Hierarchy of Auditory Cues Figure 6. Summary of neural responses to individual sounds alone and to paired sounds separated in elevation. A. Population averaged responses as a function of stimulus elevation and time post-stimulus onset to each sound by itself and to both sounds together (n = 23). Arrow on time axis demarcates the division between the early and late time period used in panels C and D. B. Weighted average of responses to both sounds together as a function of time (from bottom panel of A). Solid circles: statistically shifted from 0 toward the high frequency location (p,.05; bootstrapped t-test); open circles: not significantly shifted from 0 (p..05; bootstrapped t-test). C. Same data as 6A, but displayed as tuning curves for the early time period (0–20 ms). D. Same data as in 6A, but displayed as tuning curves for the late time period (20–50 ms). doi:10.1371/journal.pone.0010396.g006 Figure 7. The effect of relative sound level on the representation of sound location. Population averages of the early (top row) and late (bottom row) responses to each sound alone and both sounds together for sounds separated by 30u in azimuth. Red curves: responses to the high frequency sound; blue curves: responses to the low frequency sound; black curves: responses to both sounds together. The relative sound levels for the high and low frequency sounds are indicated above each corresponding row of tuning curves. Error bars indicate standard errors. Neural responses were normalized by the maximum response to either sound alone during the depicted time range, rather than across the entire time range as in Figs. 4,6 (Early: 0–20 ms; Late: 20–50 ms). doi:10.1371/journal.pone.0010396.g007 PLoS ONE | www.plosone.org 8 April 2010 | Volume 5 | Issue 4 | e10396