were reconstructed from serial frontal or sagittal sections with a camera lucida. Our investigation shows that the primate striatum receives both direct and indirect projections from M1. The direct corticostriatal projection is formed by axons that remain uniformly thin and unbranched throughout their sinuous trajectory to the ipsilateral striatum. They divide as they enter the dorsolateral sector of the post-commissural putamen, the so-called sensorimotor striatal territory. The indirect corticostriatal projection derives from a thin collateral emitted within the corona radiata by thick, long-range fibers that descend toward the brainstem. The collateral enters the putamen dorsomedially and remains unbranched until it reaches the dorsolateral sector of the putamen, where it breaks out into two to four axonal branches displaying small and equally spaced varicosities. Both direct and indirect corticostriatal axons branch moderately but occupy vast rostrocaudal striatal territories, where they appear to contact en passant several widely distributed striatal neurons. These findings reveal that, in contrast to current beliefs, the primate motor corticostriatal system is not exclusively formed by axons dedicated solely to the striatum. It also comprises collaterals from long-range corticofugal axons, which can thus provide to the striatum a copy of the neural information that is being conveyed to the brainstem and/or spinal cord.

Afferent Pathways↗

PubMed2004

Bilateral processing of motor commands in the motor cortex of the cat during target-reaching.

Single-unit activity of the motor cortex (area 4gamma) was studied in cats performing reaching with the contra- versus ipsilateral forelimb. Reaching was initiated by a tone burst (Go cue), different limbs were used in separate blocks of trials. During reaching performed with the contralateral limb, three types of neurons were observed. The first type had biphasic pattern with an initial component locked to the Go cue followed by a component locked to the onset of reaching. The second type of neurons had monophasic discharges correlated both with the onset of the stimulus and with the movement. The third type showed responses related to the movement. Activity of the same cells investigated during reaching performed with the ipsilateral limb revealed that the cue-locked responses of the cells of the first type were effector independent, i.e., similar discharges locked to the Go cue were generated. The movement-related component of these cells was drastically reduced. The activity of some cells of the second type was suppressed during reaching with the ipsilateral limb. When performance was switched between limbs, a significant change of background discharge frequency was observed in 31% of the cells. The present results suggest that the sensory cue triggers elaboration of motor commands for reaching in both motor cortices, but further sensorimotor transformation is completed in only one hemisphere but is aborted actively in the other. It is also suggested that a certain pattern of background activity may serve a tuning function for elaboration of the command in the proper hemisphere.

Action Potentials↗

PubMed1983

Penicillin-induced epileptic foci in the motor cortex: vertical inhibition.

Neuronal mechanisms responsible for a vertical restriction of focal seizure activity in the motor cortex were analysed. For this purpose intracellular recording from neurones in superficial (50-300 microns below cortical surface), middle (300-800 microns) and deep cortical layers (800-1300 microns) was performed. As a model of foci of various vertical extensions the spread of seizure activity from superficial to deeper cortical laminae following epicortical penicillin application was used. The appearance of characteristic epileptiform potentials in the surface record with a focus restricted to upper cortical laminae was accompanied (i) in superficial neurones by the development of paroxysmal depolarization shifts (PDS), (ii) in middle neurones by depolarization often followed by hyperpolarization, and (iii) in deep neurones by a sequence of membrane potential changes. The latter consisted of an initial depolarization, an early hyperpolarization, an intermediate depolarization, a late hyperpolarization and a final depolarization. The hyperpolarizing components led to complete suppression of action potentials (vertical inhibition). The early hyperpolarization and the first part of the late hyperpolarization were reduced in amplitude when the intracellular chloride activity was elevated. The intermediate depolarization was replaced by PDS with the enlargement of the epileptic focus into the cortex. The actual effect of the vertical inhibition may in part be responsible for the variability in epileptic motor phenomena coinciding with epileptiform potentials in the surface EEG.

Animals↗

PubMed1995

The superior colliculus relays signals descending from the vibrissal motor cortex to the facial nerve nucleus in the rat.

Electrical stimulation of the vibrissal motor cortex (VMCx), the superior colliculus and the facial nerve nucleus elicits vibrissal movements. A possibility of the superior colliculus as one of the relay nuclei between the VMCx and the facial nerve nucleus was investigated by injecting an anterograde neural tracer, Phaseolus vulgaris leucoagglutinin (PHA-L), into the physiologically identified VMCx and a retrograde tracer, cholera toxin B subunit (CTb), into the facial nerve nucleus in Wistar rats. In the lateral half of the superior colliculus, the termination field of axons from the VMCx overlapped with the distribution field of projection neurons to the facial nerve nucleus. In some cases, PHA-L-labeled terminal swellings were closely apposed to the somas of CTb-labeled neurons. We conclude that signals descending from the VMCx are relayed through the lateral half of the superior colliculus to the facial nerve nucleus.

