The effect of labor on olfactory exposure learning within the first postnatal hour

Trajectories of brain and behaviour development in the womb, at birth and through infancy

Birth is often seen as the starting point for studying effects of the environment on human development, with much research focused on the capacities of young infants. However, recent imaging advances have revealed that the complex behaviours of the fetus and the uterine environment exert influence. Birth is now viewed as a punctuate event along a developmental pathway of increasing autonomy of the child from their mother. Here we highlight (1) increasing physiological autonomy and perceptual sensitivity in the fetus, (2) physiological and neurochemical processes associated with birth that influence future behaviour, (3) the recalibration of motor and sensory systems in the newborn to adapt to the world outside the womb and (4) the effect of the prenatal environment on later infant behaviours and brain function. Taken together, these lines of evidence move us beyond nature-nurture issues to a developmental human lifespan view beginning within the womb.

Dynamic developmental changes in neurotransmitters supporting infant attachment learning

Infant survival relies on rapid identification, remembering and behavioral responsiveness to caregivers' sensory cues. While neural circuits supporting infant attachment learning have largely remained elusive in children, use of invasive techniques has uncovered some of its features in rodents. During a 10-day sensitive period from birth, newborn rodents associate maternal odors with maternal pleasant or noxious thermo-tactile stimulation, which gives rise to a preference and approach behavior towards these odors, and blockade of avoidance learning. Here we review the neural circuitry supporting this neonatal odor learning, unique compared to adults, focusing specifically on the early roles of neurotransmitters such as glutamate, GABA (Gamma-AminoButyric Acid), serotonin, dopamine and norepinephrine, in the olfactory bulb, the anterior piriform cortex and amygdala. The review highlights the importance of deepening our knowledge of age-specific infant brain neurotransmitters and behavioral functioning that can be translated to improve the well-being of children during typical development and aid in treatment during atypical development in childhood clinical practice, and the care during rearing of domestic animals.

The frontal sharp transient in newborns: An endogenous neurobiomarker concomitant to the physiological and critical transitional period around delivery?

The frontal sharp transient (FST) consists of transient electrical activity recorded around the transitional period from the in to ex utero environment. Although its positive predictive value is assumed, nothing is known about its functionality or origin. The objectives were (i) to define its characteristics and (ii) to develop functional hypothesis. The 128-channels high-resolution electroencephalograms of 20 healthy newborns (37.1-41.6 weeks) were studied. The morphological and time-frequency characteristics of 418 FSTs were analyzed. The source localization of the FSTs was obtained using a finite element head model (5 layers and fontanels) and various source localization methods (distributed and dipolar). The characteristics (duration, slopes, and amplitude) and the localization of FSTs were not modulated by the huge developmental neuronal processes that occur during the very last period of gestation. The sources were located beneath the ventral median part of the frontal lobe around the interhemispheric fissure, suggesting that the olfactory bulbs and orbitofrontal cortex, essential in olfaction and the mother-infant attachment relationship, are likely candidates for the generation of FSTs. FSTs may contribute to the implementation of the functionalities of brain structures involved in the higher-order processing necessary for survival ahead of delivery, with a genetic fingerprint.

Three kinds of caesarean sections: the foetal/neonatal perspective

In the age of hospital births, it is commonplace to contrast the vaginal route and the abdominal route as the basic classification. From the "point of view" of the foetus/neonate, we provide reasons to contrast "birth without labour" (that is birth by pre-labour caesarean section) and all the other vaginal and abdominal modes of birth. From a great diversity of theoretical reasons, one can anticipate that babies born by pre-labour caesarean sections are different from the others. We also provide reasons to popularize the concepts of "in labour non-emergency caesarean sections" and "planned in-labour caesarean sections".

