[Relation between midbrain auditory center neuronal responses and sound on-off time ratio in the frog].

The EPs and unit activity of the frog midbrain auditory region were tested during 1,2,5 and 10/sec presentations of the tone bursts. The maximal amplitude of the EPs and the exaltation of unit activity occurred when the burst duration was in the range 10--30 msec. The elongation of the tone bursts led to the increase of the latency and the decrease of the maximal firing rate. The synaptic mechanisms of this suppression are discussed.