Infant Stimuli Research Articles

Auditory ERP response to successive stimuli in infancy.

Background. Auditory Event-Related Potentials (ERPs) are useful for understanding early auditory development among infants, as it allows the collection of a relatively large amount of data in a short time. So far, studies that have investigated development in auditory ERPs in infancy have mainly used single sounds as stimuli. Yet in real life, infants must decode successive rather than single acoustic events. In the present study, we tested 4-, 8-, and 12-month-old infants’ auditory ERPs to musical melodies comprising three piano notes, and examined ERPs to each individual note in the melody. Methods. Infants were presented with 360 repetitions of a three-note melody while EEG was recorded from 128 channels on the scalp through a Geodesic Sensor Net. For each infant, both latency and amplitude of auditory components P1 and N2 were measured from averaged ERPs for each individual note. Results. Analysis was restricted to response collected at frontal central site. For all three notes, there was an overall reduction in latency for both P1 and N2 over age. For P1, latency reduction was significant from 4 to 8 months, but not from 8 to 12 months. N2 latency, on the other hand, decreased significantly from 4 to 8 to 12 months. With regard to amplitude, no significant change was found for either P1 or N2. Nevertheless, the waveforms of the three age groups were qualitatively different: for the 4-month-olds, the P1–N2 deflection was attenuated for the second and the third notes; for the 8-month-olds, such attenuation was observed only for the middle note; for the 12-month-olds, the P1 and N2 peaks show relatively equivalent amplitude and peak width across all three notes. Conclusion. Our findings indicate that the infant brain is able to register successive acoustic events in a stream, and ERPs become better time-locked to each composite event over age. Younger infants may have difficulties in responding to late occurring events in a stream, and the onset response to the late events may overlap with the incomplete response to preceding events.

Postpartum depression and brain response to infants: Differential amygdala response and connectivity

ABSTRACTRecent evidence suggests that postpartum depression is associated with reduced amygdala (AMY) response to negative stimuli. However, given the anhedonic features of PPD, it is important to consider mothers’ brain response specifically to positive infant and to other positive stimuli. Mothers with (n = 28) and without (n = 17) clinically determined PPD (n = 28) viewed smiling pictures of infants (Own and Other), and positive non-infant stimuli (Non-Infant). First, we examined group differences in AMY response across conditions. Next, psychophysiological interaction was used to examine group differences in AMY connectivity across conditions. Connectivity estimates were then correlated with measures of maternal mood and anxiety. PPD mothers, compared to non-PPD mothers, showed overall increased AMY response across conditions in the right AMY. Despite this, PPD mothers demonstrated decreased bilateral AMY–right insular cortex (IC) connectivity as compared to non-PPD mothers when they view Own–Other infants. Furthermore, decreasing AMY–IC connectivity was associated with increasing symptoms of depression and anxiety. These differences were evident only for infant stimuli and did not apply to all positively valenced stimuli. Thus, PPD mothers show altered brain response and connectivity in regions strongly implicated in the processing of socially and emotionally relevant stimuli, as well as interoception and the evaluation of subjective emotional experience.

THE IMPACT OF DEPRESSION ON MATERNAL RESPONSES TO INFANT FACES IN PREGNANCY.

ABSTRACTResearch has suggested that prenatal depression may be associated with disrupted maternal responses to infant stimuli, with depressed pregnant women not showing the bias toward distressed infants as that observed in nondepressed pregnant women. The current study examined the effects of depression on self‐ reported responses to infant stimuli, in early pregnancy. Women with clinical depression (n = 38), and nondepressed women (n = 67) were recruited from a wider cognitive behavioral therapy trial. They completed Maternal Response Scales in which they were presented with images of distressed, neutral, and happy infant faces, with no time limit. The women rated their responses to these images along three dimensions—wanting to comfort, wanting to turn away, and feelings of anxiety—using Likert scales via a computerized task. There was evidence that women with depression in pregnancy showed different responses than did women without depression. Women with depression were substantially more likely to be in the highest quartile for ratings of wanting to turn away, odds (OR) ratio = 4.15, 95% confidence intervals (CIs) = 1.63–10.5, p = .003, and also were substantially less likely to be in the highest quartile for wanting to comfort a distressed infant face, OR = 0.22, 95% CIs = 0.09–0.54, p < .001. Findings are consistent with there being both a heightened avoidant and a reduced comforting response toward distressed infants in depressed pregnant women, providing some support that depression disrupts maternal preparations at a conscious level.