Neonatal Suckling, Oxytocin, and Early Infant Attachment to the Mother

The neuropeptide oxytocin (OT) promotes maternal care and social affiliation in adults but its importance in infant attachment still remains unknown. True animal models of infant attachment are extremely rare, and the sheep (in complement to non-human primates) is one of the few that provides the opportunity to investigate its neuroendocrinological basis. In the lamb, access to the udder has strong rewarding properties for the establishment of a preferential relationship with the mother. Therefore, the present study explored the possible involvement of OT through its release during close social contacts with the mother. The first experiment revealed that lambs having free access to the udder from birth onward developed, by 12 h of age, a clear preference for their mothers over another maternal ewe. Delaying access to the udder for six, four or even only 2 h starting at birth, by covering the ewe's udder, resulted in the lack of such a preference without affecting general activity. These effects persisted in most cases at 24 h but by 72 h of age a bond with the mother was clearly expressed. Experiment two showed that social interactions with the mother were followed by a release of OT in the plasma when lambs had the possibility to suckle. Non-nutritive interactions were without effects. Preliminary data on two subjects suggested that OT might also increase in the cerebrospinal fluid after suckling. Finally, in the third experiment, oral administration of a non-peptide OT receptor antagonist (L-368-899, Merck) over the first 4 h after birth led to decreased exploration of the mother's body compared to lambs receiving saline, and impaired the expression of a preference for the mother at 24 h. The effects were no longer observed at 48 h. Our findings demonstrate that both delayed access to the mother's udder and OT receptor antagonist alter the onset of mother preference in newborn lambs. This suggests that central OT facilitates the development of filial attachment through its release during suckling.

Birth signalling hormones and the developmental consequences of caesarean delivery

Rates of delivery by caesarean section (CS) are increasing around the globe and, although several epidemiological associations have already been observed between CS and health outcomes in later life, more are sure to be discovered as this practice continues to gain popularity. The components of vaginal delivery that protect offspring from the negative consequences of CS delivery in later life are currently unknown, although much attention to date has focused on differences in microbial colonisation. Here, we present the case that differing hormonal experiences at birth may also contribute to the neurodevelopmental consequences of CS delivery. Levels of each of the 'birth signalling hormones' (oxytocin, arginine vasopressin, epinephrine, norepinephrine and the glucocorticoids) are lower following CS compared to vaginal delivery, and there is substantial evidence for each that manipulations in early life results in long-term neurodevelopmental consequences. We draw from the research traditions of neuroendocrinology and developmental psychobiology to suggest that the perinatal period is a sensitive period, during which hormones achieve organisational effects. Furthermore, there is much to be learned from research on developmental programming by early-life stress that may inform research on CS, as a result of shared neuroendocrine mechanisms at work. We compare and contrast the effects of early-life stress with those of CS delivery and propose new avenues of research based on the links between the two bodies of literature. The research conducted to date suggests that the differences in hormone signalling seen in CS neonates may produce long-term neurodevelopmental consequences.

The Calming Effect of Maternal Breast Milk Odor on Term Infant: A Randomized Controlled Trial

Purpose: This study was carried out to assess the effect of the odor of breast milk and formula milk on reducing the acute pain of newborn infants during the heel-prick blood sampling. Methods: Eighty-four newborn were randomly assigned into two groups (formula milk group and breast milk group) with 42 infant searches. The pain that the newborn felt before, during, and after heel-prick blood sampling was assessed using Neonatal Infant Pain Scale; their heart rate and blood oxygen saturation were measured with a pulse oximeter. Saliva samples were taken from newborns before and after sampling, and their salivary cortisol level was measured. During sampling, the crying duration of newborn was recorded with a chronometer. Results: The pain threshold and heart rates of the newborn in the breast milk group were significantly lower than those in the formula milk group (p < 0.001). Salivary cortisol in the formula milk group increased and oxygen saturation levels in these infants decreased significantly more as compared to the breast milk group (p < 0.05). Conclusions: The odor of breast milk may be helpful in reducing the pain of newborn during heel-prick blood sampling.

