Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Motor Cortex”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,423 records · Page 79Linked to original sources
PubMed2003

Systematic changes in motor cortex cell activity with arm posture during directional isometric force generation.

We report here the activity of 96 cells in primate primary motor cortex (MI) during exertion of isometric forces at the hand in constant spatial directions, while the hand was at five to nine different spatial locations on a plane. The discharge of nearly all cells varied significantly with both hand location and the direction of isometric force before and during force-ramp generation as well as during static force-hold. In addition, nearly all cells displayed changes in the variation of their activity with force direction at different hand locations. This change in relationship was often expressed in part as a change in the cell's directional tuning at different hand locations. Cell directional tuning tended to shift systematically with hand location even though the direction of static force output at the hand remained constant. These directional effects were less pronounced before the onset of force output than after force onset. Cells also often showed planar modulations of discharge level with hand location. Sixteen proximal arm muscles showed similar effects, reflecting how hand location-dependent biomechanical factors altered their task-related activity. These findings indicate that MI single-cell activity does not covary exclusively with the level and direction of net force output at the hand and provides further evidence that MI contributes to the transformation between extrinsic and intrinsic representations of motor output during isometric force production.

Animals↗
PubMed2003

Preservation of motor neuron Ca2+ channel sensitivity to insulin-like growth factor-1 in brain motor cortex from senescent rat.

Despite the multiple effects on mammals during development, the effectiveness of the insulin-like growth factor-1 (IGF-1) to sustain cell function and structure in the brain of senescent mammals is almost completely unknown. To address this issue, we investigated whether the effects of IGF-1 on specific targets are preserved at later stages of life. Voltage-gated Ca2+ channels (VGCC) are well-characterized targets of IGF-1. VGCC regulate membrane excitability and gene transcription along with other functions that have been found to be impaired in the brain of senescent rodents. As the voluntary control of movement has been reported to be altered in the elderly, we investigated the expression, function and responsiveness of high (HVA)- and low-voltage-activated (LVA) Ca2+ channels to IGF-1, using the whole-cell configuration of the patch-clamp and RT-PCR in the specific region of the rat motor cortex that controls hindlimb muscle movement. We detected the expression of alpha 1A, alpha 1B and alpha 1E genes encoding the HVA Ca2+ channels P/Q, N and R, respectively, but not alpha 1C, alpha 1D, alpha 1S encoding the L-type Ca2+ channel in this region of the brain cortex. IGF-1 enhanced Ca2+ channel currents through P/Q- and N-type channels but not significantly through the R-type or LVA channels. IGF-1 enhanced the amplitude but did not modify the voltage dependence of Ca2+ channel currents in young (2- to 4-week-old), young adult (7-month-old) and senescent (28- to 29-month-old) rats. These results support the concept that despite the reported decrease in circulating (liver) and local (central nervous system) production of IGF-1 with ageing, key neuronal targets such as the VGCC remain responsive to the growth factor throughout life.

Aging↗
PubMed2004

Cingulate cortical cells projecting to monkey frontal eye field and primary motor cortex.

We compared the distribution of cingulate cortical cells projecting to the frontal eye field (FEF) and primary motor cortex (MI) using a multiple retrograde labeling technique. Two fluorescent tracers were injected into physiologically identified FEF and MI in each monkey. The location of cells projecting to the forelimb area of MI served to identify the rostral (CMAr) and caudal (CMAc) cingulate motor areas. We found two foci of cells projecting to the FEF: rostral (CEFr) and caudal (CEFc) cingulate eye field. The CEFr was located rostral to the CMAr, while the CEFc was located rostro-ventral to the CMAc. Cells projecting to the FEF and MI scarcely overlapped, indicating that each area receives different sets of information from the cingulate cortex.

Amidines↗
PubMed1985

[Reactions of neurons of the motor cortex of the cat to acoustic stimulation and their role in the performance of an instrumental alimentary reflex].

