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[The effect of acute ethanol administration on the neuronal activity of the motor cortex of the rabbit in its food-acquisition behavior].

Units activity of anterolateral area of rabbits motor cortex, realizing instrumental food-acquisition behaviour was studied at acute injection of ethanol and in control experiments (injection of physiological solution) in order to compare possible ethanol effects on the motor area of the cortex with effects revealed by us earlier at studying the activity of the limbic cortex units in the same experimental conditions. It was shown that after ethanol injection the number of active units and the pattern of the motor cortex units specialization in contrast to the limbic one remained constant. Nevertheless, composition of the motor cortex units involved in subserving the behaviour changed because of recruitment [correction of recrutation] of one cells (from V-VI layers of the cortex) in this process and exclusion of other ones (from II-IV layers). The value of activation frequency ratio to the frequency of the background of the involved units increased.

Animals↗
PubMed2002

I feel my hand moving: a new role of the primary motor cortex in somatic perception of limb movement.

The primary motor cortex (MI) is regarded as the site for motor control. Occasional reports that MI neurons react to sensory stimuli have either been ignored or attributed to guidance of voluntary movements. Here, we show that MI activation is necessary for the somatic perception of movement of our limbs. We made use of an illusion: when the wrist tendon of one hand is vibrated, it is perceived as the hand moving. If the vibrated hand has skin contact with the other hand, it is perceived as both hands bending. Using fMRI and TMS, we show that the activation in MI controlling the nonvibrated hand is compulsory for the somatic perception of the hand movement. This novel function of MI contrasts with its traditional role as the executive locus of voluntary limb movement.

Adult↗
PubMed2005

Activity of the motor cortex during scratching.

In awake cats sitting with the head restrained, scratching was evoked using stimulation of the ear. Cats scratched the shoulder area, consistently failing to reach the ear. Kinematics of the hind limb movements and the activity of ankle muscles, however, were similar to those reported earlier in unrestrained cats. The activity of single neurons in the hind limb representation of the motor cortex, including pyramidal tract neurons (PTNs), was examined. During the protraction stage of the scratch response, the activity in 35% of the neurons increased and in 50% decreased compared with rest. During the rhythmic stage, the motor cortex population activity was approximately two times higher compared with rest, because the activity of 53% of neurons increased and that of 33% decreased in this stage. The activity of 61% of neurons was modulated in the scratching rhythm. The average depth of frequency modulation was 12.1 +/- 5.3%, similar to that reported earlier for locomotion. The phases of activity of different neurons were approximately evenly distributed over the scratch cycle. There was no simple correlation between resting receptive field properties and the activity of neurons during the scratch response. We conclude that the motor cortex participates in both the protraction and the rhythmic stages of the scratch response.

Animals↗
PubMed2006

Intensity modulation of TMS-induced cortical excitation: primary motor cortex.

The intensity dependence of the local and remote effects of transcranial magnetic stimulation (TMS) on human motor cortex was characterized using positron-emission tomography (PET) measurements of regional blood flow (BF) and concurrent electromyographic (EMG) measurements of the motor-evoked potential (MEP). Twelve normal volunteers were studied by applying 3 Hz TMS to the hand region of primary motor cortex (M1(hand)). Three stimulation intensities were used: 75%, 100%, and 125% of the motor threshold (MT). MEP amplitude increased nonlinearly with increasing stimulus intensity. The rate of rise in MEP amplitude was greater above MT than below. The hemodynamic response in M1(hand) was an increase in BF. Hemodynamic variables quantified for M1(hand) included value-normalized counts (VNC), intensity (z-score), and extent (mm(3)). All three hemodynamic response variables increased nonlinearly with stimulus intensity, closely mirroring the MEP intensity-response function. VNC was the hemodynamic response variable which showed the most significant effect of TMS intensity. VNC correlated strongly with MEP amplitude, both within and between subjects. Remote regions showed varying patterns of intensity response, which we interpret as reflecting varying levels of neuronal excitability and/or functional coupling in the conditions studied.

Adult↗
PubMed2004

Effects of sensorimotor restriction and anoxia on gait and motor cortex organization: implications for a rodent model of cerebral palsy.

