The Lombard Effect: From Acoustics to Neural Mechanisms

Understanding the neural underpinnings of vocal-motor control in humans and other animals remains a major challenge in neurobiology. The Lombard effect - a rise in call amplitude in response to background noise - has been demonstrated in a wide range of vertebrates. Here, we review both behavioral and neurophysiological data and propose that the Lombard effect is driven by a subcortical neural network, which can be modulated by cortical processes. The proposed framework offers mechanistic explanations for two fundamental features of the Lombard effect: its widespread taxonomic distribution across the vertebrate phylogenetic tree and the widely observed variations in compensation magnitude. We highlight the Lombard effect as a model behavioral paradigm for unraveling some of the neural underpinnings of audiovocal integration.