TEMPORAL STABILITY IN THE DISTRIBUTION OF BEHAVIORAL STATES FOR INDIVIDUAL HUMAN FETUSES

Although behavioral state analyses have been useful in differentiating between groups of normal and at-risk fetuses, the large between-subje ct differences in the percent time spent in the various behavioral sla tes poses a major obstacle in identifying abnormal neurological functi oning in individual fetuses. Does this variability represent a true di fference in state organization between fetuses, or does it simply refl ect individual fluctuations in state control at the time of observatio n? To answer this question, we examined each of 33 human fetuses for 4 h on three separate days between 38 and 40 weeks gestation. The perce nt time spent in each behavioral state and in transition and insertion periods was determined for each of the three 4-h study sessions, and within-subject analysis of variance was performed to obtain an objecti ve measure of state profile consistency for each fetus. We found that, on the average, fetuses exhibited remarkable within-subject consisten cy in their state profiles. However, even among this group of low-risk fetuses, there were significant differences in the degree of state or ganization achieved by individual fetuses. These findings, which indic ate the existence of a well-developed central nervous system before bi rth, suggest that individual differences in the consistency of behavio ral state profiles may be indexing important between-subject differenc es in neurological development. (C) 1997 Elsevier Science Ireland Ltd.