The highly stereotyped song of adult zebra finches is dynamically maintained. Neurons in the premotor nucleus robustus arcopallialis (RA) occasionally emit sequences of bursts that match patterns produced during singing. This suggests the hypothesis that alteration during sleep of premotor output is a mechanism for maintenance of adult song. We previously described apparent changes to the temporal patterns of premotor bursts in RA following sleep (SFN 2001, 318.3). In this study we quantified changes to the structure of bursts recorded in RA single units during female-directed singing, comparing the occurrence of such changes across sleeping and wakeful intervals. For each premotor burst, we defined pre- or post-interval features as spikes reliably produced with consistent relative timing. A structural change was defined as a significant change in features produced between pre- and post-interval bursts, combined with a change in the mean number of spikes/burst > 0.5. Of all burst types recorded before and ...