Electrophysiological Evidence for an Early Categorical Processing of Tones

Previous studies discovered electrophysiological evidence for tone categorical effects with mismatch negativity (140 ms 250 ms), and P300 (300 ms 700 ms). The present study further investigates the detailed time course of categorical perception of pitch contours by native Mandarin speakers. N1 components (90 ms 150 ms) of within-category change, across-category change, and no-change conditions for speech and nonspeech stimuli were analyzed. The current results showed: 1) Speech sounds were detected early in comparison to non-speech sounds, as indexed by the shorter peak latency of N1; 2) Significant N1 amplitude difference between conditions of across-category change and no-change signified an early signature of tone categorical effect; 3) The tone categorical effect in terms of N1 amplitude existed only in speech context, suggesting a speech specific processing underlying speech perception.