The role of the dorsomedial nucleus (DM) of intercollicular complex with regard to sexual difference of distance calls in Bengalese finches

The acoustic structures of distance calls in sexually mature Bengalese finches (Lonchura striata var, domestica) show distinct sexual differences. We conducted a neuroethological study to identify the neural mechanism in the brain by which sexually mature male and female birds produce these acoustically different distance calls. Bilateral lesions of the dorsomedial (DM) nucleus of the intercollicular complex, known as the midbrain vocal center, eliminated distance calls in sexually mature males and females, but electrical stimulation of the DM in males and females induced calls that showed sexual differences and were acoustically similar to the distance calls of males and females. These results confirm that the DM in both sexes is one of the nuclei of the vocal control system that controls calling behavior. Neural tracer was injected into the DM in order to identify sexual differences in the neural input and output connections in the DM. Anatomical tracing of DM revealed the existence of labeled somata in the ipsilateral robust nucleus of the archistriatum (RA) in males. After bilateral RA lesions, however, males produced distance calls that were acoustically similar to female distance calls. These results suggest that the DM is one of the nuclei which generate the distance call patterns of both sexes, and that the neural information from the RA to the DM change the distance call pattern of male.