Olfaction scaffolds the developing human from neonate to adolescent and beyond

The impact of the olfactory sense is regularly apparent across development. The fetus is bathed in amniotic fluid (AF) that conveys the mother's chemical ecology. Transnatal olfactory continuity between the odours of AF and milk assists in the transition to nursing. At the same time, odours emanating from the mammary areas provoke appetitive responses in newborns. Odours experienced from the mother's diet during breastfeeding, and from practices such as pre-mastication, may assist in the dietary transition at weaning. In parallel, infants are attracted to and recognize their mother's odours; later, children are able to recognize other kin and peers based on their odours. Familiar odours, such as those of the mother, regulate the child's emotions, and scaffold perception and learning through non-olfactory senses. During juvenility and adolescence, individuals become more sensitive to some bodily odours, while the timing of adolescence itself has been speculated to draw from the chemical ecology of the family unit. Odours learnt early in life and within the family niche continue to influence preferences as mate choice becomes relevant. Olfaction thus appears significant in turning on, sustaining and, in cases when mother odour is altered, disturbing adaptive reciprocity between offspring and carer during the multiple transitions of development between birth and adolescence. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

Cesarean Section or Natural Childbirth? Cesarean Birth May Damage Your Health

The increasing popularity of Cesarean birth has become a social concern in many countries. This paper reviews the literature on the effects of Cesarean section on children's psychological health. The results show that Cesarean birth may have adverse effects on children's sensory perception, sensory integration ability, neuropsychiatric development, and the infant-mother relationship. However, there remain deficiencies in extant research methods, research content, subject groupings, and interpretation of research results. Future research should improve research methods, broaden the research content, and refine the grouping of children born by Cesarean section. The exploration of neural mechanisms is also needed, as well as research directed toward suggesting effective interventions to reduce unnecessary Cesarean sections.

Responses of Human Neonates to Highly Diluted Odorants from Sweat

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.

The endocrinology of human caregiving and its intergenerational transmission

Variation in the quality of parental care has a tremendous impact on a child's social–emotional development. Research investigating the predictors of this variability in human caregiving behavior has mostly focused on learning mechanisms. Evidence is currently accumulating for the complementary underlying role of steroid hormones and neuropeptides. An overview is provided of the hormones and neuropeptides relevant for human caregiving behavior. Then the developmental factors are described that stimulate variability in sensitivity to these hormones and neuropeptides, which may result in variability in the behavioral repertoire of caregiving. The role of genetic variation in neuropeptide and steroid receptors, the role of testosterone and oxytocin during fetal development and parturition, and the impact of experienced caregiving in childhood on functioning of the neuroendocrine stress and oxytocin system are discussed. Besides providing a heuristic framework for further research on the ontogenetic development of human caregiving, a neuroendocrine model is also presented for the intergenerational transmission of caregiving practices. Insight into the underlying biological mechanisms that bring about maladaptive caregiving behavior, such as neglect and insensitive parenting, will hopefully result in more efficient approaches to reduce the high prevalence of such behavior and to minimize the impact on those affected.

Physiological mechanisms, behavioral and psychological factors influencing the transfer of milk from mothers to their young

This article is part of a Special Issue "Parental Care".Producing milk to support the growth of their young is a central element of maternal care in mammals. In spite of the facts that ecological constraints influence nursing frequency, length of time until weaning and the composition of milk, there is considerable similarity in the anatomy and physiology of milk production and delivery across mammalian species. Here we provide an overview of cross species variation in nursing patterns and milk composition as well as the mechanisms underlying mammary gland development, milk production and letdown. Not all women breastfeed their infants, thus in later sections we review studies of factors that facilitate or impede the initiation and duration of breastfeeding. The results of these investigations suggest that the decisions to initiate and maintain breastfeeding are influenced by an array of personal, social and biological factors. Finally, studies comparing the development of breastfed and formula fed infants as well as those investigating associations between breastfeeding, maternal health and mother/infant interaction are reviewed. Leading health agencies including the World Health Organization and CDC advocate breastfeeding for at least the first 6months postpartum. To achieve these rates will require not only institutional support but also a focus on individual mother/infant dyads and their experience.

Two-day-old newborn infants recognise their mother by her axillary odour

AIM

The aim of this study was to verify the influence of mother to child skin-to-skin contact and the ability of 2-day-old infants to recognise their own mother's axillary odour.

