The Neural Basis of Vocal Learning in Songbirds
Our laboratory is interested in how the nervous system mediates behavior,
especially complex behaviors that must be learned. Birdsong provides a
very useful model system for the study of these issues. Song is an
intricate motor act that is learned in distinct phases during a bird's
life, and depends on the animals auditory experience. There are critical
periods for song learning, just as there are for some types of human
learning. The juvenile bird uses auditory feedback to refine and correct
his vocalizations, in a manner analogous to the acquisition of speech by
human infants. Moreover, a discrete set of brain areas, called the song
system, controls song learning and production. Finally, both the song
system and the adult song behavior are sexually dimorphic, and are
regulated by sex steroids. All of these features give birdsong the
potential to shed light on the neural basis of learning, and on factors
which control and limit learning.
At present the laboratory is focussed on a particular song circuit
which behavioral studies suggest plays a special role in song
learning. In juvenile birds, we have shown that the neurons in
this pathway respond to a variety of sounds. Once the bird has
learned its song, however, these same neurons are highly selective:
they respond robustly to the sound of the bird's own song, and weakly
or not at all to very similar songs of conspecific individuals or
even the bird's own song played in reverse. The temporally and
acoustically complex auditory response properties of these neurons
suggest that they encode a neural representation of song, formed
during learning. Furthermore, the development of this circuit very
early during song learning and its synaptic output to the vocal motor
pathway make it a likely location for the sensory learning of tutor
song later used to guide motor song development. Using a variety of
physiological, behavioral, pharmacological, and theoretical techniques,
we are studying how the different features of song are represented
in this network, how the animal's auditory experience and vocal
learning shape its neuronal properties, and what the crucial function
of this pathway might be.
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