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PubMedDate not supplied

[The temporal organization of the functional connection of the motor cortex neurons in the cat].

Conditioned food-procuring response to time (2 minutes interval) was elaborated in cats, multiunit activity of the motor cortex being recorded. On the basis of single spike trains discriminated from the multiunit activity the cross-correlation histograms were built and the spikes composing their peaks were analysed in real time. This secondary analysis of the histograms allowed to ascertain the dynamics of functional connections between the neurons during the phase of active waiting according to the distribution of coincident impulses. A concentration of coincident impulses of simultaneously recorded cells was observed in different moment of time. In some neuronal pairs the concentration of coincident impulses was revealed to the end of the conditioned interval. The data obtained are considered as a manifestation of the conditioned reaction at the level of neuronal interaction.

Animals↗
PubMed1999

Human motor-cortex oxygenation changes induced by cyclic coupled movements of hand and foot.

Near-infrared spectroscopy (NIRS) was used to assess human motor-cortex oxygenation changes in response to cyclic coupled movements of hand and foot. Using a highly sensitive NIRS instrument, we showed that it was possible to detect reproducible oxygenation patterns using single cycles (20 s) of easy and difficult association tasks. No significant differences in the time corresponding to the maximal changes in concentration of oxy- and deoxyhemoglobin ([O(2)Hb] and [HHb], respectively) were found during easy and difficult association as well as cycles. Only [O(2)Hb] showed a significantly higher value at the end of the difficult association during the first cycle. No significant differences were found for [O(2)Hb] and [HHb] in the other cycles. We conclude that NIRS is a useful addition to functional magnetic resonance imaging in investigating the time course of cortical activation.

Adult↗
PubMed1992

Demonstration of human motor cortex activation using SPECT.

Recent advances in single photon emission computed tomography (SPECT) have allowed improved image resolution with lower doses of labelled tracer. Capitalizing on these improvements, the authors have developed a new SPECT protocol for imaging neuronal activation. We outline this technique and describe how it can demonstrate increased human motor cortex activity in normal subjects performing a motor task. The ability to accurately demonstrate neuronal activation with SPECT using this method may have important scientific and clinical implications.

Adult↗
PubMed1989

[The effect of acetylcholine and cholinergic transmission blockers on the neuronal impulse activity of the cat motor cortex in a conditioned reflex].

Influence of acetylcholine, atropine, d-turbocurarine and hexonium on the background and evoked impulse activity of the motor cortex neurons was investigated in cat under instrumental placing reaction. Only those neurons were analyzed whose responses preceded conditional movement. It was shown that acetylcholine increased the background impulse activity in one group of cortical neurons and decreased it in the other neuronal group. During iontophoretic application of acetylcholine the background activity of some neurons declined in spite of the increase of their evoked conditional response. Atropine inhibited background impulse activity, the conditional impulse response being preserved. The background impulse activity increased and evoked conditional response was inhibited during iontophoretic application. Hexonium inhibited the background activity and conditional evoked impulse activity. It is suggested that cholinergic fibers in the natural state participate in supporting the background activity of cortical neurons by means of m-cholinoreceptors and at the sam time they evoke the impulse activity linked with conditional responses through n-cholinoreceptors.

Acetylcholine↗
PubMed1993

[Influence of lesion of motor cortex on second somatosensory area emanating descending modulation on thalamic intralaminar nuclei].

The present study was undertaken to verify further the participation of motor cortex (MCtx) in the somatosensory area II(SII) emanating descending modulation of thalamic intralaminar nuclei (ILN). Neuronal responses in ILN to noxious stimulation of the superficial peroneal nerve were extracellularly recorded in 34 cats. The effects of electrical stimulating SII on nociceptive responses of neurons in ILN before and after lesion of MCtx were observed and compared. It was shown that electrical stimulation of SII obviously inhibited the nociceptive responses in the majority of neurons recorded (11/13) in ILN in the cats with MCtx intact (P < 0.05). After lesion of MCtx the inhibitory effect still remained (n = 10, P < 0.05), but weakened to a certain extent compared with that before lesion. In the animals with the lesion involving MCtx and the underlying subcortical structures electrical stimulating SII facilitated the nociceptive responses of ILN neurons (n = 7, P < 0.05). The results further support the idea that SII emanating descending modulation on ILN is in part fulfilled via MCtx.

