Corticomotoneuronal Connections Research Articles

Activation thresholds for corticomotoneuronal connections to hand muscles following stroke

Activation thresholds for corticomotoneuronal connections to hand muscles following stroke

The development of cortico-motoneuronal projections investigated using magnetic brain stimulation in the infant macaque.

1. The effects of magnetic brain stimulation on electromyographic (EMG) activity recorded from arm and hand muscles have been investigated in five infant and six adult macaque monkeys under ketamine sedation. 2. In the adults, brief, short-latency EMG responses could be readily evoked with magnetic stimuli of 40-50% of the maximum stimulator output (1.5 T). 3. In a cross-sectional study of five infant macaques, it was difficult to evoke EMG responses in young infants (less than 5 months old). Clear short-latency responses were first evoked in an animal 5.75 months old. This change was accompanied by an increase in the probability of occurrence of the responses. 4. In a longitudinal study of two infant monkeys over a period ranging from 2.5 to 14.5 months of age we found that clear short-latency responses were first evoked at 4 and at 5.5 months, respectively. In both animals there was a steady fall in response threshold which reached the adult range at 6.5 and 8 months, respectively. EMG responses in animals older than 8 months were indistinguishable from those in adults. 5. In the longitudinal study we also noted that the latency of EMG responses to magnetic brain stimulation declined with age. Since there were no comparable changes in the peripheral conduction time in these animals, we attribute this result to a decrease in central conduction time. 6. Parallel behavioural observations of the natural behaviour of the same animals within a colony indicated that mature precision movements of the fingers were not used until 5-6 months of age. 7. In two adult monkeys, the latency of EMG responses evoked in the extensor digitorum and first dorsal interosseous muscles by direct stimulation of the corticospinal tract, via electrodes implanted in the medullary pyramids, was found to be 0.7-1.7 ms shorter than that of responses evoked by magnetic stimuli. It is argued that at least the earliest component of these latter responses is conducted over the cortico-motoneuronal pathway. 8. The mechanisms likely to contribute to the late appearance of EMG responses to brain stimulation are discussed. One of these is probably the establishment of mature cortico-motoneuronal connections, which are not present at birth.

Activation thresholds for corticomotoneuronal connections to hand muscles following stroke : D.A. Ingram, and S.F. Farmer (The London Hospital, London, U.K.)

Activation thresholds for corticomotoneuronal connections to hand muscles following stroke : D.A. Ingram, and S.F. Farmer (The London Hospital, London, U.K.)

Transcranial stimulation of motor cortex in upper motor neurone syndrome: its relation to the motor deficit

The purpose of this investigation was to clarify the functional significance of the fastest cortico-motoneuronal connections in chronic upper motor neurone syndromes. Using magnetoelectrical stimulation of motor cortex the intactness of cortico-motoneuronal connections was assessed in 51 patients presenting with variable degrees of impairment. There was a gross correlation between clinical impairment of the patient and the degree of pathology of cortico-motoneuronal efferents. Covariation of clinical data with transcranial stimulation was better than covariation with the size of lesion on CT scans. In some patients, however, definite clinical impairment, especially stimulation was better than covariation with the size of lesion on CT scans. In some patients, however, definite clinical impairment, especially affecting distal fractionated movements, was associated with completely normal responses. There was no evidence of response abnormality in distal muscles ipsilateral to the hemispheric lesion. The data indicate that motor deficit can exist in the presence of normal cortico-motoneuronal conduction times, showing that intactness of these connections is not a sufficient condition for preservation of voluntary motor activities. This underlines the importance of other pathways for the pathogenesis of upper motor neurone syndromes.

Corticomotoneuronal connections in the rat: Evidence from double‐labeling of motoneurons and corticospinal axon arborizations

