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PubMed1982

Exact cortical extent of the origin of the corticospinal tract (CST) and the quantitative contribution to the CST in different cytoarchitectonic areas. A study with horseradish peroxidase in the monkey.

The complete cortical extent of the origin of the corticospinal tract (CST) and the quantitative contribution to the CST of different cytoarchitectonic areas were established, using the technique of retrograde labeling with horseradish peroxidase (HRP) in the monkey. HRP was applied to the transected stump of the cut CST at the level of the first segment of the cervical spinal cord (Cl). Labeled cells were plotted on the projection drawings of every 10th frontal sections and reconstructed on the cortical surface of the hemisphere. The CST cortex occupied the upper two thirds of Brodmann's areas 6, 4, 3, and 1-2 combined. It also covered completely areas 5, 31, and 32, as well as, a part of areas 7 (the parietal operculum) and insula. These areas included not only the entire cortical fields corresponding to the limbs and trank representations of the precentral motor (MI), supplementary motor (MII), primary somatosensory (SI), and the second somatic sensory (SII) areas, but expanded more widely than the delimitation for the CST cortex by the earlier studies. The contralateral and ipsilateral hemispheres contained 74,710 and 3,130 CST cells respectively. Area 4 on the contralateral hemisphere contained about a half (50.8%) of the total CST cells, and 79.0% of CST cells of both hemispheres was located in the cortex anterior to the central sulcus (MI and MII); area 6 (11.9%), area 4 (51.6%), area 3 a (5.9%), area 32 (9.6%). Remaining 18.1% of CST cells occurred in the postcentral areas (SI); area 3 b (2.6%), area 1-2 (4.4%), area 5 (8.8%), area 31 (2.3%). Area 7 and insula (SII) contained only 3% of CST cells. About an half of CST cells resided in the sulcal cortex. Earlier findings on the CST cells were also confirmed, i.e., the CST cells are located exclusively in the deeper portion of the cortical layer 5, are distributed in a cluster, and are all pyramidal shape of various sizes. Soma diameters of labeled CST cells were determined, and the size distribution in each area revealed that the large-sized CST cells were located only in areas 4 and 3 a. Areas 6, 3 b, 32, 31, and insula contained only the small-sized CST cells, and other areas contained the small and medium types. To determine the origin of the total fibers contained in the pyramidal tract (PT), HRP was also applied to the cut stump of the PT at the level of the upper-most medullar pyramid. The results are discussed in comparison with the findings on the CST system.

Animals↗

PubMed1987

[Impairment of the accuracy of tracking movements in lesions of the cerebellum and pyramidal system in man].

Kinematic and electromyographic characteristics of step-tracking movements performed with and without visual guidance have been studied in 3 groups of patients suffering from hereditary lesions of intermedial and lateral systems of the cerebellum and pyramidal tract. Lesions of the intermedial cerebellum not changing parameters of the first preprogrammed component altered deeply the maintenance phase that was performed as large oscillations around a required level. Lesions of the lateral cerebellum, on the contrary, were followed by inability to control accurately the amplitude of steps which were performed with a constant hypermetric error; the maintenance phase of movement was not disturbed in this group. In patients suffering from pyramidal lesions the initial rapid limb position adjustment was replaced by slow approximating tracking; the maintenance component of the movement was performed with fluctuations and constant drift towards the ground. It is concluded that whereas the lateral cerebellar system is involved in central motor program mechanisms, the intermedial cerebellum is essential for accurate postural maintenance.

Acoustic Stimulation↗

PubMed2002

Improved white matter fiber tracking using stochastic labeling.

Diffusion tensor imaging (DTI) promises a robust means of visualizing in vivo white matter fibers in individual subjects, and of inferring direct connectivity between distant points in the brain. By following the primary eigenvector of the diffusion tensor, trajectories may be defined that trace the path of the underlying fiber tract. However, fiber tracking is prone to cumulative error from acquisition noise and partial volume, which limits the repeatability of such techniques. An image-processing method based on stochastic labeling, by which the noisy primary eigenvectors may be reconfigured according to anatomically reasonable assumptions, is described. The method's potential to improve fiber tracking is first demonstrated on numerical test data. It is then applied to real data acquired from healthy volunteers. Trajectories defined within the corpus callosum and the pyramidal tracts are rendered using 3D graphic imaging software, and the results are compared before and after processing. Fiber tracking was shown to produce anatomically plausible results, and typical errors were largely resolved by the method. Further, the sensitivity of trajectories to their start point was greatly reduced after processing. The use of stochastic labeling may therefore improve the reliability of experiments using white matter fiber tracking.