METHODS

We tested the responses of 19 vaginally delivered, breastfeeding newborns to their mothers' axillary odours using a paired-choice test. The eight males and 11 females were exposed to their own mother's axillary odour and the odour of another unfamiliar new mother taking part in the study, and their responses to each woman were taped for 60 sec. We did this by assessing how long their heads were orientated towards pads carrying the scents of their mothers and the unfamiliar women.

RESULTS

The average time that the infants' heads were orientated towards the olfactory stimulus of their own mothers was 20.53 sec, which was significantly longer than the 11.13 sec recorded for the unfamiliar women (p < 0.05). In addition, this orientation increased significantly with the newborn infants' age in hours (Spearman's Rho = 0.58, p < 0.01) and their recognition time significantly decreased (Spearman's Rho = -0.52, p < 0.05).

CONCLUSION

Two-day-old breastfeeding newborn infants who experienced skin-to-skin contact with their mothers were able to recognise their axillary odour.

Neuroendocrinology of childbirth and mother-child attachment: the basis of an etiopathogenic model of perinatal neurobiological disorders

This review focuses on the neuroendocrine mechanisms in the mother and the newborn that are involved in the generation and consolidation of mother-child attachment. The role that different hormones and neurotransmitters play on the regulation of these mechanisms during parturition, the immediate postpartum period and lactation is discussed. Interferences in the initiation of mother-child attachment may have potential long-term effects for the behavior and affection of the newborn. Therefore, the possible consequences of alterations in the physiological neuroendocrine mechanisms of attachment, caused by elective Cesarean section, intrapartum hormonal manipulations, preterm delivery, mother-infant postpartum separation and bottle-feeding instead of breastfeeding are also discussed.

The response of newly born mice to odors of murine colostrum and milk: unconditionally attractive, conditionally discriminated

It is a general rule that milk conveys chemosensory cues that are attractive to mammalian neonates. This study investigated whether compositional fluctuations in milk along lactation induce variations in newborn mouse pups' (Mus musculus, strain BALB/c) attraction to milk odor. Pups differing in suckling experience were exposed to the odor of milk sampled from females varying in lactational stage. Immediately after birth, suckling-inexperienced (P0) and suckling-experienced (P0suck ) pups were assayed in a series of paired-choice tests contrasting murine milk [of lactation days 0, 3, 15 (abridged L0, L3, L15, respectively)] and a blank (water) to evaluate olfactory detection and attraction of milk odor. Preference tests further paired these milk two-by-two to assess their relative attraction. Results showed first that P0 and P0suck pups detect and positively orient to any milk odor. When L0 is presented against L15 milk, P0 pups orient for a similar duration towards these odor stimuli, whereas P0suck pups spend more time toward the odor of L0 than of L15 milk. Finally, P0suck pups orient similarly to odors of L0 milk collected before/after the first suckling episode (L0 and L0suck , respectively), but the odor of L0 milk was more attractive than that of L3 milk. Thus, mouse pups' positive orientation toward the odors of murine colostrum (assumed to correspond to L0/L0suck milk) and later-lactation milk appears unconditional of previous suckling experience, whereas their ability to discriminate or display preference between milk differing in lactation stage appears conditional on postnatal exposure effects.

Plasticity of the human olfactory system: the olfactory bulb

In the last years, an increasing interest has been paid to the olfactory system, particularly to its abilities of plasticity and its potential continuous neurogenesis throughout adult life. Although mechanisms underlying adult neurogenesis have been largely investigated in animals, to some degree they remain unclear in humans. Based on human research findings, the present review will focus on the olfactory bulb as an evidence of the astonishing plasticity of the human olfactory system.

