Experience-dependent plasticity in the preattentive processing of linguistic pitch contours: Evidence from crosslanguage and crossdomain studies

Bharath Chandrasekaran, Purdue University

Abstract

Using the mismatch negativity (MMN), a cortical index of preattentive change-detection, it is well established that language experience influences the automatic cortical processing of segmental information in speech, i.e. consonants and vowels. The studies included in this dissertation shed light on the nature and limits of experience-dependent plasticity related to processing of linguistic pitch, a suprasegmental cue. Study 1 measured MMN responses from Chinese and English listeners listening to sequences of Mandarin tones in a speech context. The results suggest that cortical processing of linguistic pitch contours may be shaped by the saliency of acoustic dimensions underlying the pitch patterns of a particular language. Study 2 examined the number and relative weighting of dimensions underlying the preattentive processing of lexical tones by applying multidimensional scaling (MDS) analysis on the MMN responses from Chinese and English listeners. MDS revealed two dimensions common to Chinese and English, interpretively labeled as ‘height’ and ‘contour.’ The ‘contour’ dimension was found to be more important for Chinese than English participants suggesting that specific pitch dimensions are differentially weighted by language experience. In study 3, we examined whether experience-dependent plasticity is specific to speech by eliciting MMN responses to nonspeech iterative ripple noise (IRN) stimuli in a crosslanguage (Chinese, English) design. Results from support the notion that experience-dependent plasticity is not restricted to the speech-domain. Study 4, using a crosslanguage design, explored the extent to which acoustic versus phonetic change detection processes contribute to experience-dependent plasticity of linguistic pitch contours at attention-dependent and preattentive stages of processing. Findings suggest that acoustic features of pitch contours, regardless of their categorical status, may drive experience-dependent neural plasticity at early cortical stages of processing. At attentive stages of processing, however, perception is strongly influenced by tonal categories. Studies 5 and 6 were designed to examine whether neuroplasticity to linguistic pitch is domain-specific. The two studies examined MMN responses in a cross-domain design (Chinese, musicians) to nonspeech Mandarin linear and curvilinear pitch contours. Results show that neuroplasticity to time-varying pitch contours is highly sensitive to the context of the long-term experience (music vs. language).

Degree

Ph.D.

Advisors

Krishnan, Purdue University.

Subject Area

Linguistics|Psychobiology|Cognitive psychology

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