Chronic or acute perinatal asphyxia (PA) has been correlated with the subsequent development of cerebral palsy (CP), a developmental neurological disorder characterized by spasticity and motor abnormalities often associated with cognitive deficits. Despite the prevalence of CP, an animal model that mimics the lifetime hypertonic motor deficits is still not available. In the present study, the consequences of PA on motor behavior, gait and organization of the primary motor cortex were examined in rats, and compared with the behavioral and neurological consequences of early postnatal movement-restriction with or without oxygen deprivation. Rats subjected to PA had mild increases in muscular tone accompanied by subtle differences in walking patterns, paralleled by significantly altered but relatively modest disorganization of their primary motor cortices. Movement-restricted rats, suffering PA or not, had reduced body growth rate, markedly increased muscular tone at rest and with active flexion and extension around movement-restricted joints that resulted in abnormal walking patterns and in a profoundly distorted representation of the hind limbs in the primary motor cortex. Within the sensorimotor-restricted groups, non-anoxic rats presented the most abnormal pattern and the greatest cortical representational degradation. This outcome further supports the argument that PA per se may represent a substrate for subtle altered motor behaviors, and that PA alone is sufficient to alter the organization of the primary motor cortex. At the same time, they also show that early experience-dependent movements play a crucial role in shaping normal behavioral motor abilities, and can make a powerful contribution to the genesis of aberrant movement abilities.

Animals↗
PubMed1977

[Transcallosal modulation of a focus of maximal activity in the motor cortex].

In acute experiments on cats, when recording EPs from 170 symmetrical points of the motor cortex, callosal influence on the maximal activity focus (MAF) was studied in conditions of stimulation of the sciatic nerves with different stimuli. After callosal transection, weak stimuli enlarged the MAF, strong one-narrowed it. The transcallosal modulation in intact brain is supposed to aid to delineate the MAF in the motor cortex and to exaggerate the differences between MAFs occurring at stimulation with different stimuli.

Animals↗
PubMed2006

Selective and nonselective benzodiazepine agonists have different effects on motor cortex excitability.

Transcranial magnetic stimulation (TMS) is a useful method to study pharmacological effects on motor cortex excitability. Zolpidem is a selective agonist of the benzodiazepine receptor subtype BZ1 and has a distinct pharmacological profile compared to diazepam. To study the different effects of these two drugs on the cortical inhibitory system, TMS was performed before and after administration of a single oral dose of zolpidem (10 mg) and diazepam (5 mg) in six healthy volunteers. TMS tests included the determination of resting and active motor threshold (MT) and measurements of the amplitudes of motor evoked potentials, intracortical facilitation (ICF), short-latency intracortical inhibition (SICI), and long-latency intracortical inhibition (LICI), and determination of the cortical silent period (CSP). Both drugs were without effect on the active or resting MT and decreased the ICF. Prolongation of the CSP and enhancement of LICI only in the presence of zolpidem point to a specific BZ1-related mechanism underlying the long-lasting component of cortical inhibition. This selective modulation of the CSP and the LICI points to a specific role of BZ1 receptors in the control of inhibitory neuronal loops within the primary motor cortex.

Administration, Oral↗
PubMed2000

The Organization of the Frontal Motor Cortex.

Recent anatomic and functional data radically changed our ideas about the organization of the motor cortex in primates. Contrary to the classic view, the motor cortex does not consist of two main areas, primary and supplementary motor areas, but of a mosaic of cortical areas with specific connections and functional properties.

Journal Article↗
PubMed1985

Two different mechanisms control inhibition of spike discharge in neurons of cat motor cortex after stimulation of the pyramidal tract.

Intracellular recordings were made from neurons of the motor cortex of awake cats while the pyramidal tract (PT) was stimulated at the level of the facial nucleus. In some neurons IPSPs of 35-120 ms peak latency were recorded that diminished in size or reversed with hyperpolarizing current. During these IPSPs a decrease in input resistance reflective of a conductance increase was measured. More often, however, PT stimulation produced IPSPs with comparable latencies that increased in size with hyperpolarizing current. These IPSPs diminished with depolarizing current, and in some instances they appeared to reverse with strong depolarization. During these IPSPs an increased input resistance reflective of a decreased conductance was measured. The results indicate that two different mechanisms control rapid inhibition of spike discharge in neurons of the motor cortex after PT stimulation.

Animals↗
PubMed2004

The mRNA expression of AMPA type glutamate receptors in the primary motor cortex of patients with amyotrophic lateral sclerosis: an in situ hybridization study.

The pathogenetic mechanisms leading to progressive neurodegeneration in amyotrophic lateral sclerosis (ALS) have not been fully elucidated. One possible factor responsible for the selective motor neuron loss in the motor cortex, brain stem and spinal cord is glutamate-induced excitotoxicity particularly mediated via alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) type glutamate receptors. Data about the expression pattern of AMPA receptors in the primary motor cortex are lacking so far. The pharmacological and physiological properties of AMPA receptors are defined by the heteromeric composition of the four different receptor subunits. Different expression patterns of these subunits at motor neurons may provide a molecular basis for increased vulnerability to excitotoxic damage. Using in situ hybridization histochemistry we did not detect any significant differences in the distribution of AMPA receptor mRNA in the motor cortex of ALS patients compared to controls.