The experience of being born: a natural context for learning to suckle

Understanding the developmental origins of congenital capabilities such as sucking is fundamental knowledge that can contribute to improving the clinical management of early feeding and facilitate the onset of oral ingestion. We describe analyses in rats showing that sensory stimulation in utero and during birth establishes the newborn's sucking responses to maternal cues. We mimicked elements of labor and delivery (viz., compressions simulating labor contractions, stroking simulating postnatal maternal licking of the newborn, and postnatal thermal flux), and used them to induce postnatal respiration and nipple attachment in caesarian-delivered pups. We report herein new data showing that, by simulating a fetal rat's experience of being born, specific components of vaginal birth provide sufficient conditions for the odor learning that guides newborn's sucking responses. In contrast, the absence of in utero compressions was associated with poor sucking onset. Knowing how birth stimuli contribute to the first nipple attachment and constitute a context for learning to suckle is an important step toward better management of some early feeding problems. It can serve also as a foundation for understanding the challenges of facilitating sucking by babies born prematurely so that they do not experience the typical contingencies mediating onset of oral ingestion.

Neonatal neurobehavioral organization after exposure to maternal epidural analgesia in labor

OBJECTIVE

To explore relationships between maternal epidural analgesia and two measures of neurobehavioral organization in infants at the initial feeding 1 hour after birth.

DESIGN

Prospective comparative design.

SETTING

Inner-city community hospital, Chicago, Illinois.

PARTICIPANTS

Convenience sample of 52 low-risk, mainly Black and Latino, mother/infant dyads.

METHODS

Mothers self-selected to labor with epidural or no labor pain medication. Neonatal neurobehavioral organization was measured in term infants at the initial feeding 1 hour after birth. A nutritive sucking apparatus generated data on total number of sucks and sucking pressure. Video recordings of infants (before and after the initial feeding) were coded for behavioral states, with analysis on frequency of alertness.

RESULTS

Total number of sucks and sucking pressure were not related to epidural exposure, although an epidural drug dosage effect on total number of sucks was evident when gender was a factor. Unmedicated girls demonstrated more sucks than girls in the high-dosage epidural group (p=.027). Overall, girls exhibited stronger sucking pressure than boys (p=.042). Frequency of alertness was not related to epidural exposure, although longer labor was related to greater alertness (p=.003), and Latino infants were more alert than Black infants (p=.002).

CONCLUSIONS

Results suggest attenuated neonatal nutritive sucking organization in girls after exposure to high maternal epidural dosages. In comparison to boys, girls may have enhanced neurobehavioral organization at birth. Race/ethnicity and alertness may have spurious associations in which hidden factors drive the relationship.

Mere odor exposure learning in the rat neonate immediately after birth and 1 day later

Rat pups are more resistant to retroactive associative interference 3 hr after birth than 24 hr later [Cheslock et al. [2004] Developmental Science, 7, 581-598]. The present experiments tested the effect of age, retention interval and dam presence during the retention interval on odor-induced motor activity subsequent to mere odor exposure. Rats were exposed to an hour of odor immediately after birth or approximately 1 day later and tested after a given retention interval (3 or 27 hr [Exp 1]; 0, 30, 75, or 180 min [Exp. 2]). They spent the retention interval either in the presence or absence of a foster dam (Exp. 1 and 3). After the retention interval, pups were tested in a 4-min activity test including a 2-min baseline period and 2 min of odor exposure. Overall activity was scored during tape-playback. Odor-exposed pups were more active than nonexposed pups during reexposure to the odor during testing, but this was true only for P0 pups. In contrast, P1 pups without prior odor exposure were active during testing and behaviorally quieted in the presence of the odor they were previously exposed to. Though 1 day apart, newborn rats just hours old lack many of the experiences that a 1-day-old has had including nursing, huddling, and being groomed. These experiences are associated with, among other stimuli, a barrage of olfactory cues (e.g., colostrum, saliva, dander, feces, and urine). P0 and P1 pups also differ in their proximity from the birthing experience and associated neurochemical changes. The age-related pattern of responding to odors based on previous odor exposure was discussed in relation to these and other possibilities.

Basic consciousness of the newborn

The newborn shows several signs of consciousness, such as being awake and aware of him/herself and mother. The infant processes olfactory and painful inputs in the cortex, where consciousness is believed to be localized. Furthermore, the newborn expresses primary emotions such as joy, disgust, and surprise and remember rhymes and vowels to which he or she has been exposed during fetal life. Thus, the newborn infant fulfills the criteria of displaying a basic level of consciousness, being aware of its body and him/her-self and somewhat about the external world. Preterm infants may be conscious to a limited degree from about 25 weeks, when the thalamocortical connections are established.

