Pitch processing of dynamic lexical tones in the auditory cortex is influenced by sensory and extrasensory processes.

Abstract

The aim is to evaluate how language experience (Chinese, English) shapes processing of pitch contours as reflected in the amplitude of cortical pitch response components. Responses were elicited from three dynamic curvilinear nonspeech stimuli varying in pitch direction and location of peak acceleration: Mandarin lexical Tone2 (rising) and Tone4 (falling), and a flipped variant of Tone2, Tone2' (nonnative). At temporal sites (T7/T8), Chinese listeners' Na-Pb response amplitudes to Tones2 and 4 were greater than those of English listeners in the right hemisphere only; a rightward asymmetry for Tones2 and 4 was restricted to the Chinese group. In common to both Fz-to-linked T7/T8 and T7/T8 electrode sites, the stimulus pattern (Tones2 and 4> Tone2') was found in the Chinese group only. As reflected by Pb-Nb at Fz, Chinese subjects' amplitudes were larger than those of English subjects in response to Tones2 and 4, and Tones2 and 4 were larger than Tone2', whereas for English subjects, Tone2 was larger than Tone2' and Tone4. At frontal electrode sites (F3/F4), regardless of component or hemisphere, Chinese subjects' responses were larger in amplitude than those of English subjects across stimuli. For either group, responses to Tones2 and 4 were larger than Tone2'. No hemispheric asymmetry was observed at the frontal electrode sites. These findings demonstrate that cortical pitch response components are differentially modulated by experience-dependent, temporally distinct but functionally overlapping, weighting of sensory and extrasensory effects on pitch processing of lexical tones in the right temporal lobe and, more broadly, are consistent with a distributed hierarchical predictive coding process.