Song learning is an excellent model system for understanding skill acquisition, including human vocal learning. The neural network that subserves birdsong learning comprises a set of brain regions that are well defined anatomically and are accessible for physiological study. This includes (1) the ascending auditory pathways; (2) several higher- order auditory areas including the caudomedial neostriatum (Ncm); (3) the anterior forebrain pathway (AFP) of the song system, and (4) the motor control pathway of the song system. The Hvc paraHVc region is at a nexus of these four pathways, and is essential for highly processed auditory information reflective of song learning to gain access to the rest of the song system. Auditory feedback to the motor system enables a bird to match his own song to a previously memorized song model during a learning episode (the """"""""two-step model"""""""" of vocal learning), a process which may involve HVc. The anatomical representation of the songmodel - whether distributed or localized - is not yet known but recent progress suggests the participation of the Ncm and there is also evidence for a role of the AFP in song memorization. In these experiments, the involvement of specific brain regions in song memorization will be examined in the zebra finch, Taeniopygia guttata, a well-studied model system. Using a newly-developed behavioral assay, young birds will be trained at an early age (9-25 days) to discriminate between conspecific tutor songs. Training will occur during the song memorization period, hence training will affect which songs birds commit to memory. As the connections of the motor control pathway are not fully established at that age, it will be possible to isolate the sensory phase of song learning and disambiguate it from the sensorimotor phase. The ability to recognize tutor songs from a set of novel songs will be tested both immediately before and after ibotenic acid or electrolytic lesioning of the HVc-paraHVc region. A negative result (no effect on song discrimination) will suggest region afferent to HVc are involved in song memory formation. Depending on the outcome of the behavioral/lesion experiments, physiological recordings in either the Ncm or other afferent regions (negative outcome) or HVc (positive outcome) will be conducted to assess learning-related changes in the response properties of single neurons. Test stimuli will include the same stimuli used to train and test the birds' song discrimination prior to the physiological experiments. These experiments may give initial insight into the mechanisms that lead to the formation, storage and retrieval of auditory memories in songbirds.
| Adret, Patrice; Meliza, C Daniel; Margoliash, Daniel (2012) Song tutoring in presinging zebra finch juveniles biases a small population of higher-order song-selective neurons toward the tutor song. J Neurophysiol 108:1977-87 |
| Adret, Patrice; Margoliash, Daniel (2002) Metabolic and neural activity in the song system nucleus robustus archistriatalis: effect of age and gender. J Comp Neurol 454:409-23 |
