Abstract:
The zebra finch is a songbird species of which the male needs to learn its vocalizations from a tutor that is usually the father. The song is biologically important for both reproduction and social interactions, making perception a key parameter in singing behaviour. It is not surprising, then, that brain nuclei involved in song production and perception have been intensively investigated in recent times. However, most of these studies have addressed the issues of song selectivity and auditory processing in the forebrain, while only a few studies have focused on earlier stages of the ascending auditory pathway. While it is known that some forebrain nuclei will respond specifically to either the bird’s own song or to conspecific vocalizations, where in the auditory pathway the emergence of this specificity originates remains unknown. However, since most auditory information reaching forebrain structures passes through the midbrain nucleus mesencephalicus lateralis, pars dorsalis (MLd), this nucleus is a prime candidate for early tuning to complex sounds, including conspecific signals. We have investigated the tuning properties of MLd neurons to either simple sounds such as white-noise and pure tones, or complex sounds, namely conspecific and heterospecific songs. Preliminary data show that neurons in MLd can be classified into two main categories: units that responded to all types of stimuli and units that showed a higher level of selectivity. These selective neurons could represent a first stage in the processing of complex song.
