FIG. 11.

Effects of interaural differences in input-rate functions on rate–ITD tuning. Differences due to interaural differences in threshold A_th (A and B) and in envelope delay ITD_env (C and D) are shown. The pulse rate is 500 pps and f_m is equal to 50 Hz in A and C and 100 Hz in B and D. The low level of synaptic strength (G_e = 1.4 nS) was used for all simulations except for conditions marked (‘acoustic’) where G_e = 1.6 nS and SI = 0.9. (All other conditions have SI = 0.99 as in Figs. 5–10.) A, B Input functions r(t) with different profiles between ipsilateral and contralateral stimuli lead to asymmetric rate–ITD_fine tuning when ITD_env is zero, but not for whole-waveform delays (when ITD_whole = ITD_fine = ITD_env). The different r(t) shapes were generated by using different A_th values for the two bilateral inputs. In A, A_th is equal to 0.6 and 0.7 for contralateral and ipsilateral stimuli, respectively; equal to 0.1 for both. In (B), the corresponding values for A_th are 0.6 and 0.4 for contralateral and ipsilateral stimuli with equal to 0.2 for both. C, D Input functions r(t) with different envelope delays ITD_env also lead to asymmetric rate–ITD_fine tunings. The response rate also decreases as a result of desynchronized rate profiles between ipsilateral and contralateral stimuli; here A_th = 0.6 and were used for the pulse trains on both sides.