Corpus Callosum↗

PubMedDate not supplied

[Acceptor of action results as a structural functional basis of dynamic stereotype activities of the brain].

The system mechanisms of brain dynamic stereotypes formation are considered. The brain dynamic stereotypes are shown to be formed on the structures of acceptor of action results by dominating motivations and reinforcements. Acceptors of action results are widely spread in brain structures. They are presented in functional systems which form behavioral acts of animals with spreading neural excitations in collaterals of axons of pyramidal tract. Reinforcing excitations form specific architectonic of acceptors of action results, which include brain structures corresponding to modalities of parameters of reinforcements. Dominating motivations, which predict future events, excite molecular engrams of action results which were formed by previous reinforcements.

Brain↗

PubMed1981

[Neuronal analysis of the projection of the caudal trigeminal nucleus to the nucleus of the facial nerve in cats].

Peculiarities of the trigeminal nucleus caudalis neurons which are projected to the facial nucleus were studied by microelectrode recording in cats. It is shown that the mentioned neurons are localized predominantly in ventral parts of the trigeminal nucleus caudalis and adjacent lateral reticular formation. Mono- and polysynaptic activation of efferent trigeminal neurons to pyramidal impulsation is described. Repetitive discharges of these neurons to stimulation of their axons, direct stimulation of the trigeminal nucleus caudalis as well as to that of the pyramidal tract and facial nerve are recorded. The significance of the obtained data in the light for the understanding of the synaptic mechanisms of regulation of facial motoneurons activity is discussed.

Animals↗

PubMed2004

Diffusion tensor MRI as a diagnostic tool of upper motor neuron involvement in amyotrophic lateral sclerosis.

BACKGROUND: Clinical identification of upper motor neuron (UMN) dysfunction in amyotrophic lateral sclerosis (ALS) is often difficult, particularly early in the course of the disease, or when lower motor neuron (LMN) dysfunction is prominent. Diffusion tensor MR imaging (DTI) can provide unique information on axonal organization by measuring diffusion anisotropy and the directionally independent diffusion. OBJECTIVE: The purpose of this study was to assess water diffusion changes along pyramidal tracts of the brainstem in patients with ALS and to investigate possible correlations between changes of diffusion properties and various clinical parameters. METHODS: We studied 16 patients (M:F=9:7, 50.5+/-12.4 years) with ALS as defined by clinical and electrophysiological examinations. These patients were compared with 11 healthy, age and sex-matched controls (M:F=5:6, 54.5+/-9.9 years). DTI was performed using a single shot SE-EPI with 25 noncollinear diffusion gradient directions (b=1000 s/mm(2)) and with no diffusion gradient on a 3.0-T MR system. RESULTS: By multifactorial ANOVA, the effects of group (patient versus control) and anatomical level on fractional anisotropy (FA) and mean diffusivity (MD) were significant (p<0.001 for both parameters), whereas the effect of side (left versus right) and interactions between factors (group by side and group by anatomical level) were not (p>0.05). In all subjects, FA and MD varied greatly depending on the anatomical level, and FA was highly variable even between contiguous slices in the pons and medulla, whereas relatively constant FA values were noted at the level of the midbrain. Cerebral peduncle was the only area that showed significant differences of diffusion properties between patients and controls (p<0.001 for FA, p=0.001 for MD). Correlation analysis revealed a significant inverse relationship between the FA value and the extent of UMN signs (r=-0.81, p<0.001). CONCLUSIONS: Alteration of diffusion properties in the cerebral peduncle in ALS may reflect pathological changes in structures rather than regional architectural variations of the corticospinal tracts or experimental artifacts.

Adult↗

PubMed1985

Primary lateral sclerosis; a debated entity.

