Figure 4.

Perturbation of feedback alters syllable timing. a, Example of localized slowing of song in response to AAF. Top, Spectrograms illustrating timing measurements for targeted portions of songs produced on a catch trial with normal feedback and an interleaved trial with altered feedback. The duration from the beginning of the targeted syllable to the beginning of the first syllable after feedback termination (the target segment) was measured for both conditions, as well as the duration of the subsequent segment of the bird's song (the target + 1 segment). Bottom, The distribution of target segment durations under normal (n = 81) and feedback perturbed (n = 62) conditions. The average target segment duration (inverted triangles) was significantly increased by feedback perturbation (*p < 0.05). b, Summary of effects of altered feedback on duration of targeted segments (target) and subsequent segments (target + 1) at stereotyped sequences (n = 22 birds) and branch points (n = 18 birds). For branch points, durations were analyzed only for the primary transition because these had the largest sample sizes. Each point indicates the percentage of increase in average segment duration for feedback trials relative to the average duration on catch trials. Altered feedback caused a significant slowing of song that was localized to the target segment, and this effect was significantly greater at branch points (*p < 0.05).