[Morphophysiological analysis of the formation of mechanisms of the activity-rest cycle in human ontogenesis].

The natural behavior of normal and anencephalic fetuses at 20 to 41 weeks of the development was studied by ultrasound monitoring and continuous recording of heart rate (HR) and motor activity (MA), followed by processing and presentation on [symbol: see text]CM computer. The statistical characteristics of HR and MA changes in the anencephalic fetuses were corrected by the degree of CNS deficiency. The comparative study of 20 normal and 34 anencephalic fetuses showed: 1) when the spinal cord was present, stable HR (about 150 bpm) seems to be due to cardiac automatism and sharp decelerations unaccompanied by MA were recorded; 2) in fetuses with the medulla oblongata present showed a decrease in baseline HR up to 140 bpm, repeated pronounced decelerations and spontaneous single motor acts dissociated with the latter; 3) when a rudiment of the midbrain was present, some reductions in the amplitude of decelerations and manifestation of weak accelerations, cluster motor acts, brief episodes of the active state were revealed; 4) the quiet state was observed in fetuses with the cerebral cortex; 5) the rest-activity cycle formed with further differentiation of the cerebral cortex.