Animals↗
PubMed2005

Stereotactic linac-based radiosurgery in the treatment of cerebral arteriovenous malformations located deep, involving corpus callosum, motor cortex, or brainstem.

PURPOSE: To evaluate patient outcome and obliteration rates after radiosurgery (RS) for cerebral arteriovenous malformations (AVM) located deep, in the motor cortex or brainstem and those involving corpus callosum. METHODS AND MATERIALS: This analysis is based on 65 patients. AVM classification according to Spetzler-Martin was 13 patients Grade 2, 39 Grade 3, 12 Grade 4, and 1 Grade 5. Median RS-based AVM score was 1.69. Median single dose was 18 Gy. Mean treatment volume was 5.2 cc (range, 0.2-26.5 cc). Forty patients (62%) experienced intracranial hemorrhage before RS. Median follow-up was 3.0 years. RESULTS: Actuarial complete obliteration rate (CO) was 50% and 65% after 3 and 5 years, respectively. CO was significantly higher in AVM <3 cm (p < 0.02) and after doses >18 Gy (p < 0.009). Annual bleeding risk after RS was 4.7%, 3.4%, and 2.7% after 1, 2, and 3 years, respectively. AVM >3 cm (p < 0.01), AVM volume >4 cc (p < 0.009), and AVM score >1.5 (p < 0.02) showed a significant higher bleeding risk. Neurologic dysfunction improved, completely dissolved, or remained stable in 94% of patients. CONCLUSIONS: Surgically inaccessible AVM can be successfully treated using RS with acceptable obliteration rates and low risk for late morbidity. The risk of intracranial hemorrhage is reduced after RS and depends on RS-based AVM score.

Adolescent↗
PubMed2001

Descending spinal cord volleys evoked by transcranial magnetic and electrical stimulation of the motor cortex leg area in conscious humans.

1. Descending corticospinal volleys evoked after transcranial magnetic or electrical stimulation of the leg area of the motor cortex were recorded from an electrode in the spinal epidural space of six conscious patients who had electrodes implanted for treatment of chronic pain, and from one anaesthetised patient undergoing surgery for a spinal tumour. 2. At threshold, the shortest-latency volley (L1 volley) was evoked by stimulation with an anode 2 cm lateral to the vertex. Anodal stimulation at the vertex also elicited a volley at this latency in two patients, but in the other patients the first volley evoked appeared 1-1.3 ms later (L2 volley), at the same latency as the initial volley evoked by magnetic stimulation. High-intensity stimulation of any type could evoke both the L1 and L2 waves as well as later ones (L3, L4, etc.) that had a periodicity of about 1.5 ms. 3. Voluntary contraction increased the amplitude of the L2 and later volleys, but had no effect on the L1 volley. 4. Intracortical inhibition between pairs of magnetic stimuli resulted in clear suppression of the L4 and later waves. The L2 and L3 waves were unaffected. 5. In the anaesthetised patient the L1 volley occurred 1.7 ms later than the volley produced by transmastoid stimulation of the corticospinal pathways in the brainstem. 6. The L1 volley is likely to be a D wave produced by the direct activation of pyramidal axons in the subcortical white matter; the L2 and later volleys are likely to be I waves produced by the trans-synaptic activation of corticospinal neurones. The implication is that electrical stimulation with an anode at the vertex is more likely to evoke I waves preferentially than stimulation over the hand area. A more secure way to ensure D wave activation of corticospinal fibres from the leg area is to place the anode 2 cm lateral to the vertex.

Adult↗
PubMed2002

Modulation of input-output curves by low and high frequency repetitive transcranial magnetic stimulation of the motor cortex.

