Increment and decrement tone frequency effects in English-speaking adults

Mismatch negativity (MMN) has been shown to vary in amplitude and latency depending on deviance magnitude. However, how tone deviance direction affects its generation is poorly understood due to paucity of data. The present study sought to determine whether increment and decrement frequencies with deviance magnitudes of 20, 40, and 50 Hz yield differential MMN responses. English-speaking adults were presented two sets of standard and deviant pure tones in a passive event-related potential (ERP) oddball paradigm. Both stimulus sets had the same standard tone of 200 Hz. Each standard tone was accompanied by a set of either increment or decrement deviant tones. The increment tones were 220, 240, and 250 Hz, and the decrement tones were 180, 160, and 150 Hz. Thus, regardless of direction, deviance magnitudes were kept the same at 20 Hz, 40 Hz, and 50 Hz across each stimulus set. Results showed that ERP amplitudes varied according to deviance direction. Decrement stimuli of 160 Hz and 150 Hz elicited larger MMN responses than their corresponding increment stimuli (240 Hz and 150 Hz). These outcomes are consistent with data that indicate that the perception of low and high pitch is mediated by differential discrimination thresholds.