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PubMed1987

Motor cortex stimulation in intact man. 1. General characteristics of EMG responses in different muscles.

This paper is the first of two papers describing our five-year experience with the technique of electrical stimulation of the human motor cortex. In this first paper we illustrate the basic distribution and behaviour of electromyographic responses in limb muscles to anodal stimulation of the motor cortex in intact, awake human subjects. These responses may be recorded at short latency, with estimates of conduction velocities from the brain to the spinal cord suggesting transmission in rapidly conducting pathways, such as the corticomotoneuronal component of the corticospinal tract. The site at which the stimulus activates these motor pathways to produce responses at such short latency is likely to be at, or adjacent to the origin of these major descending motor pathways in the cerebral cortex. The best stimulating sites for activation of arm or leg muscles corresponds to the known somatotopic arrangement of the cerebral cortex. The electromyographic response characteristics are different in the contracting, as compared with the relaxed muscle; the EMG response latency shortens, its size becomes larger and its threshold is lowered when the muscle is voluntarily made to contract. The mechanisms that are responsible for these characteristics are examined in the following paper.

Adult↗

PubMed1992

Performance in an escape task induces fos-like immunoreactivity in a specific area of the motor cortex of the rat.

The expression of the c-fos proto-oncogene was studied in two different areas of the motor cortex and in the hippocampus of the rat after performance in an escape task in a Skinner box. Performance in this task caused an increase in the number of cells showing fos-like immunoreactivity in layers V and VI of the forelimb motor-sensory cortex with respect to yoked animals which had received the same amount, frequency and duration of aversive stimulation and manipulation as the trained animals. Therefore, this increase is the specific effect of performing the behavioral task. In the hindlimb motor-sensory cortex there were no differences between the trained and the yoked animals in any of the cortical layers. No differences were observed in the dentate gyrus of the hippocampus between trained and yoked animals, while the control animals showed a much lower fos-like immunoreactivity. In conclusion, infragranular layers in the forelimb representation of the primary motor cortex become activated with respect to the expression of fos-like immunoreactivity after performance in an escape task in a Skinner box. This result is consistent with the idea that even in complex structures such as the cerebral cortex, specific trace systems become activated for the performance of complex behavioral tasks.

Analysis of Variance↗

PubMed1976

[Morphological studies on interneuronal relations in the feline motor cortex].

Three types of neuronal joinings in the cat motor cortex are described. The joinings of the 1st type (nests, barrels) consist of some pyramidal cells, apical dendrites of which form the bundles. The consolidation of neurons is achieved by means of dendro-dentritic contacts, pyramidal neuron collaterals and the associative transcortical afferents. The joinings of the 2nd type (distant) are formed with the participation of intracortical connections between the pyramidal and stellate neurons and are placed as concentric formation. The joinings of the 3rd type are formed with the help of projection thalamo-cortical afferents and large horizontal collaterals of basket cells.

Animals↗

PubMedDate not supplied

[Effect of the microiontophoretic application of acetylcholine on the formation of conditioned reactions in motor cortex neurons].

In alert rabbits the activity of the motor cortex neurones was recorded with simultaneous application of acetylcholine to them in the process of defensive conditioning. Conditioned reorganization, mainly of activation type, were found in 60% of neurones. In most cases conditionally reacting cells were sensitive to acetylcholine. Ionophoretic application of the transmitter promoted the formation of conditioned neuronal responses and increased them in comparison with conditioned reactions evoked in absence of acetylcholine. It is supposed that the influence of acetylcholine on conditioned cellular process is realized due to its action on the state of excitability of the cortical neurones.

Acetylcholine↗

PubMed1990

Estimation of facial central motor delay by electrical stimulation of the motor cortex of the dog.

Central delay time (CD) has been estimated for activation of limb muscles by electrical or transcranial magnetic coil (TMC) stimulation of motor cortex and ventral root outflow. In the present study, we used surface electrical stimulation of the motor cortex of the right hemisphere to produce evoked compound muscle action potentials (CMAP) from the contralateral orbicularis oris (o.r.), and orbicularis oculi (o.c.), in dogs. Monopolar electrical stimulation of the facial nerve at the cerebello-pontine (CP) angle yielded CMAP activation of ipsilateral facial muscles. These latencies when subtracted from those obtained by direct cortical stimulation established CD for activation of the seventh cranial nerve. Preliminary data with single pulse magnetic stimulation at high outputs (greater than 80%) revealed CMAP with onset latencies similar to the direct facial nerve stimulation at the CP angle by electrical means.

