Sequential grouping of tone sequence as reflected by the mismatch negativity

The human sequential grouping that organizes parts of tones into a group was examined by the mismatch negativity (MMN), a component of event-related potentials that reveals the sensory memory process. The sequential grouping is accomplished by the combinations of some factors, e.g., temporal and frequency proximity principles. In this study, auditory oddball stimuli in which each of the stimuli consisted of series of tone bursts, were applied to the subjects, and the MMN elicited by the deviation of the frequency of the last tone in the stimulus was investigated. The relationship between the expected phenomena of sequential grouping of tones and observed magnitudes of MMN was evaluated. It was shown that the magnitudes of MMN changed according to the configuration (number of tones, frequency) of tone sequence to be stored. This result suggested that the sequential grouping of presented tones was achieved on the preattentive auditory sensory memory process. It was also shown that the relative change of MMN magnitudes corresponded to the conditions of sequential grouping, which had been proposed by the auditory psychophysical studies. The investigation of MMN properties could reveal the nature of auditory sequential grouping.