[Certain nonlinear properties of motor reactions induced by motor cortex stimulation in the unanesthetized cat].

Nonlinear properties of muscle contraction evoked by macrostimulation of motor cortex were studied in chronic unrestrained cats. Frequency modulated stimulation pulse train was used, the modulation was performed by low frequency (0.2 +/ 10.0 Hz) harmonical signal. Time decrement of the evoked muscle contraction was accompanied by a pronounced increase in its phase lag which reached 20-30 degrees after 3-4 periods of stimulation. The phase lag increase was also observed with diminishing of stimulation intensity. When stimulus intensity varied from 1.7 to 1.2 threshold, the maximal increment of the phase lag reached 30-40 degrees. Possible mechanisms of the observed nonlinear properties of the motor signal transformation are discussed.