Fig. 10.

Responses predicted for an EI neuron with ipsilaterally evoked EPSPS to multiple sounds. A: Responses predicted for an initial sound in the contralateral sound field followed by second sound in the ipsilateral sound field. If the second sound follows at short temporal interval that would allow the EPSP evoked by the first sound to summate with the EPSP evoked by the second sound, the EPSP evoked by the second sound would be boosted to a suprathreshold level. With longer intervals, the excitation evoked by the first sound would have decayed, causing the second sound to only evoke only a subtrheshold EPSP, as it would if the second sound were presented alone. B: In this case the first sound is presented in the ipsilateral sound field and only evokes a subthreshold EPSP. However, since it is more intense at the ipsilateral than the contralateral ear, it also persistently inhibits the DNLL. A second sound in the contralateral sound field that follows shortly thereafter, will not only partially summate with the depolarization evoked by the first sound, but the second sound will evoked a larger than expected response because the second sound evokes only excitation. The inhibition normally evoked in the ipsilateral DNLL by the second sound is eliminated due to the persistent inhibition evoked by the first sound.