Neurophysiological and Behavioral Responses of Mandarin Lexical Tone Processing

Area of Science:

• Auditory Neuroscience
• Psycholinguistics
• Speech Perception

Background:

• Language experience shapes auditory perception, enhancing discrimination of speech contrasts.
• This enhancement occurs at both behavioral-perceptual and pre-attentive levels, evidenced by event-related potential (ERP) mismatch negativity (MMN) responses.
• Potential mechanisms include improved acoustic resolution and/or altered long-term memory representations in the auditory cortex.

Purpose of the Study:

• To investigate whether cross-linguistic differences in processing Mandarin lexical tone depend on acoustic resolution or long-term memory representations.
• To examine the role of interstimulus interval (ISI) duration in modulating auditory processing of lexical tones.

Main Methods:

• Utilized a passive, oddball discrimination task with short (approx. 600 ms) and long (approx. 2,600 ms) ISIs.
• Presented bisyllabic nonword tokens differing in Mandarin lexical tone categories using an oddball paradigm.
• Collected both event-related potentials (ERPs) and behavioral discrimination/identification data.

Main Results:

• Robust MMNs were observed for both easy and difficult lexical tone differences at short ISIs for both Mandarin and English speakers.
• At long ISIs, MMN amplitude remained stable or increased for Mandarin speakers but decreased for English speakers.
• Mandarin listeners exhibited a larger late negativity (LN) response and superior behavioral performance, particularly with similar tone pairs under long ISIs.

Conclusions:

• Acoustic correlates of lexical tone are robust and easily discriminated at short ISIs when auditory sensory memory is strong.
• Language-specific experience becomes crucial for robust lexical tone discrimination at longer ISIs (beyond 2.5 seconds).
• Findings suggest that long-term memory representations play a significant role in language-specific auditory processing.