From Vocal to Neural Encoding: A Transversal Investigation of Information Transmission at Long Distance in Birds

Abstract

Acoustic communication in the natural world requires both emitter and receiver to adapt to the loss of information due to the transmission of sound in the environment. At the emitter’s end, encoding information into propagation-resistant features may ensure its transmission on ecologically relevant distances. At the receiver’s end, making sense of the degraded signal merged with added noise enables animals to produce behaviorally relevant responses. In this chapter, I use a songbird model to investigate both sides of the transmission chain, examining how individual vocal signatures are encoded, degraded and finally discriminated, with a particular emphasis on the receiver’s neural encoding of degraded information. The cornerstone of this focal study is the use of naturally degraded vocalizations, combining various aspects of the challenges faced by animals performing auditory scene analysis, in order to address the complexity of real-life ecological constraints. While the individual signature of our songbird model, the zebra finch, is very resistant to propagation-induced degradation, single neurons in the avian auditory cortex have the ability to discriminate highly degraded individual vocal signatures, without prior familiarization or training. In the light of past and recent findings in birds and mammals, I delve further into significant insights uncovered by the research on neural processing and ensemble coding, and discuss the roles of perceptual plasticity and learning in the neural interface between brain and behavior.