Evidence for dissociation of spatial and nonspatial auditory information processing

Several lines of evidence suggest that visual information processing is seg regated into the ventral "what", and dorsal "where" pathways. But the quest ion whether information processing in the auditory system is also parceled to spatial and nonspatial domains remains open. In the present study, we pe rformed simultaneous EEG and MEG recordings during auditory location and pi tch delayed matching-to-sample tasks to find out whether working memory pro cessing of the auditory stimulus attribute affects the transient components of the evoked potentials. In both tasks, identical blocks of tone stimuli of one of two frequencies were presented in one of two locations; the only difference between the tasks was the instruction to attend either to the fr equency or to the location. In the match condition, the NI latency was shor ter and the N1m amplitude larger in the location task compared to the pitch task. Furthermore, the right-hemisphere generator of N1m elicited in the m atch condition of the location task was situated significantly medially to the, N1m generator in the match condition of the pitch task. Latency and am plitude task-related differences in the N1/N1m components as well as the so urce location differences indicate at least partial segregation of neuronal mechanisms involved in working memory processing of spatial and nonspatial auditory information. (C) 2001 Academic Press.