Dynamics of oralrespiratory coordination in full-term and preterm infants: II. Continuing effects at 3 months post term

Thirty-two infants participating in a longitudinal study of the effects of premature birth on sucking and breathing were tested at 3 months post term. They were assigned at a previous test to either a healthy full-term, healthy preterm, or high risk preterm group on the basis of birth weight, postconceptional age at birth, and perinatal medical status. Positive and negative sucking pressure as well as chest and abdominal breathing movements were recorded during nutritive sucking. The high risk preterms used a simpler and more stable pattern of coordination between sucking and breathing, were more likely to interrupt breathing at milk onset, and produced longer phase lags between positive and negative sucking pressure.     

Effects of fluid delivery on the sucking response of the human newborn

Two experiments were conducted with human newborns to compare sucking behavior under nutritive and nonnutritive sucking conditions using several fixed-ratio schedules of reinforcement. Results showed that: (1) nutritive sucking produces higher over-all sucking rates but lower within-burst rates, (2) burst lengths are longer during nutritive than nonnutritive sucking, (3) fewer bursts per unit time occur during nutritive sucking, (4) fluid termination following nutritive sucking produces a sharp response decrement, suggestive of a negative contrast effect when compared with sucking rates under continuous no-fluid sucking. Response diminution occurs in the first 2–3 min of sucking under all conditions, reflecting the necessity of control comparisons in studies documenting sucking change under changing stimulus or reinforcement conditions.     

Discrimination of color and pattern novelty in one-month human infants

Visual discrimination of novel colors and patterns by one-month infants was studied in two experiments where visual reinforcers were presented contingent upon infants' rate of nonnutritive, high-amplitude sucking. Discrimination was measured by recovery of sucking to the presentation of novel visual reinforcing stimuli following decrements in sucking to familiar visual stimuli. In Expt 1, following decrement to familiar stimuli, independent groups received either a change in color, pattern, both color and pattern, or no stimulus change. Reliable recovery was demonstrated for the three stimulus novelty groups relative to the no-change control. Experiment 2, employing achromatic visual reinforcers also showed reliable recovery to pattern change relative to no-change controls. These findings with one-month infants indicate discrimination between familiar and novel visual reinforcers on the basis of color and pattern differences and an increase due to novelty in the reinforcing effectiveness of visual stimuli. Individual subject differences in response decrement magnitude during familiarization were positively correlated with amount of response recovery to novelty.     

Effects of nonnutritive sucking on state and activity: Term-preterm comparisons

The effects of ad libitum access to a pacifier on the behavioral state and motor activity of preterm infants have been compared with those observed in full-term neonates. Regardless of maturity, nonnutritive sucking (NNS) decreases the amount of time spent in active states and increases that spent in quiescent states, lengthens the longest state bout, and decreases the frequency of state transitions. NNS also reduces overall motor activity as well as that during Active Sleep. Provided such ad libitum sucking opportunity, preterm infants thus appear to derive no less benefit from NNS than do term neonates. This result contrasts with an earlier finding that preterms are less soothed by NNA than are term infants.     

Learning at the breast: preference formation for an artificial scent and its attraction against the odor of maternal milk

Human newborns are known to display spontaneous attraction to the odor of human milk. This study aimed to assess whether the positive response to human milk odor can be explained by nursing-related learning, and whether it can be easily reassigned to a novel odor associated with nursing. Infants were exposed or not to a novel odor (camomile, Ca) during nursing, and tested on day 3-4 for their preference for camomile in comparison with either a scentless control (Exp. 1), a scented control (Exp. 2), or maternal milk (Exp. 3). Prior experience with Ca modified the newborns' responses. While the Ca odor became more attractive than a scented control in the Ca-exposed group, the Ca-non-exposed group did not differentiate either stimulus. In Exp. 3, the Ca-non-exposed group preferred the milk odor to the Ca odor, whereas the Ca-exposed group displayed on average equal attraction to both stimuli. Thus, a novel odor can be learned at the breast, and gain similar attractive power than the odor of mother's milk. In sum, reinforcements related with the early episodes of breastfeeding mediate the rapid development of novel odor preferences in human infants.     

