AUDITORY-EVOKED MAGNETIC-FIELDS TO TONES AND PSEUDOWORDS IN HEALTHY-CHILDREN AND ADULTS

Neuromagnetic responses to tones and pseudowords were measured with a 24-channel magnetometer in nine adults and in 23 children, the latter aged 0.3-15 years. Both stimulus types elicited substantially similar responses in all subjects. At 0.9-s interstimulus interval (ISI), the adult response was a stable P1m-N1m-P2m-N2m sequence peaking at 50, 10 0, 200, and 250 ms, respectively. A biphasic P1m-N1,2m response with p eaks at 100 and 260 ms occurred in children up to 12 years of age. At longer ISIs (1.2-2.4 s), an adult-type N1m response appeared in most c hildren. N1m amplitude suppression at short ISIs was stronger in child ren than in adults and may reflect a longer refractory period of the N 1 generator neurons during early childhood than later in life. Peak la tencies of P1m, N1m, and N2m decreased with age, most rapidly < 7 year s of age. All deflections originated in nearby cortical areas within t he posterior sylvian fissure, and may serve as functional landmarks fo r that anatomic area.