Mismatch between anticipated and actually presented sound stimuli in humans.

In a tone sequence of continuously ascending frequency or ascending intensity, a tone was occasionally repeated. The repeated tone elicited an anterior negative wave, the latency of which was comparable to the mismatch negativity. However, the amplitude of the negative wave was larger over the left hemisphere than over the right hemisphere. The negative wave might reflect a discrepancy between an expected tone and an actually presented tone.