The organization of non-nutritive sucking in the premature infant

Changes in non-nutritive sucking contingent upon the repeated presentation of unpatterned and patterned light stimulation were examined in a sample of 18 premature infants. Stimulus contingent sucking change in chronologically younger infants tended to be somewhat shorter in duration than that of the chronologically older infants and showed stimulus contingent sucking acceleration as well as suppression. Evidence was also found for less orienting among infants showing abnormalities in their sucking behavior. No evidence for habituation was found in any subgroup. Possible factors contributing to the strength and nature of stimulus contingent non-nutritive sucking changes in infants are discussed.     

Long-lasting memory for an odor acquired at the mother's breast

Whether neonatal odor memory can persist into toddlerhood and influence behaviors that tap processes related to cognition (attention and exploration), motivation (choice and consumption), and emotion (hedonic processing) remains under-researched. Using a quasi-experimental longitudinal design, we examined whether an odor experienced at the mother's breast can be retained at 7 and 21 months. The prescribed prophylactic use of a camomile-scented balm defined two groups: infants exposed (CaE) or never exposed (CaNE) to camomile odor. At 7 months, exploratory responses to three similar objects differing in odor (including camomile) were analyzed. At 21 months, three tasks were used to assess toddlers' (i) facial responses; (ii) exploratory responses to three similar, but differently odorized objects; and (iii) choices between two bottles carrying different odors. CaE infants displayed preferential responses for camomile odor at both ages in every task. In contrast, CaNE infants behaved either randomly or more negatively to camomile odor. This study indicates that early odor memories acquired during breastfeeding can be reactivated and influence behavioral processes until at least toddlerhood.     

Effects of auditory stimulation upon non-nutritive sucking by premature infants.

Changes in non-nutritive sucking contingent upon presentation of an auditory stimulus previously found capable of eliciting heart-rate acceleration was investigated in a sample of 24 premature infants. Across 30 10-sec. presentations of the stimulus, only transient changes in sucking rate during the first 6 trials were observed, and these effects obtained primarily for those infants showing few abnormalities in their non-nutritive sucking behavior. These results were discussed as reflecting possible differences in infants' attention associated with sucking pathology and the dependence of psychological assessment upon the specific response index used.     

Preference for infant-directed speech in preterm infants

The current study explores the effects of exposure to maternal voice on infant sucking in preterm infants. Twenty-four preterm infants averaging 35 weeks gestational age were divided randomly into two groups. A contingency between high-amplitude sucking and presentation of maternal voice was instituted for one group while the other group served as a yoked control. No significant differences were observed in sucking of the two groups, but the degree of pitch modulation of the maternal voice predicted an increase in the rate of infant sucking.     

Olfactory preferences resulting from mere exposure in human neonates

Twenty-four (12 males, 12 females) healthy, full-term neonates were exposed to an artificial odorant within the first day after birth for approximately 24 hrs to determine if mere exposure would lead to a subsequent preference for that odor. In choice tests following the treatment period, female infants displayed preferential orientation to the exposure odor. Males, in contrast, displayed no evidence of preference for the exposure odor; rather, they demonstrated a right turning bias regardless of odor location. These data suggest that familiarization with an odor shortly after birth is sufficient for female infants to develop preferential responsiveness to that odor.     

