Luc Marlier

Facial and Autonomic Responses to Biological and Artificial Olfactory Stimuli in Human Neonates: Re-Examining Early Hedonic Discrimination of Odors

Responses of awake and asleep 3-day-old human neonates were recorded to the presentation of artificial (vanillin, butyric acid, formula milks) and biological (breast milk, amniotic fluid) odorants matched on subjective intensity and trigeminal dimensions. The responses included behavioral (facial and oral movements) and autonomic (respiration, differential skin temperature) measures. The neonates reacted with significant facial and respiratory changes to low concentrations of olfactory stimuli during the various behavioral states. The analysis of olfacto-facial configurations revealed that behavioral markers of disgust (nose wrinkling, upper lip raising) discriminated between some odors judged as being pleasant and unpleasant by adult raters (vanillin vs. butyric acid). However, although some early predisposition to process the affective significance of stimuli may be suggested, no convincing evidence was obtained that neonates discriminated the hedonic valence of odors within the same perceptual space as adults. Finally, neonates evinced a differential pattern of respiratory responding to the presentation of milk odors according to the mode of feeding (breast vs. bottle feeding), suggesting that early olfactory discrimination may be mediated by stimuli with high ecological salience.

Olfactory function in the human fetus: evidence from selective neonatal responsiveness to the odor of amniotic fluid.

This study was aimed at characterizing the level of specificity of the human newborns response to an odor experienced in utero. Three groups of breast-fed infants and 3 groups of bottle-fed infants were examined on Postnatal Day 3 for their differential head-turning response when exposed to paired-choice tests contrasting the odors of either familiar (f) amniotic fluid (AF) or nonfamiliar (nf) AF or either of these AF odors and a control (C) stimulus. In fAF versus nfAF tests, the infants oriented preferentially to the odor of fAF, regardless of their feeding regimen (i.e., of their postnatal reexposure to AF-like cues in maternal milk). The fAF or nfAF versus C tests showed that this response pattern was caused by a true positive orientation toward fAF and not by avoidance from nfAF odor. This highly selective neonatal response to fAF odor is consistent with the hypothesis that the human fetus can detect and store the unique chemosensory information available in the prenatal environment and that this information becomes coupled with positive control of behavior.

Responsiveness to the Odour of Amniotic Fluid in the Human Neonate

Two-day-old newborns were videotaped during a double-choice test contrasting the odours of their amniotic fluid (AF) and of a control stimulus. To control for early motor asymmetries, the lateral position of both stimuli was balanced both between and within subjects. On average, neonates oriented their nose for a significantly longer duration toward the odour of AF. Regardless of the nature of the stimulus, neonates also evinced a marked head-turning bias to the right side. The nature of the odour stimulus and side of presentation interacted so that infants turned their nose longer to the AF odour when it was presented from the right side. These data indicate that newborns can detect the AF odour, and that they remain attracted towards it for at least 2 days after birth.

Olfactory Stimulation Prevents Apnea in Premature Newborns

Objective. Methylxanthines and doxapram are currently used to treat apnea of prematurity but are not fully effective and often present undesirable side effects. The present study examines whether exposure to an odor known to modulate the infants respiratory rate could reduce the frequency of apneic spells. Method. Fourteen preterm newborns born at 24 to 28 gestational weeks presenting recurrent apnea despite caffeine and doxapram therapy were exposed to a pleasant odor diffused during 24 hours in the incubator. Efficiency of the olfactory treatment was judged by comparing frequency and severity of apneas occurring during the day of odorization with that observed the day before (baseline) and the day after (posttreatment control). Apnea was defined as any complete cessation of breathing movements for >20 seconds, or less if associated with hypoxia or bradycardia. Results. Concerning all types of apneas, a diminution of 36% was observed and seen in 12 of 14 infants. Apneas without bradycardia were reduced (44%) during the day with odorization, and this diminution affected all the infants. The frequency of apnea with moderate bradycardia (heart rate between 70 and 90 beats per minute) was maintained while the frequency of apnea associated with severe bradycardia (heart rate <70 beats per minute) decreased strongly (45%) and affected all the infants. No side effects were observed. Conclusion. The introduction of a pleasant odor in the incubator is of therapeutic value in the treatment of apneas unresponsive to caffeine and doxapram.

