AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 2 496-R500, Copyright © 1991 by American Physiological Society
Characterization of electroencephalographic state in fetal baboons
R. I. Stark, J. Haiken, D. Nordli and M. M. Myers
Department of Pediatrics, Columbia College of Physicians and Surgeons, New York, New York 10032.
Long-term recordings of the electroencephalograms (EEGs) from the non-human
fetal primate have been visually scored for state. Data were obtained from
three fetuses using recently developed techniques for chronic
instrumentation of the pregnant baboon. Seven days or more after surgery,
nine chart records of 4-5 h in duration were analyzed. These records were
made during an interval in gestation from 143 to 153 days (term = 175 to
185 days). Criteria for differentiation of EEG state were based on the
presence (state 1) or absence (state 2) of trace alternant, which is the
predominant characteristic of EEG activity during quiet sleep in human
preterm and term infants. Two patterns of EEG activity were readily
distinguished at both standard (30 mm/s) and compressed (30 mm/min) EEG
chart speeds. On a minute-by-minute basis, there was an overall concurrence
of 82.9% for EEG state when scored from compressed and standard EEG
records. From the compressed records, state 1 was present on average 38.3%
of the time, with a mean epoch duration of 15.1 min, while epochs of state
2 averaged 25.9 min. We conclude that at least two EEG states are present
at this gestation in the fetal baboon. These two states can be reliably
defined visually by scoring methods directly comparable to those used for
EEG recognition of sleep states in the human newborn infant. To validate
the conclusion that these fetal state assignments based on patterns of EEG
activity correspond to sleep states, it will be necessary to determine if
the oscillations of other physiological parameters are coherent with these
patterns.
