Significance of fetal behavioral studies

Observations of fetal behavior may help clarify developmental progression of central nervous system function. Lorenz hypothesized that one can presume brain function from behavior, and we have shown this concept could be adapted to the study of human fetuses. An interesting phenomenon is the correlation of fetal micturition with onset of eye movement (EM), a period that includes rapid eye movement (REM). In contrast, micturition rarely occurs during quiet sleep in neonates: Arousal signs are typically noted beforehand. We investigated to clarify the perinatal transition in behaviors by examining the relationship between onset of EM periods and micturition in human fetuses at term and in neonates. EM, crying, and eye-open periods were observed for 6 normal term neonates until micturition occurred. In 29 term fetuses, the time lag between onset of an EM period and micturition was measured using real-time ultrasound instruments. The time lag between onset of EM and micturition in neonates was significantly different (P > 0.05) from the time lag for term fetuses. The frequency of micturition within 8 minutes of EM onset was significantly lower in neonates (P > 0.05) than in term fetuses. The relationship between onset of EM periods and micturition differs between term fetuses and neonates less than one month of age, which suggests that the neuronal relationships among brain centers for these behaviors dramatically shift during the perinatal period.