OBJECTIVES: Exploring the modulatory effects of different frequencies of repetitive transcranial magnetic stimulation (rTMS) on the excitability of the motor cortex as measured by the input-output curve technique (I-O curve). METHODS: Sixteen healthy subjects participated in this experiment. On two different sessions, conducted 1 week apart, rTMS was applied either at a frequency of 20 or 1 Hz at 90% of individual motor threshold (MT) for a total of 1600 pulses each. Before and after rTMS, the cortical excitability was assessed by measuring MT and the size of motor evoked potentials (MEPs) collected at different intensities of stimulation. RESULTS: The analysis on the whole population showed a significant decrease of cortical excitability after 1 Hz rTMS and an increase after 20 Hz rTMS. A subsequent cluster analysis pointed out the presence of two distinct groups of subjects with opposite responses at the same frequency of stimulation. Significant variations on MT were found for both groups only for the facilitatory effect irrespective of the frequency of stimulation. CONCLUSIONS: The results provide further insight into interindividual differences in the effects of rTMS and suggest the existence of subpopulations with specific patterns of response to rTMS.

Adult↗
PubMed2004

Direct recording of the output of the motor cortex produced by transcranial magnetic stimulation in a patient with cerebral cortex atrophy.

OBJECTIVE: To examine the descending motor activity evoked by transcranial magnetic stimulation (TMS) in a chronic alcoholic patient with a slight atrophy of the peri-central cortex and compare with that observed in neurologically intact subjects. METHODS: EMGs from the first dorsal interosseous (FDI) muscle, and descending activity from an electrode implanted in the high cervical epidural space for relief of pain were recorded after TMS of the hand area of motor cortex. A figure-of-8 coil was used to induce either a posterior-anterior (PA) or a latero-medial (LM) flow across the central sulcus. RESULTS: In intact subjects, LM stimulation evoked the earliest volley, which we termed a D wave. This was followed by later, presumed I waves at intervals of about 1.5 ms. At a stimulus intensity of 120% resting threshold (RMT), up to 5 I waves were seen. PA stimulation rarely evoked D waves at intensities up to 120% RMT, but 3 or 4 I waves were visible in all subjects. The patient had an increased resting threshold, and the descending volleys were dominated by a D wave. I waves were unclear, with two possible small peaks at 5.5 and 7.2 ms. CONCLUSIONS: The lack of I waves in the patient was probably due to an impairment of interneuronal circuitry in the context of the brain damage related to chronic alcohol abuse, and is consistent with a trans-synaptic origin of the I waves in humans. The intact D wave is consistent with the assumption that the D wave represents direct stimulation of the axons of intact corticospinal neurones in the subcortical white matter. The patient's increased RMT reflects the fact that usually multiple descending volleys are needed to discharge resting spinal motoneurones.

Alcoholism↗
PubMed1986

Response properties of the non-pyramidal tract neuron in the kitten motor cortex during early postnatal development: an intracellular HRP study.

Response properties of the non-pyramidal tract neurons (non-PTNs) of the kitten motor cortex were examined with intracellular horseradish peroxidase (HRP) staining under Nembutal anesthesia. Thirty-one neurons were identified as non-PTNs and their responses were analyzed with stimulation of the cerebellar nuclei (CN) and/or the medullary pyramid (Py). Excitatory postsynaptic potentials (EPSPs) were induced both by CN and Py stimulation even at birth, whereas inhibitory postsynaptic potentials (IPSPs) were first detected during the third postnatal week in layers II-III pyramidal neurons, which is much later than in PTNs. This indicates that the intracortical circuits responsible for IPSPs in the superficial cortical layers develop later than in layer V.

Animals↗
PubMed1999

Functional MRI of human primary somatosensory and motor cortex during median nerve stimulation.

