Neural mechanisms of the Lombard effect

Alena Lemazina, Lisa Trost, Susanne Hoffmann

Birds use vocalizations in various behavioral contexts such as finding a mate and defending a territory. However, after the initial production, sound can be altered by ambient noise and initial physical properties of vocalizations can be lost. In group living birds for instance, vocalizations can be masked by sounds produced by conspecifics. Birds use different strategies to overcome the masking. The bird that is being masked can for example increase the amplitude of its vocalizations. This behavior is called “Lombard effect”. It has been suggested that the Lombard effect in mammals is elicited by a subcortical network, which can be modulated by cortical brain. To understand how the Lombard effect is controlled by the avian brain, we record simultaneous vocal and neural activity in domestic canaries while their vocalizations are masked by vocalizing conspecifics or playbacks of artificial noise. The results will help us to determine to which extent the bird’s vocal control system is involved in the amplitude adjustment of vocalizations and to which extent masking effects depend on the masker source