Figure 1.

(A) The acoustic waveform of the target stimulus [da]. The formant transition and vowel regions are bracketed. The periodic amplitude modulations of the stimulus, reflecting the rate of the fundamental frequency (F₀ = 100 Hz), are represented by the major peaks in the stimulus waveform (10 ms apart). (B) Pre- (black) and posttraining (red) grand average brainstem responses of trained subjects recorded to the [da] stimulus in quiet (top) and in the 6-talker babble (bottom) condition over the entire response. Overlay of pre- and posttraining responses shows that the posttraining brainstem response recorded in 6-talker babble exhibits a more robust representation of F₀. This enhancement is demonstrated by larger amplitudes of the prominent periodic peaks occurring every 10 ms in this time region. The transition portion of the response reflects the shift in formants of the stimulus as it moves from the onset burst of the stop consonant to the vowel portion of the syllable. The steady-state portion of the response reflects phase locking to stimulus periodicity in the vowel.