Activation of olfactory cortex in newborn infants after odor stimulation: a functional near-infrared spectroscopy study

Effects of vanilla odor on hypoxia-related periodic breathing in premature newborns: A pilot study

BACKGROUND

Periodic breathing (PB)-related intermittent hypoxia can have long-lasting deleterious consequences in preterm infants. Olfactory stimulation using vanilla odor is beneficial for apnea of prematurity in the first postnatal days/weeks. We aimed to determine for the first time whether vanilla odor can also decrease PB-related intermittent hypoxia.

METHOD

This pilot study was a balanced crossover clinical trial including 27 premature infants born between 30 and 33+6 weeks of gestation. We performed 12-h recordings on two nights separated by a 24-h period. All infants were randomly exposed to vanilla odor on the first or second study night. The primary outcome was the desaturation index, defined as the number per hour of pulse oximetry (SpO2) values <90 % for at least 5 s, together with a drop of ≥5 % from the preceding value. Univariate mixed linear models were used for the statistical analysis.

RESULTS

Overall, exposure to vanilla odor did not significantly decrease the desaturation index (52 ± 22 events/h [mean ± SD] on the intervention night vs. 57 ± 26, p = 0.2); furthermore, it did not significantly alter any secondary outcome. In a preliminary post hoc subgroup analysis, however, the effect of vanilla odor was statistically significant in infants with a desaturation index of ≥70/h (from 86 ± 12 to 65 ± 23, p = 0.04).

CONCLUSION

In this pilot study, vanilla odor overall did not decrease PB-related intermittent hypoxia in infants born at 30-33+6 weeks of gestation, which is when they are close to term. Preliminary results suggesting a beneficial effect in infants with the highest desaturation index, however, justify further studies in the presence of PB-related intermittent hypoxia as well as in infants born more prematurely.

Effects of human milk odor stimulation on feeding in premature infants: a systematic review and meta-analysis

Previous studies suggested odor stimulation may influence feeding of premature neonates. Therefore, this systematic review and meta-analysis of randomized controlled trials was conducted to assess the effect of human milk odor stimulation on feeding of premature infants. All randomized controlled trials related to human milk odor stimulation on feeding in premature infants published in PubMed, Cochrane, Library, Medline, Embase, Web of science databases and Chinese biomedical literature databases, China National Knowledge Infrastructure, China Science and Technology Journal Database (VIP) and Wanfang Chinese databases were searched, and The Cochrane Handbook 5.1.0 was used to evaluate the quality and authenticity of the literature. Relevant information of the included studies was extracted and summarized, and the evaluation indexes were analyzed using ReviewManager5.3. The retrieval time was from the establishment of the database to July 28, 2022.12 articles were assessed for eligibility, and six randomized controlled studies were eventually included in the meta-analysis (PRISMA). A total of 6 randomized controlled studies with 763 patients were finally included in the study, and the quality evaluation of literatures were all grade B. Human milk odor stimulation reduced the transition time to oral feeding in premature infants [SMD = - 0.48, 95% CI (- 0.69, - 0.27), Z = 4.54, P < 0.00001] and shortened the duration of parenteral nutrition [MD = - 1.01, 95% CI (- 1.70, - 0.32), Z = 2.88, P = 0.004]. However, it did not change the length of hospitalization for premature infants [MD = - 0.03, 95% CI (- 0.41, 0.35), Z = 0.17, P = 0.86]. The implementation of human milk odor stimulation can reduce the transition time to oral feeding and the duration of parenteral nutrition in premature infants, but further studies are needed to determine whether it can reduce the length of hospital stay in premature infants. More high-quality, large-sample studies are needed to investigate the effect of human milk odor stimulation on the feeding process and other outcomes in premature infants.

Testing detectability, attractivity, hedonic specificity, extractability, and robustness of colostrum odor-Toward an olfactory bioassay for human neonates

Human milk odor is attractive and appetitive for human newborns. Here, we studied behavioral and heart-rate (HR) responses of 2-day-old neonates to the odor of human colostrum. To evaluate detection in two conditions of stimulus delivery, we first presented the odor of total colostrum against water. Second, the hedonic specificity of total colostrum odor was tested against vanilla odor. Third, we delivered only the fresh effluvium of colostrum separated from the colostrum matrix; the stability of this colostrum effluvium was then tested after deep congelation; finally, after sorptive extraction of fresh colostrum headspace, we assessed the activity of colostrum volatiles eluting from the gas chromatograph (GC). Regardless of the stimulus-delivery method, neonates displayed attraction reactions (HR decrease) as well as appetitive oral responses to the odor of total colostrum but not to vanilla odor. The effluvium separated from the fresh colostrum matrix remained appetitive but appeared labile under deep freezing. Finally, volatiles from fresh colostrum effluvium remained behaviorally active after GC elution, although at lower magnitude. In sum, fresh colostrum effluvium and its eluate elicited a consistent increase in newborns' oral activity (relative to water or vanilla), and they induced shallow HR decrease. Newborns' appetitive oral behavior was the most reproducible response criterion to the effluvium of colostrum. In conclusion, a set of unidentified volatile compounds from human colostrum is robust enough after extraction from the original matrix and chromatographic processing to continue eliciting appetitive responses in neonates, thus opening new directions to isolate and assay specific volatile molecules of colostrum.

Functional brain network properties of healthy full-term newborns quantified by scalp and source-reconstructed EEG

OBJECTIVE

Identifying the functional brain network properties of term low-risk newborns using high-density EEG (HD-EEG) and comparing these properties with those of established functional magnetic resonance image (fMRI) - based networks.

METHODS

HD-EEG was collected from 113 low-risk term newborns before delivery hospital discharge and within 72 hours of birth. Functional brain networks were reconstructed using coherence at the scalp and source levels in delta, theta, alpha, beta, and gamma frequency bands. These networks were characterized for the global and local network architecture.

RESULTS

Source-level networks in all the frequency bands identified the presence of the efficient small world (small-world propensity (SWP) > 0.6) architecture with four distinct modules linked by hub regions and rich-club (coefficient > 1) topology. The modular regions included primary, association, limbic, paralimbic, and subcortical regions, which have been demonstrated in fMRI studies. In contrast, scalp-level networks did not display consistent small world architecture (SWP < 0.6), and also identified only 2-3 modules in each frequency band.The modular regions of the scalp-network primarily included frontal and occipital regions.

CONCLUSIONS

Our findings show that EEG sources in low-risk newborns corroborate fMRI-based connectivity results.