Action Potentials↗

PubMedDate not supplied

Transformation of the afferent tactile signal into a motor command in the cat motor cortex.

Activity of 112 neurons of the precruciate motor cortex in cats was studied during a forelimb placing reaction to tactile stimulation of its distal parts. The latent period of response of the limb to tactile stimulation was: for flexors of the elbow (biceps brachii) 30-40 msec, for the earliest responses of cortical motor neurons about 20 msec. The biceps response was observed for 5-10 msec after the end of stimulation of the cortex with a series of pulses lasting 25 msec. Two types of excitatory responses of the neurons were identified: responses of sensory type observed to each tactile stimulation of the limb and independent of the presence or absence of motion, and responses of motor type, which developed parallel with the motor response of the limb and were not observed in the absence of motion. The minimal latent period of the responses of motor type was equal to the latent period of the sensory responses to tactile stimulation (20 +/- 10 msec). Stimulation of the cortex through the recording microelectrode at the site of derivation of unit activity, which increased during active flexion of the forelimb at the elbow (11 stimuli at intervals of 2.5 msec, current not exceeding 25 microA), in 70% of cases evoked an electrical response in the flexor muscle of the elbow.

Action Potentials↗

PubMed1998

Corticostriatal input zones from the supplementary motor area overlap those from the contra- rather than ipsilateral primary motor cortex.

To investigate the degree of convergence of corticostriatal inputs from the primary motor cortex (MI) and the supplementary motor area (SMA), we analyzed the extent to which corticostriatal inputs from forelimb representations of these motor-related areas spatially overlap in the macaque monkey. Of particular interest was that corticostriatal input zones from SMA overlapped those from MI of the contralateral hemisphere more extensively than from MI of the ipsilateral hemisphere.

Animals↗

PubMed2006

Neurochemical diversity of neurogliaform cells in the human primary motor cortex.

Neurogliaform cells of area 4 of the human motor cortex were found to express choline acetyl transferase (ChAT), gamma-aminobutyric acid, and calbindin. GABA- and calbindin-positive NGCs were mainly localized in layers II and VI and were relatively rare in layer I of the cortex. ChAT-positive NGCs were observed in the upper and middle thirds of layer II, occurring occasionally in layer I and the upper portion of layer III. Their numbers were low compared to those of GABA- and calbindin-positive NGCs in layers II/III. The dendrites of ChAT-positive NGCs were short and few in number. Axonal arborizations of neighboring ChAT-positive cells interpenetrated considerably so that each ChAT-positive cell body was normally surrounded by axonal trees of the parent and a few other ChAT-positive NGCs. NGC axon collaterals surrounded small neuropil areas containing perikarya presumptive pyramidal neurons. The findings are discussed in the context of information processing in cortical modules and interaction of excitatory and inhibitory interneurons.

Acetylcholine↗

PubMed1989

Short latency somaesthetic responses in motor cortex, transmitted through the spino-thalamic system, in the cat.

Evidence is presented that in the cat, the spinothalamic system contributes to short latency somaesthetic responses in motor cortex efferent cells. Intracellular recordings performed on identified pyramidal tract cells and corticospinal cells show that these cells are still activated and/or inhibited from the periphery after a set of central nervous lesions leaving intact only the ventral half of the spinal cord. The responses were attributed to the spinothalamic system. The ascending system is activated through collaterals of afferent fibres running in the dorsal columns of the spinal cord. This peripheral link to the motor cortex might participate in updating the motor command on the basis of information feedback from the periphery.

Action Potentials↗

PubMed1996

Expression of different metallothionein messenger ribonucleic acids in motor cortex, spinal cord and liver from patients with amyotrophic lateral sclerosis.