O contato pele a pele ao nascimento e o choro de recém-nascidos durante vacinação contra Hepatite B

OBJETIVO: Testar a efetividade do contato pele a pele entre mãe e filho após o nascimento na redução do comportamento de estresse/dor manifestado pelo choro do recém-nascido (RN), decorrente do procedimento de vacinação contra a Hepatite B. MÉTODOS: Estudo comparativo quase-experimental abrangendo 40 RN a termo, divididos em dois grupos, com ou sem contato pele a pele com suas mães após o nascimento, e que foram comparados quanto ao tempo de choro durante a vacinação contra Hepatite B. RESULTADOS: Variações no tempo de choro foram observadas nos dois grupos durante as fases desse procedimento. CONCLUSÃO: O efeito do contato na diminuição do tempo de choro dos RN, não foi demonstrado estatisticamente. Clinicamente, a Síndrome do Chamado pelo Estresse foi observada, bem como a efetividade do período de contato, na modulação do comportamento de choro dos neonatos, enquanto estes estiveram sob o momento terapêutico.

Olfactory learning in the rat immediately after birth: Unique salience of first odors

An infant rat's chance of survival is increased when it remains close to the nest. Early olfactory learning supports such adaptive behavior. Previous experiments indicated that non-associative odor exposure immediately after birth promoted later attachment to a similarly scented artificial nipple. The goal of the current experiments was to extend these findings on olfactory learning in the hours after birth by: exposing pups to more than one odor exposure (Experiment 1), dissecting the role of timing versus order of odor exposure (Experiment 2), testing the odor specificity of these effects (Experiments 3 and 4), and evaluating associative odor conditioning soon after birth (Experiment 5). Without explicit prior odor experience, pups only hours old do not respond much to a novel odor. Prior non-associative odor experience increases later motor activity to that same odor and to novel odors. Furthermore, these findings may be specific to certain amodal dimensions of the (in our case) lemon odor exposure. Single odor non-associative and associative conditioning was equally effective immediately after birth and during the third postnatal hour. Nevertheless, pups given two mere odor exposures responded to the first one more than the second at test, regardless of whether the exposures began immediately or 2 hr after birth. Possible mechanisms for these findings concerning early olfactory learning are discussed.

The emergence of human consciousness: from fetal to neonatal life

A simple definition of consciousness is sensory awareness of the body, the self, and the world. The fetus may be aware of the body, for example by perceiving pain. It reacts to touch, smell, and sound, and shows facial expressions responding to external stimuli. However, these reactions are probably preprogrammed and have a subcortical nonconscious origin. Furthermore, the fetus is almost continuously asleep and unconscious partially due to endogenous sedation. Conversely, the newborn infant can be awake, exhibit sensory awareness, and process memorized mental representations. It is also able to differentiate between self and nonself touch, express emotions, and show signs of shared feelings. Yet, it is unreflective, present oriented, and makes little reference to concept of him/herself. Newborn infants display features characteristic of what may be referred to as basic consciousness and they still have to undergo considerable maturation to reach the level of adult consciousness. The preterm infant, ex utero, may open its eyes and establish minimal eye contact with its mother. It also shows avoidance reactions to harmful stimuli. However, the thalamocortical connections are not yet fully established, which is why it can only reach a minimal level of consciousness.

Olfactory preference for own mother and litter in 1-day-old rabbits and its impairment by thermotaxis

We investigated the ability of rabbit pups to display preferences towards various elements of their postnatal environment during the stage of confinement in the nest. Subjects were submitted to a two-choice test during the first week after birth to assess if they could detect and discriminate between does, litters of pups, or nesting materials of the same developmental stage. On D1 and D7, pups were attracted to any lactating doe, litter, or nest when compared to an empty compartment. When two stimuli were opposed, pups preferred their own nest to an alien one on D1 and D7 but not their mother nor their siblings when opposed to alien does or pups. However, additional tests indicated that this lack of preference for kin conspecifics resulted from a predominant attraction to thermal cues over individual odors. Indeed, pups were strongly attracted to a warm compartment (37 degrees C) than to a cooler one (20 degrees C) and once thermal cues were controlled for in the testing situation, the pups were specifically attracted to odors of their own mother's hair and of their siblings. No preference was observed towards the mother's uterine secretions. In conclusion, pups can recognize olfactory cues emanating from their mother and their siblings the day after birth. The preference for nesting materials would reflect in major part the combined attraction to maternal and sibling odors present in the nest.

