Doctor of Philosophy
Scott A. MacDougall-Shackleton
Songbirds produce a wide array of vocalizations, including song, and learned and innate calls. Songs and calls can be functionally defined. Songs are typically used to attract potential mates and defend one’s territory, whereas calls are used for everything else, such as advertising the presence of a predator, or location of a food source, and maintaining contact with members of one’s flock. The purpose of this thesis was to better understand the neural mechanisms underlying call production and perception in two songbird species; the black-capped chickadee (Poecile atricapillus) and the zebra finch (Taeniopygia guttata). My objectives were to (1) understand the involvement of the song-control system in the production of calls (Chapter 2, 3), (2) understand how bird calls are perceived in the brain (Chapter 4), (3) and if the song-control system is involved in the neural basis of perception of bird calls (Chapter 5). Black-capped chickadees were used to examine the motor-driven immediate-early gene (IEG) expression in the song-control nuclei, HVC and the robust nucleus of the arcopallium (RA). Chickadees that produced primarily gargle calls, an aggressive vocalization used in antagonistic encounters had the most IEG expression in HVC and RA, therefore are involved in the production of calls in chickadees. Chickadees were subjected to HVC lesions, and their gargle and chick-a-dee calls were compared pre- to post-lesion. The gargle calls were shorter, much more variable and were missing several notes post-lesion, whereas the chick-a-dee calls were also affected but not to the same degree. Therefore HVC is crucial for the normal production of the gargle and chick-a-dee calls. To explain this neural basis of perception of learned calls, chickadees were exposed to fee-bee, gargle, chick-a-dee and tseet vocalizations and IEG expression was examined in the auditory forebrain. The gargle elicited the most IEG expression. Finally intact male and female zebra finches, as well as HVC lesioned males were exposed to female and male long-calls and IEG expression in the auditory forebrain was measured. The auditory forebrain showed more IEG expression for male long-calls only in HVC lesioned males. Overall these results indicated the integral function of the song-control system in call production and perception, and would suggest that these structures should be collectively called the vocal-control system.
Mischler, Shannon Katie, "The neural mechanisms underlying the perception and production of learned vocalizations in songbirds" (2017). Electronic Thesis and Dissertation Repository. 5017.