Auditory Evoked Magnetic Fields to Tones and Pseudowords in Healthy Children and Adults

摘要

Neuromagnetic responses to tones and pseudowords were measured with a 24-channel magnetometer in 9 adults and in 23 children aged 0.3 through 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, 100, 200, and 250 ms, respectively. A biphasic P1m-N1,2m response with peaks 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 children. N1m amplitude suppression at short ISIs was stronger in children than adults, and may reflect a longer refractory period of the N1 generator neurons during early childhood than later in life. The peak latencies of P1m, N1m, and N2m decreased with age, most rapidly before age 7. All deflections originated in nearby cortical areas within the posterior sylvian fissure, and can serve as functional landmarks for that anatomic area.