Animals↗

PubMed1994

Numerical study of coding of the movement direction by a population in the motor cortex.

The fundamental statistical aspects of population coding of the movement direction in the motor cortex are studied numerically. The activity of neurons in a population is simulated using pseudorandom numbers so that the directional selectivity of the neurons is similar to that observed experimentally. Accuracy of the coding, which is evaluated by the root-mean-square (rms) error, is analyzed for various population sizes, degrees of variability of neuronal activity, and degrees of nonuniformity of distribution of the preferred directions. The dependence of the rms error on the population size shows a good fit to the inverse square-root law, from which it is estimated that a single population must contain around 10,000 neurons in order to attain the accuracy that allows 1 deg rms error, for example. The coding is studied further for populations with different types of tuning function. The results support the hypothesis proposed by Georgopoulos et al. (1988) except that the tuning function 'must be tuned in the sense that the average value of the function for movements with components in the preferred direction is larger than for movements away from the preferred direction'.

Cell Count↗

PubMed1983

The projection from the motor cortex to the inferior olive in the cat. An experimental study using axonal transport techniques.

The cortico-olivary projection has been investigated in the cat with the methods of retrograde transport of horseradish peroxidase and wheat-germ agglutinin conjugated with horseradish peroxidase as well as autoradiographic techniques using tritium-labelled amino acids. The projection arises from cells in cortical layer V and terminates mainly ipsilaterally and less densely contralaterally. The strongest termination site is in the caudal medial accessory olive adjacent to subnucleus beta. Projections to that area originate in the medial portions of areas 4 and 6 rostral to the cruciate sulcus. Regions of the motor cortex related to axial back and neck, proximal forelimb and face musculature plus the frontal eye field are represented in largely overlapping areas of the caudal medial accessory olive. A second zone of termination is present in the rostral olive at the junction of the ventral lamella of the principal olive and the medial border of the dorsal accessory olive. Projections to that area arise from a central portion of area 4 at the border between the anterior sigmoid gyrus and the presylvian gyrus. This area contains portions of the representation of the muscle groups controlling the neck and proximal forelimb (shoulder and elbow) only. The frontal eye field, which in the cat influences both extraocular and neck musculature, is also an important direct source of input to this portion of the inferior olive. Contralateral terminations are distributed symmetrically. Combining this information with the olivocerebellar distribution, cerebellar cortical areas corresponding to this direct cortical input are defined. Taking into account that the cortico-olivary fibers appear to arise only from those portions of the motor cortex involved in the control of axial and proximal forelimb muscles, it is suggested that the cortico-olivo-cerebellar projections play a preponderant role in the cerebellar control of posture.

Animals↗

PubMed1996

The relationship of vibrissal motor cortex unit activity to whisking in the awake rat.

Rats actively sweep their whiskers back and forth to locate and palpate objects within their immediate environment. Microstimulation studies in anesthetized rats have demonstrated the presence of a large vibrissal motor representation in agranular cortex. However, the manner in which motor cortex neurons contribute to whisking behavior in the awake animal is unknown. This study represents an initial investigation of the relationship between the activity of task-related neurons in vibrissal motor cortex and the electromyographic (EMG) activity of the deep vibrissal pad muscles in the awake, freely whisking rat. Each animal was gently held in an experimenter's hands while the animal whisked the air. A spring-loaded, metal microelectrode mounted in a removable, miniature microdrive provided stabile recordings of motor cortex unit activity. Fine-wire electrodes implanted in the mystacial pad simultaneously recorded facial muscle activity. Results showed that the discharge of task-related neurons was correlated with changing levels of muscle output. Unit discharge was related in a tonic or phasic-tonic fashion to EMG activity. No units were found to discharge rhythmically in a 1:1 fashion with the periodicity of the whisking pattern. These findings support a role for vibrissal motor cortex in the initiation and modulation of the overall level of mystacial pad muscular output, but not in the generation of bursts of EMG activity responsible for individual whisking sweeps.

Animals↗

PubMed1979

Intracellular synaptic potentials of primate motor cortex neurons during voluntary movement.

