Neural correlates of individual differences in processing of rising tones in Cantonese: implications for speech perception and production

Abstract

Two aspects of the F0 - the F0 level (high, middle, low) and the F0 contour (static, rising, falling) – are generally considered the perceptual correlates of lexical tones in tone languages, including Mandarin Chinese (Gandour, 1983), Cantonese (Khouw & Ciocca, 2007), and Thai (Gandour, Potisuk, & Dechongkit, 1994). Besides the dominant role of spectral information, much attention has recently been paid to the importance of temporal information in parsing the acoustic signal into relevant segments for decoding during auditory/speech processing (Luo & Poeppel, 2012). Acoustic cues from the temporal waveform envelope have also been shown to successfully cue tone perception in Mandarin Chinese (Whalen & Xu, 1992) as well as Cantonese (Zhou, 2012). Of the various cues to amplitude envelope, rise time, defined as the time taken for a sound to reach its maximum amplitude (Rosen, 1992), is proposed to be an important perceptual cue for the representation of amplitude envelope. The amplitude rise time has been found to be important in facilitating prosodic and syllable segmentation processes in children (Carpenter & Shahi, 2013; Leong, Hämäläinen, Soltesz, & Goswami, 2011), which are arguably critical for the formation of well-specified phonological representations (Goswami, 2011). Hence, one may question whether the rise time of sound amplitude envelope may likewise play a role in processing lexical tones. In other words, to process tones efficiently may entail the encoding of both spectral and temporal cues present in the speech signal to derive tone representations. The present study is the first examination of neural processes underlying the discrimination of the high rising and low rising tones T2/T5 in Hong Kong Cantonese (HKC) from two groups of typically-developed native speakers of HKC with comparable language and musical backgrounds. The participant groups represented, respectively, the pattern of good perception and good production of all Cantonese tones [+Per+Pro], and that of good perception of all tones but poor production of specifically the T2/T5 distinction [+Per-Pro]. Electrophysiological responses to the contrasts of pitch and amplitude envelope between T2 and T5 were measured to allow us to assess the timing and strength of neural activities associated with the auditory stimuli unfolding over time. Any difference in neural response between the two groups would shed light on how the acoustic cues of pitch and amplitude envelope are differentially represented in their auditory memory, and enable us to consider the relationship between perception and production.