Investigating the Syntactical and Acoustic Control of Repeated Syllables In the Bengalese Finch Restricted; Files Only

Abstract

Understanding how animals regulate motor variability is important to uncovering the mechanisms of behavioral flexibility. To achieve external goals, animals must regulate their motor behaviors in a defined sequence of well-learned movements, thereby demonstrating a hierarchical structure of motor control. This principle also applies to birdsong, which exhibits variability at both syntactical (macro-level) and acoustic (micro-level) scales. However, it remains unclear whether such variability reflects structured regulation or arises from random processes. To address this gap, we investigate whether repeat syllables in Bengalese finch song as a form of learned vocal motor behavior would reflect structured regulations or random processes, or a combination of both. Using a dataset of spontaneous, well-learned vocalizations from an adult Bengalese finch, we analyzed sequential patterns and acoustic features of repeat syllables.

After demonstrating that repeat length probabilities deviated from both uniform and Markovian models, we applied a model fitting process; and the distribution was best modeled by a shifted log-normal distribution. This pattern suggests that repeat length is governed by multiplicative, feedback-sensitive mechanisms rather than random processes. Further analysis showed that a predictable set of three-syllable motifs preceded and followed repeat sequences regardless of length, indicating that repeats are probably embedded within larger structures.

Acoustically, we examined five features across repeat iterations: fundamental frequency (pitch), spectral entropy (noisiness), Wiener entropy (spectral flatness), syllable amplitude, and syllable duration. All these features individually showed a possible lack of directed acoustic drift. Instead, we observed a gradual drift in the first 4 syllables of a repeat sequences regardless of eventual length in global representations of all these acoustics in a lower-dimensional space.

In conclusion, these findings show that repeat syllables in birdsong possibly reflect a mix of pre-planned hierarchical control and drift either under neural control or due to biomechanical factors. Further works could use these salient behavioral features that reflect non-random control to explore how the brain organizes neural signals to drive variation. This work offers ideas into the mechanisms by which learned motor behaviors maintain stability and flexibility.

 

 

Table of Contents

Introduction……………………………………………………………………………………..…1

Methods………………………………………………………………………………………...….7

Results……………………………………………………………………………………………14

Discussion……………………………………………………………………………….…….…18

Tables and Figures……………………………………………………………………………….24

References………………………………………………………………………………………..29

About this Honors Thesis

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School	Emory College
Department	Psychology
Subfield / Discipline	Neuroscience and Animal Behavior
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Psychology, Behavioral Sciences Biology, Neuroscience
Keyword	Motor Control Bengalese Finch Songbird Motor Variability Vocal Control Computational Neuroscience
Committee Chair / Thesis Advisor	Samuel Sober, Emory University Daniel Dilks, Emory University
Committee Members	Hillary Rodman, Emory University Kristen Frenzel, Emory University

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