[Role of parameters of rhythmic cortical stimulation in synaptic activation of motor neurons].

Postsynaptic potentials (PSPs) evoked by stimulation of contralateral motor cortex with trains of square stimuli were recorded intracellularly in cat lumbar motoneurons. The influence of number of stimuli in a train and of interval between them upon amplitude, duration and latency of PSPs, was analysed. Rise of stimuli frequency in a train of constant duration (i.e. rise of number of stimuli accompanied by shortening of intervals) produced a snyaptic effect that was much more pronounced than in cases of shortening of intervals between equal number of stimuli (i.e. reduction of a train) or in cases of increase of number of stimuli with equal intervals (elongation of a train). Possible neuronal mechanisms of the leading role of train frequency in supraspinal activation of motoneurons are discussed.