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At least 19 recordsLinked to original sources
PubMed2003

Embryonic origins of a motor system: motor dendrites form a myotopic map in Drosophila.

The organisational principles of locomotor networks are less well understood than those of many sensory systems, where in-growing axon terminals form a central map of peripheral characteristics. Using the neuromuscular system of the Drosophila embryo as a model and retrograde tracing and genetic methods, we have uncovered principles underlying the organisation of the motor system. We find that dendritic arbors of motor neurons, rather than their cell bodies, are partitioned into domains to form a myotopic map, which represents centrally the distribution of body wall muscles peripherally. While muscles are segmental, the myotopic map is parasegmental in organisation. It forms by an active process of dendritic growth independent of the presence of target muscles, proper differentiation of glial cells, or (in its initial partitioning) competitive interactions between adjacent dendritic domains. The arrangement of motor neuron dendrites into a myotopic map represents a first layer of organisation in the motor system. This is likely to be mirrored, at least in part, by endings of higher-order neurons from central pattern-generating circuits, which converge onto the motor neuron dendrites. These findings will greatly simplify the task of understanding how a locomotor system is assembled. Our results suggest that the cues that organise the myotopic map may be laid down early in development as the embryo subdivides into parasegmental units.

Animals↗
PubMed1979

Electrophysiologic analysis of the motor system after stroke: the "suppressive" effect of vibration.

The "suppressive" effect of vibration on the H-reflex was studied in 18 patients with motor system deficits due to cerebrovascular lesions of less than 3 weeks duration. No meaningful difference was found in the degree of H-reflex suppression between clinically involved and uninvolved sides in the patients, several of whom had increased deep tendon reflexes at the time of examination. It is concluded that hyperreflexia of "spasticity" cannot be explained purely on the basis of lack of presynaptic inhibition, even if it were one of the underlying mechanisms responsible for the suppression of the H-reflex by vibration, as previously claimed. Not only specific lesions themselves but also changes with the passage of time after CNS damage are important for understanding and treatment of motor system abnormalities.

Cerebrovascular Disorders↗
PubMed1975

[Transfer characteristic of the motor system of the hand obtained by electrical stimulation and its bearing on force tremor (author's transl)].

Pulse duration modulated signals were used to stimulate the extensor muscles of the hand. From this and from the isometric tension responses the frequency response of the human motor system was obtained. From the transfer characteristics of the components of the motor system which were taken from literature the frequency response of a closed-loop circuit model could be calculated. The theoretical frequency response was compared to the observed data. With increasing loop gain the model would show the characteristics of a filter tuned to the frequency of force-tremors.

Adult↗
PubMed1978

Effect of diazepam on the gamma motor system indicated by the responses of the muscle spindle of the triceps surae muscle of the decerebrate cat to the muscle stretch.

The experiments were performed on 37 intercollicularly decerebrate cats. The triceps surae muscle was subjected to trapezoidal stretches of 10 mm/s or 2 mm/s over a length of 14 mm. The reflex arc was left partially or fully intact. The effect of diazepam given intravenously on the discharge frequencies of group Ia afferent fibres from muscle spindles in the belly of the triceps surae muscle was studied. Diazepam depressed both the dynamic and the static gamma motor responses. When gamma motor fibres were selectively blocked by procaine a parallel shift of the tension-extension curve was observed. From comparison of the effect of procaine and diazepam on the phasic and static responses of the muscle spindle it was concluded that directly after the injection of diazepam the gamma motor activity was completely abolished at a dose as low as 0.1 mg/kg whereas the alpha motor system was only partly depressed even at higher doses. Differences in the effect of diazepam on the dynamic and static gamma system respectively, could not be found.

Action Potentials↗
PubMed1976

Somatostatin and thyrotropin releasing hormone: central effect on sleep and motor system.

The hypothalamic hormones, somatostatin (SRIF or GH-RIH) and thyrotropin releasing hormone (TRH) applied intraventricularly into rat brain had a considerable effect on motor function and resulted in profound alterations in the sleep-waking pattern. While TRH induced primarily an increase in exploratory and motor stereotyped behavior, the effect of somatostatin was striking and prolonged: stereotyped circular running in many instances evolved into catatonia, paraplegia-in extension and/or tonic-clonic seizures.

Animals↗
PubMed1978

Analysis and modelling of human motor control systems.

In this contribution the aims and possibilities of model studies and simulations are briefly discussed. Next, a simulation kit for the peripheral motor control system is presented in outline and, finally, some results which can be obtained with it are given.

Arm↗