Infants' discrimination of internal and external pattern elements

Human infants' discrimination of changes in internal and external elements of compound visual patterns was investigated in four experiments employing a familiarization-novelty paradigm in which visual reinforcing patterns were presented contingent upon rate of high-amplitude nonnutritive sucking. In Experiment 1, 4-month infants discriminated changes in the shape of internal, external and both internal and external figures. One-month infants discriminated external changes in both internal and external figures, but failed to show reliable response recovery when only internal figures were changed. Experiments 2 and 3 failed to explain the 1-month results on the basis of poor resolution of internal figures by showing comparable discrimination of small and large singly-presented figures and by failing to find improved internal discrimination with large separation between internal and external figures. In Experiment 4, 1-month infants showed response recovery to figure additions made adjacent to the initial figure, but not to internal additions. The results are interpreted in terms of attentiveness by young infants to external pattern elements and may indicate early processing of figure-ground information. The developmental differences observed suggest an increased breadth of attention to pattern elements.     

Interventions in early infancy

Infants of high-risk pregnancies and deliveries may need early intervention to facilitate attachment both to and from their caregivers. Three early interventions are described: (1) giving high-risk pregnant women video feedback during prenatal ultrasound, which reduced maternal anxiety, obstetric complications, and fetal activity and improved neonatal outcome (increased weight gain, better performance on the Brazelton, and decreased irritability); (2) providing preterm neonates nonnutritive sucking opportunities to reduce stress during heelsticks and gavage feedings; and (3) providing preterm neonates and preterm cocaine-exposed neonates massage therapy, which facilitated weight gain and better performance on the Brazelton scale. Following improved neonatal behavior, infants would be expected to have better interactions with their caregivers.     

Reinforcement from the sucking environment and subsequent modification of sucking behavior in the human neonate

The reinforcing aspects of sucking behavior in 36 human newborns was examined in a limited instrumental conditioning paradigm where sucking was both operant and reinforcer. During training, response density (rate based on sucking opportunity time) and latency were measures of two components of nonnutritive sucking, contingent negative pressure suction, and incidental jaw movement. The strategy for determining the reinforcing aspects of sucking involved comparisons of three types of sucking stimuli as reinforcers. The nature of modified operant sucking was investigated during extinction by examining number of sucks per burst, number of bursts emitted, and interburst interval time. The feedback from sucking which acted as reinforcement was concluded to be response density. Sucking was modified by changes in pausing behavior, including response latency and pauses between bursts of sucks. The number of sucks per burst also showed a significant change under certain conditioning arrangements.     

Affective matching of odors and facial expressions in infants: shifting patterns between 3 and 7 months

Recognition of emotional facial expressions is a crucial skill for adaptive behavior. Past research suggests that at 5 to 7 months of age, infants look longer to an unfamiliar dynamic angry/happy face which emotionally matches a vocal expression. This suggests that they can match stimulations of distinct modalities on their emotional content. In the present study, olfaction–vision matching abilities were assessed across different age groups (3, 5 and 7 months) using dynamic expressive faces (happy vs. disgusted) and distinct hedonic odor contexts (pleasant, unpleasant and control) in a visual‐preference paradigm. At all ages the infants were biased toward the disgust faces. This visual bias reversed into a bias for smiling faces in the context of the pleasant odor context in the 3‐month‐old infants. In infants aged 5 and 7 months, no effect of the odor context appeared in the present conditions. This study highlights the role of the olfactory context in the modulation of visual behavior toward expressive faces in infants. The influence of olfaction took the form of a contingency effect in 3‐month‐old infants, but later evolved to vanish or to take another form that could not be evidenced in the present study.     

Neonatal sucking: Effects of quantity of the response-contingent fluid upon sucking rhythm and heart rate

The temporal organization of neonatal nutritive sucking and heart rate were studied in two consecutive 4-min periods to analyze the effects of two quantities of response-contingent fluid. One group of newborns experienced only the larger amount, a second experienced the smaller, and two other groups experienced both in counterbalanced order. Cumulative pausing time and intersuck intervals (sucking rate within bursts) were both affected by the amount of fluid delivered at each response. At the start of sucking bursts, heart rate accelerated to a stable level. Within-burst heart rates were higher with increased quantity of contingently delivered fluid. The results are discussed in relation to the distinction between nutritive and nonnutritive sucking and to previous findings on the effects of fluid sweetness upon sucking.     

