SEARCH · PubMed Health

Results for “Pyramidal Tracts”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 1,009 records · Page 56Linked to original sources

PubMed2000

MRI pontine hyperintensity after supratentorial ischemic stroke relates to poor clinical outcome.

BACKGROUND AND PURPOSE: MRI studies in patients with atherosclerosis often reveal ill-defined hyperintensity in the pons on T2-weighted images. This pontine hyperintensity (PHI) does not fulfill the criteria of a brain infarct, and its clinical relevance is not established. We examined the frequency, as well as the radiological and clinical correlates, of PHI in poststroke patients. METHODS: Three hundred nineteen patients were studied 3 months after supratentorial ischemic stroke with the use of 1.0-T MRI. Brain infarcts, atrophy, white matter hyperintensities, and PHI were registered. The clinical outcome was assessed 3 and 15 months after the stroke. RESULTS: Of the patients, 152 (47.6%) had PHI. The risk factors for stroke did not differ in patients without or with PHI. PHI was related to a higher frequency (P=0.002) and larger volume (P<0.001) of supratentorial brain infarcts, to parietal (P=0.020) and temporal (P=0.002) atrophy, to central atrophy (P< or =0.040), and to white matter hyperintensity grade (P<0.001). Brain infarcts that affected the corpus striatum (putamen, caudate, and pallidum) (P< or =0. 011) or pyramidal tract (P<0.001) were more frequent in patients with PHI. The 3- and 15-month outcomes were worse in patients with PHI (P< or =0.004). The total volume of brain infarcts (OR 1.22), mean atrophy (OR 3.59), and PHI (OR 3.76) were independent correlates of a poor 15-month outcome. CONCLUSIONS: PHI after supratentorial ischemic stroke deserves attention because it relates to poor clinical outcome.

Activities of Daily Living↗

PubMed1995

Thalamocortical and corticocortical excitatory postsynaptic potentials mediated by excitatory amino acid receptors in the cat motor cortex in vivo.

Intracellular recordings were made from neurons in the motor cortex of an anaesthetized cat, together with iontophoretic application of excitatory amino acid receptor agonists and antagonists, in order to evaluate the role of such receptors in excitatory postsynaptic potentials evoked from stimulation of afferent and recurrent pathways in vivo. Excitatory postsynaptic potentials which were evoked by stimulation of the ventrolateral thalamus were found to be largely insensitive to antagonism by N-methyl-D-aspartate receptor antagonists, although they were susceptible to blockade by the non-N-methyl-D-aspartate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione. Increasing the ventrolateral thalamus stimulation frequency from 0.5 or 1 to 5 Hz caused an increase of evoked excitatory postsynaptic potential amplitudes and number of action potentials. These augmented excitatory postsynaptic potentials remained insensitive to application of N-methyl-D-aspartate antagonists. In contrast, recurrent excitatory postsynaptic potentials evoked by stimulation of the pyramidal tract were found to be sensitive to N-methyl-D-aspartate receptor antagonists and/or non-N-methyl-D-aspartate receptor antagonists in some neurons. These results demonstrate the involvement of both N-methyl-D-aspartate- and non-N-methyl-D-aspartate receptors in synaptic responses of cat motor cortex neurons in vivo, and that the synaptic pharmacology of the thalamic input may differ from that of the local recurrent pathways.

2-Amino-5-phosphonovalerate↗

PubMed1997

Epilepsy with myoclonus and post-natal development of the motor system in humans: a hypothesis.

