Song learning, social attention, and brain development in birds
Résumé
Birdsong learning and human language development showed numerous parallels that made song of birds a rich and useful model for understanding environmental pressures that allow vocalisations set up. In birds, song learning is a complex phenomenon that involves development of typical specific vocal structures and the correct usage of these vocalisations. Moreover, neuro-ethological studies on songbirds provide opportunities to link brain development and behavioural expression. Social environment plays a key role in these processes but mechanisms still remain poorly understood. A lack of social stimulation reduces song learning and alters the development of brain structures involved in song perception and social segregation leads to similar effects on neuronal development that a physical separation. Our studies on European starling song development indicated that young birds have to develop strong social links with tutor in order to develop fully typical song. An equilibrate ratio between adult and young appeared to the more efficient situation to elicit learning and seemed to enhance attention focalisation towards tutor. We showed also that socially pertinent visual stimuli coupled with species typical song increased both the quality and the quantity of song copying as well as long term memory of song learned. Multimodal stimulations are also important in the development of auditory area. Indeed, more than half of field L neurons are sensitive to the association between the song and the image of the singer. Selective attention, based on inter modal and socially pertinent stimulation could be a key to understand the link between "social brain" and "vocal brain" in bird and also in human.