Bottle-fed neonates prefer an odor experienced in utero to an odor experienced postnatally in the feeding context

The head-orientation response of 2- and 4-day-old bottle-feeding neonates was studied in paired-choice odor tests. Three tests were conducted at Days 2 and 4 after birth to assess the development of the relative response between two salient odors from the prenatal and postnatal environments: (a) amniotic fluid (AF) versus formula milk (FM), (b) FM versus control stimulus (distilled water), and (c) AF versus control stimulus. At both ages, AF and FM elicited positive orientation when presented simultaneously with the control stimulus, indicating that both odors were detectable and attractive to the infants. However, when AF and FM were presented concurrently, the infants expressed significantly longer orientation response toward AF odor than toward FM odor at the age of 2 and 4 days. Within the first 4 days of life, bottle-feeders thus display olfactory preference for a prenatal substrate over a postnatal substrate to which they were recurrently exposed in the feeding situation.

Maternal and Paternal Perception of Individual Odor Signatures in Human Amniotic Fluid – Potential Role in Early Bonding?

Both human mothers and fathers are able to discriminate the odors of 2 samples of amniotic fluid (AF), one from their own newborn infant and one from an unrelated infant. Moreover, both parents are able to accurately identify the odor of the AF from their own infant. They report qualitative similarity descriptions of their infant’s AF odor to the odor of the actual newborn infant and to the odor of the mother, especially at the end of gestation. These data indicate that human AF carries individualized odor properties, the roles of which in the initiation of parent-infant interactions are hypothesized.

Exploring the olfactory environment of premature newborns: a French survey of health care and cleaning products used in neonatal units.

Aim:  To assess the main determinants of the newborn’s nosocomial olfactory environment.

Olfaction in Premature Human Newborns: Detection and Discrimination Abilities Two Months Before Gestational Term

It remains unclear at what stage during early ontogeny humans do have the ability to process olfactory information. Numerous studies have demonstrated olfactory detection, discrimination, preference and memory in full-term infants examined within hours or days after birth (see Schaal, 1988 for a review). Recent data have revealed that olfaction is functional before birth. Newborns evince selective responsiveness to complex or pure odorants, which they could only, or mainly contact in the prenatal environment (Marlier et al., 1998; Schaal et al., 1998, 2000).

Fetal Olfactory Cognition Preadapts Neonatal Behavior in Mammals

Several evolutionary adaptations have appeared in mammals that allow them to cope with the physical challenges presented during the early postnatal period. One set of general adaptations facilitates the maternal transmission of sensory information to the fetal and neonatal niches. The other set of adaptations results in fetuses and neonates developing the necessary sensory, cognitive, and motor abilities to be fully prepared to utilize maternally-provided information, even during the traumatic interval surrounding birth.

A safe, low-cost, and portable instrumentation for bedside time-resolved picosecond near infrared spectroscopy

Continuous wave Near InfraRed Spectroscopy (NIRS) has been used successfully in clinical environments for several years to detect cerebral activation thanks to oxymetry (i.e. absorption of photons by oxy- and deoxy- hemoglobin) measurement. The goal of our group is to build a clinically-adapted time-resolved NIRS setup i.e. a setup that is compact and robust enough to allow bedside measurements and that matches safety requirements with human patients applications. Indeed our group has already shown that time resolution allows spatial resolution and improves sensitivity of cerebral activation detection. The setup is built with four laser diodes (excitation wavelengths: 685, 780, 830 and 870 nm) whose emitted light is injected into four optical fibers; detection of reflected photons is made through an avalanche photodiode and a high resolution timing module used to record Temporal Point Spread Functions (TPSF). Validation of the device was made using cylindrically-chaped phantoms with absorbing and/or scattering inclusions. Results show that recorded TPSF are typical both of scattering and absorbing materials thus demonstrating that our apparatus would detect variation of optical properties (absorption and scattering) deep within a diffusive media just like a cerebral activation represents a rise of absorption in the cortex underneath head surface.