Figure 6.

Predicted PSPs computed from various combinations of conductances show that the suppression of excitation with binaural signals is due to both an ipsilateral inhibition and a reduction in the contralateral excitation. Contralateral tones were 30 dB SPL and ipsilateral tones were 20 dB SPL in all panels. A, PSP evoked by monaural stimulation of the contralateral ear is far above threshold. Bottom shows the response that was computed from the contralaterally evoked excitatory and inhibitory conductances. B, Control binaural response is maximally suppressed and was generated from both the binaural excitatory and binaural inhibitory conductances. C, Simulation of conditions that would generate a de novo EI formation. The maximal excitatory response is only partially suppressed by the ipsilateral inhibition, showing that the ipsilaterally evoked inhibition does not by itself have sufficient strength to generate the maximal suppression evoked by the entire circuit in B. D, The binaural suppression in the LSO of contralaterally evoked excitation also generates a partially suppressed response in the IC. The suppressed IC response was generated without the ipsilaterally evoked inhibition from the contralateral DNLL. Threshold indicates the amplitude of the EPSP at which spikes were initiated in the response evoked by the tone at the contralateral ear.