Olfactory learning in the rat neonate soon after birth

The first hours of a newborn rat's life entail locating and attaching to the mother's nipple not only for nutrition but also for protection and warmth. The present study sought to characterize olfactory learning in the rat neonate immediately after birth. Newborn rats were exposed to an odor at various time periods soon after birth and tested for behavioral activation and attachment to a surrogate nipple in the presence of this odor at 4-5 hr postpartum. Regardless of when pups were presented the odor (0, 1, or 2 hr after birth) motor activity was greater among pups previously exposed to the odor than pups with no odor experience. Similarly, latency to attach to the nipple in the presence of the odor was lower among odor-preexposed pups, especially when odor exposure began within an hour of cesarean delivery. Odor exposure immediately after birth for just 15 min was sufficient to increase motor activity and to decrease latency to attach to a similarly scented surrogate nipple. These results suggest that olfactory experience very soon after birth can shape subsequent olfactory responses. The relative importance of the dearth of postnatal experience or of elevated neurochemicals immediately after birth and possible associative mechanisms underlying this learning is discussed.

Latching-on and suckling of the healthy term neonate: breastfeeding assessment

Increasing breastfeeding duration and exclusivity is an acknowledged public health priority. Breastfeeding problems, especially with the healthy term neonate latching-on or feeding with a suboptimal latch, are common reasons for early breastfeeding termination when they result in inadequate breastfeeding, poor milk transfer, and sore nipples. This article describes clinical strategies for systematic latch-on and suckling assessment with the goal of improving the skills of clinicians who provide care for breastfeeding women.

Preference of 12-h-old kids for their mother goat is impaired by pre-partum-induced anosmia in the mother

We investigated whether kids were able to discriminate their own mother from an alien one in a two-choice test on the day of birth when they had access to acoustic, visual and olfactory cues from their mother, and whether this discrimination depended on the selective maternal behaviour of the mother (i.e. exclusive nursing of own kids). When given the choice between their own mother and an alien equivalent dam, 8-h-old kids did not show a significant preference for their dam, whereas 12- and 24-h-old kids did. When given the choice between their own and an alien mother that were both non-selective because they had been rendered peripherally anosmic by irrigation of the nostrils with zinc sulphate, 12-h-old kids did not show a significant preference for their mother. These results are similar to those reported in sheep and may suggest that the contrast of behaviour between their own and an alien mother existing in normosmic does is important for discrimination of dams by kids at this age. Finally, testing 8-h-old kids in a smaller enclosure resulted in some improvement of their performance, although they still failed to display a significant preference for their mother. On the whole, kids are able to discriminate between their own and an alien mother goat as early as previously reported in lambs. The impairment of this ability when mothers are anosmic and not selective suggests that acceptance behaviours displayed by the mother may serve as one of the cues orientating the choice of the kid when given the choice between intact mothers. Finally, the present results do not suggest the existence of fundamental differences in the establishment of a preference for the mother between lambs, which are followers, and kids, which are hiders.

