Mismatch negativity of higher amplitude for melodic ascendance than descendance.

The auditory system prefers, presumably because of evolutionary adaptation, melodically upward over downward steps in sound frequency. The mismatch negativity (MMN) of event-related potentials (ERPs) to auditory oddball stimuli, an index of preattentive auditory change detection, is also augmented for the upward relative to the downward steps. We aimed to test whether this melodic MMN asymmetry shows specificity to the oddball stimuli. Auditory ERPs were recorded in adult humans during a visual task. In an oddball condition, a repeated 400 Hz tone was occasionally (P=0.01) replaced either by a 380 Hz or by a 420 Hz tone. In a same-rate condition, the tones of the three frequencies occurred at equal probabilities (P=0.33). In the oddball condition, frontally augmented ERPs of negative polarity (MMN) were found to be of higher amplitude for the 420 Hz tone than for the 380 Hz tone. In the same-rate condition, ERPs did not distinguish between the tones. The findings associate the melodic MMN asymmetry with the neural detection of oddball tones in particular.