Magnetoencephalographic (MEG) localization of the auditory N400m: effects of stimulus duration

The effects of stimulus duration on the elicitation and equivalent current dipole (ECD) localization of the auditory N400(m) were studied in two subje ct groups, either familiar or unfamiliar with Finnish language, using a sen tence-processing paradigm with incongruent ending words of either short or long duration. tong-duration words elicited a broad response at around 400 ms, the generator location(s) of which could not be reliably determined usi ng ECD estimation. In contrast, short-duration words elicited a sharp, stro ng-amplitude response at about 400 ms latency and it's source location coul d be reliably determined as being in the vicinity of auditory cortex. Subje cts unfamiliar with the Finnish language elicited no response at the 400 ms range. Thus, the use of short-duration words appears to be an important pr erequisite for-the elicitation and localization of N400m. The differential amplitude behaviour of the N400m between the two subject groups further sug gests that comprehension of the semantic content of the speech message is a lso required. NeuroReport 12:249-253 (C) 2001 Lippincott Williams & Wilkins .