SIGNIFICANCE

EEG source analysis characterizes functional connectivity at the bedside of low-risk newborn infants soon after birth.

fNIRS neuroimaging in olfactory research: A systematic literature review

There are a number of key features which make olfaction difficult to study; subjective processes of odor detection, discrimination and identification, and individualistic odor hedonic perception and associated odor memories. In this systematic review we explore the role functional near-infrared spectroscopy (fNIRS) has played in understanding olfactory perception in humans. fNIRS is an optical neuroimaging technique able to measure changes in brain hemodynamics and oxygenation related to neural electrical activity. Adhering to PRISMA guidelines, results of this search found that generally the majority of studies involving healthy adult subjects observed increased activity in response to odors. Other population types were also observed, such as infants, individuals with autism, attention deficit hyperactivity disorder (ADHD), post-traumatic stress disorder (PTSD), mild cognitive impairment (MCI) and dysosmia. fNIRS coverage heavily favored the prefrontal cortex, temporal and parietal regions. This review finds that odor induced cortical activation is dependent on multiple factors, such as odorant type, gender and population type. This review also finds that there is room for improvement in areas such as participant diversity, use of wearable fNIRS systems, physiological monitoring and multi-distance channels.

Motion artifacts removal and evaluation techniques for functional near-infrared spectroscopy signals: A review

With the emergence of an increasing number of functional near-infrared spectroscopy (fNIRS) devices, the significant deterioration in measurement caused by motion artifacts has become an essential research topic for fNIRS applications. However, a high requirement for mathematics and programming limits the number of related researches. Therefore, here we provide the first comprehensive review for motion artifact removal in fNIRS aiming to (i) summarize the latest achievements, (ii) present the significant solutions and evaluation metrics from the perspective of application and reproduction, and (iii) predict future topics in the field. The present review synthesizes information from fifty-one journal articles (screened according to three criteria). Three hardware-based solutions and nine algorithmic solutions are summarized, and their application requirements (compatible signal types, the availability for online applications, and limitations) and extensions are discussed. Five metrics for noise suppression and two metrics for signal distortion were synthesized to evaluate the motion artifact removal methods. Moreover, we highlight three deficiencies in the existing research: (i) The balance between the use of auxiliary hardware and that of an algorithmic solution is not clarified; (ii) few studies mention the filtering delay of the solutions, and (iii) the robustness and stability of the solution under extreme application conditions are not discussed.

Sensory stimulation for apnoea mitigation in preterm infants

Apnoea, a pause in respiration, is ubiquitous in preterm infants and are often associated with physiological instability, which may lead to longer-term adverse neurodevelopmental consequences. Despite current therapies aimed at reducing the apnoea burden, preterm infants continue to exhibit apnoeic events throughout their hospital admission. Bedside staff are frequently required to manually intervene with different forms of stimuli, with the aim of re-establishing respiratory cadence and minimizing the physiological impact of each apnoeic event. Such a reactive approach makes apnoea and its associated adverse consequences inevitable and places a heavy reliance on human intervention. Different approaches to improving apnoea management in preterm infants have been investigated, including the use of various sensory stimuli. Despite studies reporting sensory stimuli of various forms to have potential in reducing apnoea frequency, non-invasive intermittent positive pressure ventilation is the only automated stimulus currently used in the clinical setting for infants with persistent apnoeic events. We find that the development of automated closed-looped sensory stimulation systems for apnoea mitigation in preterm infants receiving non-invasive respiratory support is warranted, including the possibility of stimulation being applied preventatively, and in a multi-modal form. IMPACT: This review examines the effects of various forms of sensory stimulation on apnoea mitigation in preterm infants, namely localized tactile, generalized kinesthetic, airway pressure, auditory, and olfactory stimulations. Amongst the 31 studies reviewed, each form of sensory stimulation showed some positive effects, although the findings were not definitive and comparative studies were lacking. We find that the development of automated closed-loop sensory stimulation systems for apnoea mitigation is warranted, including the possibility of stimulation being applied preventatively, and in a multi-modal form.

Effect of Olfactory Stimulation with Breast Milk on Pain Responses to Heel Stick in Premature Infants: A Randomized Controlled Trial

Purpose: This study aimed to evaluate the effect of breast milk olfactory stimulation on pain response in premature infants during heel stick tests. Methods: A quasi-experimental randomized controlled trial was conducted in the neonatal intensive care unit of a tertiary-level hospital in Seoul, Korea. A breast milk group was provided olfactory stimulation with breast milk 30 seconds before the start of heel stick sampling, and a control group underwent heel stick sampling without olfactory stimulation. To evaluate infants' pain response, the heel stick procedure was video recorded, and pain response was assessed separately by two blinded research assistants using the Premature Infant Pain Scale (PIPS) through behavioral response, heart rate on physiological monitoring, and blood oxygen saturation on pulse oximetry through the video recording. Results: Forty-eight premature infants (gestational age, within 28-37 weeks, n = 24; control) were included in this study. The pain scores of the breast milk group were significantly lower than those of the control group (z = -2.04, p = 0.021). Conclusion: Breast milk odor may reduce pain in premature infants during heel stick tests.

Early Postpartum Maternal and Newborn Responses to Auditory, Tactile, Visual, Vestibular, and Olfactory Stimuli

OBJECTIVE

To compare maternal psychological well-being, newborn behavior, and maternal and newborn salivary oxytocin (OT) and cortisol before and after two maternally administered multisensory behavioral interventions or an attention control group.

DESIGN

Randomized prospective clinical trial.

SETTING

U.S. Midwest community hospital.

PARTICIPANTS

Newborns and their mothers (n = 102 dyads) participated. Mothers gave birth vaginally at term gestation and had no physical or mental health diagnoses. Newborns with low Apgar scores, receipt of oxygen, suspected infection, or congenital anomalies were excluded.

METHODS

Dyads were randomly assigned to the auditory, tactile, visual, and vestibular (ATVV) intervention, the ATVV with odor from a baby lotion (ATVVO), or the attention control (AC) Group. Maternal psychological well-being, newborn behavior, and endocrine responses (salivary cortisol and OT) were measured before and after the intervention.

RESULTS

Newborns in the ATVV and ATVVO groups exhibited increases in potent engagement behaviors (p < .0001 and p = .001, respectively). Newborns in the AC group exhibited a decrease in potent engagement (p = .013) and an increase in potent disengagement (p = .029). Mothers in the ATVVO group exhibited an increase in OT (p = .01) and the largest change in OT (p = .02) compared to mothers in the ATVV and AC groups. We noted no change in maternal psychological well-being or newborn endocrine responses.

CONCLUSION

Inclusion of an odor via lotion with a behavioral intervention (ATVV) influenced maternal OT more than the behavioral intervention alone. Newborns were behaviorally responsive to the interventions; however, endocrine measures were not associated with intervention changes.

Fetal programming of human energy homeostasis brain networks: Issues and considerations

In this paper, we present a transdisciplinary framework and testable hypotheses regarding the process of fetal programming of energy homeostasis brain circuitry. Our model proposes that key aspects of energy homeostasis brain circuitry already are functional by the time of birth (with substantial interindividual variation); that this phenotypic variation at birth is an important determinant of subsequent susceptibility for energy imbalance and childhood obesity risk; and that this brain circuitry exhibits developmental plasticity, in that it is influenced by conditions during intrauterine life, particularly maternal-placental-fetal endocrine, immune/inflammatory, and metabolic processes and their upstream determinants. We review evidence that supports the scientific premise for each element of this formulation, identify future research directions, particularly recent advances that may facilitate a better quantification of the ontogeny of energy homeostasis brain networks, highlight animal and in vitro-based approaches that may better address the determinants of interindividual variation in energy homeostasis brain networks, and discuss the implications of this formulation for the development of strategies targeted towards the primary prevention of childhood obesity.

