Auditory brain map, effects of age

Brain maps of late auditory evoked cortical potentials were obtained with the Brain Atlas III system in school-aged children and adults. All subjects were judged as neurologically normal, right-handed, and having normal hearing. The stimulus was a 100 ms burst of 500 Hz pure tone at 75 dB HL presented separately to the left and right ear. The results showed a frontoparietal maximum of negative activity corresponding to N1 and designated as the focus of N1 (FN1). FN1 had latencies of 108 ms (left stimulation (stim] and 113 ms (right stim) and amplitudes of -6.0 microV (left stim) and -4.8 microV (right stim) in children and a latency of 90 ms and an amplitude of -6.5 microV in adults. Among the children, more had ipsilateral than contralateral FN1, usually on the right side. The distance between the centers of gravity of FN1s obtained on stimulation of the two ears was significantly smaller in the maps of children than adults (p less than 0.01). The present findings indicated that the topography of the electrical activity changes during adolescence.