FIG. 7.

EEG-based envelope coding fidelity and intelligibility are shaped not just by peripheral envelopes, but also by TFS. Comparing the target PLV spectra (z-scored with respect to a null distribution that is common across conditions) for intact and vocoded SiB at 4 dB SNR shows that 64-channel envelope vocoding significantly degrades envelope coding of the target relative to the background in central auditory neurons, even though the envelopes at the cochlear level are very similar before and after vocoding. Concomitantly, intelligibility is far worse for the vocoded condition compared to the intact condition, demonstrating that the integrity of peripheral envelope cues alone cannot account for speech intelligibility. This result shows that central neural envelope coding and intelligibility are shaped by factors other than just peripheral envelopes, such as stimulus TFS, which supports source segregation and selective attention. Note that the dashed lines indicate z = 1.64, i.e., the 95th percentile of the noise floor distribution.