Infants’ brain activity to cartoon face using functional near-infrared spectroscopy

In this study, to investigate whether infants showed face-specific brain activity to a cartoon human face, we conducted a functional near-infrared spectroscopy (fNIRS) experiment and a behavioral experiment. In the fNIRS experiment, we measured the hemodynamic responses of 5- and 6-month-old infants to cartoon female and cartoon character faces using fNIRS. The results showed that the concentration of oxy-Hb increased for cartoon female faces but not for cartoon character faces. This indicates that face-specific brain activity occurred for cartoon female faces but not cartoon character faces, despite the fact that both are faces. In the behavioral experiment, we examined whether the 5- and 6-month-old infants preferred cartoon female faces to cartoon character faces in the upright and inverted conditions. The results showed a preference for cartoon female faces in the upright but not in the inverted condition. This indicates that 5- and 6-month-old infants can perceive cartoon female faces, but not cartoon character faces, as faces. The results of the two experiments indicated that face-specific brain activity occurred for cartoon female faces. This indicates that infants can perceive cartoon female faces as faces.

Comparison of the analgesic effect of inhaled lavender vs vanilla essential oil for neonatal frenotomy: a randomized clinical trial (NCT04867824)

It is necessary to treat neonatal pain because it may have short- and long-term adverse effects. Frenotomy is a painful procedure where sucking, a common strategy to relieve pain, cannot be used because the technique is performed on the tongue. In a previous randomized clinical trial, we demonstrated that inhaled lavender essential oil (LEO) reduced the signs of pain during neonatal frenotomy. We aimed to find out whether inhaled vanilla essential oil (VEO) is more effective in reducing pain during frenotomy than LEO. Randomized clinical trial with neonates who underwent a frenotomy for type 3 tongue-ties between May and October 2021. Pain was assessed using pre and post-procedure heart rate (HR) and oxygen saturation (SatO2), crying time, and NIPS score. Neonates were randomized into "experimental" and "control" group. In both groups, we performed swaddling, administered oral sucrose, and let the newborn suck for 2 min. We placed a gauze pad with one drop of LEO (control group) or of VEO (experimental group) under the neonate's nose for 2 min prior to and during the frenotomy. We enrolled 142 neonates (71 per group). Both groups showed similar NIPS scores (2.02 vs 2.38) and crying times (15.3 vs 18.7 s). We observed no differences in HR increase or in SatO2 decrease between both groups. We observed no side effects in either of the groups.

CONCLUSIONS

We observed no appreciable difference between LEO and VEO; therefore, we cannot conclude which of them was more effective in treating pain in neonates who underwent a frenotomy.

TRIAL REGISTRATION

 This clinical trial is registered with www.

CLINICALTRIALS

gov with NCT04867824.

WHAT IS KNOWN

• Pain management is one of the most important goals of neonatal care as it can have long-term neurodevelopmental effects. • Lavender essential oil can help relieve pain due to its sedative, antispasmodic, and anticolic properties.

WHAT IS NEW

• Lavender and vanilla essential oils are safe, beneficial, easy to use, and cheap in relieving pain in neonates who undergo a frenotomy for type 3 tongue-ties.

Accent discrimination abilities during the first days of life: An fNIRS study

Humans are biologically endowed with the faculty of language. However, the way neonates can crack this complex communicative code is yet not totally understood. While phonetic discrimination has been widely investigated in neonates, less is known about the role of supra-segments patterns in the recognition of native language. Therefore, the aim of this study was to evaluate accent discrimination abilities in newborns in a sentential prosody paradigm. We used near-infared spectroscopy to investigate accent discrimination in 21 full-term born infants within the first days of life. Sentential prosody was used to investigate: (a) native accent, (b) foreign accent, and (c) flattened accent. Neonates revealed a significantly smaller hemodynamic response to native accent compared to flattened accent and foreign accent, respectively. Cluster-based permutation analysis revealed two clusters with a significant difference between the two conditions native accent and foreign accent. The first cluster covered the middle and superior frontal, middle and superior temporal, central, and parietal areas within the left hemisphere. The second cluster, located in the right hemisphere, covered inferior, middle, and superior frontal, central, middle and superior temporal areas. We therefore conclude that neonates can differentiate prosodic features like accents within the same language a few days after birth.

Olfactory sensory and perceptual evaluation in newborn infants: A systematic review

Fetuses are able to process olfactory stimuli present in the womb and continue to show a preference for these odors for months after birth. Despite the accumulated knowledge about their early ability to perceive odors, there is a lack of validated scales for odor response in newborns. The evaluation of reactions of the olfactory system to environmental stimuli in infants has been defined by methodological theoretical approaches of experimental and clinical assessment tools. These approaches are mainly based on psychophysical approaches and predominantly use behavioral and physiological measures. Examples can be found in studies describing early abilities of newborn babies for behaviors or heart rate variability showing memory of maternal food preferences or mother's breast milk. This systematic review aimed to determine whether validated odor assessment tools can be feasibly used in studies. Particularly in light of the current COVID-19 pandemic and evidence of associated olfactory impairment resulting from SARS-COV-2 infection, the study is also motivated by the need for tools to assess olfactory function in neonates.

An interactionist perspective on the development of coordinated social attention

Infants' ability to coordinate their attention with other people develops profoundly across the first year of life. Mainly based on experimental research focusing on infants' behavior under highly controlled conditions, developmental milestones were identified and explained in the past by prominent theories in terms of the onset of specific cognitive skills. In contrast to this approach, recent longitudinal research challenges this perspective with findings suggesting that social attention develops continuously with a gradual refinement of skills. Informed by these findings, we argue for an interactionist and dynamical systems view that bases observable advances in infant social attention skills on increasingly fine-tuned mutual adjustments in the caregiver-infant dyad, resulting in gradually improving mutual prediction. We present evidence for this view from recent studies leveraging new technologies which afford the opportunity to dynamically track social interactions in real-time. These new technically-sophisticated studies offer unprecedented insights into the dynamic processes of infant-caregiver social attention. It is now possible to track in much greater detail fluctuations over time with regard to object-directed attention as well as social attention and how these processes relate to one another. Encouraged by these initial results and new insights from this interactionist developmental social neuroscience approach, we conclude with a "call to action" in which we advocate for more ecologically valid paradigms for studying social attention as a dynamic and bi-directional process.

