| Abstract: | Two studies of motor response thresholds (RTs) to electricalstimulation at the wrist in newborns were done. Adult controls were employed. Strength-duration curves for infant and adult RTs and adult sensory thresholds (STs) were plotted. RTs of infants are approximately 1.75 times higher than those for adults. Adult RTs are consistently 3 to 4 times higher than STs. Test-retest reliabilities were satisfactory. RTs of half of the newborns were notably variable. No relationship between RT variability and stages of the neonatal wakefulness-sleep cycle could be established, but RTs were significantly, although not markedly, higher during rapid-eye-movement (REM) episodes than during nREM. For evoked potential studies with newborns it has been decided to use as a stimulus a constant-current square-wave electrical pulse of 0.5 msec duration at RT during nREM sleep. |
