Poster Session B, Sunday, March 24, 8:00 – 10:00 am, Pacific Concourse
Prefrontal cortex aids adaptation to accented speech
Esti Blanco-Elorrieta1,2, Laura Gwilliams1,2, Alec Marantz1,2, Liina Pylkkänen1,2; 1New York University, 2NYU Abu Dhabi Institute
Speech is a complex and ambiguous acoustic signal that significantly varies across speakers; yet, the human experience is typically one of effortless comprehension. In the case of accents, a ubiquitous source of this variability, listeners are able to adapt to non-canonical pronunciations rapidly. The goal of this study is to build upon previous behavioural literature to uncover the neurobiological bases of this perceptual attunement process. 24 native English participants were exposed to spoken words of a “canonical” American talker and an “accented” talker. Accents contained systematic phonological substitutions (e.g. [s]<->[sh]). Participants performed a simple word-picture matching task while magneto-encephalography (MEG) was recorded. We found that activity in the auditory cortex, superior and middle temporal gyrus varied depending on accentness, and this was not influenced by exposure. Critically, prefrontal regions did show an interaction between the presence of an accent and amount of exposure: while activity decreased for canonical speech as the experiment went on, the amount that accented speech engaged prefrontal regions remained constant. Grainger causality analyses revealed that these responses emerged in prefrontal and travelled to auditory regions, suggesting the recruitment of top-down processing to decode the accented signal, and plausibily an adaptation mechanism based on error detection. In sum, our results provide the first characterization of how the perceptual system adapts to systematic yet idiosyncratic variations of speech, and posits the prefrontal cortex as the locus of the necessary signals to recalculate phonetic classification and subsequent identification of lexical items.
Topic Area: PERCEPTION & ACTION: Audition