Figure 3.

Comparison of single polarity (black), added (blue), and subtracted (red) FFRs to the evoking stimulus ‘da’ (gray) in the time (left) and frequency (right) domains. The single polarity FFR contains responses to both the stimulus envelope and temporal fine structure. While the lower frequencies, especially the fundamental frequency and lower harmonics (H2, H3) are consequences of half-wave rectification and envelope encoding, the higher frequencies (particularly the local maxima at H7, H12) are likely the result of temporal fine structure encoding. The mid frequencies are likely a mix of both envelope and temporal fine structure encoding. This can be seen in the lower-frequency bias of the added response, which falls off in encoding strength after the 6th harmonic, and the more faithful representation in the subtracted domain of the frequencies present within the stimulus (e.g., unlike in the added response the encoding of first-formant peak H7 in the subtracted response is stronger than neighboring nonformant harmonics).