Different responses of AI neurons at varied intervals between paired stimuli.

<p><b>A</b>) Five superimposed waveforms of the paired sound-evoked responses in AI neurons after train stimulation of the MGBv at incremental intervals between the paired stimuli. <b>B</b>) The statistical broken line chart of the average amplitude of the EPSPs in (A). When the frequency of the train stimuli was 10 Hz, the amplitudes of the sound-evoked EPSPs significantly increased immediately after the train stimulation of the MGBv (compared with the control level), and then decreased to a level lower than the control group when the stimulus interval was extended to 700 ms. Finally, when the stimulus interval was approximately 800 ms, it reached the average amplitude of sound-evoked EPSPs without train stimulation (that is, the level of the control group). In contrast, the 100 Hz train electrical stimulation of the MGBv at first decreased the amplitudes of sound-evoked EPSPs in AI neurons to a significant low level. The amplitudes of the EPSPs then increased to the level of control group. The amplitudes of the EPSPs in both the high- and low-frequency group reached the control level and stabilized at the plateau when the stimulus interval was longer than 800 ms. (*<i>P</i><0.05, **<i>P</i><0.01).