Classification of Prefrontal Cortex Activity Based on Functional Near-Infrared Spectroscopy Data upon Olfactory Stimulation

The sense of smell is one of the most important organs in humans, and olfactory imaging can detect signals in the anterior orbital frontal lobe. This study assessed olfactory stimuli using support vector machines (SVMs) with signals from functional near-infrared spectroscopy (fNIRS) data obtained from the prefrontal cortex. These data included odor stimuli and air state, which triggered the hemodynamic response function (HRF), determined from variations in oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) levels; photoplethysmography (PPG) of two wavelengths (raw optical red and near-infrared data); and the ratios of data from two optical datasets. We adopted three SVM kernel functions (i.e., linear, quadratic, and cubic) to analyze signals and compare their performance with the HRF and PPG signals. The results revealed that oxyHb yielded the most efficient single-signal data with a quadratic kernel function, and a combination of HRF and PPG signals yielded the most efficient multi-signal data with the cubic function. Our results revealed superior SVM analysis of HRFs for classifying odor and air status using fNIRS data during olfaction in humans. Furthermore, the olfactory stimulation can be accurately classified by using quadratic and cubic kernel functions in SVM, even for an individual participant data set.

Central Nervous System Processing of Floral Odor and Mother's Milk Odor in Infants

Newborns have a functioning sense of smell at birth, which appears to be highly significant for feeding and bonding. Still, little is known about the cerebral odor processing in this age group. Studies of olfactory function relied mostly on behavioral, autonomic, and facial responses of infants. The aim of the present study was to investigate central odor processing in infants focusing on electroencephalography (EEG)-derived responses to biologically significant odors, namely a food and a non-food odor. A total of 21 term-born, healthy infants participated (11 boys and 10 girls; age range 2-9 months, mean 5.3 ± 2.2 months). Odor stimuli were presented using a computer-controlled olfactometer. Breast milk was used as food odor. Farnesol was presented as a non-food odor. In addition, odorless air was used as a control stimulus. Each stimulus was presented 30 times for 1 s with an interstimulus interval of 20 s. EEG was recorded from 9 electrodes and analyzed in the frequency domain. EEG amplitudes in the delta frequency band differed significantly after presentation of food (breast milk) odor in comparison to the control condition and the non-food odor (farnesol). These changes were observed at the frontal recording positions. The present study indicates that central odor processing differs between a food and a non-food odor in infants. Results are interpreted in terms of focused attention towards a physiologically relevant odor (breast milk), suggesting that olfactory stimuli are of specific significance in this age group.

Cortical Oxygenation Changes during Gastric Tube Feeding in Moderate- and Late-Preterm Babies: A NIRS Study

Smell and taste of food can trigger physiological responses facilitating digestion and metabolism of nutrients. Controlled experimental studies in preterm babies have demonstrated that smell activates the orbitofrontal cortex (OFC) but none have investigated the effect of taste stimulation. Using cotside Near-Infrared Spectroscopy (NIRS), we measured changes in OFC cerebral oxygenation in response to gastric tube feeds five and 10 days after birth in 53 assessments of 35 moderate- to late-preterm babies enrolled in a randomized trial. Babies were randomly assigned to receive smell and taste of milk before gastric tube feeds (intervention group, n = 16) or no exposure (control group, n = 19). The majority of babies were born at 33 weeks of gestation (range 32–34) and 69% were boys. No differences in OFC cerebral oxygenation were observed between control and intervention groups. Gastric tube feeds induced activation of the OFC (p < 0.05), but sensory stimulation alone with smell and taste did not. Boys, but not girls, showed activation of the OFC following exposure to smell of milk (p = 0.01). The clinical impact of sensory stimulation prior to tube feeds on nutrition of preterm babies, as well as the impact of environmental inputs on cortical activation, remains to be determined.

Design and validation of a mechanically flexible and ultra-lightweight high-density diffuse optical tomography system for functional neuroimaging of newborns

Significance: Neonates are a highly vulnerable population. The risk of brain injury is greater during the first days and weeks after birth than at any other time of life. Functional neuroimaging that can be performed longitudinally and at the cot-side has the potential to improve our understanding of the evolution of multiple forms of neurological injury over the perinatal period. However, existing technologies make it very difficult to perform repeated and/or long-duration functional neuroimaging experiments at the cot-side. Aim: We aimed to create a modular, high-density diffuse optical tomography (HD-DOT) technology specifically for neonatal applications that is ultra-lightweight, low profile and provides high mechanical flexibility. We then sought to validate this technology using an anatomically accurate dynamic phantom. Approach: An advanced 10-layer rigid-flexible printed circuit board technology was adopted as the basis for the DOT modules, which allows for a compact module design that also provides the flexibility needed to conform to the curved infant scalp. Two module layouts were implemented: dual-hexagon and triple-hexagon. Using in-built board-to-board connectors, the system can be configured to provide a vast range of possible layouts. Using epoxy resin, thermochromic dyes, and MRI-derived 3D-printed moulds, we constructed an electrically switchable, anatomically accurate dynamic phantom. This phantom was used to quantify the imaging performance of our flexible, modular HD-DOT system. Results: Using one particular module configuration designed to cover the infant sensorimotor system, the device provided 36 source and 48 detector positions, and over 700 viable DOT channels per wavelength, ranging from 10 to ∼ 45    mm over an area of approximately 60    cm 2 . The total weight of this system is only 70 g. The signal changes from the dynamic phantom, while slow, closely simulated real hemodynamic response functions. Using difference images obtained from the phantom, the measured 3D localization error provided by the system at the depth of the cortex was in the of range 3 to 6 mm, and the lateral image resolution at the depth of the neonatal cortex is estimated to be as good as 10 to 12 mm. Conclusions: The HD-DOT system described is ultra-low weight, low profile, can conform to the infant scalp, and provides excellent imaging performance. It is expected that this device will make functional neuroimaging of the neonatal brain at the cot-side significantly more practical and effective.

Newborn crawling and rooting in response to maternal breast odor

A growing literature shows that perception and action are already tightly coupled in the newborn. The current study aimed to examine the nature of the coupling between olfactory stimuli from the mother and the newborn's crawling and rooting (exploratory movements of the head). To examine the coupling, the crawling and rooting behavior of 28 2-day-old newborns were studied while they were supported prone on a mobility device shaped like a mini skateboard, the Crawliskate®, their head positioned directly on top of a pad infused with either their mother's breast odor (Maternal) or the odor of water (Control). Video and 3D kinematic analyses of the number and types of limb movements and quantification of displacement across the surface revealed that newborns are significantly more efficient crawlers when they smell the maternal odor, moving greater distances although performing fewer locomotor movements. In addition, the newborns made significantly more head rooting movements in the presence of the maternal odor. These findings suggest that the circuitry underlying quadrupedal locomotion and exploratory movements of the head is already adaptable to olfactory information via higher brain processing. Moreover, the coupling between olfaction and the two action systems, locomotion and rooting, is already differentiated. As crawling enables the newborn to move toward the mother's breast immediately after birth and facilitates mother-infant interaction, the results of this study highlight the potential value of using maternal odors to stimulate mobility in infants at risk of motor delay and/or deprived of this odor when born prematurely.

Human neonates prefer colostrum to mature milk: Evidence for an olfactory bias toward the "initial milk"?

OBJECTIVES

Colostrum is the initial milk secretion which ingestion by neonates warrants their adaptive start in life. Colostrum is accordingly expected to be attractive to newborns. The present study aims to assess whether colostrum is olfactorily attractive for 2-day-old newborns when presented against mature milk or a control.

