Figure 2.

Effects of AGFa microstimulation at nonaligned AGFa-OT sites. Conventions are the same as in Fig. 1. A) Mean firing rate of the OT site plotted as a function of stimulus ITD for trials with (blue) and without (black) AGFa microstimulation. Error bars represent s.e.m. Black arrowhead: best ITD_{no stim} = +10 μs; blue arrowhead: best ITD_stim = +13 μs; red arrow: best ITD of the AGFa stimulation site = +38 μs. B) Mean firing rate and best-fit sound level response functions with (blue) and without (black) AGFa microstimulation. Responses are to a sound with the best ITD and best ILD values for this site. Error bars represent ± 1 s.e.m. Parameters of the fitted curves are indicated in the upper left. C) Effects of AGFa microstimulation on sound level response functions fit to the response data at nonaligned sites. Each panel plots the distribution of modulation indices across the population, with arrows marking the mean modulation index. The mean modulation index was significantly different from zero for n and r_max (asterisks). D) Top: Population ABL curves measured with (blue circles and line) and without (black circles and line) AGFa microstimulation. Ordinate shows normalized response; abscissa shows stimulus ABL normalized to the threshold ABL without AGFa stimulation (plotted as ABL = 0 dB). In most cases, errorbars are smaller than the symbol. Bottom: Difference in the normalized sound level response functions measured with versus without AGFa microstimulation. Significant suppression of responses was observed for responses to sound levels at and above threshold. E) Distribution of the changes in response threshold with AGFa microstimulation. Distrbution is shifted toward positive values indicating that higher sound levels were required to drive responses with AGFa microstimulation. The median value of the distribution is +0.8 dB.