Neural sensitivity to phonetic category structure

Abstract

Much of the recent work on the neural bases of speech perception has concentrated on the phenomenon of categorical perception, and in particular the observation that listeners appear to ignore or be insensitive to acoustic variation within the phonetic category. This has led to a search for phoneme-level processes in the brain, while neglecting a crucial aspect of the speech category, namely, that phonetic categories contain rich internal structure. Pioneering research on phonetic category structure from Joanne L. Miller and her colleagues shows us that listeners are not only sensitive to variation within the phonetic category, but that this sensitivity is modulated by speech rate, context, and talker identity. Recent work from our group using fMRI shows that the neural systems underlying phonetic processing are likewise sensitive to phonetic category structure, with neural responses in the temporal lobes that reflect to the “goodness of fit” of a token to its phonetic category. In this paper I discuss evidence for the neural encoding of phonetic category structure, and in particular the sensitivity of this encoding to context and to experience.