Stimulation Of Sensorimotor Cortex Research Articles

Cortical epileptic afterdischarges in immature rats are differently influenced by NMDA receptor antagonists

Epileptic afterdischarges elicited by stimulation of sensorimotor cortex were chosen to test anticonvulsant effects of NMDA receptor antagonists in developing rats (12, 18 and 25 days old) with implanted electrodes. Afterdischarges were elicited four times with 10-min intervals in the experiments with dizocilpine and 20 min with the other two drugs. Dizocilpine (0.5 or 1 mg/kg), CGP 40116 (0.1, 0.5 or 1 mg/kg) or 2-amino-7-phosphonoheptanoic acid (AP7, 30 or 60 mg/kg) was injected intraperitoneally between the first and second stimulation. Intensity of movements accompanying stimulation was diminished regularly only by CGP 40116. Duration of afterdischarges was reduced and intensity of clonic seizures was decreased by CGP 40116 in all age groups; dizocilpine exhibited similar action in 25- and 18-day-old rats, AP7 only in 25-day-old animals. Anticonvulsant action of the three NMDA antagonists exhibited different developmental profiles in our model; this difference might be due to developmental changes of NMDA receptors.

Magnetic stimulation of motor and somatosensory cortices suppresses perception of ulnar nerve stimuli

Magnetic stimulation of sensorimotor cortex interferes with the detection of electro-cutaneous stimulation. However, it is uncertain whether this interference is due to activation of the somatosensory or the motor cortex. Here, transcranial magnetic stimuli (TMS) were delivered separately over somatosensory and motor cortex contralateral to the right ulnar nerve in 12 subjects. In separate trials, TMS were given 100 ms before and 20 ms after 60 ms trains of electro-cutaneous ulnar nerve stimuli, and their effect on the subjective perception of peripheral stimuli was assessed. TMS of both motor and somatosensory cortex interfered with the perception of afferent stimuli when given before or after stimulation of the ulnar nerve. Perception was more strongly suppressed by motor cortex stimulation than by somatosensory cortex stimulation, when given before or after the peripheral stimulus. A similar proportion of errors was induced by sensory cortex stimulation between the two stimulus timing intervals. This study suggests that the inhibition of the afferent volley is unlikely to be the result of antidromic activation of thalamocortical connections or corticospinal gating. A phenomenon akin to sensory masking is the most plausible explanation for much of the suppression of sensory perception by stimulation of the motor or somatosensory cortex. The more powerful suppressive effect of motor cortex stimulation may be due to multiple mechanisms.

Interaction of excitatory amino acid agonists with cortical afterdischarges in developing rats.

To determine the role of excitatory amino acids (EAAs) in genesis of two types of epileptic afterdischarges. Cortical stimulation and recording electrodes were implanted in 12-, 18-, and 25-day-old rats. Epileptic afterdischarges were induced by rhythmic stimulation of sensorimotor cortex. The stimulation was repeated 6 times with 20-min intervals. Ten minutes after the first afterdischarge, N-methyl-d-aspartate, homocysteine, or kainic acid was injected. The doses were chosen individually for different age groups to be subconvulsive. Type and duration of afterdischarges as well as type and severity of motor correlates were evaluated. N-methyl-d-aspartate prolonged afterdischarges only in 12-day-old rats, whereas two other drugs did it in all age groups. Motor correlates of afterdischarges were changed to flexion seizures in 12-day-old rats after N-methyl-d-aspartate and homocysteine; in 25-day-old rats homocysteine led to generalized tonic-clonic seizures (i.e., both patterns seen after substantially higher doses of these drugs in nonstimulated rats). Seizures lasted tens of minutes. Kainic acid did not change the motor pattern in any age group, but nonconvulsive EEG seizures were recorded in the interstimulation periods mainly in 18- and 25-day-old rats. Increased transition into the limbic type of afterdischarges appeared only after homocysteine in 18- and 25-day-old rats. A mutual potentiation of epileptic phenomena was induced by two agents. The actions of N-methyl-d-aspartate and kainic acid differ in all age groups; the effects of homocysteine were identical with those of N-methyl-d-aspartate in 12-day-old rats but not later. Only homocysteine augmented transition into the limbic type of afterdischarges.

Effect of thyrotropin-releasing hormone on the development of cardiac arrhythmias during stimulation of sensorimotor cortex in cats.

Preliminary intravenous injection of thyrotropin-releasing hormone in a dose of 20 g/kg to cats with developing myocardial ischemia during stimulation of the cerebrocortical sensorimotor zone had a pronounced antiarrhythmic effect.