Prenatal experience with low-frequency maternal-voice sounds influence neonatal perception of maternal voice samples

By sucking on a nonnutritive nipple in the presence of one discriminative stimulus, newborns were reinforced with a low-pass filtered tape recording of their mothers' voices. Sucking in the presence of a different discriminative stimulus was reinforced with unfiltered maternal-voice recordings. Filtered versions simulated maternal-voice sounds that were available before birth and unfiltered versions simulated maternal-voice sounds available after birth. Newborns in the control group could be reinforced with the same stimuli in the same way, but the voices were unfamiliar to them. Infants hearing their mothers' voices had no preference for either version, but infants hearing the unfamiliar voices preferred the unfiltered version. The difference in the between-groups responsiveness to the low-pass voice samples is consistent with the hypothesis that prenatal experience with low-frequency characteristics of maternal voices influences early postnatal perception of maternal voices.     

Preterm newborn pain research review

This narrative review is based on a literature search of PubMed and PsycINFO for research on preterm newborn pain published during the last ten years. The high prevalence of painful procedures being performed with preterm newborns without analgesia (79%), with a median of 75 painful procedures being received during hospitalization and as many as 51 painful procedures per day highlights the importance of this problem. This review covers the pain assessments that have been developed, the short-term effects of the painful procedures, the longer-term developmental outcomes and the pharmacological and alternative therapies that have been researched. The most immediate effects reported for repeated painful procedures include increased heart rate, oxidative stress and cortisol as well as decreased vagal activity. Lower body weight and head circumference have been noted at 32 weeks gestation. Blunted cortisol reactivity to stressors has been reported for three-month-olds and thinner gray matter in 21 of 66 cerebral regions and motor and cognitive developmental delays have been noted as early as eight months. Longer-term outcomes have been reported at school age including less cortical thickness, lower vagal activity, delayed visual– perceptual development, lower IQs and internalizing behavior. Pharmacological interventions and their side effects and non-pharmacological therapies are also reviewed including sucrose, milk and nonnutritive sucking which have been effective but thought to negatively affect breast-feeding. Full-body interventions have included tucking, swaddling, kangaroo care and massage therapy. Although these have been effective for alleviating immediate pain during invasive procedures, research is lacking on the routine use of these therapies for reducing long-term pain effects. Further, additional randomized controlled replication studies are needed.     

早产儿预防性应用抗生素的临床决策思路

近年来,随着对滥用抗生素所引起的细菌耐药性和二重感染的认识的逐步深入,预防性应用抗生素在临床上越来越受到限制。但由于早产儿感染的临床隐匿性和易并发严重并发症等特点,预防早产儿感染的发生和进一步的发展,就显得尤为重要。通过对早产儿发生感染的易感因素、感染诱因和临床特点的分析研究,来探讨早产儿临床预防应用抗生素的必要性、合理性及临床决策思路。     

Odorization of a novel object can influence infant's exploratory behavior in unexpected ways

Although much is known about the development of object exploration during infancy, it remains to be understood whether and how olfaction can influence infants' interactions with novel objects. To address these issues, sixteen infants aged 7-15 months were videotaped during two consecutive 5-min free play sessions with a scented or an unscented version of visually similar objects. Results indicate that adding an odor to a novel object influenced the infants' behavior: the infants exhibited more and longer manipulations and mouthing of the unscented object than of the scented object. The differential responsiveness to the scented, relative to the unscented, object was noted after a 2-min delay following test onset, suggesting that in the present conditions infants do not immediately detect or react to the added odor. It may be concluded that infants do detect an odorant added on a novel object, show odor-based discrimination of visually similar objects, and express withdrawal of the scented, relative to the unscented, object. The implications of these findings for understanding how infants use their senses, namely their olfactory sense, in early exploratory behavior are discussed.