Neuronal reactions evoked in the motor cortex by single and series of sound clicks were studied in trained and untrained cats in chronic experiments. Presentation of conditional stimuli (single sound click) led to appearance of instrumental conditional movement for 7s after the conditioning. At the same time neuronal reaction to conditional sound stimulus did not influence neuronal activity directly connected with instrumental movements. Neuronal reactions to conditional stimuli did not prevent instrumental reflex. They carried out motor function during unconditional defense reaction which appeared in response to acoustic stimuli. Presence or absence of reactions to acoustic conditional stimuli depended on signal significance of stimuli, their physical parameters and level of excitability of the animal.

Animals↗
PubMed2000

Paraspinal motor evoked potentials by magnetic stimulation of the motor cortex.

The authors studied five patients with MS and four patients with HTLV-1 associated myelopathy (HAM) to investigate the usefulness of paraspinal motor evoked potentials (MEP) after magnetic stimulation of the motor cortex. In patients with MS, MEP disappeared or onset latencies were delayed below the lesion. In patients with HAM, the onset latencies were prolonged bilaterally. Thus, paraspinal MEP are very useful in detecting spinal cord lesions.

Adult↗
PubMed2005

Human motor cortex excitability during the perception of others' action.

Neuroscience research during the past ten years has fundamentally changed the traditional view of the motor system. In monkeys, the finding that premotor neurons also discharge during visual stimulation (visuomotor neurons) raises new hypotheses about the putative role played by motor representations in perceptual functions. Among visuomotor neurons, mirror neurons might be involved in understanding the actions of others and might, therefore, be crucial in interindividual communication. Functional brain imaging studies enabled us to localize the human mirror system, but the demonstration that the motor cortex dynamically replicates the observed actions, as if they were executed by the observer, can only be given by fast and focal measurements of cortical activity. Transcranial magnetic stimulation enables us to instantaneously estimate corticospinal excitability, and has been used to study the human mirror system at work during the perception of actions performed by other individuals. In the past ten years several TMS experiments have been performed investigating the involvement of motor system during others' action observation. Results suggest that when we observe another individual acting we strongly 'resonate' with his or her action. In other words, our motor system simulates underthreshold the observed action in a strictly congruent fashion. The involved muscles are the same as those used in the observed action and their activation is temporally strictly coupled with the dynamics of the observed action.

Electromagnetic Fields↗
PubMed1988

A light and electron microscopic study of serotonin-immunoreactive fibers and terminals in the monkey sensory-motor cortex.

Immunocytochemical methods were used to study the distribution and ultrastructure of serotonin (5-hydroxytryptamine; 5-HT) immunoreactive fibers innervating the monkey sensory-motor cortex. Beaded 5-HT positive fibers were found in all cortical layers of both areas but with relatively fewer in middle cortical layers. Examination of 2 micron-thick plastic sections at the light microscope level, revealed that the vast majority of the bouton-like structures on the fibers lay in the neuropil and not adjacent to neuronal somata. A few beaded immunoreactive fibers were seen around certain pyramidal and non-pyramidal cell somata, very occasionally forming modest pericellular ramifications. Serial reconstructions made from electron micrographs after resectioning the 2 micron-thick sections, revealed that the dilatations of the fibers are 5-HT positive boutons but the boutons examined rarely formed morphologically identifiable synaptic contacts. Of 191 reconstructed boutons only 5 made contacts with obvious membrane specializations, all of which were of the asymmetrical type. No immunoreactive synaptic contacts were seen on pyramidal cell somata in the cortex, nor on dendrites or somata in the white matter underlying the cortex, although 5-HT positive boutons commonly lay closely adjacent to neuronal profiles in both sites. 5-HT fibers in the cortex and white matter have a similar morphological appearance and both myelinated and unmyelinated types are seen.

Animals↗
PubMed1995

Activity in the human primary motor cortex related to arm and finger movements.

With the purpose of mapping representations of the finger and proximal arm in the human primary motor cortex (MI), we measured regional cerebral blood flow (rCBF) in eight right-handed normal volunteers during self-paced finger and proximal arm movements. Each movement activated two different fields in MI, one located deep in the anterior lip of the central sulcus and the other relatively close to the surface of the precentral gyrus. Arm fields were located higher than finger fields. A superficial arm field and a deep finger field partially, overlapped. The results indicate that there are two spatially separate motor representations of the finger and proximal arm in the human MI.

