Neural mechanisms of vocal sequence generation in songbirds
Open Access
- Author:
- Zhang, Yisi
- Graduate Program:
- Physics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 07, 2014
- Committee Members:
- Alexay Kozhevnikov, Dissertation Advisor/Co-Advisor
Alexay Kozhevnikov, Committee Chair/Co-Chair
Dezhe Jin, Committee Member
Jun Zhu, Committee Member
Christine Dolan Keating, Committee Member - Keywords:
- Motor sequence
songbird
neural circuitry
syntax
temperature
auditory feedback
hemisphere - Abstract:
- Complex learned sequential behaviors, such as speaking, playing musical instruments and singing, occur in daily life. To understand the neural mechanisms governing the generation and learning of these complex motor sequences, the vocal system of songbirds has been used as an excellent model. Many studies have been focused on how the stereotyped song sequence is generated by the neural circuit of zebra finches. A more complex aspect of the birdsong, the syntactic organization of the vocal sequences that is common in both birdsong and human language, has not been well studied. The Bengalese finches sing variable songs that follow certain syntactic rules, and therefore can be used as a tool to study the syntax control of birdsong. This thesis progressively investigates where the song syntax is encoded in the Bengalese finch vocal system using various perturbation methods. The first section of the thesis demonstrates that HVC, a premotor song control nucleus, plays an active role in encoding the syntax. Changing temperature in HVC strongly affects the length of the syllable repeats. In addition, the transition probabilities at several branching points are altered by temperature. In contrast, changing temperature in the downstream area RA does not affect song syntax. These findings suggest that the neural activity in HVC generates the syntax and is not instructed by inputs from higher order areas. Auditory feedback plays an important role in shaping the syntax of Bengalese finch songs. The second section explored how the real-time distorted auditory feedback (DAF) affects the syntax. The syllable repeats are reduced by DAF, which is similar to the effect of cooling HVC. This suggests that the auditory feedback influence on syntax may be mediated via HVC. Songbird singing is controlled by bilateral brain hemispheres. The third part of the thesis investigates the function of the two HVCs in timing and syntax control by unilaterally changing temperature in HVC. The left HVC is found to control the timing of the syllables, while both HVCs control the timing of the gaps. Most syllable repeats are controlled by only one hemisphere. The transition probabilities at the branching points are controlled by both hemispheres. The final part of the thesis develops a method that can wirelessly stimulate the neural circuit in behaving small animals. The device is tested in a zebra finch whose song is altered by electric pulses during singing. Potential experiments are proposed for studying the neural mechanisms of syntax generation using this device. Taken together, all the four projects are dedicated to study the neural mechanisms of the syntactic sequence generation of birdsong.