Epilepsy with myoclonus is thought to be linked to the motor system. At birth, development of the central nervous system in humans is far from being achieved. Post-natal changes take place at different levels in this neuronal system. These modifications suggest that the motor cortex is a highly dynamic structure during post-natal development. They may account for the age-dependence of various epileptic syndromes. (1) The number of synapses increases during the early post-natal years and then decreases to reach the adult level around puberty. (2) Neurons differentiate and synthesize various neurotransmitters. (3) Dendrites grow actively and participate in the formation of local cortical circuits. (4) Electrophysiological properties of cortical neurons change during the first months of rodent development. This could reflect modifications of the ion channels present in the cell membrane. (5) The pyramidal tract myelinate and exuberant collaterals are selectively removed. These two processes are dependent on neuronal electrical activity. It has been demonstrated that selective collateral stabilization is promoted by glutamate release and stimulation of the N-methyl-D-aspartate (NMDA) receptor. So, seizures occurring during the neonatal period may interact with these normal developmental features. Furthermore, neuronal electrical activity and seizures stimulate the transcription of specific messenger RNAs coding for neurotrophic factors like nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF). The overproduction of neurotrophic factors leads to maldevelopment of the cortex.

Animals↗

PubMed1987

Mechanisms regulating the activity of facial nucleus motoneurons--III. Synaptic influences from the cerebral cortex and subcortical structures.

Peculiarities of synaptic processes in facial motoneurons evoked by stimulation of various regions of the cerebral cortex and subcortical structures were studied in acute experiments on cats by intracellular recording technique. Stimulation of the motor cortex as well as gyrus proreus and pyramidal tract was shown to evoke polysynaptic excitatory and inhibitory postsynaptic potentials in facial motoneurons. Stimulation of the lateral hypothalamus produced exclusively excitatory polysynaptic effects. It was also found that stimulation of the head of nucleus caudatus and globus pallidus evokes a polysynaptic activation in facial motoneurons, while stimulation of nucleus amygdala centralis leads to mono- and polysynaptic excitation of these neurons. Convergence of the above effects on the same motoneurons is shown to exist. Possible pathways and mechanisms of descending influences on the activity of facial motoneurons is discussed.

Animals↗

PubMed2002

[Neuron correlates of the action result acceptor in a functional biotechnical complex structure].

This study presents data illustrating neurophysiological features of the efferent-afferent convergence on the cortex neurons. It was established that, during the process of combining stimulation of the pyramidal tract (PT) axons with electrical skin reinforcement, a significant amount of neurons under study changed parameters of the activity evoked by the PT-stimulation. The most clear reconstruction of the PT-responses was obtained in experiments with inclusion of neurons into biotechnical complex by means of the feed back: "neuron-computer-stimulating devices-animal", representing an analogue of the functional system. The role of afferent-efferent convergence of the CNS neurons is discussed in dynamic deployment of the action result acceptor in the functional system of natural behavioural act.

Afferent Pathways↗

PubMedDate not supplied

[The correlation between the changes in synaptic efficiency and cellular excitability in the acquisition of a conditioned reflex analog].

By calculating correlation coefficients was revealed the positive linear correlation between the conditioned changes of direct and indirect components of the pyramidal tract response pointing to a correlation between changes of synaptic efficiency and coincident shifts of cellular excitability. Coincidence of the maximal value of this connection with that of cellular excitability dependent on the activation of the lateral hypothalamus points to the role of this subcortical motivational structure in starting intracellular reactions leading to a formation of a common molecular substrate underlying interaction of the membrane and synaptic mechanisms. Precedence of the maximal manifestation of this interaction to the highest increase of synaptic efficiency testifies to the contribution of this process to the manifestation of the basic mechanism of conditioned reflex.

Animals↗

PubMed1983

Pyramidal influences on ventral thalamic nuclei in the cat.

In pericruciate cortex-ablated 'pyramidal cats', discharge changes in single neurons of ventral thalamic nuclei were studied, following stimulation of ipsilateral medullary (MPT) and contralateral cervical (CPT) pyramidal tract. It was seen that cells in ventrolateral nucleus, ventroanterior nucleus and ventromedial nucleus were not significantly (2.2%) modified by impulses coming from MPT and CPT. Conversely, a very high percentage (58.8%) of cells in ventrobasal complex (VB) responded to MPT stimulation (64.4% in ventroposterolateral nucleus, VPL, and 40.7% in ventroposteromedial nucleus, VPM). A considerable number (34.8%) of VPL cells responsive to MPT, were influenced by CPT, while none of the cells in VPM were. The most frequent effect observed in VB neurons, on MPT and CPT stimulation, was excitation followed by depression of discharge.