Parental brain: cerebral areas activated by infant cries and faces. A comparison between different populations of parents and not.

Literature about parenting traditionally focused on caring behaviors and parental representations. Nowadays, an innovative line of research, interested in evaluating the neural areas and hormones implicated in the nurturing and caregiving responses, has developed. The only way to permit a newborn to survive and grow up is to respond to his needs and in order to succeed it is necessary, first of all, that the adults around him understand what his needs are. That is why adults’ capacity of taking care of infants cannot disregard from some biological mechanisms, which allow them to be more responsive to the progeny and to infants in general. Many researches have proved that exist specific neural basis activating in response to infant evolutionary stimuli, such as infant cries and infant emotional facial expression. There is a sort of innate predisposition in human adults to respond to infants’ signals, in order to satisfy their need and allow them to survive and become young adults capable of taking care of themselves. This article focuses on research that has investigated, in the last decade, the neural circuits underlying parental behavioral responses. Moreover, the paper compares the results of those studies that investigated the neural responses to infant stimuli under different conditions: familiar versus unknown children, parents versus non-parents and normative versus clinical samples (depression, addiction, adolescence, and PTSD).

Evolutionary-based threat modulates perception of looming visual stimuli in human infants

Research with both human and non-human primates suggests that the visual system exhibits specialized processing of evolutionary-based threats. Adult humans (Ohman & Mineka, 2001) and monkeys (Shibasaki & Kawai, 2009) detect images of snakes and spiders faster than neutral images during visual search. Moreover, human infants orient more quickly to a threatening compared to a non-threatening image, when presented with two images simultaneously (e.g., a snake and a flower). Taken together, these results suggest a perceptual bias for threat that exists prior to the development of overt fear and that may be innate in human development (LoBue & DeLoache, 2009). Yet differential orientating in infants and visual search paradigms typically used with adult humans and nonhuman primates are heavily dependent on contrast images; there are also influences of stimulus familiarity and strategic processes (Frischen, Eastwood, & Smilek, 2008), raising questions about the mechanisms underlying the perceptual basis of sensitivity to evolutionarily-based threats. The current study extends existing research by examining infants’ defensive blinking in a visual looming paradigm. We tested 60 6- to 12- month-old infants. Infants were presented with images of snakes, spiders, rabbits, and butterflies. Each image loomed towards them, one at a time, at six velocities, creating different time-to-contacts (TTCs). As in previous studies (Kayed & van der Meer, 2000), analyses revealed that infants’ blinks scaled according to TTC. We also found that defensive blinking was modulated by the threat value of stimuli. Infants blinked sooner to snakes and spiders compared to rabbits and butterflies at all TTCs (ps < .05). Critically, this effect cannot be accounted for by familiarity, as infants looked longer overall to the non-threatening than threatening animals (p < .05). That infants’ defensive blinks were modulated by the threat value of the animal provides evidence for specialized spatiotemporal perceptual processing of evolutionary-based threat. Meeting abstract presented at VSS 2015

Oxytocin and vasopressin enhance responsiveness to infant stimuli in adult marmosets

