Efficiency of endoneural stimulation with 5- to 24-fold multielectrodes

Optimal selective stimulation of nerve with endoneurally (intrafascicularly) inserted multi-microelectrodes means that each electrode activates, with its own threshold stimulation current, as few distinct motoneurons as possible, preferably only one, If the latter is the case, the efficiency of a multi-electrode is 100%. However, neighbouring electrodes may control the same motor fiber(s), as there are generally more fibers than electrodes and because the position of fibers is largely unknown. In that case, efficiency is less than 100%. This paper reports on experiments in rat peroneal nerve with 5- and 24-fold wire multi-microelectrode arrays, The threshold force of the twitch recruitment curve of the corresponding EDL muscle was used to monitor nerve activation, It was found that on average the threshold force efficiency was 0.48=48%, After re-inspection of the data, taking into account that neighbouring electrodes have a higher probability to activate the same motor units, in contrast to distant electrodes, the average efficiency even rises to 81%. For several reasons, threshold forces do not correspond to motor unit forces, implying that the threshold-force-efficiency can not be regarded as motor-unit-efficienc

The restless legs syndrome (Ekbom's syndrome)

The restless legs syndrome is a condition of unknown aetiology characterized by nocturnal paraesthesiae in the lower limbs,an irreversible tendency to move the limbs, pain in the distribution of the paraesthesiae, and psychiatric disturbances. The syndrome may occur at any age and in either sex and usually runs a course over many years with spontaneous improvements and exacerbations. An association with iron deficiency has been suggested but in most cases no apparent cause has been found, and treatment at present is symptomatic with analgesics and sedatives. The differential diagnosis includes phenothiazine-induced akathisia and meralgia paraesthetica

STRUCTURAL-CHANGES OF THE SOLEUS AND THE TIBIALIS ANTERIOR MOTONEURON POOL DURING DEVELOPMENT IN THE RAT

The morphological development of motoneuron pools of two hindlimb muscles of the rat, soleus (SOL) and tibialis anterior (TA), was studied in rats ranging in age between 8 and 30 postnatal days (P8-P30). Motoneurons were retrogradely labelled by injecting a cholera toxin B subunit solution directly into the muscles. This resulted in extensive labelling of motoneurons as well as their dendritic trees. The distribution of cross sectional areas of neuronal somata was determined for both muscles at various ages. Somal size increased considerably between P8 and P12, whereas growth was moderate between P12 and P20. The size distribution of SOL motoneurons was bimodal from P20, whereas the size distribution of TA motoneurons remained largely unimodal. The morphological development of the dendritic tree was studied qualitatively.The development of dendritic arborization within the SOL and the TA motoneuron pool showed major differences. The arborization pattern of dendrites of TA motoneurons was basically multipolar at all ages. In contrast, dendrites of SOL neurons tended to line up with the rostro-caudal axis and became organized in longitudinal bundles from P 16 onwards. The relatively late appearance of dendrite bundles in the soleus motoneuron pool suggests that they might be related to the fine-tuning of neuronal activity rather than patterning of motor activity. The occurrence of dendrite bundles in SOL and not in TA motoneuron pools suggests that they may be related to the different afferent organization of this postural muscle or to its tonic activation pattern