Animals↗

PubMed1996

Parapyramidal rostroventromedial medulla as a respiratory rhythm modulator.

After inhalation of 15% CO2, immunoreactions to glutamate and glutamic acid decarboxylase were found in some c-Fos or c-Jun-labeled neurons distributed in the reticular region just dorsal to the pyramidal tract in the rostroventromedial medulla (parapyramidal RVMM). This region forms vertically the narrow strip between the nucleus raphe pallidus and nucleus parapyramidalis superficialis, and extends rostrocaudally from the level just ahead of the inferior olivary complex to the level just behind the nucleus of the trapezoid body. When we placed lesions with kainate in the parapyramidal RVMM, hyperpneic and tachypneic responses to brief inhalation of 15% CO2 were completely abolished, and the eupneic rhythm changed into the gasping rhythm. This study suggests that the parapyramidal RVMM consists of neuronal substrates that subserve as the respiratory rhythm modulator.

Animals↗

PubMed1991

[Mapping in tumor surgery of the central region].

A prerequisite for successful operations of the central area is the exact pre- and intraoperative localization of the motor strip and the pyramidal tract. The craniocerebral landmarks--the coronal suture and bregma--and the central anatomy in the CT and the MRI favors their localization. According to the anatomical variations and the displacement of the brain by the lesion, these landmarks are not very reliable in identifying the central region in all cases. A safe intraoperative localization of the motor strip is possible with the combination of electrical cortical stimulation and recording of somatosensory evoked potentials. With these methods the results of operations of central lesions are good and the risk of severe postoperative morbidity is low.

Adult↗

PubMed1993

[Two autopsy cases of sporadic amyotrophic lateral sclerosis with 20-year-clinical course without respirators].

The present paper concerns the clinicopathological study of two patients with sporadic amyotrophic lateral sclerosis (ALS) with 21 or 22 years' clinical course without respirators. The two cases developed marked upper motor neuron signs and continually progressive paralysis. Involvement of the facial and bulbar muscles remained fairly mild. At autopsy, the anterior horns showed marked loss of motor neurons associated with numerous reactive astrocytes. On the other hand, the motor cortex and the pyramidal tract showed diminution of Betz cells and large myelinated fibers but no positive materials by fat stain. In addition, the anterolateral funiculi of the spinal cords revealed widespread myelin pallor. One of the case showed intracytoplasmic eosinophilic inclusions in some neurons of the medullary reticular formation. Recent articles have reported several rapidly progressive ALS patients who developed ophthalmoplegia, while on respirators, and widespread degeneration in the CNS. By contrast, our extremely slowly progressive ALS patients developed alterations confined to upper and lower motor neurons. There may exist some diversities in ALS.

Aged↗

PubMed1989

Induction of rhythmic jaw movements by stimulation of the mesencephalic reticular formation in the guinea pig.

This study was designed to investigate whether stimulation of the mesencephalic reticular formation (MRF) induces rhythmic jaw movements (RJMs) and, if it does so, to determine the RJM-inducing region in the MRF in ketamine-anesthetized guinea pigs. The results were as follows: (1) Repetitive electrical stimulation of the MRF at the level of the red nucleus induced rhythmic EMG bursts in the anterior digastric muscle (DIG). (2) The duration and cycle time of the rhythmic DIG EMG burst induced from the medial MRF were longer than those induced from the lateral MRF. (3) Repetitive MRF stimulation after paralysis still induced rhythmic multiple-unit activities in the anterior digastric motoneuron pool. (4) Neither precollicular decerebration nor cerebellectomy affected the MRF induction of RJMs. (5) Transverse hemisection at the rostral border of the pons abolished the RJMs induced from the contralateral, but not ipsilateral, MRF. Midline section of the midbrain abolished RJMs induced from the MRF on either side. (6) A lesion in the pontine pyramidal tract abolished the RJMs induced by stimulation of the ipsilateral cortical masticatory area (CMA), but not those induced from the contralateral MRF. (7) A unilateral lesion of the oral portion of the gigantocellular reticular nucleus, where the rhythm generator for the CMA-induced RJMs is located, abolished RJMs induced from not only the CMA, but also MRF on the contralateral side. (8) Microinjection of L-glutamate into the lateral, but not medial, MRF induced RJMs similar to those elicited by repetitive electrical stimulation of the same site.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1978