Peculiarities of ischemic cardiac arrhythmias in cats against the background of stimulation of sensorimotor cortex and administration of selective opiate receptor agonists.

In acute experiments on Nembutal-anesthetized cats, the effect of opiate receptor agonists DAGO, DSLET, and dinorphin A(1-13) on the incidence of idioventricular rhythm disturbances, including ventricular tachycardia and fibrillation, was studied under conditions of occlusion of circumflex branch of the left coronary artery and stimulation of the sensorimotor cortex. The most pronounced effects were observed with DSLET and dinorphin A(1-13). These preparations completely prevented ventricular fibrillation. DAGO produced a less pronounced protective effect probably because of parallel increase in plasma catecholamine concentration.

Induction of c-Fos-like protein in bulbar catecholaminergic neurones by electrical stimulation of the sensorimotor cortex in the rat

The sensorimotor cortex (SMC) establishes a functional connectivity with the nucleus tractus solitarius (NTS) and the rostral ventrolateral medulla (RVLM). These bulbar nuclei are known to contain catecholaminergic neurones involved in the cardiovascular control. The aim of the present study was to establish the proportion of catecholaminergic neurones activated by electrical stimulation of SMC. For this purpose, double immunocytochemical procedures were used to reveal the distribution of Fos protein and tyrosine hydroxylase (TH). The results showed that, in the NTS, 7% of the neurones immunoreactive for TH expressed Fos-protein, versus 34% in the RVLM. These data provide evidence that the SMC activated preferentially catecholaminergic neurones of the RVLM which are known to be involved in cardiovascular control via spinal preganglionic neurones.

Effect of a subconvulsant dose of kainic acid on thresholds for phenomena elicited by electrical stimulation of sensorimotor cortex in rats.

Electrical stimulation of sensorimotor cortex was used to study early and late effects of administration of kainic acid in a dose (6 mg/kg i.p.) eliciting only nonconvulsive seizures in rats. Thresholds for elicitation of four phenomena--movements directly related to stimulation; epileptic afterdischarges (ADs) of the spike-and-wave type; clonic seizures accompanying these ADs; and mixed type of ADs where spike-and-wave activity transgresses into limbic type of epileptic phenomena--were measured. Acute administration of kainic acid resulted in a decrease of the threshold for elicitation of mixed type of ADs. In contrast, 1 week after kainic acid administration, the thresholds for stimulation-bound movements, spike-and-wave ADs and concomitant clonic seizures were increased, but the threshold for mixed type of ADs remained unchanged. The changes in thresholds tended to decrease 2 weeks after kainic acid but statistical significance was reached only for stimulus-bound movements. In addition, repetition of stimulation series after 1 as well as 2 weeks markedly influenced the thresholds.

Delayed motor stereotypies and psychoaffective disorders in rats evoked by rhythmic electrical stimulation of the right sensorimotor cortex

Persistent behavioral and postural changes were detected in rats 4–5 days after rhythmic electrical stimulation of the right sensorimotor cortex, which evoked anxiety, aggressive behavior, and fear. Characteristic motor disorders were the manege moving, whose direction correlated with the turn of the head, retropulsions, rhythmic upward jerks of the head (tics), and orofacial dyskinesia (sniffing, mastication, and gnawing). These symptoms rose during 2–3 weeks and then attenuated albiet being retained in a weakened from throughout the entire (up to one year) observation period. The possible mechanisms of genesis of the delayed behavioral disorders and other neuropathophysiological syndromes evoked by rhythmic electrical stimulation of the sensorimotor cortex are discussed.

5-Hydroxytryptamine modifies neuronal responses to glutamate in the red nucleus of the rat.

The effects of 5-hydroxytryptamine (5-HT) on the responses of red nucleus (RN) neurones to glutamate (glu) and its agonists were studied using a microiontophoretic technique in anaesthetised rats. Extracellular unitary recordings of RN neuronal activity showed that 5-HT application induced a significant and reversible depression of glu-evoked excitations in 85% of the RN units tested. This effect was independent of the action of the amine on background firing, which appeared enhanced in the majority of cases but was either depressed or uninfluenced in other cases. Microiontophoretic 5-HT also depressed the excitatory responses evoked in RN neurones by electrical stimulation of sensorimotor cortex. Methysergide application, which prevented the enhancing effects of 5-HT on the background firing, was scarcely effective in antagonising the depression of glu responses. In contrast, the serotonergic effects on the glu responses were reduced by the iontophoretically applied antagonist of 5-HT1A receptors, NAN-190. Microiontophoretic 5-HT was also able to influence the neuronal responses evoked by glu agonists quisqualate (quis) and N-methyl-D-aspartate (NMDA), acting on non-NMDA and NMDA receptors respectively. In fact 5-HT depressed quis-evoked excitations and induced mixed effects on NMDA responses, which were reduced in 45%, enhanced in 34% and unmodified in 21% of the units tested. These results suggest that 5-HT is able to modulate the motor glutamatergic input to RN by acting mostly on non-NMDA receptors. The modulation of non-NMDA and NMDA receptors by 5-HT in the RN appears significant and its functional meaning is discussed.

