Auditory signal processing in communication: perception and performance of vocal sounds

Abstract

Learning and maintaining the sounds we use in vocal communication require accurate perception of the sounds we hear performed by others and feedback-dependent imitation of those sounds to produce our own vocalizations. Understanding how the central nervous system integrates auditory and vocal-motor information to enable communication is a fundamental goal of systems neuroscience, and insights into the mechanisms of those processes will profoundly enhance clinical therapies for communication disorders. Gaining the high-resolution insight necessary to define the circuits and cellular mechanisms underlying human vocal communication is presently impractical. Songbirds are the best animal model of human speech, and this review highlights recent insights into the neural basis of auditory perception and feedback-dependent imitation in those animals. Neural correlates of song perception are present in auditory areas, and those correlates are preserved in the auditory responses of downstream neurons that are also active when the bird sings. Initial tests indicate that singing-related activity in those downstream neurons is associated with vocal-motor performance as opposed to the bird simply hearing itself sing. Therefore, action potentials related to auditory perception and action potentials related to vocal performance are co-localized in individual neurons. Conceptual models of song learning involve comparison of vocal commands and the associated auditory feedback to compute an error signal that is used to guide refinement of subsequent song performances, yet the sites of that comparison remain unknown. Convergence of sensory and motor activity onto individual neurons points to a possible mechanism through which auditory and vocal-motor signals may be linked to enable learning and maintenance of the sounds used in vocal communication. This article is part of a Special Issue entitled "Communication Sounds and the Brain: New Directions and Perspectives".

Keywords: Area X; Area X (specialized region of the avian striatum); Av; CM; DLM; DMP; Field L; Field L (avian primary auditory cortex); HVC; HVC (abbreviation used as a proper noun); LLv; LMAN; MLd; MMAN; Medial magnocellular nucleus of the anterior nidopallium; NCM; NIf; Ov; RA; UVA; VP; VTA; caudal mesopallium; caudomedial nidopallium; hypoglossal nucleus, tracheosyringeal nerve (12th cranial nerve nucleus); lateral magnocellular nucleus of the anterior nidopallium; nXIIts; nucleus avalanche; nucleus dorsolateralis anterior, pars medialis; nucleus dorsomedialis posterior thalami; nucleus interface of the nidopallium; nucleus mesencephalicus lateralis, pars dorsalis; nucleus ovoidalis; nucleus uvaeformis; robust nucleus of the arcopallium; ventral nucleus of the lateral lemniscus; ventral pallidum; ventral tegmental area.