In order to investigate the possibility of direct corticomotoneuronal (CM) connections in the rat, an anterograde-retrograde double-labeling method was developed. Phaseolus vulgaris-leucoagglutinin (PHA-L) anterograde tracing of corticospinal axons was combined with retrograde labeling of spinal motoneurons either by a conjugate of choleragen subunit B with horseradish peroxidase (CB-HRP) or by wheat germ agglutinin (WGA). The location of PHA-L injection unilaterally in the forelimb area of sensorimotor cortex and the CB-HRP or WGA injections in corresponding contralateral wrist or digit extensors or flexors were determined and matched on the basis of movement responses elicited by intracortical microstimulation. Light microscopic observation showed, in addition to the main contralateral dorsal corticospinal tract (CST), the presence of four other CST minor components in the contralateral lateral, ipsilateral ventral, and ipsilateral dorsal funiculi of the cervical spinal white matter and at the base of contralateral dorsal horn of the gray matter, respectively. PHA-L-labeled CST axonal arbors were observed from Rexed's lamina I through lamina X of contralateral spinal gray matter, most extensively in laminae VI and VII; some CST axons reached the zone of motoneuronal somata in lamina IX and a few of them also entered the lateral and occasionally the ventral funiculi, ramifying in the white matter. Between the zones of PHA-L-labeled CST axonal arbors on the one hand and CB-HRP/WGA labeled spinal motoneuronal somata with their extensive dendritic trees on the other, there was a large overlap, covering partly both the gray and the white matter. PHA-L-labeled axonal boutons (en passant or terminaux) were seen to contact the dendrites or even the somata of motoneurons in the gray matter, according to light-microscopic criteria for identification of synaptic contacts. Axodendritic CM contacts were occasionally observed in the lateral funiculus of the white matter as well. In general, only a single contact was observed between an individual PHA-L-labeled CST axon and a given retrogradely labeled motoneuron. In contrast to the common notion that direct CM connections are a specialty of primates, the present morphological data support the presence of direct CM connections also in some other mammals, such as the rat.

Corticobulbar projections to upper and lower facial motoneurons. A study by magnetic transcranial stimulation in man

To investigate the human corticofacial projections, we recorded the compound motor potentials and single motor unit potentials evoked by magnetic transcranial stimulation, in the frontalis and lower facial muscles of healthy subjects. Potentials secondary to activation of the corticobulbar tract were contralateral in lower and bilateral in upper facial muscles. Even though the latency of responses was longer than would be expected for direct cortico-motoneuronal connections, these cannot be excluded either for lower or upper facial motoneurons.

The Florey Lecture, 1987 - Conticomotoneuronal projections: synaptic events related to skilled movement

During infancy, children develop an expanding repertoire of movement skills in parallel with the maturation in their brains of direct nerve-fibre connections between the cerebral cortex and motoneurons in the spinal cord. These corticomotoneuronal connections are characteristic of primates and can be studied in monkeys; in these animals, refinement in the control of movements of the hand is also associated with increasing development of corticomotoneuronal connections. In monkeys, motoneurons innervating distally acting muscles are preferentially excited by convergent activities in corticomotoneuronal fibres. This excitation has been demonstrated to be effective in natural functional states when a conscious monkey is performing learned movement tasks. Extensive intraspinal arborizations of individual corticomotoneuronal fibres could permit the engagement of large numbers of local motoneurons and related interneurons by each of these fibres. Abolition of corticomotoneuronal influences, after section of the pyramidal tracts, causes a permanent deficit in fractionation of use of muscles of the forelimb and an inability to carry out independent movements of the fingers.

Corticomotoneuronal component of the pyramidal tract: Corticomotoneuronal connections and functions in primates

Corticomotoneuronal component of the pyramidal tract: Corticomotoneuronal connections and functions in primates

Corticomotoneuronal synapses in the monkey: light microscopic localization upon motoneurons of intrinsic muscles of the hand.

Some corticospinal neurons give rise to axons which terminate directly upon motoneurons, thereby establishing corticomotoneuronal connections. The location of corticomotoneuronal synapses upon motoneurons innervating intrinsic muscles of the hand in the monkey was demonstrated by the use of intra-axonal and intracellular horseradish peroxidase (HRP). After a number of corticospinal axons originating from the "hand" area of the precentral gyrus had been injected with HRP in the lateral funiculus at C7-C8, a number of nearby identified intrinsic hand muscle motoneurons were also injected. Connections between corticomotoneuronal fibres and motoneurons were reconstructed from longitudinal parasagittal sections treated by the cobalt-enhanced diaminobenzidine method. Corticospinal axons in the lateral funiculus gave rise to main collaterals which provided an extensive arborization in lamina IX, where it was predominantly longitudinal, and in the adjacent intermediate zone. En passant and single or clustered groups of terminal boutons arose from preterminal branches of these arbors. Seven light-microscopically identified corticomotoneuronal synapses were found. They were located upon the dendrites of recipient motoneurons at 40 micron to 750 micron from the soma and ranged in size from 0.6 X 3.0 micron to 2.4 X 3.6 micron. The results suggest that each main collateral of a corticomotoneuronal axon establishes very few synaptic contacts, and possibly only one, with the dendrites of recipient motoneurons. This small number of contracts per motoneuron is consistent with the small amplitudes of minimal and unitary corticomotoneuronal EPSPs recorded from forelimb and hand motoneurons.