In earlier studies of sporadic amyotrophic lateral sclerosis (ALS), a disease of unknown etiology, the amount of metallothioneins (MTs), a group of small (6-7 kDa) metal-binding proteins, appeared higher in liver, kidney and spinal cord from patients than from non-neurologic controls. Immunohistochemically, the expression of MT in the central nervous system appeared limited to glia. Since the highly conserved MTs isotypes share antigenic epitopes, they could not be distinguished by immunological methods. It thus proved necessary to estimate the expression of each individual MT messenger ribonucleic acid (mRNA) by performing reverse transcriptase polymerase chain reaction (RT-PCR)-mediated analysis of tissue samples. Tissues selected included liver, motor cortex and cervical cord at C6; MT mRNAs analyzed included MT1A, 1B, 1E, 1F, 1G, 2A, and 3. Also, special care was taken to avoid interference by amplification of the 6 MT pseudogenes. Except of MT3, already known as brain-specific, and MT1B which was not expressed in any tissue, mRNA levels of the other MT genes tended to be higher in ALS than in control liver samples, but the differences did not attain statistical significance. In the nervous system, the diverse MT genes were expressed over a greater range in ALS than in controls, but exhibited no change in a consistent direction. At the motor cortex, changes seemed to be less pronounced than at C6. MT3 was expressed in the motor cortex and the cord. The results provide no evidence for either the induction of a specific MT repertoire, or for the inability of glia to express any MT gene in ALS. Because the semi-quantitative RT-PCR technique does not permit detailed comparisons between the subtypes of MT expressed in the various tissues, the question whether a single inductor may be held responsible for the elevation of MT in the ALS liver and nervous system remains open. In conclusion, ALS tissue remains capable of expressing all the major MT genes. MT, present in protoplasmic glia, arises locally and is not secondary to increases of hepatic or renal MT. Because MT3 is also expressed by the normal and ALS spinal cord, it is a central nervous system-specific and not only a brain-specific protein. Thus, the excess of MT in ALS liver seems to be an effect of slower catabolism rather than faster synthesis of protein.

Adult↗

PubMed1982

Motor deficit following interruption of sensory inputs to the motor cortex of the monkey.

The possible functional role of sensory inputs in voluntary movements was examined by severing the sensory input pathways to the motor cortex. The somatic sensory cortex and the dorsal column, which are known to be the two major sources of the peripheral inputs to the motor cortex, were ablated or sectioned. The deficit produced by sensory cortex ablation or dorsal column section was not prominent and the function recovered within a week or two as long as the other input was intact, but elimination of both inputs produced severe impairment in movements such as loss of orientation in space and of manipulation of individual fingers. The possible role of the afferent input is discussed and it is proposed that it participates in the smooth pursuit of movement by continuously changing the excitability of cortical efferent zones.

Animals↗

PubMed1997

Reaching movements with similar hand paths but different arm orientations. I. Activity of individual cells in motor cortex.

This study shows that the discharge of many motor cortical cells is strongly influenced by attributes of movement related to the geometry and mechanics of the arm and not only by spatial attributes of the hand trajectory. The activity of 619 directionally tuned cells was recorded from the motor cortex of two monkeys during reaching movements with the use of similar hand paths but two different arm orientations, in the natural parasagittal plane and abducted into the horizontal plane. Nearly all cells (588 of 619, 95%) showed statistically significant changes in activity between the two arm orientations [analysis of variance (ANOVA). P < 0.01]. A majority of cells showed a significant change in their overall level of activity (ANOVA, main effect of task, P < 0.01) between arm orientations before, during, and after movement. Many cells (433 of 619, 70%) also showed a significant change in the relation of their discharge with movement direction (ANOVA, task x direction interaction term, P < 0.01) during movement, including changes in the dynamic range of discharge with movement and changes in the directional preference of cells that were directionally tuned in both arm orientations. Similar effects were seen for the discharge of cells while the monkey maintained constant arm postures over the different peripheral targets with the use of different arm orientations. Repeated data files from the same cell with the use of the same arm orientation showed only small changes in the level of discharge or in directional tuning, suggesting that changes in cell discharge between arm orientations cannot be explained by random temporal variations in cell activity. The distribution of movement-related preferred directions of the whole sample differed between arm orientations, and also differed strongly between cells receiving passive input predominantly from the shoulder or elbow. The electromyographic activity of most prime mover muscles at the shoulder and elbow was also strongly affected by arm orientation, resulting in changes in overall level of activity and/or directional tuning that often resembled those of the proximal arm-related motor cortical cells. A mathematical model that represented movements in terms of movement direction centered on the hand could not account for any of the arm-orientation-related response changes seen in this task, whereas models in intrinsic parameter spaces of joint kinematics and joint torques predicted many of the effects.

Analysis of Variance↗

PubMed1997

Cerebellar input to corticothalamic neurons in layers V and VI in the motor cortex.

