Spontaneous neuronal activity in fetuses and newborns.

We compared the magnetic cerebral activity of 10 fetal subjects at two different gestational ages. Spontaneous cerebral activity was recorded with a large array magnetometer specially designed to conform to the maternal gravid abdomen during the third trimester of pregnancy. We recorded each fetal subject at least twice: first at less than 36 weeks and again after 36 weeks gestational age. Pervasive signal artifacts of maternal magnetocardiogram (MCG), respiration, uterine wall contractions, and fetal magnetocardiogram were removed with special filtering that preserved fetal cerebral signals. We used ultrasound to locate the fetal head immediately before and after the magnetic recordings. Auditory and visual evoked responses were also recorded for each fetal subject. The calculated origin for the spontaneous cerebral signals was verified to be at the ultrasound location for the fetal head and to be similar to the calculated locations for the cerebral evoked responses. The recordings for each fetal subject at less than and greater than 36 weeks gestational age were compared to the expected EEG findings for premature infants at comparable post conceptual ages.