Biomedical Engineering Reference
In-Depth Information
T
TL
ST
vS
vTB
dTB
dS
B
Fig. 3.4.
Schematic ventro-lateral view of a songbird syrinx, showing the main
muscles involved in the production of birdsong. Muscles (or groups of muscles)
have well-defined tasks, for instance controlling the frequency of the vocalization
and active gating of the syringeal lumen. Legend: vS, syringealis ventralis muscle;
dS, syringealis dorsalis muscle; TL, tracheolateralis muscle; dTB, tracheobronchialis
dorsalis muscle; T, trachea; ST m. sternotrachealis; vTB, m. tracheobronchialis
ventralis; B, bronchus. Adapted from [Goller and Suthers 1996a]
In studies performed with brown thrashers [Goller and Suthers 1996a],
it was observed that the active separation of the labia is controlled by the
ventral tracheobronchialis ventralis muscle (vTB) and the tracheoloateralis
muscle (TL), while the active closing is mainly controlled by dorsal muscles
called the siringealis dorsalis (dS) and the dorsal tracheobronchial (dTB).
This was determined by observing that the activity of the first pair of muscles
increased significantly while the bird was taking minibreaths (identified by
falls of the pressure to values below atmospheric pressure, accompanied by
airflow), while the activity of the second pair would increase simultaneously
with falls in airflow. In this way, the bird must at least coordinate the muscles
that participate in the opening and closing of the syringeal lumen with those
involved in respiration, since the pulses of air regulated by the opening and
closing of the syrinx are produced by the compression of the posterior air sacs.
Note that the bird does not take a deep breath before beginning a song. On
the contrary, it takes minibreaths between syllables. This respiratory pattern
is replaced by a pulsatile one when a syllable is repeated very fast (more
than 30 per second for a canary, for example). In that case, the bird keeps
a high level of bronchial pressure (i.e., it does not inspire between syllables)
and controls actively the aperture of the syrinx, opening and closing the air
passage at the right speed.
On the other hand, in Sect. 3.1 we pointed out that an important dif-
ference between a human vocalization and a birdsong syllable (even one
