Maturation of the somatosensory evoked potentials in normal infants and children, with special reference to the early N1 component.

The early components of the somatosensory evoked potential (SEP) were analysed in 39 normal newborns in REM sleep, 35 normal awake children between 1 month and 9 years and 16 normal awake adults. Electrical pulses were delivered at random intervals to fingers of the contralateral hand. The SEP were averaged from several electrodes in the parietal scalp focus and several runs were compared to estimate precise latencies and durations (Fig. 5, 6, 7). The system bandpass extended to 3 kc and many precautions were taken to exclude interference. The limb temperature was carefully maintained at normal value in order to avoid undue slowing of peripheral conduction velocity. The SEP presented markedly increased latencies for near-threshold stimuli (Fig. 3) while becoming even more focalised (Fig. 1). Background data were obtained in order to standardize the parameters for the maturation study (Fig. 2, 3, 4). In the children, the early negative component was found to undergo progressive changes. It was only at the age of about 8 years that the adult pattern was approached (Fig. 8, 9, 10, 11). The duration of the early negative N1 component decreased quite progressively. The latencies to onset and to peak were also shown to follow a highly consistent pattern when the body length of the subjects was taken into account (Fig. 9, 10). By dividing the data by the body length, functions were obtained which could be said to apply to a "standard" individual whose body length did not change from birth to adulthood and remained at one meter. Such plots made it possible to appreciate the true extent of the SEP maturational changes from birth. The quantitative data thus provided should serve as a useful reference for subsequent studies on developmental changes of the brain and for clinical applications to diseased children.