The neuropeptides oxytocin (OT) and arginine-vasopressin (AVP) have been implicated in modulating sex-specific responses to offspring in a variety of uniparental and biparental rodent species. Despite the large body of research in rodents, the effects of these hormones in biparental primates are less understood. Marmoset monkeys (Callithrix jacchus) belong to a clade of primates with a high incidence of biparental care and also synthesize a structurally distinct variant of OT (proline instead of leucine at the 8th amino acid position; Pro8-OT). We examined the roles of the OT and AVP systems in the control of responses to infant stimuli in marmoset monkeys. We administered neuropeptide receptor agonists and antagonists to male and female marmosets, and then exposed them to visual and auditory infant-related and control stimuli. Intranasal Pro8-OT decreased latencies to respond to infant stimuli in males, and intranasal AVP decreased latencies to respond to infant stimuli in females. Our study is the first to demonstrate that Pro8-OT and AVP alter responsiveness to infant stimuli in a biparental New World monkey. Across species, the effects of OT and AVP on parental behavior appear to vary by species-typical caregiving responsibilities in males and females.

Neural basis of attachment-caregiving systems interaction: insights from neuroimaging studies.

The attachment and the caregiving system are complementary systems which are active simultaneously in infant and mother interactions. This ensures the infant survival and optimal social, emotional, and cognitive development. In this brief review we first define the characteristics of these two behavioral systems and the theory that links them, according to what Bowlby called the “attachment-caregiving social bond” (Bowlby, 1969). We then follow with those neuroimaging studies that have focused on this particular issue, i.e., those which have studied the activation of the careging system in women (using infant stimuli) and have explored how the individual attachment model (through the Adult Attachment Interview) modulates its activity. Studies report altered activation in limbic and prefrontal areas and in basal ganglia and hypothalamus/pituitary regions. These altered activations are thought to be the neural substrate of the attachment-caregiving systems interaction.

Neuroanatomical and neurochemical basis of parenting: Dynamic coordination of motivational, affective and cognitive processes

This article is part of a Special Issue “Parental Care”. Becoming a parent is arguably the most profound transforming experience in life. It is also inherently very emotionally and physically demanding, such that the reciprocal interaction with the young changes the brain and behavior of the parents. In this review, we examine the neurobiological mechanisms of parenting primarily discussing recent research findings in rodents and primates, especially humans. We argue that it is essential to consider parenting within a conceptual framework that recognizes the dynamics of the reciprocal mother–young relationship, including both the complexity and neuroplasticity of its underlying mechanisms. Converging research suggests that the concerted activity of a distributed network of subcortical and cortical brain structures regulates different key aspects of parenting, including the sensory analysis of infant stimuli as well as motivational, affective and cognitive processes. The interplay among these processes depends on the action of various neurotransmitters and hormones that modulate the timely and coordinated execution of caregiving responses of the maternal circuitry exquisitely attuned to the young's affect, needs and developmental stage. We conclude with a summary and a set of questions that may guide future research.

Atypical processing of voice sounds in infants at risk for autism spectrum disorder

Adults diagnosed with autism spectrum disorder (ASD) show a reduced sensitivity (degree of selective response) to social stimuli such as human voices. In order to determine whether this reduced sensitivity is a consequence of years of poor social interaction and communication or is present prior to significant experience, we used functional MRI to examine cortical sensitivity to auditory stimuli in infants at high familial risk for later emerging ASD (HR group, N = 15), and compared this to infants with no family history of ASD (LR group, N = 18). The infants (aged between 4 and 7 months) were presented with voice and environmental sounds while asleep in the scanner and their behaviour was also examined in the context of observed parent–infant interaction. Whereas LR infants showed early specialisation for human voice processing in right temporal and medial frontal regions, the HR infants did not. Similarly, LR infants showed stronger sensitivity than HR infants to sad vocalisations in the right fusiform gyrus and left hippocampus. Also, in the HR group only, there was an association between each infant's degree of engagement during social interaction and the degree of voice sensitivity in key cortical regions. These results suggest that at least some infants at high-risk for ASD have atypical neural responses to human voice with and without emotional valence. Further exploration of the relationship between behaviour during social interaction and voice processing may help better understand the mechanisms that lead to different outcomes in at risk populations.

