Figure 3. Shared and specific sequences during the emergence of multiple syllable types.

All data from Bird 1. a, Song examples during the emergence of syllables β (red) and γ (blue). Panels i: subsong stage (46 dph); ii: rhythmic repetition of protosyllable α (grey bars; 58 dph); iii: rhythmic repetition of variants of the protosyllable (β and γ; 60 dph); iv: further acoustic differentiation of β and γ (red and blue bars; 62 dph). b, Scatter plot of syllable duration versus mean pitch goodness (each dot is one syllable rendition; n=400 syllables per day; unclassified syllables gray). c, Neuron recorded during protosyllable stage (HVC_X; 56 dph). d, β-specific neuron (HVC_X; 64 dph). e, Shared neuron active during both β and γ (HVC_RA; 68 dph). f, Simultaneously-recorded pair of HVC_X neurons: shared neuron (top) and γ-specific neuron (bottom; 71 dph). g, Raster of 105 projection neurons early in syllable differentiation showing shared and specific sequences. HVC_RA neurons indicated by circles at right. h, Same as panel g but for 100 neurons recorded after differentiation of β and γ into adult syllables B and C. Scale bars: (c–f) 0.5 mV, same time scale.