METHODS

The head-orientation of waking newborns was videotaped in three experiments pairing the odors of: (a) colostrum (sampled on postpartum day 2, not from own mother) and mature milk (sampled on average on postpartum day 32, not from own mother) (n tested newborns = 15); (b) Colostrum and control (water; n = 9); and (c) Mature milk and control (n = 13).

RESULTS

When facing the odors of colostrum and mature milk, the infants turned their nose significantly longer toward former (32.8 vs 17.7% of a 120-s test). When exposed to colostrum against the control, they responded in favor of colostrum (32.9 vs 16.6%). Finally, when the odor of mature milk was presented against the control, their response appeared undifferentiated (26.7 vs 28.6%).

CONCLUSIONS

These results indicate that human newborns can olfactorily differentiate conspecific lacteal fluids sampled at different lactation stages. They prefer the odor of the mammary secretion - colostrum - collected at the lactation stage that best matches the postpartum age of their own mother. These results are discussed in the context of the earliest mother-infant chemo-communication. Coinciding maternal emission and offspring reception of chemosignals conveyed in colostrum may be part of the sensory precursors of attunement between mothers and infants.

Functional imaging of the developing brain with wearable high-density diffuse optical tomography: A new benchmark for infant neuroimaging outside the scanner environment

Studies of cortical function in the awake infant are extremely challenging to undertake with traditional neuroimaging approaches. Partly in response to this challenge, functional near-infrared spectroscopy (fNIRS) has become increasingly common in developmental neuroscience, but has significant limitations including resolution, spatial specificity and ergonomics. In adults, high-density arrays of near-infrared sources and detectors have recently been shown to yield dramatic improvements in spatial resolution and specificity when compared to typical fNIRS approaches. However, most existing fNIRS devices only permit the acquisition of ~20-100 sparsely distributed fNIRS channels, and increasing the number of optodes presents significant mechanical challenges, particularly for infant applications. A new generation of wearable, modular, high-density diffuse optical tomography (HD-DOT) technologies has recently emerged that overcomes many of the limitations of traditional, fibre-based and low-density fNIRS measurements. Driven by the development of this new technology, we have undertaken the first study of the infant brain using wearable HD-DOT. Using a well-established social stimulus paradigm, and combining this new imaging technology with advances in cap design and spatial registration, we show that it is now possible to obtain high-quality, functional images of the infant brain with minimal constraints on either the environment or on the infant participants. Our results are consistent with prior low-density fNIRS measures based on similar paradigms, but demonstrate superior spatial localization, improved depth specificity, higher SNR and a dramatic improvement in the consistency of the responses across participants. Our data retention rates also demonstrate that this new generation of wearable technology is well tolerated by the infant population.

The Effects of a Continuous Olfactory Stimulation Using Breast Milk (COSB) on Behavioral State and Physiological Responses in Korean Premature Infants

PURPOSE

This study aimed to evaluate the effects of continuous olfactory stimulation with breast milk (COSB) on behavioral and physiologic states of Korean premature infants.

DESIGN AND METHODS

We examined the COSB effects on the behavioral states and physiological responses, including heart rate and oxygen saturation, in 30 premature infants using a non-equivalent control group pre- and post-test design. Sterile 2 cm × 2 cm gauzes wet with 2 cc breast milk were placed 10 cm away from the infants' nostrils 8 times per day for 3 consecutive days. We obtained five measurements each of the behavioral state, heart rate, and oxygen saturation of the premature infants in the neonatal intensive care unit (NICU). Statistical analysis was conducted using descriptive statistics and two-way repeated-measures ANOVA.

RESULTS

The experiment group presented significantly reduced heart rate variations (p = .039). There were significant differences in the heart rate at all time-points in the control group (p < .001) but not in the experimental group, indicating more stable (p > .089) heart rates in the latter group. There were positive COSB effects on the behavioral states of premature infants at some time points.

CONCLUSIONS

COSB can be a useful intervention program for high-risk infants for partial behavioral state stabilization and significant heart rate stabilization.

PRACTICE IMPLICATIONS

COSB might enable NICU nurses to provide a useful and safe developmental care plan for the premature infants hospitalized in the NICU to improve their physiologic and behavioral condition.

Neonatal cortical perceptions of maternal breast odours: A fNIRS study

AIM

The aim was to determine whether preterm and full-term newborn infants could process maternal breast odour at a cortical level.

METHODS

Newborn infants were exposed to cloths containing their own mother's breast odour and freshly laundered control cloths for 10 seconds, while functional near-infrared spectroscopy measured cortical activation in their olfactory processing areas. We studied 45 newborn infants born at 28-41 weeks of gestation and divided them into three groups: full-term (37-41 weeks), late preterm (33-36 weeks) and very preterm (28-32 weeks). Cortical activation was defined as a regional increase of oxyhaemoglobin following maternal breast odour stimuli.

RESULTS

Full-term infants demonstrated bilateral activation of their olfactory cortices following exposure to maternal breast odour. Late preterm infants and very preterm boys exhibited unilateral cortical activation, unlike very preterm girls.

CONCLUSION

Infants born from 32 weeks, and possibly earlier, could process low concentration maternal odours at a cortical level, which suggests they were more aware of their environment. These findings could make a significant contribution to improving the sensory environment of preterm infants and improve bonding.

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'.

Impact of prematurity on neurodevelopment

The consequences of prematurity on brain functional development are numerous and diverse, and impact all brain functions at different levels. Prematurity occurs between 22 and 36 weeks of gestation. This period is marked by extreme dynamics in the physiologic maturation, structural, and functional processes. These different processes appear sequentially or simultaneously. They are dependent on genetic and/or environmental factors. Disturbance of these processes or of the fine-tuning between them, when caring for premature children, is likely to induce disturbances in the structural and functional development of the immature neural networks. These will appear as impairments in learning skills progress and are likely to have a lasting impact on the development of children born prematurely. The level of severity depends on the initial alteration, whether structural or functional. In this chapter, after having briefly reviewed the neurodevelopmental, structural, and functional processes, we describe, in a nonexhaustive manner, the impact of prematurity on the different brain, motor, sensory, and cognitive functions.

Performance Monitoring via Functional Near Infrared Spectroscopy for Virtual Reality Based Basic Life Support Training

The use of serious game tools in training of medical professions is steadily growing. However, there is a lack of reliable performance assessment methods to evaluate learner’s outcome. The aim of this study is to determine whether functional near infrared spectroscopy (fNIRS) can be used as an additional tool for assessing the learning outcome of virtual reality (VR) based learning modules. The hypothesis is that together with an improvement in learning outcome there would be a decrease in the participants’ cerebral oxygenation levels measured from the prefrontal cortex (PFC) region and an increase of participants’ serious gaming results. To test this hypothesis, the subjects were recruited and divided into four groups with different combinations of prior virtual reality experience and prior Basic Life Support (BLS) knowledge levels. A VR based serious gaming module for teaching BLS and 16-Channel fNIRS system were used to collect data from the participants. Results of the participants’ scores acquired from the serious gaming module were compared with fNIRS measures on the initial and final training sessions. Kruskal Wallis test was run to determine any significant statistical difference between the groups and Mann–Whitney U test was utilized to obtain pairwise comparisons. BLS training scores of the participants acquired from VR based serious game’s the learning management system and fNIRS measurements revealed decrease in use of resources from the PFC, but increase in behavioral performance. Importantly, brain-based measures can provide an additional quantitative metric for trainee’s expertise development and can assist the medical simulation instructors.