A New Look at the Organization of the Motor System

Publisher Summary This chapter provides an overview on the organization of the motor system. The descending pathways from the cerebral cortex and the brain stem to the spinal interneurons and motor neurons must represent the instrument by which the brain steers movements of body and limbs. They are referred as the “motor system.” In earlier years, the motor system of the brain tended to be identified with the motor cortex. In human patients, destruction of the efferent pathways of the sensorimotor area produces a severe crippling motor defect known as hemiplegia. The corticospinal fibers are mainly derived from the sensorimotor areas and terminate predominantly contralaterally in the spinal gray. A striking parallel exists between the development of the corticomotoneuronal connections and the capacity to execute highly fractionated movements. Thus, in the rhesus monkey a bilateral pyramidotomy produces a flaccid paresis of the extremities especially of their distal parts combined with a paucity of independent extremity movements.

Obligatory bimanual associated movements: Report of a non-familial case in an otherwise normal left-handed boy

Amongst the abnormal synkinesias, bilateral and obligatory associated movements affecting predominantly the hands comprise a group of movement disorders which we have divided into: (1) those occurring as an autosomal dominant hereditary condition; (2) those occurring in the presence of disease of the central nervous system, including congenital abnormalities of the cervical region; and (3) rare, sporadic cases in otherwise healthy individuals. A left-handed patient falling into the last group is reported, in whom detailed neuropsychological assessment was also undertaken. Recalling the normal bimanual synkinesias of childhood, some of the mechanisms implicated in the production of pathological bimanual synkinesias are discussed: the effect of structural lesions within the central nervous system, defects in motor inhibition and the role of sensory afferent information, the part played by the commissures and abnormal motor pathways, the question of handedness, the relationship to mirror writing, and cerebral dominance have all been considered relevant, but from increasing evidence available from experimental work on primates the possible role of direct corticomotoneuronal connections is emphasised.

Cortico-spinal connections in the rat. I. Monosynaptic and polysynaptic responses of cervical motoneurons to epicortical stimulation.

In rats the fast cortico-spinal pathway and its linkage to motoneurons of the distal portions of the forelimbs were examined by electrophysiological techniques: The results demonstrate that in non-primates, showing skilled movements of the hand and digits, a powerful direct cortico-motoneuronal connection exists which is of predominant functional significance.

Corticomotoneuronal connections of precentral cells detected by post-spike averages of EMG activity in behaving monkeys

Corticomotoneuronal connections of precentral cells detected by post-spike averages of EMG activity in behaving monkeys

The development of motor control in the rhesus monkey: evidence concerning the role of corticomotoneuronal connections.

Corticospinal fibres terminate in three areas in the spinal grey matter of the rhesus monkey: the nucleus proprius of the dorsal horn, the intermediate zone and directly upon motoneurons, particularly those inervating limb muscles. It was suggested at their earliest discovery that direct corticomotoneuronal (CM) connections might constitute a critical anatomical substrate for the type of fractionated movement exemplified by relatively independent finger movements (RIFM). The present study was undertaken in an attempt to provide further evidence in support of this idea. The evidence is based upon the anatomical finding that few CM connections are present at birth in the monkey, the bulk being formed postnatally to reach an adult density at approximately 8 months of age. There were two experimental approaches: in the first it was argued that if RIFM are dependent upon the presence of CM connections it would be expected that such movements would appear only gradually postnatally, developing in parallel with the development of the connections. In 2 normal monkeys studied from this point of view discrete distal movements did develop only gradually with RIFM reaching an adult level at 7 to 8 months of age. The second experimental appraoch was based upon the fact that pyramidal lesions in newborn animals interrupt corticospinal fibres before CM connections are formed. It was argued that such a situation might provide a better opportunity for other descending pathways to establish the connections necessary for RIFM. Five infant monkeys had bilateral pyramidal tract lesions made from 5 days to 4 weeks after birth and were observed for a period of three years. In the 4 animals in which the lesions were complete, RIFM failed to develop. In the fifth animal, in which the lesions were incomplete, there was development of some degree of RIFM. It was concluded that the development of RIFM is dependent upon fibres passing in the pyramidal tracts and that in infant monkeys, as well as in adults, other descending pathways are unable to form the connections necessary for these movements. The possible contribution to RIFM of the corticospinal fibres arise in the somatosensory cortex and terminate in the dorsal horn was studied by bilateral removal of the arm and leg area of the somatosensory cortex in one animal. Since RIFM were only minimally and transiently altered, it was concluded that such movements are not dependent upon these fibres. The different lines of evidence presented in the study are interpreted as giving further support to the idea that corticomotoneuronal connections constitute an essential anatomical substrate for fractionated movements such as RIFM. Observations were also made of the development of general locomotor activity in normal and pyramidotomized infant monkeys.

