Two EI/f cells in which ipsilateral tones evoked different responses when presented monaurally. A, Low ipsilateral intensity (0 dB SPL) evoked an EPSP and spike counts were facilitated with binaural signals that had the same low (0 dB SPL) ipsilateral intensity. Insert shows EPSP in higher magnification. IID function based on normalized spike counts is shown on right. Tone duration, 20.0 ms. B, Another EI/f cell in which low ipsilateral intensities (0 dB SPL) did not evoke any response but spike counts were facilitated with binaural signals that had the same ipsilateral intensity (0 dB SPL). Top panel shows responses to a contralateral tone at 10 dB SPL and an ipsilateral tone at 0 dB SPL, and the facilitated response to tones with the same intensities presented binaurally. Lower panel shows responses to the same stimuli while the cell was hyperpolarized. The EPSP evoked by the binaural signal is slightly larger than EPSP evoked by the contralateral signal alone, even though the ipsilateral tone presented alone evoked no response. C, EPSPs evoked by the contralateral tone and the binaural tone are superimposed. Tone duration, 5.0 ms.