Birdsong: Is it music to their ears? Open Access

Earp, Sarah Elizabeth (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/02870w49r?locale=en
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Abstract


Abstract
Birdsong: Is it Music to their Ears?
Is music uniquely human? This question has been debated among musicians and scientists alike.
One example of a possible non-human form of music is birdsong, which is believed by some to
be music, and perceived by others as simple animal vocalization. Attempts to compare song to
music have usually focused on the qualities of the sound itself, such as melody and rhythm. It
may be more informative, however, to compare the experiences of the intended listeners.
Previous studies show that areas in the neural reward circuit, including the nucleus accumbens
(nAc) and the ventral tegmental area (VTA) respond in humans listening to pleasurable music. I
investigated whether a bird's experience of birdsong is similar to the rewarding experience of
music listening in humans by exploring whether the nAc and VTA respond in white-throated
sparrows listening to song. I studied neural responses of female and male white-throated
sparrows ( Zonotrichia albicollis) exposed to either courtship song or a control sound. Half of the
birds were treated with reproductive hormones to simulate the breeding condition, and the others
were given a placebo and acted as controls. I looked at neural responses by labeling the
immediate early gene (IEG) product Egr-1, which indicates new protein synthesis in response to
a stimulus. Egr-1 expression was quantified in the nAc and the VTA. I found that females in
breeding condition had a higher IEG response to song than to the control sound, whereas the
females that were not in breeding condition and all males had similar Egr-1 responses to song
and control sounds. Overall, my results suggest that birdsong is like human music in that reward
circuits respond in the listener. In this seasonally breeding songbird, that parallel can be drawn
only for females during the breeding season, when song is expected to have positive valence.

Table of Contents


Table of Contents

Introduction...................................................................................................1
Comparing the Structures of Song and Music ..................................1
Comparing Responses in the Listener...............................................4
Behavioral Responses to Song....................................................4
Neural Responses to Music.........................................................6
The Neural Reward Circuit.........................................................6
Mapping Neural Responses ........................................................7
The Natural Function of Song: Study Predictions ............................9
Methods..........................................................................................................10

Experimental Design..........................................................................10

Animals ..............................................................................................11
Study 1 ...............................................................................................11

Hormone Treatment ....................................................................11

Sound Stimulus ...........................................................................12

Stimulus Presentation and Tissue Collection ..............................12

Histology .....................................................................................13

Quantification of Egr-1 immunoreactivity...................................13

Statistical Analysis ......................................................................14

Study 2 ..............................................................................................15


Hormone Manipulation ...............................................................15


Sound Stimuli ..............................................................................15


Data Collection and Analysis.......................................................16

Study 3 ...............................................................................................17

Results
......................................................................................................18

Study 1 ..............................................................................................18

Study 2 ...............................................................................................18

Study 3 ...............................................................................................19
Discussion ......................................................................................................20
Summary of Results...........................................................................20
Comparing Neural Responses in the Reward Circuit ........................21
Comparing Responses in the nAc: Anticipation of Reward? ......22
Comparing Responses in the VTA ..............................................24
Comparing Neural Responses Outside of the Reward Circuit...........24
Hypothalamus ..............................................................................25
Caudate Nucleus and Striatum.....................................................26
Amygdala.....................................................................................27
Hippocampus ...............................................................................28
Overview: Comparing Neural Responses..........................................28
Sex, Hormonal State, and Social Context..........................................29
Neural Responses in the Performer....................................................31
Conclusion .........................................................................................32
References ......................................................................................................33
Table 1
......................................................................................................51
Figure 1 ......................................................................................................52
Figure 2 ......................................................................................................53
Figure 3 ......................................................................................................54
Figure 4 ......................................................................................................55
Figure 5 ......................................................................................................56

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