MEG sleep pattern dependence of auditory evoked fields in young infants.

We recorded magnetic auditory evoked responses (AERs) to brief 1 kHz tones in infants ranging in age from 1.5-8.5 weeks. Long continuous MEG recordings were collected with a 37-channel sensor and were classified into one of four patterns: low-amplitude irregular, high-amplitude slow, mixed, and REM-like sleep. The AERs were characterized by a monophasic deflection with nominal latency 250 msec, followed by a broader peak with opposite polarity and approximate latency 600 msec. No strong dependences on MEG sleep pattern were observed. The latency of the 250 msec component decreased with age, but the 600 msec component showed variable latency. The signal topography of both components was compatible with a source in the auditory cortex. We conclude that sleep state does not appreciably confound recording of the AER in young infants.