Auditory pathways in the budgerigar. I. Thalamo-telencephalic projections

Area of Science:

• Neuroscience
• Auditory System
• Avian Brain

Background:

• Understanding thalamo-telencephalic pathways is crucial for deciphering sensory processing in birds.
• The budgerigar (Melopsittacus undulatus) serves as a model for studying auditory information processing.

Purpose of the Study:

• To map the thalamo-telencephalic auditory pathways in the budgerigar brain.
• To investigate the projection patterns of the nucleus ovoidalis and nucleus dorsolateralis posterior (DLP).
• To explore the potential for intermodal associations in avian telencephalic fields.

Main Methods:

• Horseradish peroxidase (HRP) histochemistry was used to trace neuronal connections.
• Amino acid autoradiography confirmed projections from the DLP to the neostriatum intermedium, pars dorsolateralis (NIDL).

Main Results:

• The nucleus ovoidalis projects to specific regions of the caudal neostriatum, including field 'L' and adjacent NIDL.
• The NIDL receives input from both the nucleus ovoidalis and the DLP, which itself receives tectal inputs.
• Distinct portions of the nucleus ovoidalis project to different subregions of field 'L' and NIDL, indicating topographical organization.
• HRP injections in NIDL lateral to known projection fields labeled neurons in other diencephalic nuclei, including the nucleus subrotundus.

Conclusions:

• The neostriatum intermedium appears to be a complex processing area for thalamic inputs in budgerigars.
• Converging pathways from auditory and visual midbrain centers suggest that intermodal associations occur in telencephalic fields.
• These associations may underpin crucial functions such as individual recognition and social signaling in budgerigars.