OBJECTIVES: Somatosensory evoked potential (SEP) studies suggested that some early cortical SEP components may be generated in the primary motor cortex (M1) rather than the primary somatosensory cortex (S1). METHODS: We now used functional magnetic resonance imaging (fMRI) to study activation of S1 and M1 by electrical median nerve stimulation in healthy volunteers. RESULTS: The hand areas of both S1 and M1 showed significant activation (correlation coefficients >0.45) in 7 of 9 subjects (activated volume S1 > M1). For comparison, a sequential finger opposition task significantly activated S1 in 7 and M1 in all 9 subjects (activated volume M1 > S1). CONCLUSIONS: These data show that the electrical stimuli used for SEP recording lead to a functional activation of S1 as well as M1.

Adult↗
PubMed1981

Variety of functional organization within the monkey motor cortex.

1. Single-unit recordings have been made from 606 neurones in the arm region of area 4 in five conscious monkeys. Their activity during a stereotyped motor task and their responses to passive natural stimulation of the limb have been investigated.2. 88% of area 4 neurones responsive to natural stimulation received their afferent input from a restricted region of the contralateral arm.3. The activity and afferent input to cell groups have been determined by comparing the properties of neurones located within 500 mum of each other and recorded in one and the same micro-electrode penetration. 115 such cell groups containing 344 neurones were investigated.4. 75/115 cell groups (65%) contained neurones with input from the same arm zone (shoulder, elbow, wrist or hand) and with a similar pattern of task-related activity. Cell groups containing neurones with identical afferent inputs never showed contrasting behaviour during movement.5. 40/115 cell groups (35%) contained neurones receiving inputs from more than one arm zone. Twenty-five cell groups (22%) had two contiguous zones (e.g. wrist and hand) represented and ten groups had input from two discontinuous zones (e.g. elbow and hand). These differences in input within a cell group were usually reflected in contrasting behaviour of its constituent neurones during movement.6. Pyramidal tract neurones (PTNs) lying immediately adjacent to one another usually received similar inputs and exhibited matching behaviour. PTNs lying further apart in the same penetration often showed different activity and responded to different stimuli.7. The topographic distribution of afferent input to area 4 revealed multiple representation of input from a single zone combined with considerable intermingling of input from all four zones. Neurones with shoulder and elbow inputs surrounded those with wrist inputs which in turn lay scattered around a central zone. This central zone only contained neurones with hand inputs, although neurones with hand inputs were found outside this central zone.8. The significance of this complex organization is discussed in terms of motor cortex input and output.

Afferent Pathways↗
PubMed2003

Chronic motor cortex stimulation for movement disorders: a promising perspective.

Five patients affected by thalamic hand and international myoclonus have been evaluated and selected for chronic motor cortex stimulation. A quadripolar electrode strip was placed epidurally under local anesthesia through an MR-image-guided single precentral burr hole placed following the morphologic recognition of the central sulcus. Intra-operative stimulation was used to induce muscle contraction at the affected site to confirm the correct placement of the electrode. A one-week trial period preceded the implant of an internal pace-maker under general anesthesia. A remarkable decrease in pain was reported by four patients together with the reduction of dystonia and rigidity in thalamic hand and marked decrease of intentional myoclonus. No complications or undesired side effects of electrode implant and stimulation were observed.

Adult↗
PubMedDate not supplied

[The activity of cat motor cortex neurons during performance of a conditoned response of placing the forepaw on a support].

The activity of 74 units of the cat precentral motor cortex was studied in the process of reaction of placing the forepaw on a support. It has been shown that the neurones controlling the flexion of the ulnar joint, the first phase of the reaction, receive an afferent tactile input primarily from the dorsal side of the paw, i.e. from region of the skin surface which is the receptive field of the reflex of placing the paw on the support. Learning the animals to lift the paw to the support in response to a touch of the ventral surface results in an increase of discharge frequency of the studied units in response to ventral stimulation similar to that recorded in response to the initially effective dorsal stimulation.

Animals↗
PubMed2001

Tetraethylammonium-induced long-term potentiation in layer V horizontal connections of rat motor cortex.