An intracellular recording technique was applied to the precentral motor cortex of the unanesthetized, chronically behaving monkey. Postsynaptic potentials, responsible for an initiation of the voluntary movement, were recorded. In total, 22 pyramidal tract neurons (PTNs) and 40 non-pyramidal tract neurons (non-PTNs) were successfully penetrated in 5 monkeys while the monkey was performing a flexion-extension wrist movement after a visual cue (reaction time, 200--350 msec). The neurons showed a negative membrane potential shift of at least 30 mV for more than 30 sec. A slowly rising PSP appeared 80--180 msec after the visual cue, and was 70--180 msec prior to an onset of the movement. Spike activities were superimposed upon this slow PSP with 20--80 msec rise time and 2--6 mV depolarization (8 PTNs and 6 non-PTNs). Since these depolarizations were variable in magnitude and latency, these were considered to be summated potentials of small EPSPs and hidden IPSPs. Membrane resistance was measured from an IR drop by a hyperpolarizing current (1.2 X 10(-9) A) passed through a recording electrode, and was 3.5 +/- 1.7 Momega in 18 PTNs and 4.5 +/- 2.5 Momega in 28 non-PTNs. There was a linear relationship in PTNs between membrane resistance and antidromic latency from the pontine pyramid. Because of the time course of PSPs, their possible dendritic origins were discussed.

Animals↗

PubMed1998

The effect of sevoflurane on myogenic motor-evoked potentials induced by single and paired transcranial electrical stimulation of the motor cortex during nitrous oxide/ketamine/fentanyl anesthesia.

To overcome anesthetic-induced depression of myogenic motor-evoked potentials (MEPs), several techniques of stimulation using paired pulses or trains of pulses are used. This study investigated the effect of sevoflurane on myogenic MEPs induced by single and paired transcranial electrical stimulation of the motor cortex. Nine patients undergoing elective spinal surgery were anesthetized with fentanyl-N2O-ketamine. Partial neuromuscular blockade (single-twitch height 15% of baseline) was maintained with vecuronium. Single and paired (interstimulus interval 2 milliseconds) electrical stimuli were delivered to the scalp, and compound muscle action potentials were recorded from the left and right tibialis anterior muscles. In all patients, baseline MEPs were recorded from both the left and right anterior tibialis muscles (in a total of 18 legs). During the administration of 0.25 MAC and 0.5 MAC sevoflurane, MEPs induced by stimulation with a single pulse could be recorded in 12 of 18 and 4 of 18 legs, respectively, and MEP amplitude was significantly reduced to 48% and 4% of the control value, respectively. During the administration of 0.75 MAC sevoflurane, MEPs following single-pulse stimulation could not be recorded in any legs. The success rate of MEP recording during the administration of sevoflurane was greater after paired stimulation than after single stimulation, and percentage MEP amplitude (percentage of the control value after single stimulation but before sevoflurane) after paired stimulation was significantly higher than after single stimulation before and during the administration of 0.25 MAC and 0.5 MAC sevoflurane. The success rate of MEP recording and MEP amplitude after paired stimulation decreased in a dose-dependent manner during the administration of sevoflurane. These results suggest that although facilitation by the second stimulus was considerable, paired stimuli are still not sufficient to overcome the depressant effects of sevoflurane in clinically used concentrations.

Action Potentials↗

PubMed1993

Neuronal specification of direction and distance during reaching movements in the superior precentral premotor area and primary motor cortex of monkeys.

1. Single-unit neuronal activity was recorded in the primary motor and superior precentral premotor areas of two rhesus monkeys during an arm reaching task. The task involved moving a cursor displayed on a video terminal using a draftsman's arm-type manipulandum. From a centrally located start box the animal was required to move to 1 of 48 target boxes at eight different directions (0-360 degrees in 45 degrees intervals) and six distances (1.4-5.4 cm in 0.8-cm increments). Both direction and distance for the upcoming movement were unpredictable. 2. The activity of 197 arm movement-related cells was recorded and evaluated for each of the 48 targets. Histological examination showed the cells to be primarily in the primary motor cortex or in the premotor area around the superior precentral sulcus. Each cell's discharge was aligned on movement onset and averaged over five trials for each target. Movement kinematics including hand path velocity were also determined. The task time was divided into three epochs, a premovement period (PT), a movement period (MT), and total time (TT = PT+MT). For each epoch the average firing was correlated with the direction and distance of the movement using various regression procedures. 3. An analysis of variance (ANOVA) showed that the majority of neurons were modulated significantly by movement direction in each of the three time periods, PT (73.7%), MT (68.3%), and TT (78.5%). The relationship of the firing to direction was fit to a cosine tuning function for each significantly modulated cell. In 86.3% of the cells the firing was correlated significantly with a cosine function of movement direction in TT. A cell's preferred direction varied little for different movement distances. The mean difference in preferred direction for the smallest possible change in distance (0.8 cm) was 12.8 +/- 11.4 degrees (SD) and 17.1 +/- 14.7 degrees for the largest change in distance (4.0 cm). 4. Correlation analysis revealed that the activity of the majority of cells was modulated significantly by distance along at least one direction in each of the three time periods, PT (46.8%), MT (68.8%), and TT (67.7%). Subsequently, a univariate linear regression model was used to quantify a cell's discharge as a function of distance. For the regressions of firing with distance with a statistically significant correlation (r > 0.8), the mean slope was 3.59 +/- 0.17 spikes.s-1.cm-1 for the total time. The existence of a significant distance modulation was not invariably correlated with a cell's preferred movement direction.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1996

Interaction between intracortical inhibition and facilitation in human motor cortex.