Expression of c-fos in bulbar nuclei involved in cardiovascular control following the electrical stimulation of sensorimotor cortex in the rat

Previous studies have shown that electrical stimulation of the sensorimotor cortex (SMC) induces responses of the autonomic nervous system such as variations in heart rate and arterial pressure. Neuroanatomical studies have shown the existence of monosynaptic projections from the SMC to the nucleus tractus solitarius (NTS), the rostral ventrolateral medulla (RVLM) and the dorsal nucleus of the vagus nerve (DNV), which are bulbar nuclei involved in cardiovascular control. The aim of the present study was to establish whether there exists a functional connectivity between the SMC and these nuclei. Electrical stimulation applied to the SMC of 7 rats for 1 h induced the expression of c-fos-protein-like immunoreactivity in the nucleus of some neurons in NTS, RVLM and DNV. These data support the view that the SMC has functional connections with bulbar neurons involved in cardiovascular control.

The mechanism of action of laser radiation on the development of ischemic arrhythmias after stimulation of the sensorimotor cortex

Acute experiments on Nembutal-anesthetized cats with occluded circumflex branch of the left coronary artery reveal an antiarrhythmic, effect of laser radiation even against the background of the sensorimotor cortex stimulation. This effect may result from the correcting influence of intra-atrial laser irradiation on the activity of bulbar cardiovascular center through the afferent fibers of the vagus nerve and the opioid peptide system.

Spatial overlap of rubrospinal and corticospinal terminals with input to the inferior olive

Somatosensory responses of cells in the dorsal accessory olive are suppressed following stimulation of the magnocellular red nucleus. Since the magnocellular red nucleus of the cat does not project directly to the dorsal accessory olive, the present experiments were designed to identify indirect pathways that might mediate suppression of olivary responsiveness. Wheat germ agglutinin-horseradish peroxidase was used to compare the location of magnocellular red nucleus terminals with the locations of cells providing input to the rostral dorsal accessory olive. Cells projecting to forelimb rostral dorsal accessory olive can be divided into two main groups: one group comprises a column of large cells located in the ventral caudal cuneate nucleus extending into lamina VI of C1 and C2, and a second group comprises smaller cells located in the ventral rostral cuneate nucleus. Terminations of fibers originating in the magnocellular red nucleus were found to target both groups of cells projecting to the dorsal accessory olive. Therefore, it is possible that the responsiveness of olivary cells is influenced via these terminations. Stimulation of sensorimotor cortex has also been shown to inhibit olivary responsiveness. Terminations from sensorimotor cortex target the same regions of cells that project to the dorsal accessory olive as those of the magnocellular red nucleus, and a similar, perhaps identical, anatomical substrate may serve to modulate olivary sensitivity by the two descending systems.

The effect of carotid artery disease on the cerebrovascular response to physiologic stimulation.

Eight of 16 patients with severe carotid artery disease, but no evidence of functional or structural brain damage, had abnormal regional cerebral blood flow (rCBF) responses to physiologic stimulation of sensorimotor cortex (unilateral reduction in six, abnormal diffuse increase in two). Thus, in patients with cerebrovascular disease the rCBF responses during physiologic tasks may not be reliable indicators of local neuronal activity.

Modifiability of spinal synapses.

Modifiability of spinal synapses.

Corticofugal influences in the rat on responses of neurons in the trigeminal nucleus interpolaris to mechanical stimulation

We recorded effects of electrical stimulation of sensorimotor cortex on the responses of 45 neurons in the interpolar trigeminal nucleus to mechanical stimulation of vibrissae. Responses elicited by peripheral mechanical stimulation were enhanced when a neuron's receptive field (RF) included the RF of the cortical stimulating locus, and suppressed when the RFs of the cortical site and the interpolar neuron did not overlap. Several interpolaris neurons influenced by cortical stimulation were shown to project to the cerebellum.