Two patients suffering from slowly progressing spastic paraparesis are presented. Both of them underwent a several years' follow-up, and extensive laboratory, radiological and neurophysiological investigations in order to rule out known specific causes for pyramidal tract involvement. After these exclusion studies, the diagnosis of primary lateral sclerosis (PLS) was derived. The present cases provide further evidence of the long-debated PLS as a disease entity.

Amyotrophic Lateral Sclerosis↗

PubMed1996

Evidence for GAP-43 within descending spinal axons in the North American opossum, Didelphis virginiana.

We have shown previously that GAP-43, a growth associated protein characteristically present in growing and regenerating axons, is relatively abundant in the spinal cord of adult opossums. In the present study, we combined the orthograde transport of the fluorescent marker Fluoro-Ruby with immunofluorescence for GAP-43 to determine if any of it is present within descending spinal axons. When Fluoro-Ruby was injected into the red nucleus and midbrain tegmentum, the medial pontine or medullary reticular formation, the medullary raphe or the lateral vestibular nucleus, axons were labeled in the expected areas of the spinal cord, but in most cases none showed evidence for GAP-43. In two of the four cases with rubral injections, however, a few labeled axons within the rubrospinal tract showed GAP-43 immunofluorescence, and in one case with an injection of the gigantocellular reticular nucleus and adjacent raphe, labeled axons within lamina IX immunostained for the protein. Since serotoninergic neurons are present within the gigantocellular reticular nucleus and adjacent raphe, and axons of the same phenotype are abundant within lamina IX, we asked whether serotoninergic axons contain GAP-43. When sections of the spinal cord were immunostained for both serotonin and GAP-43, many axons within lamina IX showed evidence for both substances. Such axons appeared to contact presumptive motoneurons. In cases with Fluoro-Ruby injections of the forelimb motor cortex, labeled axons were present within the pyramidal tract, and some of them showed evidence for GAP-43.

Animals↗

PubMed2005

Amyotrophic lateral sclerosis with predominant pyramidal signs -- early diagnosis by magnetic resonance imaging.

OBJECTIVE: To evaluate the role of magnetic resonance imaging (MRI) in the early diagnosis of amyotrophic lateral sclerosis (ALS) with predominant upper motor neuron (UMN) signs in the initial stage of the disease. PATIENTS AND METHOD: Two patients with ALS were found to have spastic quadriparesis with no wasting or fasciculation in the limbs in the early stage of the disease. Both were subjected to MRI of the head and cervical spine to look for any specific diagnostic feature. Both of them were followed with clinical evaluation and electroneuromyography (ENMG) for the definitive diagnosis of ALS. RESULTS: Magnetic resonance imaging showed selective degeneration of the pyramidal tracts in the contiguous axial cuts from subcortical white matter to cerebral peduncles. The finding was more visible in the coronal section. In addition, there was T1 hyperintensity visible along the anterior aspect of the spinal cord in the cervical region. These findings were suggestive of ALS, the diagnosis that was subsequently confirmed by serial clinical follow-up and ENMG. CONCLUSION: It is difficult to diagnose ALS in the early stage of the disease especially if the pyramidal signs predominate over the lower motor neuron (LMN) signs; MRI might be useful in such cases.

Adult↗

PubMed1977

The central nervous system in a case of neurolathyrism.

We examined the central nervous system of a 67-year-old man who showed symptoms of lathyrism after being imprisoned at age 35 and fed on a diet of chick peas, Lathyrus sativus. The most obvious changes were loss of axons and myelin in the pyramidal tract in the lumbar spinal cord. These alterations correlated with spastic paraparesis. Other changes at the same level were a mild degree of degeneration of anterior horn cells. Pallor of Goll's tracts and axonal swelling in Goll's nuclei were also observed. A few examples of senile plaques and neurofibrillary tangles were observed in Ammon's horn.

Aged↗

PubMed2001

[Corticospinal tract assessment in ALS: transcranial magnetic stimulation].

