BRAIN INDEXES OF AUTOMATIC PATTERN PROCESSING

THE extent to which the auditory system automatically encodes simple a uditory patterns was investigated by recording event-related brain pot entials (ERPs) to non-attended sounds in subjects reading a book. ERPs were recorded to tones alternating regularly in pitch and to rare bre aks in the alternating sequence. In all conditions, breaks in the patt ern elicited a right hemisphere dominant fronto-central mismatch negat ivity (MNN) at a latency of 140-220 ms. The MMN increased in amplitude and decreased in latency with increasing pitch separation and stimulu s rate. The results suggest that the processing of auditory patterns o ccurs automatically and depends on a rapidly fading short-term acousti c memory.