Prominence of M50 auditory evoked response over M100 in childhood and autism.

This study investigated the 50 ms (M50) and 100 ms (M100) components of the auditory evoked field to explore their change during development. Using MEG, neuromagnetic fields elicited by a 1 kHz sinusoidal tone were recorded in adults and two groups of children and adolescents with typical development or autism spectrum disorder. M50 amplitude was larger in children than in adults, suggesting a developmental trajectory with M50 amplitude decreasing and M100 increasing with age. Child M50 and M100 latencies were prolonged relative to adults. Children with autism did not differ from control children with respect to these observations. The M50 in relation to the M100 is a robust index of early auditory system maturation suitable for future developmental investigations.