A plausible pathway of imprinted behaviors: Skin-to-skin actions of the newborn immediately after birth follow the order of fetal development and intrauterine training of movements

We hypothesize that the competence of a newborn in the first hours after birth is the direct result of behavior training that begins during the first 12 weeks of fetal life. Correlation of Widström's 9 Instinctive Stages (behaviors of the full-term newborn during the first hours after birth) with the developmental movements during fetal life demonstrate that the fetus is invested in learning specific tasks, in a specific order, that are evolutionarily necessary for survival during the first hour and beyond.

fMRI-based Neuronal Response to New Odorants in the Newborn Brain

The sense of smell is one of the oldest and the most primitive senses mammals possess, it helps to evaluate the surrounding environment. From birth, smell is an important sensory modality, highly relevant for neonatal behavioral adaptation. Even though human newborns seem to be able to perceive and react to olfactory stimuli, there is still a lack of knowledge about the ontogeny of smell and the underlying central processing involved in odor perception in newborns. Brain networks involved in chemosensory perception of odorants are well described in adults, however in newborns there is no evidence that central olfaction is functional given the largely unmyelinated neonatal central nervous system. To examine this question, we used functional magnetic resonance imaging (fMRI) in the newborn to characterize cortical response to olfactory and trigeminal odorants. Here we show that brain response to odors can be measured and localized using functional MRI in newborns. Furthermore, we found that the developing brain, only few days after birth, processes new artificial odorants in similar cortical areas than adults, including piriform cortex, orbitofrontal cortex and insula. Our work provides evidence that human olfaction at birth relies on brain functions that involve all levels of the cortical olfactory system.

Habituation and novelty detection fNIRS brain responses in 5- and 8-month-old infants: The Gambia and UK

The first 1,000 days of life are a critical window of vulnerability to exposure to socioeconomic and health challenges (i.e. poverty/undernutrition). The Brain Imaging for Global Health (BRIGHT) project has been established to deliver longitudinal measures of brain development from 0 to 24 months in UK and Gambian infants and to assess the impact of early adversity. Here results from the Habituation-Novelty Detection (HaND) functional near-infrared spectroscopy (fNIRS) task at 5 and 8 months are presented (N = 62 UK; N = 115 Gambia). In the UK cohort distinct patterns of habituation and recovery of response to novelty are seen, becoming more robust from 5 to 8 months of age. In The Gambia, an attenuated habituation response is evident: a larger number of trials are required before the response sufficiently suppresses relative to the response during the first presented trials. Furthermore, recovery of response to novelty is not evident at 5 or 8 months of age. As this longitudinal study continues in The Gambia, the parallel collection of socioeconomic, caregiving, health and nutrition data will allow us to stratify how individual trajectories of habituation and recovery of response to novelty associate with different risk factors and adaptive mechanisms in greater depth. Given the increasing interest in the use of neuroimaging methods within global neurocognitive developmental studies, this study provides a novel cross-culturally appropriate paradigm for the study of brain responses associated with attention and learning mechanisms across early development.

The effect of smell and taste of milk during tube feeding of preterm infants (the Taste trial): a protocol for a randomised controlled trial

INTRODUCTION

Smell and taste of milk are not generally considered when tube feeding preterm infants. Preterm infants have rapid growth, particularly of the brain, and high caloric needs. Enteral feeding is often poorly tolerated which may lead to growth failure and long-term neurodevelopmental impairment. Smell and taste are strong stimulators of digestion and metabolism. We hypothesise that regular smell and taste during tube feeding will improve weight z-scores of very preterm infants at discharge from hospital.

METHODS AND ANALYSIS

Taste is a randomised, unblinded two-centre trial. Infants born at <29 weeks' gestation and/or <1250 g at birth and admitted to a participating neonatal intensive care unit are eligible. Randomisation occurs before infants receive two hourly feeds for 24 hours. Infants are randomised to either smell and taste of milk with each tube feed or tube feeding without the provision of smell and taste. The primary outcome is weight z-score at discharge. Secondary outcomes include: days to full enteral feeds, duration of parenteral nutrition, rate of late-onset sepsis, post menstrual age at removal of nasogastric tube and at discharge from hospital, anthropometric data and neurodevelopmental outcomes at 2 years of corrected age.

ETHICS AND DISSEMINATION

Human Research Ethics Committees of Mater Misericordiae (trial reference number: HREC/16/MHS/112) and the Royal Women's Hospital (trial reference number: 17/21) last approved the trial protocol (version 4.2; Date: 18 December 2018) and recruitment commenced in May 2017 and November 2017, respectively. The trial results will be published in a peer-reviewed journal and will be presented at national and international conferences.

TRIAL REGISTRATION NUMBER

ACTRN12617000583347.

Skin-to-skin contact the first hour after birth, underlying implications and clinical practice

AIM

This paper integrates clinical expertise to earlier research about the behaviours of the healthy, alert, full-term infant placed skin-to-skin with the mother during the first hour after birth following a noninstrumental vaginal birth.

METHOD

This state-of-the-art article forms a link within the knowledge-to-action cycle, integrating clinical observations and practice with evidence-based findings to guide clinicians in their work to implement safe uninterrupted skin-to-skin contact the first hours after birth.

RESULTS

Strong scientific research exists about the importance of skin-to-skin in the first hour after birth. This unique time for both mother and infant, individually and in relation to each other, provides vital advantages to short- and long-term health, regulation and bonding. However, worldwide, clinical practice lags. A deeper understanding of the implications for clinical practice, through review of the scientific research, has been integrated with enhanced understanding of the infant's instinctive behaviour and maternal responses while in skin-to-skin contact.

CONCLUSION

The first hour after birth is a sensitive period for both the infant and the mother. Through an enhanced understanding of the newborn infant's instinctive behaviour, practical, evidence-informed suggestions strive to overcome barriers and facilitate enablers of knowledge translation. This time must be protected by evidence-based routines of staff.

Impact of the odors of vanilla extract and breast milk on the frequency of apnea in preterm neonates

AIM

We developed this study using an experimental design to determine the impact of the odors of vanilla extract and breast milk on apnea frequency in preterm neonates.

MATERIALS AND METHODS

We obtained the study data from 42 preterm neonates (16 vanilla, 13 breast milk, 13 control group) who had been admitted to the Neonatal Intensive Care Unit of Istanbul University meeting the case selection criteria. All groups were monitored on the first day without any intervention. On the second and third days, breast milk was placed in the incubators of the babies in the breast milk group and the sterile gauze that was vanilla-impregnated was placed in the incubators of the babies in the vanilla group. On the fourth day, the babies were watched without any interference.

