Biomedical Engineering Reference
In-Depth Information
HVC
nIf
RA
lMAN
cerebellum
X
DLM
DM
nXIIts
AM/RAm
to syringeal
muscles
to expiratory
muscles
Fig. 8.1.
Schematic sagittal view of the brain. The areas shaded black are necessary
for adult song production, whereas the white areas are necessary for normal song
development, but not adult song production. The
solid arrows
show the motor
control pathway, while the
dashed arrows
show the anterior forebrain pathway, or
AFP. Modified after [Spiro et al. 1999]
and lMAN. lMAN sends to RA (part of the motor pathway) either the error
correction or the reinforcement signal during learning that will eventually
contribute to the reconfiguration of the connections within the motor path-
way. It is known that both the AFP and its connections to RA undergo
regressive changes as the sensitive period ends (the sensitive period being
the time in which the bird “learns” what it will eventually imitate), but the
global picture is still incomplete.
8.3 Models for the Motor Pathway: What for?
When we described the physical processes involved in the generation of bird-
song, we wrote down models based on first principles of physics. Can one
model in neuroscience? What for? There are two main reasons to attempt
to model the electrical activity of a brain when it is controlling singing. The
first one is conceptual in nature. In the process of writing down a quantita-
tive model for the voltages to be measured in the neurons involved, we realize
how complete or incomplete our conceptual models are. We can, for exam-
ple, write down differential equations for the voltages using the celebrated
Hodgkin-Huxley equations, and test whether, for the measured neural con-
ductances, the system generates patterns of activity like the ones measured.