Adult↗
PubMed1997

Involvement of the ipsilateral motor cortex in finger movements of different complexities.

Functional imaging and behavioral studies suggest involvement of the ipsilateral hemisphere in hand movements, particularly of the left hand. If this is so, transient disturbance of the motor cortex (M1) with repetitive transcranial magnetic stimulation (rTMS) may affect ipsilateral motor sequences, and the effects may differ on the two sides. We studied 15 right-handed subjects who played a simple and a complex piano sequence for 8 seconds each. Two seconds after the beginning of each sequence, rTMS was delivered to the ipsilateral or contralateral M1, or directed away from the head (control trial). Ipsilateral M1 stimulation on either side induced timing errors in both sequences, and with the complex sequence induced more timing errors in the left hand than in the right hand. Errors of the right hand with both sequences occurred in the stimulation period only, but errors of the left hand with the complex sequence occurred in both the stimulation and poststimulation periods. We conclude that the ipsilateral M1 is involved in fine finger movements. The left hemisphere plays a greater role in timing ipsilateral complex sequences than the right hemisphere and may be more involved in the processing of complex motor programs.

Adult↗
PubMed2004

Interhemispheric interaction between human dorsal premotor and contralateral primary motor cortex.

We used transcranial magnetic stimulation (TMS) in a paired pulse protocol to investigate interhemispheric interactions between the right dorsal premotor (dPM) and left primary motor cortex (M1) using interstimulus intervals of 4, 6, 8, 10, 12, 16 and 20 ms in ten healthy subjects. A conditioning stimulus over right dPM at an intensity of either 90 or 110% resting motor threshold (RMT) suppressed motor-evoked potentials (MEPs) evoked in the first dorsal interosseous (FDI) muscle by stimulation of left M1. Maximum effects occurred for interstimulus intervals (ISIs) of 8-10 ms. There was no effect if the conditioning stimulus was applied 2.5 cm lateral, anterior or medial to dPM. The effect differed from previously described M1 interhemispheric inhibition in that the threshold for the latter was greater than 90% RMT, whereas stimulation of the dPM at the same intensity led to significant inhibition. In addition, voluntary contraction of the left FDI (i.e. contralateral to the conditioning TMS) enhanced interhemispheric inhibition from right M1 but had no effect on the inhibition from right dPM. Finally, conditioning to right dPM at 90% RMT reduced short-interval intracortical inhibition (SICI; at ISI = 2 ms) in left M1 whilst there was no effect if the conditioning stimulus was applied to right M1. We conclude that conditioning TMS over dPM has effects that differ from the previous pattern of interhemispheric inhibition described between bilateral M1s. This may reflect the existence of commissural fibres between dPM and contralateral M1 that may play a role in bimanual coordination.

Adult↗
PubMed1991

[The hysteretic properties of single-joint movements evoked in nonanesthetized cats by the method of microstimulation of the motor cortex].

Hysteretic aftereffects in the elbow joint movements were studied on unanaesthetized cats. Flexor and extensor movements were evoked by microstimulation of the motor cortex. The cortically evoked movements were tested mechanically by applying the servo-controlled torque changes to the joint. Stiffness of the joint depended on the direction of previous movement and was significantly larger after changes in direction of movement. That led to uncertainty in the equilibrium value of the joint angle, which was demonstrated under cyclic changes of torque.

Animals↗
PubMed2005

Chronic administration of selective serotonin reuptake inhibitor (SSRI) paroxetine modulates human motor cortex excitability in healthy subjects.