Aged↗
PubMed1988

[Neuronal organization of field 4 of the motor cortex of the cat brain].

By means of the silver nitrate impregnation method after Golgi-Kopsch in kittens and young cats the field 4 in the cerebral motor cortex has been studied. The motor cortex of the field 4 possesses certain heteromorphism. Besides usual stellate and pyramidal neurons, that differ from real ones by some morphological signs: their body is often round, the apical dendrite is much thinner than the corresponding dendrite of a pyramidal neuron, it does not produce oblique branches along the course, never gets into the I layer, the spines arrange less densely. According to the mode of dendrites setting off, the atypical pyramidal neurons can be divided into multipolar and spindle-like with horizontal or vertical branching of the dendrites. According to the spines distribution, the multipolar atypical neurons can be divided into spinous, rare-spinous and aspinous. With respect to various cellular forms and distribution of various types of neurons in layers, every of the areas (gamma, alpha, sfu, fu) possesses specific peculiarities. The greatest variability of the neurons have the field 4 gamma and 4 alpha, where, besides stellate and pyramidal, atypical neurons can be found. The stellate neurons of the field 4 gamma are characterized with a deep arrangement, their number is essentially less, than in other areas of the field 4. In the field 4 alpha they are situated in the layers II-III. Suprafundal and fundal parts of the field do not possess pyramidal atypical neurons and are characterized with presence of large amount of the stellate neurons. In respect to the axonal branching in the suprafundal part of the field 4, 2 types of the stellate cells are distinguished.

Animals↗
PubMed2003

Impairment of motor function after frontal lobe resection with preservation of the primary motor cortex.

We investigated the clinical course and characteristics of the motor deficits in patients who underwent surgical resection of the frontal lobe for tumorous lesions. Only patients who met the following criteria were included in the present study: 1) postoperative MRI revealed that resection of the frontal lobe involved the area closely adjacent to the primary motor cortex, but 2) the D wave of the corticospinal MEP did not decrease in amplitude below 50% of the original level during surgery. The extent of resection was classified into 4 groups. In Group A (6 cases), resection was limited within the area above the superior frontal sulcus and posterior to a line vertical to the line connecting the anterior and posterior commissures at the anterior commissure (AC vertical line). Resection was extended anterior to the AC vertical line in Group B (4 cases) or below the superior frontal sulcus in Group C (5 cases). In Group D (3 cases), resection was extended to both of these two boundaries. Severe motor paresis and/or apraxia of the upper and lower extremities were noted in all patients of Group D immediately after surgery. A complete recovery in the lower extremity was observed in these patients, while disturbance in the fine movements of the upper extremity remained for more than 1 year after the surgery. Disturbance in the fine movements and/or apraxia of the upper extremity were observed immediately after surgery in 2 of the Group A patients (33%), 2 of the Group B patients (50%) and 3 of the Group C patients (60%). However, a rapid recovery occurred in these patients, and only a subtle or mild disturbance remained for more than 1 year after the surgery in one of the Group B and one of the Group C patients. Permanent and severe motor deficit is rarely induced when resection of the frontal lobe is limited to only the SMA proper (corresponding roughly to Group A), the SMA proper and pre-SMA (corresponding roughly to Group B), or the SMA proper and premotor cortex (corresponding roughly to Group C), insofar as the primary motor cortex is preserved. Disturbance in fine movements of the upper extremity is frequently induced for the long term when wide areas of the SMA proper, pre-SMA as well as premotor cortex are resected altogether (corresponding roughly to Group D).

Adult↗
PubMed1982

Swimming as a method for assessing motor cortex integrity in the rat.

Rats were tested on 6 measures of swimming behavior 1, 2 and 4 weeks after sham operations or bilateral motor cortex lesions that damaged the forelimb areas and axons controlling the axial musculature. Rats with lesions performed more forelimb kicks and showed larger body angles than control animals. Number of hindlimb kicks and speed were within normal limits. Thus, some measures of swimming can be affected by small motor cortex lesions that spare the hindlimb projections.

Animals↗
PubMed2003

Striatal dopamine release induced by repetitive transcranial magnetic stimulation of the human motor cortex.