To investigate whether corticothalamic (CT) neurons in the motor cortex (Mx) receive cerebellar input via the ventroanterior-ventrolateral nucleus of the thalamus (VA-VL), we recorded intracellular potentials from neurons in the Mx of anesthetized cats and examined effects of stimulation of the VA-VL and the brachium conjunctivum on them. After this electrophysiological identification, horseradish peroxide (HRP) was injected iontophoretically into the recorded neurons for morphological analysis. We identified 34 neurons as CT neurons by their antidromic response to stimulation of the VA-VL, of which 13 were layer VI CT neurons and 21 were layer V CT neurons. A majority of the CT neurons of both layers VI and V received monosynaptic excitatory postsynaptic potentials (EPSPs) from the VA-VL and di- or polysynaptic EPSPs from the cerebellum. The laminar distribution and morphological characteristics of single CT neurons receiving cerebellar input were analyzed on 19 HRP-labeled CT neurons. Eight layer V and six layer VI CT neurons were reconstructed from serial sections. All the reconstructed layer VI CT neurons were modified pyramidal neurons whose apical dendrites ended in layer III or V, and all the stained layer V CT neurons were typical pyramidal neurons, although the laminar and tangential distribution of recurrent collaterals of these neurons varied from neuron to neuron.

Animals↗

PubMed1994

Responses to rapid-rate transcranial magnetic stimulation of the human motor cortex.

We applied trains of focal, rapid-rate transcranial magnetic stimulation (rTMS) to the motor cortex of 14 healthy volunteers with recording of the EMG from the contralateral abductor pollicis brevis, extensor carpi radialis, biceps brachii and deltoid muscles. Modulation of the amplitude of motor evoked potentials (MEPs) produced in the target muscle during rTMS showed a pattern of inhibitory and excitatory effects which depended on the rTMS frequency and intensity. With the magnetic coil situated over the optimal scalp position for activating the abductor pollicis brevis, rTMS led to spread of excitation, as evident from the induction of progressively larger MEPs in the other muscles. The number of pulses inducing this spread of excitation decreased with increasing rTMS frequency and intensity. Latency of the MEPs produced in the other muscles during the spread of excitation was significantly longer than that produced by single-pulse TMS applied to the optimal scalp positions for their activation. The difference in MEP latency could be explained by a delay in intracortical conduction along myelinated cortico-cortical pathways. Following rTMS, a 3-4 min period of increased excitability was demonstrated by an increase in the amplitude of MEPs produced in the target muscles by single-pulse TMS. Nevertheless, repeated rTMS trains applied 1 min apart led to similar modulation of the responses and to spread of excitation after approximately the same number of pulses. This suggests that the spread might be due to the breakdown of inhibitory connections or the recruitment of excitatory pathways, whereas the post-stimulation facilitation may be due to a transient increase in the efficacy of excitatory synapses.

Adult↗

PubMed1991

The impairments in reaching and the movements of compensation in rats with motor cortex lesions: an endpoint, videorecording, and movement notation analysis.

Reaching for food by rats, with the limb contralateral to limb area motor cortex damage, was analyzed using end-point scores, videoanalysis, and Eshkol-Wachmann Movement Notation (EWMN). End point results from groups of rats with small, medium, and large lesions showed reaching success and amount of food grasped per reach decreased with increases in lesion size. Videoanalysis and EWMN showed that the impairments were attributable to: (1) an inability to pronate the paw over the food by abduction of the upper arm, and (2) an inability to supinate the paw at the wrist to orient the food to the mouth. There were no obvious impairments in locating food using olfaction, in positioning the body in order to initiate a reach, or in clasping the digits to grasp food. There were only mild impairments in lifting, aiming, and advancing the limb. In rats with medium and large lesions, loss of pronation and supination were compensated for by a variety of whole body movements. These findings are discussed in reference to neural and behavioral mechanisms underlying recovery of function and the contribution of the motor cortex to skilled movements in the rat and other species.

Animals↗

PubMed2001

Axon trajectories in local circuits of the primary motor cortex in the macaque monkey (Macaca fuscata).

The intrinsic trajectories and terminal arbors of two axons and one horizontal axon collateral within the primary motor cortex (M1) were studied in the macaque monkey using injections of biotinylated dextran amine (BDA) into the putative primary forelimb motor cortex, and two-dimensional (2-D) reconstruction of the individually labeled axons and collateral. (1) A long collateral of the main axon from a large pyramidal cell in layer Vb of the putative forelimb area on the anterior bank of the central sulcus coursed horizontally anteriorly for 3 mm and formed a terminal arbor in layer III of M1. (2) The main axon of a pyramidal cell in layer IIIa+b of the putative forelimb area on the precentral gyrus descended into the white matter and then entered the anterior bank of the central sulcus to form a terminal arbor in layers III and V. (3) The main axon of a pyramidal cell in layer IIIc of the putative forelimb area on the precentral gyrus descended and bifurcated in the white matter. One branch entered the anterior bank of the central sulcus to form a terminal field in layer VI. These results indicate that some local axons and horizontal axon collaterals arising from M1 reach their single targets within M1 to form single terminal fields.