Results obtained during transcranial magnetic stimulation (TMS) in 79 patients with ALS were compared to those obtained in 10 healthy volunteers. M and F responses evoked by peripheral stimulation of the ulnar and peroneal nerves and then motor evoked potentials (MEP) induced by TMS were recorded in the abductor digiti quinti (AV) and tibial anterior (TA) muscles bilaterally. Central motor conduction time (CMCT) was calculated using MEP and F response latencies. The MEP/M x 100% amplitude ratios were calculated. Mean CMCT was significantly (p < 0.0001) prolonged in patients with ALS (9.6 +/- 4.1 ms for AV and 20.4 +/- 9.6 ms for TA) and MEP/M x 100% amplitude ratios were higher (45 +/- 75% for AV-p < 0.001 and 27 +/- 32.7% for TA p = 0.2). In a sub-group of patients with predominant upper motor neuron (UMN) involvement, the CMCT was significantly prolonged (14.2 +/- 5.8 ms for AV and 28.5 +/- 9.1 ms for TA), but MEP/M x 100% amplitude ratio was 24.1 +/- 37.6% for AV and 11.4 +/- 12.9% TA. These results confirm usefulness of combined analysis of CMCT and MEP/M x 100% amplitude ratio as the method of assessment of pyramidal tract function in ALS.

Adult↗

PubMed1988

Motor cortical cell discharge during voluntary gait modification.

Kinematic and electromyographic data were recorded together with motor cortical cell discharge during a task which required the cat to modify its gait in order to step over 3 different types of obstacles fixed to a moving treadmill belt. In order to negotiate the obstacles the cat made large adjustments in limb trajectory which were associated with equally large changes in forelimb flexor muscle activity. Sixteen of 57 identified pyramidal tract neurones recorded from area 4 of two cats increased their peak discharge rate during this gait adjustment. It is suggested that the motor cortex plays a role in adjusting the flexor muscle activity to the requirements of the locomotor task.

Action Potentials↗

PubMed1979

Chronic and acute transtentorial herniation with tumours of the posterior cranial fossa.

In patients with expanding lesions of the posterior fossa general hyper-reflexia (and bilateral latency shifts of auditory evoked brain stem potentials) have been noted as possible symptoms of chronic ascending transtentorial herniation. After ventricular tap, this chronic herniation may evolve into acute herniation with progressive reduction of consciousness which in our experience can only be survived by decompression of the compressed brain stem. The chronic transtentorial herniation is related morphologically to demyelination of the pyramidal tracts and the auditory pathways, whereas the acute transtentorial herniation is related to microcirculatory disturbances in the reticular formation of the mesencephalo-pontine junction.

Auditory Pathways↗

PubMed2001

Corticospinal excitation of presumed cervical propriospinal neurones and its reversal to inhibition in humans.

1. This study addresses whether in human subjects indirect corticospinal excitation of upper limb motoneurones (MNs) relayed through presumed cervical propriospinal neurones (PNs) is paralleled by corticospinal activation of inhibitory projections to these premotoneurones. 2. The responses to transcranial magnetic stimulation (TMS), whether assessed as the compound motor-evoked potential (MEP) or the peak of corticospinal excitation elicited in the post-stimulus time histograms (PSTHs) of single motor units, were conditioned by weak volleys to musculo-cutaneous, ulnar and superficial radial nerves. 3. Afferent volleys, which hardly modified the H reflex, significantly facilitated the corticospinal response produced by weak TMS. In PSTHs, the central delay of the peripheral facilitation of the peak of corticospinal excitation in MNs located at either end of the cervical enlargement was longer the more caudal the MN pool, suggesting an interaction in premotoneurones located rostral to the tested MNs. 4. Small increases in the strength of TMS (approximately 2--5 % of the maximal stimulator output) caused the facilitation to disappear and then to be reversed to inhibition. The facilitatory and inhibitory effects had the same latencies and spared the initial 0.5--1 ms of the corticospinal excitatory response. Both effects were more readily demonstrable when there was a co-contraction of the target muscle and the muscle innervated by nerve used for the conditioning stimulus. 5. The above features suggest that the inhibition resulted from disfacilitation due to suppression of corticospinal excitation passing through the presumed premotoneuronal relay. The reversal of the facilitation to inhibition by stronger corticospinal volleys is consistent with a well-developed system of 'feedback inhibitory interneurones' activated by corticospinal and afferent inputs inhibiting the presumed propriospinal excitatory premotoneurones. 6. It is argued that these findings might explain why simply stimulating the pyramidal tract or the motor cortex would fail to demonstrate this indirect corticospinal projection in the macaque monkey and in humans.

