Preattentive Auditory Processing of Pitch Glide

Pitch glide is a continuously rising or falling characteristic of pitch contour in tonal languages, such as Mandarin Chinese, and is critical for tonal speech comprehension. An interesting but unanswered question is whether pitch glide can be automatically processed at a preattentive stage in the brain. To address this question, we used iterated rippled noise (IRN) as a linguistically meaningless nonspeech stimulus to evoke mismatch negativity (MMN), an indicator of automatic auditory processing, from native speakers of Mandarin Chinese. To create a pitch glide contrast, we frequently presented IRN to the subjects with a flat pitch contour at different pitch levels and infrequently varied its pitch contour from flat to flat-rise. The pitch glide contrast evoked a robust MMN response with the peak latency around 155 ms after the rising onset. In addition, the steeper rising slope was, the larger MMN was evoked. These results suggest a preattentive auditory analysis of pitch glide information, which may be fundamental for contour tone perception.