Glaze CM, Troyer TW. Development of temporal structure in zebra finch song. J Neurophysiol 109: 1025-1035, 2013. First published November 21, 2012 doi:10.1152/jn.00578.2012.-Zebra finch song has provided an excellent case study in the neural basis of sequence learning, with a high degree of temporal precision and tight links with precisely timed bursting in forebrain neurons. To examine the development of song timing, we measured the following four aspects of song temporal structure at four age ranges between 65 and 375 days posthatch: the mean durations of song syllables and the silent gaps between them, timing variability linked to song tempo, timing variability expressed independently across syllables and gaps, and transition probabilities between consecutive syllable pairs. We found substantial increases in song tempo between 65 and 85 days posthatch, due almost entirely to a shortening of gaps. We also found a decrease in tempo variability, also specific to gaps. Both the magnitude of the increase in tempo and the decrease in tempo variability were correlated on gap-by-gap basis with increases in the reliability of corresponding syllable transitions. Syllables had no systematic increase in tempo or decrease in tempo variability. In contrast to tempo parameters, both syllables and gaps showed an early sharp reduction in independent variability followed by continued reductions over the first year. The data suggest that links between syllable-based representations are strengthened during the later parts of the traditional period of song learning and that song rhythm continues to become more regular throughout the first year of life. Similar learning patterns have been identified in human sequence learning, suggesting a potentially rich area of comparative research. temporal structure; learning; birdsong; generative model SEQUENCE LEARNING is one of the touchstone questions in neuroscience (e.g., Lashley 1951; Hikosaka et al. 2002;Keele et al. 2003;Rhodes et al. 2004), and song learning in zebra finches has served as an excellent model system for understanding sequence learning and production. Adult songs are highly stereotyped and have a well-defined temporal structure spanning multiple time scales. In the zebra finch, song learning can be roughly divided into two overlapping processes (Immelmann 1969;Marler 1970;Konishi 1985;Brainard and Doupe 2000): "sensory acquisition," in which a young bird ϳ20 -65 days posthatch (dph) is exposed to the song of one or more tutors and forms an auditory template; and "sensorimotor learning," in which the juvenile bird ϳ35-90 dph learns to produce song based on that template. Once learned, songs are composed of several repeats of 500-to 1,000-ms-long "motifs," consisting of a sequence of three to seven "syllables," with 50-to 250-ms-long stereotyped vocalizations separated by silent gaps. In adult zebra finch song, the spectral features of individual song syllables are highly stereotyped, as are the timing and sequencing of syllable production. However, few studies have focu...