NEONATAL RESPONSIVENESS TO THE ODOR OF AMNIOTIC AND LACTEAL FLUIDS - A TEST OF PERINATAL CHEMOSENSORY CONTINUITY

The head-orientation response of 2- and 4-day-old breast-feeding neona tes was studied in paired-choice odor tests. Three tests were conducte d on day 2 (amniotic fluid [AF] versus Colostrum; AF versus Control; C olostrum versus Control) and on day 4 (AF versus Milk; AF versus Contr ol; Milk versus Control). At 2 days, both AF and Colostrum elicited po sitive orientation when presented simultaneously with the control stim ulus, indicating that both odors were detectable to the infants. Howev er, no differential responses were noted when AF and colostrum were pr esented concurrently, suggesting that both of these substrates were tr eated as similar sensorily and/or hedonically. On day 4, the odors of AF and transitional milk elicited attraction responses when presented in competition with a control stimulus. When the odor of milk was pres ented simultaneously with the odor of AF, the former elicited longer h ead orientation. Thus, within the first 4 days of life olfactory selec tivity changes from a null preference between cues carried in AF and i n colostrum to a positive preference for cues carried in postamniotic odors, that is, breast milk. hn additional experiment indicated that S -day-old neonates orient longer toward the odor of their own.AF than t oward the odor of alien AF, showing that prenatal odors elicit selecti ve responding for some time after birth. Altogether these results were interpreted as supporting the hypotheses that prenatal experience mig ht:influence the earliest odor preferences in the breast-feeding human neonate and that these preferences rapidly evolve according to postna tal experience.