Animals↗

PubMed1985

Forelimb electromyographic responses to motor cortex stimulation during locomotion in the cat.

The forelimb motor cortex was stimulated via chronically implanted microelectrodes whilst electromyographic (e.m.g.) responses were recorded from muscles in the contralateral forelimb in cats walking steadily at 0.5 m/s. The stimuli were brief trains of 0.2 ms pulses (11 pulses at 330 Hz), intensity 5-20 microA and e.m.g.s were recorded from the following muscles: biceps brachii, brachialis, long and lateral heads of triceps brachii, latissimus dorsi, cleidobrachialis, extensor digitorum communis, palmaris longus and flexor and extensor carpi ulnaris. During locomotion, stimulation at 20 microA readily elicited brief, short-latency changes in the normal locomotor patterns of activity in all muscles studied. The changes included production of e.m.g. at times in the step cycle when the muscles are normally inactive and brief augmentations or diminution of the normal locomotor e.m.g.s. Individual electrodes usually influenced several muscles, and muscles acting antagonistically about the same joint were sometimes co-contracted. The first effect on locomotor flexor muscles (i.e. muscles active in relation to the swing phase of the step cycle) was almost always excitatory and such effects were often phase-dependent, usually occurring when the muscle was normally active or about to become active. Extensor muscles were excited from some cortical loci but inhibited from others (inhibitions were necessarily detectable only when the muscles exhibited locomotor-related e.m.g.s). Some micro-electrodes elicited excitation during swing (when the extensors are inactive) but elicited inhibition during stance. In several muscles the latencies of the excitatory e.m.g. changes could be as short as 6 ms measured from the first pulse in the stimulus train. In flexors, but not in extensors, latencies fluctuated according to the timing of the stimuli relative to the step cycle. Reduction in stimulus intensity reduced the amplitude of the e.m.g. changes, the number of muscles influenced and often increased the latency. However, both excitations and inhibitions were sometimes evident at 5 microA and thresholds for excitatory responses were, over-all, substantially lower than in the resting animal. Longer trains of stimuli were capable of resetting the step cycle. Response thresholds were greatly increased after pyramidectomy. These findings support the view that the natural bursts of impulses discharged by pyramidal tract neurones during steady locomotion are likely to contribute to regulating forelimb muscle activity on a step-by-step basis.

Action Potentials↗

PubMed2005

Representation of facial muscles in human motor cortex.

Whether there is a projection from the primary motor cortex (M1) to upper facial muscles and how the facial M1 area is modulated by intracortical inhibitory and facilitatory circuits remains controversial. To assess these issues, we applied transcranial magnetic stimulation (TMS) to the M1 and recorded from resting and active contralateral (C-OOc) and ipsilateral orbicularis oculi (I-OOc), and contralateral (C-Tr) and ipsilateral triangularis (I-Tr) muscles in 12 volunteers. In five subjects, the effects of stimulating at different scalp positions were assessed. Paired TMS at interstimulus intervals (ISIs) of 2 ms were used to elicit short interval intracortical inhibition (SICI) and ISI of 10 ms for intracortical facilitation (ICF). Long interval intracortical inhibition (LICI) was evaluated at ISIs between 50 and 200 ms, both at rest and during muscle activation. The silent period (SP) was also determined. C-OOc and I-OOc responses were recorded in all subjects. The optimal position for eliciting C-OOc responses was lateral to the hand representation in all subjects and MEP amplitude markedly diminished when the coil was placed 2 cm away from the optimal position. For the I-OOc, responses were present in more scalp sites and the latency decreased with more anterior placement of the coil. C-Tr response was recorded in 10 out of 12 subjects and the I-Tr muscle showed either no response or low amplitude response, probably due to volume conduction. SICI and ICF were present in the C-OOc and C-Tr, but not in the I-OOc muscle. Muscle activation attenuated SICI and ICF. LICI at rest showed facilitation at 50 ms ISI in all muscles, but there was no significant inhibition at other ISIs. There was no significant inhibition or facilitation with the LICI protocol during muscle contraction. The SP was present in the C-OOc, C-Tr and I-OOc muscles and the mean durations ranged from 92 to 104 ms. These findings suggest that the I-OOc muscle response is probably related to the first component (R1) of the blink reflex. There is M1 projection to the contralateral upper and lower facial muscles in humans and the facial M1 area is susceptible to cortical inhibition and facilitation, similar to limb muscles.

Acoustic Stimulation↗