1. In seven normal subjects, subthreshold transcranial magnetic conditioning stimuli (using a figure-of-eight coil) were applied over the motor cortex in order to evoke activity in intracortical neuronal circuits. The net effect on cortical excitability was evaluated by measuring the effect on the size of EMG responses elicited in the abductor digiti minimi (ADM) muscle by a subsequent suprathreshold test stimulus. 2. A single conditioning stimulus suppressed the size of the test response at interstimulus intervals (ISIs) of 1-4 ms whereas the response was facilitated at ISIs of 6-20 ms. The facilitation could be augmented if pairs of conditioning stimuli were given. 3. Inhibition and facilitation appeared to have separate mechanisms. The threshold for inhibition (0.7 active motor threshold) was slightly lower than that for facilitation (0.8 active threshold). Similarly, the inhibitory effect was independent of the direction of current flow induced in the cortex by the conditioning shock, whereas facilitation was maximal with posterior-anterior currents and minimal with lateromedial current. 4. Direct corticospinal effects were probably not responsible for the results since facilitation of cortical test responses could be produced by conditioning stimuli which had no effect on the amplitude of H reflexes elicited in active ADM muscle. 5. Inhibition and facilitation appeared to interact in a roughly linear manner, consistent with separate inputs to a common neurone. 6. We suggest that subthreshold transcranial magnetic stimulation is capable of activating separate populations of excitatory and inhibitory interneurones in the motor cortex.

Adult↗

PubMed1995

Functional magnetic resonance imaging of sensory and motor cortex: comparison with electrophysiological localization.

Functional magnetic resonance (MR) imaging was performed using a 1.5-tesla MR system to localize sensorimotor cortex. Six neurologically normal subjects were studied by means of axial gradient-echo images with a motor task and one or more sensory tasks: 1) electrical stimulation of the median nerve; 2) continuous brushing over the thenar region; and 3) pulsed flow of compressed air over the palm and digits. An increased MR signal was observed in or near the central sulcus, consistent with the location of primary sensory and motor cortex. Four patients were studied using echo planar imaging sequences and motor and sensory tasks. Three patients had focal refractory seizures secondary to a lesion impinging on sensorimotor cortex. Activation seen on functional MR imaging was coextensive with the location of the sensorimotor area determined by evoked potentials and electrical stimulation. Functional MR imaging provides a useful noninvasive method of localization and functional assessment of sensorimotor cortex.

Adult↗

PubMed2006

Post-movement beta rebound is generated in motor cortex: evidence from neuromagnetic recordings.

Voluntary movements are accompanied by amplitude changes in cortical rhythms presumably as a result of functional activation of sensorimotor areas. Recently, the location of the neural generators involved in increasing power within the beta (15-30 Hz) frequency band following movement (post-movement beta rebound, PMBR) has come into question [Parkes, L.M, Bastiaansen, M.C.M, Norris, D.G., 2006. Combining EEG and fMRI to investigate the post-movement beta rebound. NeuroImage 29, 685-696.]. We used the synthetic aperture magnetometry (SAM) spatial filtering method to identify the time course and location of oscillatory changes within the beta and mu (8-14 Hz) frequency bands during the performance of voluntary movements. Neuromagnetic activity was recorded from 10 adult subjects during abduction of the right index finger. Changes in beta and mu source power were calculated for periods during and following movement, relative to pre-movement baseline activity. Decreases in beta band activity (event-related desynchronization, ERD) were observed during movement, with a strong increase (PMBR) beginning 230+/-170 ms following movement, lasting for 680+/-170 ms. Mu band ERD was observed both during and following movement, with little to no post-movement rebound. Beta and mu ERD were localized bilaterally to the hand region of postcentral gyrus whereas PMBR was localized bilaterally to the hand region of precentral gyrus (motor cortex). Both PMBR and beta ERD were strongest contralateral to the side of movement. These results provide further evidence that movement influences independent cortical rhythms in sensorimotor areas, and confirm previous reports of precentral generators of PMBR in the region of motor cortex, with postcentral generators of beta and mu ERD during movement.

Adult↗