Biomedical Engineering Reference
In-Depth Information
ratio
1
upsweeps
downsweeps
7
syllable
Fig. 5.11.
The ratios between the local maximum activity of the dS muscle at the
end and at the beginning of a vocalization. Seventeen syllables from two birds were
analyzed, the first six being upsweeps. Adapted from Fig. 5.8 in [Mindlin et al. 2003]
forces. The experiments described in this section, however, build confidence
in the physical model that we have presented in this chapter.
Much of the research on birdsong focuses on the neural processes involved
in the learning of the vocalizations. By illuminating the mechanisms by which
the activities of the syringeal muscles control the syrinx, we can help to
build a bridge between neural activity and vocal behavior. An implication
of this modeling effort for neurophysiologists in the field is that in order to
map central neural activity onto peripheral motor activity, it is important to
relate neural activity to the driving parameters rather than to the acoustic
properties of the emitted song [Suthers and Margoliash 2002].
5.5 Lateralization
The functional lateralization of the brain remains an open problem. In bird-
song production, this phenomenon is present [Allan and Suthers 1994]. The
degree of asymmetry present in the behavior ranges from low to very high.
In some species, there is a clear unilateral dominance (only one side of the
syrinx is used), while in others, there are equal contributions from both sides
[Suthers 1990]. For a long time, it was very puzzling that this functional asym-
metry did not have a clear anatomical correlation in the song control nuclei.
This problem was addressed by Goller and Suthers [Goller and Suthers 1995],
who studied the activity in the muscles controlling both sides of a brown
thrasher's syrinx. As we have seen, some muscles are involved in the con-
trol of the labial tension (and therefore of the frequency of the vocalization),
