H-reflex depression simulated by a biologically realistic motoneuron network.

The H-reflex is frequently used both in the clinic as well as in research, with the purpose of providing a better understanding of the spinal cord. For repetitive stimuli (e.g. at 1 Hz) the H-reflex depresses, probably due to synaptic depression. Experimental results from the literature provided the basis for the simulations presented here. A large network of motoneurons connected to muscle fibers was modeled and implemented as a computer simulator. Afferent fibers that excited synaptically the motoneurons fired in response to a programmable stimulus. After an initial fitting to the experimental results was achieved, the analysis of which motor units contributed to the H-reflex in two different paradigms pointed to an alternative interpretation of the human data.