Investigation on the ontogenesis in fetal learning and behavior.

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In this study, we aimed 1) to evaluate learning ability of the human fetus using the habituation and classical conditioning, 2) to clarify relationship between other behaviors and fetal learning in development, and 3) to adopt fetal learning to clinical evaluation in human fetus central nervous system function.We divided 26 fetuses at 32-37 weeks of gestation into 3 groups using combined criteria of gestational age and behavioral indicators. We investigated fetal habituation to vibroacoustic stimulation (VAS). Fetuses showed habituation from at least 32 weeks of gestation. Furthermore, fetuses less developed from behavioral standpoint took significantly more trials to achieve habituation than developed fetuses even in the same gestational age. Taken together with these data, it was proved that there was a relationship between aspects of behavioral development and habituation. Next, we tested whether a human fetus could form an association between an extrauterine tone and VAS using classical conditioning treatment. Two kinds of pure tone were used as the conditioned stimuli, one where a 500-Hz tone was always followed by a VAS of 80 Hz, the unconditioned stimulus (US), and another where a 1000-Hz tone was never followed by a VAS. In 3 human infants did not show significant response to either tone.These results indicating that there was a relationship between behavioral development and ability to habituate, that is, between the CNS development and habituation. The application of this technique to the evaluation of CNS abnormality should be considered.