Responses of Human Neonates to Highly Diluted Odorants from Sweat
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Conjugated forms of odorants contributing to sweat odor occur not only in human sweat but also in amniotic fluid, colostrum, and milk. However, it is unclear whether the released odorants are detected and hedonically discriminated by human newborns. To investigate this issue, we administered highly diluted solutions of (R)/(S)-3-methyl-3-sulfanylhexan-1-ol (MSH), (R)/(S)-3-sulfanylhexan-1-ol (SH), (E)/(Z)-3-methylhex-2-enoic acid (3M2H), and (R)/(S)-3-hydroxy-3-methylhexanoic acid (HMHA) to 3-d-old infants while their respiratory rate and oro-facial movements were recorded. Adult sensitivity to these odorants was assessed via triangle tests. Whereas no neonatal stimulus-specific response was found for respiratory rate, oro-facial reactivity indicated orthonasal detection of MSH and SH by male neonates, and of HMHA by the whole group of neonates. Dependent on the dilution of odorants, newborns evinced neutral responses or longer negative oro-facial expressions compared with the reference stimuli. Finally, newborns appeared to be more sensitive to the target odorants than did adults.
KeywordsOlfaction Human newborn 3-methyl-2-hexenoic acid 3-hydroxy-3-methylhexanoic acid 3-sulfanyl-1-hexanol 3-methyl-3-sulfanylhexan-1-ol
We express our gratitude to the parents who agreed to let their infants participate in this study, and to the midwives and staff at the maternity ward of Dijon University Hospital for their kind and invaluable support. Dr. Catherine Dacremont is thanked for continued discussion relating to this work. The constructive comments by two anonymous referees are gratefully acknowledged.
This work was supported by grants from the Bavarian Research Foundation (Bayerische Forschungsstiftung), the Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung), the Cusanuswerk Bischöfliche Studienförderung, the Regional Council of Burgundy (Conseil Régional de Bourgogne), the French National Research Agency (ANR Colostrum), and the National Center for Scientific Research (Centre National de la Recherche Scientifique).
Compliance with Ethical Standards
All procedures performed in this study were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Conflict of Interest
Helene M. Loos, Sébastien Doucet, Fanny Védrines, Constanze Sharapa, Robert Soussignan, Karine Durand, Paul Sagot, Andrea Buettner, and Benoist Schaal declare that they have no conflict of interest.
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