Effects of stimulation of sensorimotor cortex on primate spinothalamic neurons

Effects of stimulation of sensorimotor cortex on primate spinothalamic neurons

Location of cells of origin of spinothalamic tract in lumbar enlargement of the monkey.

Location of cells of origin of spinothalamic tract in lumbar enlargement of the monkey.

Responses of cat pallidal neurons to cortical and subcortical stimuli

Discharge patterns of pallidal neurons of the cat were studied during single-shock and sustained high-frequency stimulation of sensorimotor cortex (SMC), caudate nucleus, nonspecific thalamic nuclei (CM), subthalamus, midbrain reticular formation (MRF) and amygdaloid complex. Three types of spontaneous discharge pattern were found in pallidal neurons: high discharge rate (HDR), low discharge rate (LDR) and repetitive burst patterns were observed. The LDR and repetitively discharging units generally responded to a limited number of the stimulus sites, occasionally to one site exclusively, whereas HDR units generally showed a high degree of convergence. The response patterns of units responding to single-shock stimulation of MRF, CM, and subthalamus were similar. A marked facilitation lasting 20–50 msec was a consistent response which in some units was followed by a prolonged facilitation or inhibition. Sustained high-frequency stimulation always resulted in a net facilitatory effect. Single-shock stimulation of caudate nucleus and SMC generally produced a powerful inhibition. In some units facilitation preceded this inhibition, and in a small number of units, only facilitation was observed. Sustained high-frequency stimulation produced either inhibitory or facilitatory effects. Single-shock stimulation applied to amygdala caused an initial facilitation, followed in some units by inhibition or facilitation. High-frequency stimulation produced either facilitatory or inhibitory effects. The variation in response patterns to stimulation of each stimulus site was dependent upon the individual neuron and not upon the stimulus site. Analyses of the responses to a test stimulus following a conditioning stimulus suggest that the excitability changes of the neuron following single-shock stimulation are well represented by the poststimulus time histogram.

Pyramidal tract responses during seizures

1. 1. Responses to stimulation of the sensorimotor cortex were recorded from the ipsilateral medullary pyramid during seizures in locally anesthetized, paralyzed cats. Seizures were induced either by i.v. administration of Metrazol or by high frequency stimulation of the ipsilateral sensorimotor cortex. 2. 2. Changes in PT responses that were observed include: an increased fluctuation in amplitude of both D and I components during seizures as compared with the resting period and the addition of a large late I component not obtainable by strong, brief stimulation of normal cortex. In addition, paroxysmal activity in the ECoG usually accompanied that in the PT. 3. 3. Before the amplitude of the PT response can be used as a measure of the number of responding PT neurons (and hence as a measure of PT excitability) any change in size of the action potentials of PT axons during a seizure must be determined. An average decrement of 5–10% was indirectly estimated from the decrement in population responses to direct stimulation of PT axons at several intensities. 4. 4. The PT response to a test stimulus given more than 250 msec after the onset of an antecedent paroxysmal PT discharge usually had the largest late I wave, some enhancement of the early I waves, but a slightly reduced D wave. Such reduction is mainly attributable to reduced size of the individual axonal potentials and is only occasionally attributable to reduced excitability of PT neurons. By contrast, a test stimulus given during the latter part of a paroxysmal discharge, or soon thereafter, elicited an enhanced D wave and reduced I waves. 5. 5. The interneuronal circuits subserving the late I wave are located in the homolateral sensorimotor cortex because of the following: 1. (a) After unilateral topical application of Metrazol to the sensorimotor cortex, the late I wave response was initially confined to the same side. 2. (b) The late I wave was not elicited by subcortical stimulation of white matter during a seizure. 3. (c) Late I waves could still be elicited by stimulation of the sensorimotor cortex after extensive acute ipsilateral thalamic lesions (including the ventral thalamic group), or after an extensive lesion of the ipsilateral head of the caudate nucleus, or after contralateral hemispherectomy. 4. 6. All I wave responses were markedly depressed during the post-ictal period. 5. 7. The characteristic changes in PT responses during seizures did not depend in contamitant changes in arterial pressure. 6. 8.The findings suggest that at certain times during a seizure, PT neurons have their excitability at, and occasionally slighly below, control levels until powerfully driven by the cortical interneuronal circuits subserving either the late I waves or paroxysmal discharges.

Central influences on spinal afferent conduction.

Central influences on spinal afferent conduction.