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Poster B55, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

Lexical tone processing with and without awareness in Cantonese-speaking congenital amusics: Evidence from event-related potentials

Caicai Zhang1,2, Jing Shao1;1The Hong Kong Polytechnic University, 2Shenzhen Institutes of Advanced Technology

Congenital amusia (amusia hereafter) is a neurodevelopmental disorder that impacts the perception of music negatively. Despite the well-studied behavioral deficits, a full understanding of the neural underpinnings of amusia remains to be achieved. It has been found that pre-attentive pitch processing was normal or nearly normal in amusics, as indicated by normal mismatch negativity (MMN) to pitch deviations, whereas attentive processing exhibited impairment, as indicated by the absence of P300 to the same pitch deviations. Many studies have found that amusia affects the perception of lexical tones in tonal language speakers behaviorally. The current study examined how lexical tones are processed with and without attention in a group of tonal language speakers with amusia, a question that has not be investigated before. Event-related potentials (ERPs) to Cantonese tone pairs with small pitch differences (mid level-low level, or T3-T6; high rising-low rising, or T2-T5) and large pitch differences (high level-low falling, or T1-T4) were examined in pre-attentive (MMN) and attentive (P300) conditions. Twenty-four Cantonese-speaking amusics and 24 controls participated in the experiment. The three tone pairs were presented in forward and backward order: /ji33/-/ji22/ (T3-T6), /ji22/-/ji33/ (T6-T3), /ji25/-/ji23/ (T2-T5), /ji23/-/ji25/ (T5-T2), /ji55/-/ji21/ (T1-T4), and /ji21/-/ji55/ (T4-T1). Each pair was presented in an oddball paradigm, with the first stimulus serving as the standard and the second stimulus as the deviant. The same set of stimuli was presented to the subjects in the pre-attentive (MMN) and attentive (P300) conditions. In the pre-attentive condition, amusics and controls exhibited similar MMN responses to all tone pairs. There was also a significant effect of tone pair, where the MMN elicited by T1-T4 and T3-T6 was significantly larger than that elicited by T2-T5. In the attentive condition, significant group differences were found in the time-windows of P3a (350-450 ms after auditory onset) and P3b (500-800 ms after auditory onset), where reduced P3 amplitude was elicited in the amusics. For the P3a amplitude, apart from the group effect, there was a significant effect of tone pairs, where T1-T4 elicited significantly larger amplitude than T3-T6, followed by T2-T5, but no interaction effect of group by tone pair. For the P3b amplitude, there was a significant group by tone pair interaction. Post-hoc analyses revealed that the significant group difference was mostly attributable to tone pairs with small acoustic differences. There was a significant group difference for T2-T5, and a marginally significant group difference for T3-T6, but no significant difference for T1-T4. In summary, the results revealed that without attention, normal MMNs were shown for the lexical tone pairs in the amusics; however, when required to actively detect the same tonal changes, the amusics showed reduced P3 amplitude, especially to the acoustically similar ones. These findings suggested that the amusic brain responds to lexical tone differences normally pre-attentively, but showed impairment at consciously detecting the same lexical tone differences, which are consistent with that the findings reported on non-tonal language speakers. These findings provide further insights on the neurodynamic functioning of the amusics in lexical tone perception.

Topic Area: Perception: Speech Perception and Audiovisual Integration

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