An intracellular analysis of EEG arousal in cat motor cortex.

1. Changes in the resting potential and the effective membrane resistance were measured in 77 cells in cat precruciate cortex during the transition from cortical slow wave phase to EEG arousal. 2. These 77 neurones were classified into the recipient cells of the following five different actions on the EEG arousal: (1) postsynaptic excitation (E cells), (2) postsynaptic inhbition (I cells), (3) disinhibition (DI cells), (4) disfacilitation (DF cells) and (5) disfacilitation followed by excitation (DF-E cells). 3. The location of E cells ranged from laminae I to V, but the majority was found in lamina II. Most I cells were located in the upper half of lamina III, and a few in lamina V. DF, DI and DF-E cells existed deeply from the lower half of lamina III to laminae V-VI. 4. Slow pyramidal tract (PT) cells (n = 6) all belonged to the E cell group, whereas fast PT cells were divided into the DF (n = 10) and DF-E cell groups (n = 4). 5. It is postulated that the EEG arousal is initiated with a direct excitation of laminae I-II cells, followed by excitation and inhibition to the upper lamina III cells and further processed to laminae III-VI cells with indirect excitation, inhibition, disinhibition and disfacilitation. The model of four vertical transmission relays is proposed to depict the casade pattern of information being processed through the cortex during the EEG arousal.

Animals↗

PubMed1988

Ultrastructural study of chromatolytic neurons in an adult-onset sporadic case of amyotrophic lateral sclerosis.

Ultrastructural features of chromatolytic neurons observed in a sporadic case with amyotrophic lateral sclerosis (ALS) are reported. A 70-year-old woman died of weakness and atrophy of the four limbs, bulbar and facial muscles, and hyperreflexia, of 3 1/2 years' duration. Neuronal loss was marked in the anterior horn of the spinal cord, with degeneration of the pyramidal tracts. Most of the remaining neurons showed chromatolysis. Some of the chromatolytic neurons contained faintly eosinophilic inclusions with a halo. Few spheroids were observed. Hypoglossal nuclei, nucleus ambiguus, motor nuclei of N.VII and N.V were well populated, but contained several chromatolytic neurons. Ultrastructurally, the chromatolytic neurons contained aggregates of fibrils thicker than the 10-nm neurofilaments. These fibrils were arranged randomly, and were closely associated with granular materials as well as rough endoplasmic reticulum. Neurofilamentous accumulations reported to be common in sporadic ALS were rare in this case. No Bunina body was observed.

Actin Cytoskeleton↗

PubMedDate not supplied

The functional role of an increase in cell excitability and synaptic efficiency in the new cortex during learning.

Data were obtained in experiments on nonimmobilized and nonanesthetized rabbits, during the development of an analog of a CR, with recording of the response of the pyramidal tract, suggesting temporal specificity in the manifestations of membrane and synaptic plasticity, the participation of these mechanisms in both representations of the combined stimuli, and primarily unidirectional changes in the degree of their participation in these points of the cortex. It is concluded that temporary membrane plasticity creates conditions through the mechanisms of synchronization and summation for the passage of excitation from the sensory link to the motor output of the new connection. The gradual reorganization of excitatory and inhibitory connections to the output elements of the conditioned reflex act, determined by the mechanisms of synaptic plasticity, determine and strengthen the specialized character of the developed reaction.