Brain dopamine is implicated in the regulation of movement, attention, reward and learning. Dysfunction of dopamine plays a role in Parkinson's disease, schizophrenia and drug addiction. It is released in the striatum when dopamine neurons in the midbrain undergo burst firing. Several animal studies have shown that dopamine can also be released under direct control of glutamatergic corticostriatal efferents. However, the existence and physiological significance of this mode of action remain controversial. We have shown previously that repetitive transcranial magnetic stimulation (rTMS) of the human prefrontal cortex led to focal dopamine release in the ipsilateral caudate nucleus, supporting the corticostriatal mode of dopamine release. Using the same experimental approach, we sought to confirm this hypothesis. We used [11C]raclopride and PET to measure changes in extracellular dopamine concentration following rTMS of the motor cortex in six healthy human subjects. rTMS of the left primary motor cortex caused a reduction in [11C]raclopride binding in the left putamen compared with rTMS of the left occipital cortex. There were no changes in binding in the right putamen, caudate nucleus or nucleus accumbens. The area of statistically significant change in binding corresponded closely to the known projection zone of corticostriatal efferents originating in monkey motor cortex. This finding has implications for the functional role of subcortical dopamine.

Adult↗
PubMed2005

Reduction of the hand representation in the ipsilateral primary motor cortex following unilateral section of the corticospinal tract at cervical level in monkeys.

BACKGROUND: After sub-total hemi-section of cervical cord at level C7/C8 in monkeys, the ipsilesional hand exhibited a paralysis for a couple of weeks, followed by incomplete recovery of manual dexterity, reaching a plateau after 40-50 days. Recently, we demonstrated that the level of the plateau was related to the size of the lesion and that progressive plastic changes of the motor map in the contralesional motor cortex, particularly the hand representation, took place following a comparable time course. The goal of the present study was to assess, in three macaque monkeys, whether the hand representation in the ipsilesional primary motor cortex (M1) was also affected by the cervical hemi-section. RESULTS: Unexpectedly, based on the minor contribution of the ipsilesional hemisphere to the transected corticospinal (CS) tract, a considerable reduction of the hand representation was also observed in the ipsilesional M1. Mapping control experiments ruled out the possibility that changes of motor maps are due to variability of the intracortical microstimulation mapping technique. The extent of the size reduction of the hand area was nearly as large as in the contralesional hemisphere in two of the three monkeys. In the third monkey, it represented a reduction by a factor of half the change observed in the contralesional hemisphere. Although the hand representation was modified in the ipsilesional hemisphere, such changes were not correlated with a contribution of this hemisphere to the incomplete recovery of the manual dexterity for the hand affected by the lesion, as demonstrated by reversible inactivation experiments (in contrast to the contralesional hemisphere). Moreover, despite the size reduction of M1 hand area in the ipsilesional hemisphere, no deficit of manual dexterity for the hand opposite to the cervical hemi-section was detected. CONCLUSION: After cervical hemi-section, the ipsilesional motor cortex exhibited substantial reduction of the hand representation, whose extent did not match the small number of axotomized CS neurons. We hypothesized that the paradoxical reduction of hand representation in the ipsilesional hemisphere is secondary to the changes taking place in the contralesional hemisphere, possibly corresponding to postural adjustments and/or re-establishing a balance between the two hemispheres.

Animals↗
PubMed1979

The origin of the hind limb vasodilatation evoked by stimulation of the motor cortex in the cat.

In cats under Althesin anaesthesia, the hind limb area of the motor cortex has been stimulated by means of monopolar, semi-micro-electrodes with careful experimental control so as to avoid reflex effects evoked through stimulation of meningeal afferent fibres or stimulus spread to non-cortical structures. 2. Localized cortical stimulation which elicited muscle contractions in the contralateral hind limb also elicited vasodilation in the same limb: the stimulus threshold was the same for both effects, and the magnitude of the dilatation was related to the strength of contraction. 3. Reduction of the somatic motor response, caused by lesions in the medullary pyramidal tract, was accompanied by a parallel reduction of the vascular response. 4. Prevention of the motor response by gallamine or by spinal cord section at L4--L5 (which leaves the sympathetic outflow to the hind limbs intact) led to abolition of the vascular response. During recovery from gallamine, contraction and vasodilatation returned in parallel. 5. The muscle vasodilatation was insensitive to atropine or guanethidine. 6. It is concluded that the hind limb vasodilatation observed on stimulation of the motor cortex is simply a post-contraction hyperaemia, and that it is independent of the sympathic nervous system. Previous conclusions of a sympathetically mediated vasodilatation probably resulted from inadequate control of the stimulus or a failure to recognize weak muscle contractions.

Animals↗