The possibility for the induction of long-lasting synaptic plasticity by the potassium channel blocker tetraethylammonium (TEA) was investigated in adult rat motor cortex in vitro. Brief application of TEA (25 mM) resulted in a long-term potentiation (LTP(K)) of field potentials evoked in layer V intralaminar connections by 59+/-17%. This effect could be prevented by preincubation with nifedipine, a voltage-dependent calcium channel blocker (20 microM), but not by N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovalerate (APV, 100 microM). LTP(K) induction resulted in a smaller relative potentiation of a response to the second pulse of a pair (60 ms interpulse interval). These results indicate a potential of layer V horizontal connections for a NMDA receptor-independent form of persistent synaptic enhancement.

2-Amino-5-phosphonovalerate↗
PubMed2000

Plasticity of the human motor cortex in patients with arteriovenous malformations: a functional MR imaging study.

BACKGROUND AND PURPOSE: The capacity of the human brain to recover from damage has been explained on the basis of plasticity, according to which remaining areas assume functions that would normally have been performed by the damaged brain. Patients with cerebral arteriovenous malformations (AVMs) involving primary motor areas may present without significant neurologic deficits. We used functional MR imaging to investigate the organization of cortical motor areas in patients with AVMs. METHODS: Cortical motor hand and foot representations were mapped in nine right-handed patients harboring AVMs occupying the hand (n = 6) or foot (n = 3) region of the primary motor cortex (M1). None of the patients exhibited motor deficits. Simple movements of the hand and foot were performed. In eight patients, both right and left extremities were tested; in one patient, only the hand contralateral to the AVM was examined. Localization of activation in the affected hemisphere was compared with that in the unaffected hemisphere and evaluated with respect to the normal M1 somatotopic organization shown in earlier functional MR imaging investigations. RESULTS: Cortical activation showed three patterns: 1) functional displacement within the affected M1 independent of the structural distortion induced by the AVM (n = 4), 2) presence of activation within the unaffected M1 ipsilateral to the moving extremity without activation in the affected M1 (n = 3), and 3) prominent activation in nonprimary motor areas without activation in either the affected or unaffected M1 (n = 2). CONCLUSION: Preliminary evidence suggests that brain AVMs lead to reorganization within the somatotopic representation in M1 and to occasional abnormal expansion into nonprimary motor areas.

Adult↗
PubMed2003

Motor cortex stimulation in a patient with intractable complex regional pain syndrome type II with hemibody involvement. Case report.

The authors describe the effectiveness of motor cortex stimulation (MCS) in a patient with complex regional pain syndrome (CRPS) Type II, formerly known as causalgia, with hemibody allodynia. During MCS, a subjective sensation of warm paresthesia developed in the painful hand and forearm and spread toward the trunk. Pain and allodynia in the areas associated with this sensation were alleviated significantly. The analgesic effect of stimulation proved to be long lasting and was still present at the 12-month follow up. The authors speculate that MCS might exert its effect through the modulation of thalamic activity in this particular case of CRPS with hemisensory deficit. A central mechanism associated with functional disturbance in noxious-event processing in the thalamus might have an important role in the pathogenesis of the condition.

Adult↗
PubMed1990

Somatosensory evoked potentials and motor cortex stimulation in myelopathies.

Short latency somatosensory evoked potentials (SSEPs) to stimulation of the tibial nerve at the ankle and at the knee and motor action potentials (MAPs) recorded from the tibial muscle during transcranial stimulation of the motor cortex were recorded in 21 patients with myelopathy. The electrophysiological results were compared with the clinical evolution over 12 months. Both scalp SSEPs and MAPs were absent in 10 patients with clinically 'complete cord transection.' The clinical and electrophysiological data remained unchanged in these patients. Scalp SSEPs were present at the first examination in all 11 patients with clinically 'incomplete cord lesion.' All these patients improved in the following year. The clinical recovery was almost complete in 3 patients who had normal scalp SSEPs but varied markedly in 8 patients with abnormal SSEPs. Normal MAPs were obtained in 1 of the 3 patients who showed the best clinical recovery. In the other subjects, MAP findings did not show a clear correlation with either the clinical signs or the course.

Action Potentials↗