MISMATCH NEGATIVITY TO CHANGES IN A CONTINUOUS TONE WITH REGULARLY VARYING FREQUENCIES

By using the mismatch negativity (MMN) component of the event-related potential, it was demonstrated that changes within a repetitively presented tone pattern can be automatically (i.e., involuntarily and attention-independently) detected by the human brain. Patterns consisting of 5 tones, immediately succeeding one another and differing in frequency, were delivered to subjects reading a self-selected book. There was a frequent, ''standard'' (P = 0.90) and an infrequent, ''deviant'' (P = 0.10) pattern presented in random order. The deviant pattern elicited the MMN even when the auditory stimulation was continuous, that is, no empty between-pattern interval indicated the beginning of a tone pattern. It may be concluded that the MMN mechanism is not necessarily timed by an ''external'' reference but is able to use ''internal'' units extracted from the repetitive structure inherent in the incessant flow of acoustic signals. The MMN paradigm seems to provide a tool to illuminate the organization of acoustic signals into auditory units.