Examining the role of dorsomedial nucleus (DM) of the Intercollicular complex in the context of song production in zebra finches

Abstract

Communication is vital for survival in the animal kingdom. Communication through vocal learning is an ability possessed by very few taxa. Zebra finch serves as a good model system to study evolution of vocal learning. Akin to humans, juvenile finches memorise the song from an adult tutor in the plastic phase and ultimately produce the same song for life. Song is a stereotyped sequence of sounds consisting of various elements called syllables. The underlying neural circuitry is highly specialised and involves both telencephalic and midbrain nuclei. DM (dorsomedial nucleus of the intercollicular complex), a midbrain nucleus is primarily known for producing unlearned vocalisations- ‘calls’. DM, however, is also anatomically a part of the circuitry for producing song but it’s role in song production remains elusive. The role of DM was assessed by lesioning. Lesions were not specific to DM and caused damage in the surrounding area ICo (intercollicular complex). Songs were altered in a few birds which led to the production of unrecognizable syllables and loss of song tempo. Upon correlating changes in song with sites of lesions, changes could be attributed to lesions in central part of ICo lying in the medial portion of the brain. Lesions in some other parts of ICo did not affect song. The role of DM was further assessed by recording neural activity in DM during song. Preliminary data shows changes in neural activity during song. Effect of DM lesions was different from what is seen for lesions of other song nuclei. My results suggest that certain parts of ICo are important for normal song production. More generally, my study suggests that the song circuitry is highly decentralised with telencephalic and midbrain areas contributing to normal song production.