The aim of the study was to investigate the effect of chronic administration of paroxetine (selective serotonin reuptake inhibitor: SSRI) on motor cortex excitability in healthy subjects by means of transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI) and behavioral motor tests. In a randomized, double-blind, crossover study, twenty-one right-handed subjects received 20 mg daily of either paroxetine or a placebo over a period of 30 days separated by a period of 3 months wash-out. The TMS study is presented here correlated with some results of the motor behavior study (finger tapping test) and the fMRI study (primary sensorimotor cortex (S1M1) volume of activation). TMS was used to test motor threshold (MT), motor evoked potential recruitment curve (RC), cortical silent period (CSP) and paired-pulse intracortical inhibition and facilitation (ICI, ICF). Chronic administration of paroxetine did not modulate ICI or CSP but induced a significant enhancement of mean ICF (ANOVA P=0.04), which significantly correlated with increase of speed in a finger tapping test (P=0.02). This suggests a modulation of cortical interneuronal excitatory pathways without changes in the excitability of cortical inhibitory GABAergic interneurons. A decrease of RC (ANOVA P=0.05) was also observed after 30 days intake of paroxetine in comparison with placebo and was associated with changes of fMRI activation intensity (left S1M1 hypoactivation, ), without changes of S1M1 activation volume. Finally, the different modulation of RC and ICF after chronic administration of paroxetine compared to single dose (opposite effects) emphasizes the different pharmacological action of the drug at cortical level depending on its acute or long-term administration.

Adult↗
PubMed1977

[Relationship between blood flow in the motor cortex and neuronal and total bioelectrical activity of the rabbit brain].

In unrestrained rabbits, the local blood flow (LBF), the unit activity in the motor cortex, the EEG, and the EMG of forelimbs were simultaneously recorded during different kinds of stimulation. The EEG arousal response and the increase in the firing rate of unspecific neurons were only followed by the increase in the LBF on adequate stimulation or movement, whereas on inadequate stimulation it was the decrease in the LBF. With the specific neurons, the increase or decrease in their firing rate corresponded either to enhancement or to reduction of the LBF on adequate and inadequate stimulation. The above correlations were only revealed at the normal functional state of the cerebral cortex. The energy expenditure of specific neurons is suggested to be the main factor in the mechanism for the LBF control.

Animals↗
PubMed2003

Direct demonstration of reduction of the output of the human motor cortex induced by a fatiguing muscle contraction.

A brief period of strong muscle contraction suppresses the amplitude of EMG responses evoked in relaxed muscle by transcranial magnetic stimulation (TMS) of the contralateral motor cortex. Here we investigate this phenomenon in more detail by recording the descending motor volleys evoked by TMS from electrodes in the cervical epidural space of three conscious patients implanted with chronic electrical stimulators for control of pain. We confirm that fatigue suppresses I waves evoked by TMS. In addition, D waves were suppressed in two of the patients, suggesting that axonal excitability might also be compromised by a period of intense muscle contraction.

Adult↗
PubMed1978

[Sources of the afferent pathways of the motor cortex in cats revealed by using the peroxidase method].

By means of the method based on the retrograde axonal transport of exogenic horse-radish peroxidase, there have been stated the sources of afferent pathways of the motor cortex and the structure of neurons sending their axons to the given region. The marked neurons have been found in ipsilateral (SI, SII, Pr, Limb.) and contralateral cortex (MI, Limb.), as well as in the diencephalon (LP, VPL, Hp), the mesencephalon (NR, SN, TM) and the pons (TP). The complex investigation (the peroxidase method and electron microscopy) allowed to get an idea on morphological substrate of disynaptic pathways.

Animals↗
PubMedDate not supplied

[The effect of 2-amino-5-phosphopentanoic acid (AP5)--a NMDA glutamate receptor blocker--on the neuronal activity of the motor cortex in a cat performing the conditioned reflex of placing its paw on a lever].

During cats' performance of the forepaw placing reaction, which was conditioned by a short electrical stimulation (4 msec, 500 Hz) of the contralateral parietal cortex (area 5), two types of stimulus-related responses could be recorded in the contralateral motor cortex. The primary short-latency responses (peak latency about 10 msec, duration up to 30-50 msec) were little sensitive to the application of AP5, a glutamate-NMDA-receptor blocker. The secondary long-latency responses (peak latency 65 msec, duration up to 150-200 msec) were suppressed in 44% of cases of AP5 application. The excitatory movement-related responses were suppressed by AP5 in 18% of cases. An increase in the latency of the conditioned movement itself was observed in 19% of cases. AP5 caused a decrease in the background firing in 46% of spontaneously active neurons. The number of cases of enhancement of separate response components and background neuronal activity and the number of cases of a decrease in the movement latency under the action of AP5 did not exceed those expected at random data distribution.

2-Amino-5-phosphonovalerate↗