RESULTS

On the second, third and fourth days of the study, we determined that apnea frequency in the vanilla group neonates was significantly lower (P < .00) as compared to the breast milk and control groups.

CONCLUSION

Using vanilla extract in neonates suffering from apnea to reduce its frequency is an effective method.

Sniffin' Away the Feeding Tube: The Influence of Olfactory Stimulation on Oral Food Intake in Newborns and Premature Infants

Because of their immaturity, many premature infants are fed via nasogastric tube. One objective of the neonatal care is to feed infants orally early. The olfactory function of premature infants is developed before birth and odorants have a significant impact on nutrition in infants. The aim of the study was to test whether odor stimulation has a positive effect on the transition from gavage to oral feeding in infants. Participants were premature infants with gestational age of more than 27 weeks, with full or partial gavage feeding, stable vital parameters and without invasive ventilation. Before each feeding procedure an odorant was presented in front of the infant's nose. Infants were randomized into 1 of 3 groups and received either rose odor (not food-associated), vanilla odor (food-associated), or placebo (no odor). The primary outcome of the study was defined as the time until complete oral nutrition. About 150 children born at a postnatal age of 9.5 ± 7.8 days were included in this study. The duration until complete oral nutrition was reached after 11.8 ± 7.7 (vanilla), 12.2 ± 7.7 (rose), and 12.9 ± 8.8 (control) days. A nearly linear relation between odor presentation frequency and effect size was detectable. For infants that received the intervention for more than 66.7% of the time the length of gavage feeding (8 ± 5.4) and hospitalization (11 ± 6.5) was significantly lower in the vanilla group when compared with control (15 ± 7.3 and 21 ± 13.7, respectively). Odor stimulation with vanilla has an impact on oral feeding in premature infants, however the odor has to be presented on regular basis.

Birth practices: Maternal-neonate separation as a source of toxic stress

Maternal-neonate separation for human newborns has been the standard of care since the last century; low birth weight and preterm infants are still routinely separated from their mothers. With advanced technology, survival is good, but long-term developmental outcomes are very poor for these especially vulnerable newborns. The poor outcomes are similar to those described for adversity in childhood, ascribed to toxic stress. Toxic stress is defined as the absence of the buffering protection of adult support. Parental absence has been strictly enforced in neonatal care units for many reasons and could lead to toxic stress. The understanding of toxic stress comes from discoveries about our genome and epigenetics, the microbiome, developmental neuroscience and the brain connectome, and life history theory. The common factor is the early environment that gives (a) signals to epigenes, (b) sensory inputs to neural circuits, and (c) experiences for reproductive fitness. For human newborns that environment is direct skin-to-skin contact from birth. Highly conserved neuroendocrine behaviors determined by environment are described in this review. The scientific rationale underlying skin-to-skin contact is presented: autonomic development and regulation of the physiology leads to emotional connection and achieving resilience. Maternal-neonate separation prevents these critical neural processes from taking place, but also channel development into an alternative developmental strategy. This enables better coping in a stressful environment in the short term, but with permanently elevated stress systems that negatively impact mental and physical health in the long term. This may explain the increasing incidence of developmental problems in childhood, and also Developmental Origins of Health and Disease. Arguments are presented that maternal-neonate separation is indeed a source of toxic stress, and some suggestions are offered toward a "zero separation" paradigm.

Towards the Womb of Neonatal Intensive Care

Within the mother's womb, life finds its first stirrings. The womb shelters the fetus, the growing child within. We recognize the existential traces of a wombed existence when a newborn calms in response to being held; when a newborn stills in response to his or her mother's heartbeat; and, when a newborn startles in the presence of bright light. Yet, how does experiential human life begin within another human being? What are the conditions and paths of becoming for the fetus within the womb? And for the child born early, what "womb" welcomes the premature child in neonatal intensive care?

Hemodynamic responses to emotional speech in two-month-old infants imaged using diffuse optical tomography

Emotional speech is one of the principal forms of social communication in humans. In this study, we investigated neural processing of emotional speech (happy, angry, sad and neutral) in the left hemisphere of 21 two-month-old infants using diffuse optical tomography. Reconstructed total hemoglobin (HbT) images were analysed using adaptive voxel-based clustering and region-of-interest (ROI) analysis. We found a distributed happy > neutral response within the temporo-parietal cortex, peaking in the anterior temporal cortex; a negative HbT response to emotional speech (the average of the emotional speech conditions < baseline) in the temporo-parietal cortex, neutral > angry in the anterior superior temporal sulcus (STS), happy > angry in the superior temporal gyrus and posterior superior temporal sulcus, angry < baseline in the insula, superior temporal sulcus and superior temporal gyrus and happy < baseline in the anterior insula. These results suggest that left STS is more sensitive to happy speech as compared to angry speech, indicating that it might play an important role in processing positive emotions in two-month-old infants. Furthermore, happy speech (relative to neutral) seems to elicit more activation in the temporo-parietal cortex, thereby suggesting enhanced sensitivity of temporo-parietal cortex to positive emotional stimuli at this stage of infant development.

The human newborn's umwelt: Unexplored pathways and perspectives

Historically, newborns, and especially premature newborns, were thought to "feel nothing." However, over the past decades, a growing body of evidence has shown that newborns are aware of their environment, but the extent and the onset of some sensory capacities remain largely unknown. The goal of this review is to update our current knowledge concerning newborns' perceptual world and how ready they are to cope with an entirely different sensory environment following birth. We aim to establish not only how and when each sensory ability arises during the pre-/postbirth period but also discuss how senses are studied. We conclude that although many studies converge to show that newborns are clearly sentient beings, much is still unknown. Further, we identify a series of internal and external factors that could explain discrepancies between studies, and we propose perspectives for future studies. Finally, through examples from animal studies, we illustrate the importance of this detailed knowledge to pursue the enhancement of newborns' daily living conditions. Indeed, this is a prerequisite for assessing the effects of the physical environment and routine procedures on newborns' welfare.

Brain mechanisms that underlie music interventions in the exercise domain

In this chapter we review recent work from the realms of neuroscience and neuropsychology to explore the brain mechanisms that underlie the effects of music on exercise. We begin with an examination of the technique of electroencephalography (EEG), which has proven popular with researchers in this domain. We go on to appraise work conducted with the use of functional magnetic resonance imaging (fMRI) and then, looking more toward the future, we consider the application of functional near-infrared spectroscopy (fNIRS) to study brain hemodynamics. The experimental findings expounded herein indicate that music has the potential to guide attention toward environmental sensory cues and prevent internal, fatigue-related signals from entering focal awareness. The brain mechanisms underlying such effects are primarily associated with the downregulation of theta waves across the cortex surface, reduction of communication among somatosensory regions, and increased activation of the left inferior frontal gyrus. Taken holistically, research in this subfield of exercise psychology demonstrates a vibrant and reflexive matrix of attentional, emotional, behavioral, physiological, and psychophysiological responses to music across a variety of exercise modalities and intensities. The emergent hypotheses that we propose can be used to frame future research efforts.

