Does a pitch center exist in auditory cortex? A mismatch negativity study

Abstract

Pitch sensation can be evoked by different acoustic cues which should be processed by different strategies for extracting pitch. However, in resent studies a general pitch center was hypothesized exist at some level of the auditory pathway for a general pitch sensation independent of other acoustic features. In this study, the existence of pitch center was examined by testing that whether the mismatch negativity (MMN) response, an index of preattentive auditory processing, can be elicited by pitch deviations in a passive oddball paradigm that composed of four different pitch-evoking stimuli (i.e., sinusoidal tone, resolved complex, iterated rippled noise, and pulse train). Although the pitch-evoking cues in these pitch-evoking stimuli were disparate, they evoked a fixed pitch of 200 Hz (or 283 Hz in a reversed oddball paradigm). Occasionally a deviant sound was encountered which evoked a different pitch (283 Hz, or 200 Hz in the reversed oddball paradigm). The results showed no significant MMN response was elicited by the deviant, regardless of the type of pitch-evoking stimuli, suggesting the absence of pitch center in the pre-attentive auditory processing stage.