Animals↗

PubMedDate not supplied

[Long-term changes in synaptic efficiency and cellular excitability during learning].

Temporal analysis of changes of pyramidal tract response on the model of prolonged potentiation revealed the significant role of the mechanism of increase of the cell general excitability at the initial stage of trace processes formation ("dominant" analogue) what probably contributes to better consolidation of basic CR mechanism--the increase of synaptic links efficiency. During the elaboration of CR to stimulation of two cortical points the increase of cellular excitability was more expressed in those experiments where the reinforcement was supplemented by stimulation of the lateral hypothalamus eliciting alimentary reaction. These data allow to consider the membrane plasticity to be a cortical mechanism of motivational reinforcement component determining dominant properties of CR generalization stage.

Animals↗

PubMed1988

Supraspinal control of a short-latency cutaneous pathway to hindlimb motoneurons.

The effects of two supraspinal systems on transmission through a short latency hindlimb cutaneous reflex pathway were studied in cats anesthetized with pentobarbital or alpha-chloralose. Fleshman et al. (1984) described a mixed excitatory-inhibitory input from low threshold superficial peroneal (SP) afferents to flexor digitorum longus (FDL) motoneurons with central latencies so short as to suggest a disynaptic component in the initial excitatory phase of the PSP. In the present study, conditioning stimulation of either the red nucleus (RN) or the pyramidal tract (PT) caused a marked decrease in latency and increase in amplitude of both the excitatory and inhibitory components of the SP PSP in FDL motoneurons and several other motoneuron species. The minimal central latencies of the conditioned initial excitatory phase of the PSPs were on the order of 1.5 ms, consistent with the possibility of a disynaptic linkage. The facilitatory effects of RN and PT conditioning were observed in both anesthetic conditions, although preparation-specific differences in latency were observed. Lesion experiments suggested that the interneurons involved in this pathway are located caudal to the L5 segment, most likely in segments L6 and L7.

Anesthetics↗

PubMed2003

Combined functional MRI and tractography to demonstrate the connectivity of the human primary motor cortex in vivo.

In this study, we combined advanced MR techniques to explore primary motor cortex (M1) connectivity in the human brain. We matched functional and anatomical information using motor functional MRI (fMRI) and white matter tractography inferred from diffusion tensor imaging (DTI). We performed coregistered DTI and motor task fMRI in 8 right-handed healthy subjects and in 1 right-handed patient presenting with a left precentral tumour. We used the fast-marching tractography (FMT) algorithm to define 3D connectivity maps within the whole brain, from seed points selected in the white matter adjacent to the location of the maximum of fMRI activation. Connectivity maps were then anatomically normalised and analysed using statistical parametric mapping software (SPM99) allowing group comparisons (left versus right hemisphere in control subjects and patient versus control subjects). The results demonstrated, in all control subjects, strong connections from M1 to the pyramidal tracts, premotor areas, parietal cortices, thalamus, and cerebellum. M1 connectivity was asymmetric, being more extensive in the dominant hemisphere. The patient had differences in M1 connectivity from the control group. Thus, fMRI-correlated DTI-FMT is a promising tool to study the structural basis of functional networks in the human brain in vivo.

Adult↗

PubMed1975

[Evolution of the astroglial reaction in the pyramidal pathway after injury of the rat motor cortex].

Investigation of astrocytes in the pyramidal tract of the rat 2 to 100 days after a lesion of the motor cortex indicates that the glial reaction, with increase in size of astrocytes and in affinity for Cajal's gold-sublimate, begins at the lesion and extends to the distal segments of the spinal cord. But this reaction recedes and disappears in lumbar and dorsal cord about 70 days after the operation. It persists in the cervical cord and in the brain. On the other hand, a characteristic increase in activity of glutamate andglucose-6-phosphate dehydrogenases is restricted to the vicinity of the lesion and does not even encroach upon the posterior limb of the internal capsule.

Animals↗