Adult↗

PubMed1997

Decreased sympathetic outflow to muscles in patients with cervical spondylosis.

To clarify the pathogenesis of neurologic symptoms of a vascular nature that may accompany cervical spondylosis (CS), we measured the sympathetic outflow to muscles (muscle sympathetic nerve activity: MSNA) in 8 ambulatory patients with CS and 10 healthy volunteers (controls). The burst rate and incidence of MSNA at rest were significantly lower in patients with CS than in controls (P < 0.01). There were no differences between the 2 groups in either resting heart rate or blood pressure. During a head-up tilting, the changes in MSNA were slightly greater in CS patients than controls due to reduced baseline levels of MSNA in CS patients. The burst incidence of MSNA in CS was significantly negatively correlated with the severity of pyramidal tract symptoms (P < 0.05). The decreased MSNA at rest in CS patients may be due to a spinal cord compression resulting from posterior spondylotic changes in the cervical spine.

Aged↗

PubMed1986

Neurophysiological evaluation of associated demyelinating peripheral neuropathy and multiple sclerosis: a case report.

A case of combined multiple sclerosis and demyelinating neuropathy is presented. Percutaneous electrical stimulation of the cortex and spinal cord has shown that pyramidal tract conduction time was prolonged and conduction velocity in the cord was 4 m/s. Motor conduction velocity in proximal segments of peripheral nerves was slowed to the same extent as in distal segments.

Evoked Potentials↗

PubMedDate not supplied

MR appearance of gray and white matter at the cervicomedullary region.

To study the appearance of gray and white matter in the cervicomedullary region, six fresh cadavers were imaged with a 1.5-T MR scanner and then sectioned with a cryomicrotome. The pyramidal tracts, fasciculus cuneatus and gracilis, inferior olivary nuclei, supraspinal nuclei, spinal trigeminal nuclei, and medial lemnisci were identified by MR in the cervicomedullary region.

Adult↗

PubMed1990

Specificity of corticospinal axon arbors sprouting into denervated contralateral spinal cord.

Previous studies have reported considerable plasticity in the rodent corticospinal pathway in response to injury. This includes sprouting of intact axons from the normal pathway into the contralateral spinal cord denervated by an early corticospinal lesion. We carried out the present study to obtain detailed information about the time course, origin, and degree of specificity of corticospinal axons sprouting in response to denervation. Hamsters (Mesocricetus auratus) ranging in age from 5 to 23 days received unilateral lesions of the left medullary pyramidal tract. Two weeks after the lesion, small regions of the right sensorimotor cortex opposite the lesion were injected with the plant lectin Phaseolus vulgaris leucoagglutinin (PHA-L). After a further 2 week survival period, immunohistochemistry was carried out on frozen sections of the fixed brains and spinal cords. Detailed morphological analysis of PHA-L labeled corticospinal axons revealed that sprouting from the intact corticospinal pathway into the contralateral denervated spinal cord occurred only at local spinal levels and not at the pyramidal decussation. Arbors sprouting into the denervated cord frequently arose from corticospinal axons that branched into the normal side of the cord as well. Sprouting was maximal after early lesions (5 days) and declined with lesions at later ages up to 19 days. Sprouting corticospinal axons arborized with the same degree of functional and topographic specificity as previously reported for normal corticospinal arbors (Kuang and Kalil: J. Comp. Neurol. 292:585-598, '90), such that axons arising from somatosensory cortex projected only to the dorsal horn, those from motor cortex innervated only the ventral horn, and normal forelimb and hindlimb topography was preserved. Sprouting fibers also had normal branching patterns. Parallel studies of developing corticospinal arbors showed that sprouting could not be attributed to maintenance or expansion of early bilateral connections. These results suggest that local signals, most likely similar to those governing normal corticospinal development, elicit corticospinal sprouting and determine specificity of axon arbors.

Aging↗