Time course of minimal corticomotoneuronal excitatory postsynaptic potentials in lumbar motoneurons of the monkey.

Time course of minimal corticomotoneuronal excitatory postsynaptic potentials in lumbar motoneurons of the monkey.R Porter, and J HoreR Porter, and J HorePublished Online:01 May 1969https://doi.org/10.1152/jn.1969.32.3.443MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByShort-term synchrony in diverse motor nuclei presumed to receive different extents of direct cortical inputDouglas A. Keen, Li-Wei Chou, Michael A. Nordstrom, and Andrew J. Fuglevand15 December 2012 | Journal of Neurophysiology, Vol. 108, No. 12Forelimb Movements and Muscle Responses Evoked by Microstimulation of Cervical Spinal Cord in Sedated MonkeysChet T. Moritz, Timothy H. Lucas, Steve I. Perlmutter, and Eberhard E. Fetz1 January 2007 | Journal of Neurophysiology, Vol. 97, No. 1Synchrony between Neurons with Similar Muscle Fields in Monkey Motor CortexNeuron, Vol. 38, No. 1Comparison of peripheral Ia and corticomotoneuronal composite EPSPs in human motoneuronsElectroencephalography and Clinical Neurophysiology/Electromyography and Motor Control, Vol. 101, No. 5Superposition of antidromic responses in pyramidal tract cell clustersExperimental Neurology, Vol. 89, No. 3The corticomotoneuronal component of the pyramidal tract: Corticomotoneuronal connections and functions in primatesBrain Research Reviews, Vol. 10, No. 1Corticospinal neurons with a special role in precision gripBrain Research, Vol. 261, No. 2On the use and interpretation of cross-correlation measurements in the mammalian central nervous systemJournal of Neuroscience Methods, Vol. 1, No. 2A comparative study of ventrolateral and recurrent excitatory postsynaptic potentials in large pyramidal tract cells in the catBrain Research, Vol. 160, No. 1Corticomotoneuronal connections of precentral cells detected by post-spike averages of EMG activity in behaving monkeysBrain Research, Vol. 114, No. 3Effects of trans-membrane polarization and tea injection on monosynaptic actions from motor cortex, red nucleus and group Ia afferents on lumbar motoneurons in the monkeyBrain Research, Vol. 82, No. 1Functions of the mammalian cerebral cortex in movementProgress in Neurobiology, Vol. 1The meaning for motoneurones of the temporal pattern of natural activity in pyramidal tract neurones of conscious monkeysBrain Research, Vol. 34, No. 1Synaptic actions evoked from the red nucleus on the spinal alpha-motoneurons in the rhesus monkeyBrain Research, Vol. 32, No. 2Time course of pyramidal activation of pontine nuclei cells in the catBrain Research, Vol. 19, No. 2 More from this issue > Volume 32Issue 3May 1969Pages 443-51 https://doi.org/10.1152/jn.1969.32.3.443PubMed4306900History Published online 1 May 1969 Published in print 1 May 1969 Metrics

Collateral pyramidal influences on the corticorubrospinal system.

Collateral pyramidal influences on the corticorubrospinal system.

Direct and common connections among identified neurons in Aplysia.

Direct and common connections among identified neurons in Aplysia.

Recurrent Facilitation in Cat Pyramidal Tract Cells

Recurrent Facilitation in Cat Pyramidal Tract Cells

RELATION OF DISCHARGE FREQUENCY TO CONDUCTION VELOCITY IN PYRAMIDAL TRACT NEURONS.

RELATION OF DISCHARGE FREQUENCY TO CONDUCTION VELOCITY IN PYRAMIDAL TRACT NEURONS.

RECURRENT COLLATERAL INHIBITION IN PYRAMIDAL TRACT NEURONS.

RECURRENT COLLATERAL INHIBITION IN PYRAMIDAL TRACT NEURONS.