Abstract:
Inhibition has been shown to play an important role in determining the critical period
of development of sensory systems but its role in motor system is unknown. Here, I
study the zebra finch, a bird that develops a motor skill during a critical developmental
period. In juvenile zebra finches, learning of song syllables during critical period is
accompanied by a corresponding stepwise increase in inhibition in HVC (used as
proper name). Adult zebra finches have crystallized songs which are protected from
further change influenced by external auditory playback by the inhibitory interneuron
network in HVC. In this study, I show that pharmacological inactivation of the inhibitory
interneuron network in adults leads to reopening of the critical period and induces
plasticity in song. Since HVC is a relay center between the auditory and motor
systems, I provided an additional auditory playback during pharmacological
interneuron inactivation and observed its effect on the changes in song. I quantified
changes in spectral features of song syllables and changes in linearity, consistency
and stereotypy of syllable sequencing. My results show that the limitation of HVC
interneuron efficacy leads to a window of opportunity for zebra finches to learn a new
song which seems to be guided by imitation learning. Reopening of the critical period
in later stages of development by limiting interneuron signaling opens possible
avenues for fine-tuning learned motor sequences in a guided manner.
