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Inspiratory muscle activity during bird song
J M Wild1, F Goller, R A Suthers
1Medical Sciences Program, Program for Neural Science, Indiana University, Bloomington 47405, USA.
Journal of Neurobiology
|September 11, 1998
Summary
Birdsong is punctuated by minibreaths, which are brief inspirations. Inspiratory muscle activity, specifically in the scalenus and levatores costarum muscles, drives these minibreaths during singing in songbirds.
Area of Science:
- Bioacoustics
- Animal Behavior
- Comparative Physiology
Background:
- Birdsong appears continuous but contains brief inspiratory periods called minibreaths.
- The neural and muscular control mechanisms underlying these minibreaths are not fully understood.
Purpose of the Study:
- To investigate if inspiratory muscle activity accompanies and potentially causes minibreaths in songbirds.
- To elucidate the role of specific inspiratory muscles in the respiratory control of vocalizations.
Main Methods:
- Electromyography (EMG) was used to record activity in inspiratory (M. scalenus, Mm. levatores costarum) and expiratory muscles.
- Air sac pressure and tracheal airflow were simultaneously measured in zebra finches and cowbirds.
- EMG data were analyzed in relation to respiratory events during quiet breathing and singing.
Main Results:
- Inspiratory muscle EMG consistently preceded negative air sac pressure during quiet breathing and singing in both species.
- During singing, inspiratory muscle EMG amplitude increased 5-12 fold and duration decreased significantly during minibreaths.
- Inspiratory and expiratory muscle activities were stereotyped and temporally organized, defining song structure.
Conclusions:
- Minibreaths are driven by specific inspiratory muscle activity, not by expiratory muscle modulation.
- The precise timing and modulation of inspiratory and expiratory muscles are crucial for generating the complex temporal patterns of bird song.