Oxytocin increases VTA activation to infant and sexual stimuli in nulliparous and postpartum women

After giving birth, women typically experience decreased sexual desire and increased responsiveness to infant stimuli. These postpartum changes may be viewed as a trade-off in reproductive interests, which could be due to alterations in brain activity including areas associated with reward. The goal of this study was to describe the roles of oxytocin and parity on reward area activation in response to reproductive stimuli, specifically infant and sexual images. Because they have been shown to be associated with reward, the ventral tegmental area (VTA) and nucleus accumbens (NAc) were targeted as areas of expected alterations in activity. Oxytocin was chosen as a potential mediator of reproductive trade-offs because of its relationship to both mother–infant interactions, including breastfeeding and bonding, and sexual responses. We predicted that postpartum women would show higher reward area activation to infant stimuli and nulliparous women would show higher activation to sexual stimuli and that oxytocin would increase activation to infant stimuli in nulliparous women. To test this, we measured VTA and NAc activation using fMRI in response to infant photos, sexual photos, and neutral photos in 29 postpartum and 30 nulliparous women. Participants completed the Sexual Inhibition (SIS) and Sexual Excitation (SES) Scales and the Brief Index of Sexual Function for Women (BISF-W), which includes a sexual desire dimension, and received either oxytocin or placebo nasal spray before viewing crying and smiling infant and sexual images in an fMRI scanner. For both groups of women, intranasal oxytocin administration increased VTA activation to both crying infant and sexual images but not to smiling infant images. We found that postpartum women showed lower SES, higher SIS, and lower sexual desire compared to nulliparous women. Across parity groups, SES scores were correlated with VTA activation and subjective arousal ratings to sexual images. In postpartum women, sexual desire was positively correlated with VTA activation to sexual images and with SES. Our findings show that postpartum decreases in sexual desire may in part be mediated by VTA activation, and oxytocin increased activation of the VTA but not NAc in response to sexual and infant stimuli. Oxytocin may contribute to the altered reproductive priorities in postpartum women by increasing VTA activation to salient infant stimuli.

Large auditory evoked potentials to rare emotional stimuli in preterm infants at term age

Large auditory evoked potentials to rare emotional stimuli in preterm infants at term age

Depressed Mothers Show Increased Anxiety and Negativity and Differential Salivary Cortisol in Response to Infant Cries

Objective: The impact of postpartum depression on mother-infant interaction, affective responses to infant cries, as well as hormonal and autonomic responses to infant stimuli were examined in a sample of primiparous and multiparous women. Methods: A sample of 140 depressed and non-depressed women where randomly assigned to one of two conditions: 1) cry (pain; hunger); and 2) neutral (female neutral voice). Emotional response scores, salivary cortisol, and heart rate were collected. Depression was designated if women scored 12 or above on the Edinburgh Postpartum Depression Scale (EPDS). Results: Depressed mothers reported feeling more anxious and negative when listening to infant cries and responded more strongly to the pain as opposed to the hunger cries compared to non-depressed mothers. Depressed mothers also showed higher overall cortisol levels compared to non-depressed mothers, with non-depressed mothers demonstrating a slight increase in response to the cries, while depressed mothers had a blunted response to the cries. No differences were reported in maternal heart-rate. Conclusions: PPD has a clear impact on a mother’s interaction with her infant which in turn, can have substantial effects on the infant’s social and emotional development.

Understanding the effects of one's actions upon hidden objects and the development of search behaviour in 7-month-old infants.

Infants' understanding of how their actions affect the visibility of hidden objects may be a crucial aspect of the development of search behaviour. To investigate this possibility, 7-month-old infants took part in a two-day training study. At the start of the first session, and at the end of the second, all infants performed a search task with a hiding-well. On both days, infants had an additional training experience. The 'Agency group' learnt to spin a turntable to reveal a hidden toy, whilst the 'Means-End' group learnt the same means-end motor action, but the toy was always visible. The Agency group showed greater improvement on the hiding-well search task following their training experience. We suggest that the Agency group's turntable experience was effective because it provided the experience of bringing objects back into visibility by one's actions. Further, the performance of the Agency group demonstrates generalized transfer of learning across situations with both different motor actions and stimuli in infants as young as 7 months.

