Figure 8.

Transition selectivity in auditory–vocal mirroring HVC_X neurons. A, In 29 HVC_X neurons, nine neurons exhibited robust phase-locked activity to specific syllables (10 syllables) in response to the BOS playback (neuronal reliability in time window of 100 ms, width >0.75). The mean timing of auditory activity to the associated syllables was similar to the mean timing of motor-related activity. Error bars represent ±SD. Red symbols indicate activities of the neurons that displayed auditory response in junction or branching transition segments where the same neurons were confirmed to generate burst spikes during singing. B, Example of all-or-none type transition selective activity of auditory–vocal mirroring HVC_X neuron (a13 in A). C–J, Comparison of the firing properties in the alternative transition segments between the vocal and auditory phase. Relative firing rates shown in C–F were normalized to the mean value in primary transitions. Primary or secondary transitions were determined by the average firing rate in the vocal phase. The same symbols as in A represent the same activities. Red and blue indicate activities in the motor phase and those in the auditory phase, respectively. Error bars in C–F indicate ±SD. *p < 0.05; **p < 0.001. N.S., Not significant.