This study was designed to investigate the effects of sound stimulation on the spike activities of TTM motoneurons. 10 adult cats were used for the experiment and the head of the animal was fixed in a stereotaxic instrument and a small portion of the cerebellum and occipital lobe was aspirated to expose the floor of the fourth ventricle. A glass-insulated silver wire microelectrode with a tip diameter of 2-3μm was inserted into the TTM motoneuron region(P 6.0, L 4.0, D-2.5), according to the brain atlas of Snider and Niemer. The changes of firing spikes and the architectonic distributions of response after sound stimulation were observed as follows. Typical antidromic monosynaptic spikes after stimulation the TTM motoneurons Tand their latency time was within average 1ms. Firing spikes were increased by sound frequency, especially in high frequencies such like 4KHz and 8KHz and the threshold was 85-90dB SPL usually. Topographic orientation seemed to exist on TTM nucleus, but it was not uncertain that this findings were applied to human.