Fig. 2.

Bilateral lesions of Area X block vocal plasticity and acute song variability. (A) Spectrograms illustrate striking changes in the song of a deafened bird (second group) but not in those of an intact bird (first group), a bird that received lesions of Area X before deafening (third group), nor a hearing bird with lesions of Area X (fourth group). Pre- and 8-wk-postoperative songs are shown. Syllables are labeled with letters; question marks denote unidentifiable syllables. (B) Summary of spectral (Upper) and temporal (Lower) similarity between preoperative and 8-wk-postoperative song. Each point corresponds to one bird; *P < 0.005; **P < 0.001. (C) Percent differences in fundamental frequency (FF) variability between pre- and 1–3 d postoperative syllables (control: 16 syllables in four sham-lesion birds; deaf only: 23 syllables in five birds; lesion-deaf: 13 syllables in four birds; lesion-hearing: 28 syllables in nine birds). Error bars, SEM; *P < 0.02; **P < 10⁻⁴.