Establishment of vocal communication and discrimination between ewes and their lamb in the first two days after parturition

In sheep, the mother-young relationship is characterized by an exclusive bond that relies on the rapid establishment of mutual recognition. However, the role of acoustic cues has been underestimated and neglected in this early discrimination. Therefore, the aim of the present study was (1) to characterize the vocal behavior of ewes and their lambs during the first 15 days postpartum and (2) to investigate the ability of newborn lambs and their mothers to discriminate each other from alien subjects within the first 48 hr postpartum on the basis of acoustic cues only. Ewes started to vocalize in the last 3 hr preceding parturition, emitting mainly high-pitched bleats. However, the bleating activity was highest during the first 3 hr following birth, consisting mainly of low-pitched bleats. Thereafter it decreased sharply until 24 hr postpartum, with most of the activity coming from the mother. In a two-choice test, ewes discriminated their own from an alien lamb on the basis of acoustic cues only at 24 hr postpartum, while lambs did so for their mother at 48 hr, which in both cases was much earlier than reported so far. We conclude that early vocal recognition between the ewe and her lamb may play an important role for the maintenance of mother-young contact.

Preliminary evidence of a sensitive period for olfactory learning by human newborns

AIM

To test the hypothesis that a brief window of time immediately after delivery may be a particularly sensitive period for olfactory learning by human neonates.

METHODS

Fifty-five vaginally delivered newborns were exposed to an odorant for 30 min beginning 4-37 min after birth (Early exposure) or 12-h post-partum (Late exposure). Several days later, newborns' head orientation responses to the exposure odour versus an unfamiliar odour or an odourless control stimulus were tested.

RESULTS

Infants in the Early exposure group spent significantly more time oriented towards the familiar scent rather than a novel odour (Z = 2.869; n = 28; p < 0.01), or an odourless stimulus (Z = 2.550; n = 28; p < 0.01). Infants in the Late exposure condition did not respond differentially to the exposure odour versus a novel odour (Z = 1.105; n = 27, p = 0.27), and spent more time oriented towards an odourless stimulus than to the exposure odour (Z = 2.042; n = 27, p < 0.05).

CONCLUSION

Infants in the Early exposure group, but not in the Late exposure group, became familiar with the exposure odour and retained a memory trace of it during the test trials.

Trace conditioning in 1-day-old rats

A recent test of 3-hr-old rats indicated surprisingly effective trace conditioning with a 60-s trace interval. The present study tested similar trace conditioning in pups 24-hr-old, in the absence of circumstances that immediately follow birth and might promote cognition. In Experiment 1 pairing an olfactory CS with a gustatory US yielded conditioning despite a 120-s trace. Experiment 2 determined that ambient CS odor remaining in the vicinity of the conditioning surface was not sufficient to result in the olfactory-gustatory association. Experiment 3 applied conditioning procedures more like those previously used for the 3-hr-old infant and more stringent than those applied in Experiment 1. With these procedures the 24-hr-old pups nevertheless acquired the CS-US contingency with a 60-s trace. Perhaps perinatal tolerance for long trace intervals is linked to their substantial experience in dealing with odors and tastes prenatally and postnatally.

Mother and newborn baby: Mutual regulation of physiology and behavior— A selective review

This article reviews 30 years of work demonstrating that interactions between mother and newborn infant in the period just after birth influence the physiology and behavior of both. Close body contact of the infant with his/her mother helps regulate the newborn's temperature, energy conservation, acid-base balance, adjustment of respiration, crying, and nursing behaviors. Similarly, the baby may regulate--i.e., increase--the mother's attention to his/her needs, the initiation and maintenance of breastfeeding, and the efficiency of her energy economy through vagus activation and a surge of gastrointestinal tract hormone release resulting in better exploitation of ingested calories. The effects of some of these changes can be detected months later. Parallels to animal research and possible mechanisms are discussed.

Antenatal olfactory learning influences infant feeding

The aim is to know whether antenatal olfactory learning have a greater effect than postnatal olfactory learning on infant feeding even in the absence of triggering signals. We evaluated the sucking behavior of infants completely separated from their mothers for 10-14 days since birth. The 12 infants admitted to Chiba Children's Hospital were studied at 10-14 days of age. Oral feeding was initiated at 4-7 days of age. The sucking and expression pressures, frequency, and sucking efficiency were measured during bottle-feeding with exposure to odors of mother's milk, formula, and water. The mother's milk odor elicited more frequent sucking with higher expression pressure than did formula or water. In conclusion, the odor preferences acquired independently from postnatal experience may have a greater effect than postnatal olfactory learning on sucking activity.