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Supplemental Digital Content 1
(a) Amplitude Envelopes of the stimuli shown in Figure 1b (BOS, LR, OR, WR from the top).
Amplitude envelopes are computed as follows: first, values in a sound wave were squared and low-pass filtered with cutoff frequency of 1176 Hz; then they were square-rooted and low-pass filtered with cutoff frequency of 14.7 Hz. (b) Correlation coefficients between the amplitude envelope of the BOS and that of reversed stimuli. Correlation coefficient between BOS and LR is high, which indicates that global amplitude modulation of BOS is preserved in LR compared to other reversed stimuli. Error bars are SD.
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Supplemental Digital Content 2
Photographs of the brain section showing the HVC (a) and Area X (b), stained with Cresyl Violet after the electrophysiological recording. The boundaries of the HVC (a) and the Area X (b) are marked by the dotted lines. The traces of electrodes are shown by arrowheads.
