Neuroplasticity in the processing of pitch dimensions: a multidimensional scaling analysis of the mismatch negativity

An auditory electrophysiological study was conducted to explore the influence of language experience on the saliency of dimensions underlying cortical pitch processing.

Mismatch negativity (MMN) responses to Mandarin tones were recorded in Chinese and English participants (n=10 per group) using a passive oddball paradigm. Stimuli consisted of three tones (T1: high level; T2: high rising; T3: low falling-rising). There were three oddball conditions (standard/deviant): T1/T2, T1/T3, T2/T3. In the T1/T2 and T1/T3 conditions, each tonal pair represented a contrast between a level and a contour tone; the T2/T3 condition, a contrast between two contour tones. Twenty dissimilarity matrices were created using the MMN mean amplitude measured from the Fz location for each condition per participant, and analyzed by an individual differences multidimensional scaling model.

Two pitch dimensions were revealed, interpretively labeled as 'height' and 'contour'. The latter was found to be more important for Chinese than English subjects. Using individual weights on the contour dimension, a discriminant function showed that 17 out of 20 participants were correctly classified into their respective language groups.

The MMN can serve as an index of pitch features that are differentially weighted depending on a listener's experience with lexical tones and their acoustic correlates within a particular tone space.