Neural specializations for speech and pitch: moving beyond the dichotomies

Abstract

The idea that speech processing relies on unique, encapsulated, domain-specific mechanisms has been around for some time. Another well-known idea, often espoused as being in opposition to the first proposal, is that processing of speech sounds entails general-purpose neural mechanisms sensitive to the acoustic features that are present in speech. Here, we suggest that these dichotomous views need not be mutually exclusive. Specifically, there is now extensive evidence that spectral and temporal acoustical properties predict the relative specialization of right and left auditory cortices, and that this is a parsimonious way to account not only for the processing of speech sounds, but also for non-speech sounds such as musical tones. We also point out that there is equally compelling evidence that neural responses elicited by speech sounds can differ depending on more abstract, linguistically relevant properties of a stimulus (such as whether it forms part of one's language or not). Tonal languages provide a particularly valuable window to understand the interplay between these processes. The key to reconciling these phenomena probably lies in understanding the interactions between afferent pathways that carry stimulus information, with top-down processing mechanisms that modulate these processes. Although we are still far from the point of having a complete picture, we argue that moving forward will require us to abandon the dichotomy argument in favour of a more integrated approach.

Mapping the unconscious maintenance of a lost first language

“…For speakers of nontonal languages, right hemisphere frontal and temporal regions specialized for processing acoustic frequency information, such as nonphonemically relevant prosody and intonation, are activated when listening to tones (22,23). In contrast, speakers of tonal languages recruit relevant left frontal, temporal, and parietal-occipital language regions (24); left frontal operculum (25); and the left premotor cortex, pars opercularis, and pars triangularis (26) when processing lexical tone in various experimental paradigms.…”

Individual differences in the acquisition of second language phonology

“…In support of the idea that different learning mechanisms exist for speech and non-speech sounds, there exists evidence from other studies for speech-specific neural mechanisms when stimulus complexity is controlled (Liebenthal, Binder, Spitzer, Possing, & Medler, 2005;Scott, Blank, Rosen, & Wise, 2000;Scott, Rosen, Lang, & Wise, 2006), or when the same stimuli are first perceived as nonspeech and then later as speech (Dehaene-Lambertz et al, 2005;Dufor, Serniclaes, Sprenger-Charolles, & Démonet, 2007). More generally, it is likely that the neural mechanisms underlying the processing of abstract, linguistically relevant properties versus of the underlying acoustic characteristics of stimuli interact in a complex and non-exclusive manner, and that they depend on linguistic experience as well as on neural top-down processing mechanisms which interact with afferent pathways which carry stimulus information (Zatorre & Gandour, 2007).…”

Computational prosodic markers for autism

“…To illustrate this point, consider again the reported ASD-TD difference in the balance between pitch and duration in the Focus task. There is considerable evidence for lateralization of temporal and pitch processing in speech perception (for a recent review, see Zatorre & Gandour, 2008). Some studies indicate that temporal processing of auditory (including speech) input may be impaired in ASD (e.g., Cardy, Flagg, Roberts, Brian, & Roberts, 2004; Groen, van Orsouw, ter Huurne, Swinkels, van der Gaag, Buitelaar, et al, 2009), while pitch sensitivity may be a relative strength (e.g., Bonnel, Mottron, Peretz, Trudel, Gallun, E., & Bonnel, 2003).…”