The state of art of biological processes in paternal care

This review of the state of art aimed to present the most recent data on neuronal, neurochemical, hormonal and genetic bases of paternal care using MEDLINE and PsycInfo databases (1970-2013). An integrated model of biological substrates that assist men in the transition to fatherhood is presented. Guided by a genetic background, hypothalamic-midbrain-limbic-paralimbic-cortical circuits were found to be activated in fathers when infant stimuli are presented. A set of specific neuropeptides and steroid hormones are produced and seem to be related to brain activation, potentiating the paternal phenotype. Together, genetic, brain and hormonal processes suggest the existence of biological bases of paternal care in humans, activated and enhanced by infant stimuli and responsive to variations in the father-infant relationship.

Relationship status and sex differences in emotion lateralisation: An examination contrasting the processing of emotional infant and adult faces

When processing facial emotion, most individuals are right hemisphere dominant; however there is variability in this pattern with males typically being more strongly lateralised than females. Relationship status has been found to influence the processing of facial stimuli in women, and therefore, in this research the lateralised processing of facial emotion is considered whilst taking into account the participant’s relationship status and sex. Using the chimeric faces test, with both infant and adult facial stimuli, it was shown that partnered participants, but not single participants, were more strongly lateralised for the processing of adult stimuli than infant stimuli, and that partnered women did not show any hemispheric bias. These findings suggest that the neuropsychological processing of emotion may change dependent on an individual’s relationship status, and are discussed in terms of the possible evolutionary significance of infant faces for individuals who are in a relationship and who wish to have children.

Reduced neonatal regulatory T cell response to microbial stimuli associates with subsequent eczema in high-risk infants.

Regulatory T cells (Treg) play an essential role in early immune programming and shaping the immune response towards a pro-allergic or tolerant state. We evaluated cord blood Treg and cytokine responses to microbial and non-microbial stimuli in infants at high risk of allergic disease and their associations with development of allergic disease in the first year. Cord blood mononuclear cells from 72 neonates were cultured with toll-like receptors (TLR2) ligands: lipoteichoic acid (LTA) and heat-killed Lactobacillus rhamnosus GG (HKL); TLR4 ligand: lipopolysaccharide (LPS); ovalbumin (OVA); anti-CD3; or media for 48 h. Treg numbers and Treg cytokines were assessed in relation to allergic disease outcomes during the first year of life (eczema and atopic sensitization). Infants with eczema (n = 24) had reduced percentages of FoxP3(hi)CD25(hi) Treg in LTA (p = 0.01, adj p = 0.005) and HKL (p = 0.04, adj p = 0.02) stimulated cultures as well as reduced IL-10 (p = 0.01) production following HKL stimulation compared to those without eczema (n = 48). No differences in Treg or cytokine responses to LPS, OVA or anti-CD3 were seen. Infants who developed sensitization had lower percentages of Treg following TLR2 stimulation (but not other stimuli) compared to non-sensitized infants. High-risk children who develop allergic disease in the first year of life have deficient Treg responses to microbial stimuli but not allergen from the time of birth, which may contribute to failure of immune tolerance development in infancy.

Salivary α-Amylase Reactivity to Infant Crying in Maltreating Mothers.

Deviant physiological reactivity to infant stimuli has been suggested to underlie maladaptive parenting behavior. Our study involved 44 maltreating and 42 non-maltreating mothers. During a standardized cry paradigm, mothers listened to nine cry sounds of varying pitches. Saliva was collected at baseline, after each cry sound, and after a recovery episode. Salivary α-amylase (sAA) as a marker of autonomic nervous system (ANS) activity was assayed from saliva samples. Maltreating mothers showed lower overall sAA levels and an attenuated reactivity pattern to infant crying as compared to non-maltreating mothers. No effect of type of maltreatment (neglect only vs. neglect and abuse) was found. Furthermore, positive correlations between sAA and heart rate (HR) for non-maltreating mothers differed significantly from non-significant correlations between sAA and HR for maltreating mothers. This suggests anomalous asynchrony between different aspects of the ANS in maltreating mothers. Results indicate a lack of functional autonomic (re)activity as a contributing risk factor to child maltreatment.

