Abstract
Birdsong is a complex behavior that exhibits hierarchical organization. While the representation of singing behavior and its hierarchical organization has been studied in some detail in avian cortical premotor circuits, our understanding of the role of the thalamus in adult birdsong is incomplete. Using a combination of behavioral and electrophysiological studies, we seek to expand on earlier work showing that the thalamic nucleus Uvaeformis (Uva) is necessary for the production of stereotyped, adult song in zebra finch (Taeniopygia guttata). We confirm that complete bilateral lesions of Uva abolish singing in the ‘directed’ social context, but find that in the ‘undirected’ social context, such lesions result in highly variable vocalizations similar to early babbling song in juvenile birds. Recordings of neural activity in Uva reveal strong syllable-related modulation, maximally active prior to syllable onsets and minimally active prior to syllable offsets. Furthermore, both song and Uva activity exhibit a pronounced coherent modulation at 10Hz—a pattern observed in downstream premotor areas in adult and, even more prominently, in juvenile birds. These findings are broadly consistent with the idea that Uva is critical in the sequential activation of behavioral modules in HVC.
Highlights
Many complex behaviors observed in nature exhibit a behavioral hierarchy, a system in which behaviors can be divided into ‘units’ which themselves can be divided into simpler subunits [1]
This hierarchical organization of behavior leads to key questions regarding the neural implementation of complex motor behaviors: are elements of the hierarchy explicitly represented in neural circuits? And if so, how are behavioral units or subunits represented and initiated? Here, we will examine these questions in the context of learned vocalizations of the songbird
Similar to the earlier studies, we find that in the directed social context, birds with complete bilateral Uva lesions are unable to sing
Summary
Many complex behaviors observed in nature exhibit a behavioral hierarchy, a system in which behaviors can be divided into ‘units’ which themselves can be divided into simpler subunits [1] This hierarchical organization of behavior leads to key questions regarding the neural implementation of complex motor behaviors: are elements of the hierarchy explicitly represented in neural circuits? Bouts of singing are often preceded by a series of short, soft vocalizations called introductory notes [2]. It is unclear how this behavioral hierarchy is represented in either the vocal premotor or the vocal learning circuits of the avian brain
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