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Competing Sound Sources Reveal Spatial Effects in Cortical Processing

Figure 3

Population measures of response patterns.

(A) The upper envelope and (B) the across-site mean performance are shown as grids (with performance color-coded and percent correct value shown in each box) for clean targets and at each SNR (clean, +6 dB, 0 dB, and −6 dB from top to bottom). The upper envelope performance shares its worst-performing spatial configuration with the mean, but is (by necessity) higher than the mean at all points. In fact, the upper envelope performance is at or very near ceiling for the higher two SNRs. At each SNR, the mean varies smoothly as a function of both target and masker location. For both the upper envelope and the mean, the lowest performance is when the target is ipsilateral and the masker is contralateral, and the highest performance is in the complementary configuration. Performance also improves with increasing SNR. (C) Performance increases as a function of spatial separation when considering the subset of spatial configurations in which the target source is more contralateral than or colocated with the masker (in the grids above, the lower right triangle, including the diagonal). Mean performances are shown as markers (upward triangles, circles, and downward triangles for +6, 0, and −6 dB SNR, respectively). Linear regression fits at each SNR are shown as gray lines.

Figure 3