The expression of LIM homeobox genes islet1 and islet2 is tightly regulated during development of zebrafish primary motoneurons. All primary motoneurons express islet1 around the time they exit the cell cycle. By the time primary motoneurons undergo axogenesis, specific subtypes express islet1, whereas other subtypes express islet2, suggesting that these two genes have different functions. Here...

The purpose of this communication is to report on the analysis of the effects of muscle pressure on altering motoneuron excitability. Motoneuron excitability was assessed by measuring changes in the H-reflex in 30 neurologically healthy individuals. The results indicate that muscle pressure is excitatory, but of such low intensity as to be of dubious therapeutic benefit. Methodological limitati...

In addition to rapid signaling, electrical activity provides important cues to developing neurons. Electrical activity relies on the function of several different types of voltage-gated ion channels. Whereas voltage-gated Ca2+ channel activity regulates several aspects of neuronal differentiation, much less is known about developmental roles of voltage-gated Na+ channels, essential mediators of...

30 Stroke survivors often exhibit abnormal motoneuron excitability, manifested clinically 31 as spasticity with exaggerated stretch reflexes in resting muscles. We examined whether this 32 abnormal excitability is a result of increased activation of intrinsic voltage-dependent 33 persistent inward currents (PICs), or whether it is due to enhanced synaptic inputs to the 34 motoneuron. This disti...

37 Motoneurons often fire repetitively and for long periods. In sustained voluntary contractions the 38 excitability of motoneurons declines. We provide the first detailed description of the time-course of 39 human motoneuron recovery after sustained activity at a constant discharge rate. We recorded the 40 discharge of single motor units (MUs, n=30) with intramuscular wire electrodes inserted ...

During individuated finger movements, a high proportion of synchrony effects was found in spike-triggered averages (SpikeTAs) of rectified electromyographic activity aligned on the spikes discharged by primary motor cortex (M1) neurons. Because synchrony effects can be produced even if the trigger neuron itself provides no direct synaptic connections to motoneurons, such nonoscillatory synchron...

Motoneuron activity is strongly influenced by the activation of persistent inward currents (PICs) mediated by voltage-gated sodium and calcium channels. However, the amount of PIC contribution to the activation of human motoneurons can only be estimated indirectly. Simultaneous recordings of pairs of motor units have been used to provide an estimate of the PIC contribution by using the firing r...

A computational model of the mammalian spinal cord circuitry incorporating a two-level central pattern generator (CPG) with separate half-center rhythm generator (RG) and pattern formation (PF) networks is reviewed. The model consists of interacting populations of interneurons and motoneurons described in the Hodgkin-Huxley style. Locomotor rhythm generation is based on a combination of intrins...