Early influence of auditory stimuli on upper-limb movements in young human infants: an overview.

Given that the auditory system is rather well developed at the end of the third trimester of pregnancy, it is likely that couplings between acoustics and motor activity can be integrated as early as at the beginning of postnatal life. The aim of the present mini-review was to summarize and discuss studies on early auditory-motor integration, focusing particularly on upper-limb movements (one of the most crucial means to interact with the environment) in association with auditory stimuli, to develop further understanding of their significance with regard to early infant development. Many studies have investigated the relationship between various infant behaviors (e.g., sucking, visual fixation, head turning) and auditory stimuli, and established that human infants can be observed displaying couplings between action and environmental sensory stimulation already from just after birth, clearly indicating a propensity for intentional behavior. Surprisingly few studies, however, have investigated the associations between upper-limb movements and different auditory stimuli in newborns and young infants, infants born at risk for developmental disorders/delays in particular. Findings from studies of early auditory-motor interaction support that the developing integration of sensory and motor systems is a fundamental part of the process guiding the development of goal-directed action in infancy, of great importance for continued motor, perceptual, and cognitive development. At-risk infants (e.g., those born preterm) may display increasing central auditory processing disorders, negatively affecting early sensory-motor integration, and resulting in long-term consequences on gesturing, language development, and social communication. Consequently, there is a need for more studies on such implications.

In search of neural endophenotypes of postpartum psychopathology and disrupted maternal caregiving.

This is a selective review that provides the context for the study of perinatal affective disorder mechanisms and outlines directions for future research. We integrate existing literature along neural networks of interest for affective disorders and maternal caregiving: (i) the salience/fear network; (ii) the executive network; (iii) the reward/social attachment network; and (iv) the default mode network. Extant salience/fear network research reveals disparate responses and corticolimbic coupling to various stimuli based upon a predominantly depressive versus anxious (post-traumatic stress disorder) clinical phenotype. Executive network and default mode connectivity abnormalities have been described in postpartum depression (PPD), although studies are very limited in these domains. Reward/social attachment studies confirm a robust ventral striatal response to infant stimuli, including cry and happy infant faces, which is diminished in depressed, insecurely attached and substance-using mothers. The adverse parenting experiences received and the attachment insecurity of current mothers are factors that are associated with a diminution in infant stimulus-related neural activity similar to that in PPD, and raise the need for additional studies that integrate mood and attachment concepts in larger study samples. Several studies examining functional connectivity in resting state and emotional activation functional magnetic resonance imaging paradigms have revealed attenuated corticolimbic connectivity, which remains an important outcome that requires dissection with increasing precision to better define neural treatment targets. Methodological progress is expected in the coming years in terms of refining clinical phenotypes of interest and experimental paradigms, as well as enlarging samples to facilitate the examination of multiple constructs. Functional imaging promises to determine neural mechanisms underlying maternal psychopathology and impaired caregiving, such that earlier and more precise detection of abnormalities will be possible. Ultimately, the discovery of such mechanisms will promote the refinement of treatment approaches toward maternal affective disturbance, parenting behaviours and the augmentation of parenting resiliency.

The biology of mammalian parenting and its effect on offspring social development.

Parents know the transformative nature of having and caring for a child. Among many mammals, giving birth leads from an aversion to infant stimuli to irresistible attraction. Here, we review the biological mechanisms governing this shift in parental motivation in mammals. Estrogen and progesterone prepare the uterus for embryo implantation and placental development. Prolactin stimulates milk production, whereas oxytocin initiates labor and triggers milk ejection during nursing. These same molecules, interacting with dopamine, also activate specific neural pathways to motivate parents to nurture, bond with, and protect their offspring. Parenting in turn shapes the neural development of the infant social brain. Recent work suggests that many of the principles governing parental behavior and its effect on infant development are conserved from rodent to humans.