Investigation of the Pattern of the Hemodynamic Response as Measured by Functional Near-Infrared Spectroscopy (fNIRS) Studies in Newborns, Less Than a Month Old: A Systematic Review

It has been 20 years since functional near-infrared spectroscopy (fNIRS) was first used to investigate the evoked hemodynamic response to a stimulus in newborns. The hemodynamic response to functional activation is well-established in adults, with an observed increase in concentration change of oxygenated hemoglobin (Δ[HbO2]) and decrease in deoxygenated hemoglobin (Δ[HHb]). However, functional studies in newborns have revealed a mixed response, particularly with Δ[HHb] where an inconsistent change in direction is observed. The reason for this heterogeneity is unknown, with potential explanations arising from differing physiology in the developing brain, or differences in instrumentation or methodology. The aim of this review is to collate the findings from studies that have employed fNIRS to monitor cerebral hemodynamics in term newborn infants aged 1 day-1 month. A total of 46 eligible studies were identified; some studies investigated more than one stimulus type, resulting in a total of 51 reported results. The NIRS parameters reported varied across studies with 50/51 cases reporting Δ[HbO2], 39/51 reporting Δ[HHb], and 13/51 reporting total hemoglobin concentration Δ[HbT] (Δ[HbO2] + Δ[HHb]). However, of the 39 cases reporting Δ[HHb] in graphs or tables, only 24 studies explicitly discussed the response (i.e., direction of change) of this variable. In the studies where the fNIRS responses were discussed, 46/51 cases observed an increase in Δ[HbO2], 7/51 observed an increase or varied Δ[HHb], and 2/51 reported a varied or negative Δ[HbT]. An increase in Δ[HbO2] and decrease or no change in Δ[HHb] was observed in 15 studies. By reviewing this body of literature, we have identified that the majority of research articles reported an increase in Δ[HbO2] across various functional tasks and did not report the response of Δ[HHb]. Confirming the normal, healthy hemodynamic response in newborns will allow identification of unhealthy patterns and their association to normal neurodevelopment.

Emotional Processing in the First 2 Years of Life: A Review of Near-Infrared Spectroscopy Studies

Emotional stimuli processing during childhood helps us to detect salient cues in our environment and prepares us for our social life. In early childhood, the emotional valences of auditory and visual input are salient and relevant cues of social aspects of the environment, and it is of special interest to understand how exactly the processing of emotional stimuli develops. Near‐infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool that has proven valuable in studying emotional processing in children. After conducting a systematic search of PubMed, Web of Science, and Embase databases, we examined 50 NIRS studies performed to study emotional stimuli processing in children in the first 2 years of age. We found that the majority of these studies are done in infants and the most commonly used stimuli are visual and auditory. Many of the reviewed studies suggest the involvement of bilateral temporal areas in emotional processing of visual and auditory stimuli. It is unclear which neural activation patterns reflect maturation and at what age the emotional encoding reaches those typically seen in adults. Our review provides an overview of the database on emotional processing in children up to 2 years of age. Furthermore, it demonstrates the need to include the less‐studied age range of 1 to 2 years, and suggests the use of combined audio‐visual stimuli and longitudinal studies for future research on emotional processing in children. Thus, NIRS might be a vital tool to study the associations between the early pattern of neural responses and socioemotional development later in life.

The Analgesic Effects of Maternal Milk Odor on Newborns: A Meta-Analysis

OBJECTIVE

The objective of this study was to evaluate the analgesic effects of maternal milk odor on newborns.

MATERIALS AND METHODS

We searched the literature in PubMed, MEDLINE, CINAHL, EMBASE, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) and collected all the randomized controlled trials (RCTs) investigating the effects of maternal milk odor versus scentless or other odors on procedural pain in newborns. The quality of included studies was assessed by the Cochrane Collaboration Risk of Bias tool. A meta-analysis was undertaken with the Review Manager 5.3 software and Stata version 11.0. Subgroup comparisons were prespecified according to the types of control groups.

RESULTS

Eight RCTs included a total of 453 participants. The results of meta-analysis showed that compared with the scentless group, the maternal milk odor group had lower pain scores during blood sampling (standardized mean difference, -0.81; 95% confidence interval [95% CI], -1.18 to -0.44; p < 0.001) and shorter crying time afterward (mean difference, -8.10; 95% CI, -15.46 to 0.73; p = 0.03). The maternal milk odor group had lower heart rate variability and oxygen saturation variability during and after a procedure, compared with both the scentless group and the vanilla group. However, no significant difference was identified in the mean heart rate and mean oxygen saturation in terms of the maternal milk odor group compared with amniotic fluid odor or mother's scent. The maternal milk odor group versus the formula milk odor group had shorter crying duration and lower levels of salivary cortisol after sampling.

CONCLUSIONS

Maternal milk odor appears to play an analgesic role in newborns. However, more high-quality studies are needed to confirm and quantitate the effect.

Increased activity in the right prefrontal cortex measured using near-infrared spectroscopy during a flower arrangement task

OBJECTIVE

Flower arrangement program (FAP) horticultural therapy promotes psychological, social and physiological wellness and recovery. Moreover, FAPs have been used to evaluate the outcomes related to visuospatial working memory; yet, most of these studies used subjective outcome measures such as behavioural observations and questionnaires. Few studies report objective evaluations of FAP effects in humans. In the present study, we measured the effects of an FAP task on frontal lobe activity in healthy participants using near-infrared spectroscopy. We quantified salivary amylase levels as an indicator of stress level during the FAP.

METHODS

The FAP task involved a predetermined arrangement pattern of natural materials (flowers and leaves) that required the participants to identify where a given material should be placed and temporarily memorise the designated position to complete the flower arrangement. The FAP task was compared to the block-tapping task (BTT), which is routinely used to evaluate visuospatial working memory.

RESULTS

Both the FAP task and BTT positively stimulated the right prefrontal cortex; however, stress was more effectively limited during the performance of the FAP task.

CONCLUSIONS

Our data suggest that FAP therapy may be useful for the rehabilitation of patients who are sensitive to stress.

Variability of the hemodynamic response in infants: Influence of experimental design and stimulus complexity

Measuring brain activity in developmental populations remains a major challenge despite great technological advances. Among the numerous available methods, functional near-infrared spectroscopy (fNIRS), an imaging modality that probes the hemodynamic response, is a powerful tool for recording brain activity in a great variety of situations and populations. Neurocognitive studies with infants have often reported inverted hemodynamic responses, i.e. a decrease instead of an increase in regional blood oxygenation, but the exact physiological explanation and cognitive interpretation of this response remain unclear. Here, we first provide an overview of the basic principles of NIRS and its use in cognitive developmental neuroscience. We then review the infant fNIRS literature to show that the hemodynamic response is modulated by experimental design and stimulus complexity, sometimes leading to hemodynamic responses with non-canonical shapes. We also argue that this effect is further modulated by the age of participants, the cortical regions involved, and the developmental stage of the tested cognitive process. We argue that this variability needs to be taken into account when designing and interpreting developmental studies measuring the hemodynamic response.