Mother-Infant Face-to-Face Interaction: The Communicative Value of Infant-Directed Talking and Singing

The effects of live parental infant-directed singing on infants, parents, and the parent-infant dyad: A systematic review of the literature

Singing to infants is widely accepted as an enjoyable, positive, and beneficial interaction between the parent and infant across cultures. Whilst the literature suggests that live infant-directed singing impacts the infant, the parent doing the singing and the dyad in powerful ways, no systematic review of the evidence has yet been conducted. To this end, this systematic review identified 21 studies that investigated the effect of live parental infant-directed singing. These impacts were categorized as either being directly related to the infant, the parent, or the parent-infant dyad. Three main themes - one for each of the impact categories considered - were identified using thematic analysis techniques; infant-directed singing impacts on: infants' emotional regulation, provides validation of the parent's role, and promotes affect attunement within the dyad. The findings reinforce the benefits of live parental infant-directed singing for all parties involved, particularly when parents sing to typically developing infants born at full term. In contrast, the findings were inconsistent for pre-term infants. The implications of these findings are discussed.

Bottlenose dolphin mothers modify signature whistles in the presence of their own calves

Human caregivers interacting with children typically modify their speech in ways that promote attention, bonding, and language acquisition. Although this "motherese," or child-directed communication (CDC), occurs in a variety of human cultures, evidence among nonhuman species is very rare. We looked for its occurrence in a nonhuman mammalian species with long-term mother-offspring bonds that is capable of vocal production learning, the bottlenose dolphin (Tursiops truncatus). Dolphin signature whistles provide a unique opportunity to test for CDC in nonhuman animals, because we are able to quantify changes in the same vocalizations produced in the presence or absence of calves. We analyzed recordings made during brief catch-and-release events of wild bottlenose dolphins in waters near Sarasota Bay, Florida, United States, and found that females produced signature whistles with significantly higher maximum frequencies and wider frequency ranges when they were recorded with their own dependent calves vs. not with them. These differences align with the higher fundamental frequencies and wider pitch ranges seen in human CDC. Our results provide evidence in a nonhuman mammal for changes in the same vocalizations when produced in the presence vs. absence of offspring, and thus strongly support convergent evolution of motherese, or CDC, in bottlenose dolphins. CDC may function to enhance attention, bonding, and vocal learning in dolphin calves, as it does in human children. Our data add to the growing body of evidence that dolphins provide a powerful animal model for studying the evolution of vocal learning and language.

Affective Cortical Asymmetry at the Early Developmental Emergence of Emotional Expression

Emotions have an important survival function. Vast amounts of research have demonstrated how affect-related changes in physiology promote survival by effecting short-term and long-term changes in adaptive behavior. However, if emotions truly serve such an inherent function, they should be pervasive across species and be established early in life. Here, using electroencephalographic (EEG) brain activity we sought to characterize core neurophysiological features underlying affective function at the emergence of emotional expression [i.e., at the developmental age when human infants start to show reliable stimulus-elicited emotional states (4–6 months)]. Using an approach that eschews traditional EEG frequency band delineations (like theta, alpha), we demonstrate that negative emotional states induce a strong right hemispheric increase in the prominence of the resonant frequency (∼5–6 Hz) in the infant frontal EEG. Increased rightward asymmetry was strongly correlated with increased heart rate responses to emotionally negative states compared with neutral states. We conclude that functional frontal asymmetry is a key component of emotional processing and suggest that the rightward asymmetry in prominence of the resonant frequency during negative emotional states might reflect functional asymmetry in the central representation of anatomically driven asymmetry in the autonomic nervous system. Our findings indicate that the specific mode hallmarking emotional processing in the frontal cortex is established in parallel with the emergence of stable emotional states very early during development, despite the well known protracted maturation of frontal cortex.

Exposure to early and persistent maternal depression impairs the neural basis of attachment in preadolescence

Maternal depression increases child vulnerability to psychopathology, loneliness, and social maladjustment; yet, its long-term effects on the social brain are unknown. In this prospective longitudinal study we examined the impact of early and persistent maternal depression on the neural basis of attachment in preadolescence. A community cohort was followed in two groups; children exposed to maternal depression from birth to 6 years and healthy controls. At 9 months and 6 years, mother-child interactions were coded for maternal sensitivity and affect synchrony and salivary oxytocin levels were assessed at 6 years. At preadolescence (11-13 years), children underwent magnetoencephalography (MEG) while exposed to own versus unfamiliar mother-child interaction. Own interaction elicited greater response in beta- and gamma-band oscillations across a wide cluster in temporal and insular cortices, including the Superior Temporal Sulcus, Superior Temporal Gyrus, Inferior Temporal Gyrus, and insula. Beta activations were predicted by maternal sensitivity across early childhood and gamma by affect synchrony. Oxytocin was related to beta response to social cues. Maternal depression impacted child's brain response in two ways. First, maternal depression significantly increased the prevalence of child affective disorder and such children showed no neural differentiation between attachment and non-attachment stimuli. Second, maternal depression decreased maternal sensitivity, affect synchrony, and child oxytocin across early childhood and these were longitudinally associated with aberrant neural response to attachment-specific and social-general cues in preadolescence. Our findings are the first to describe mechanisms by which maternal depression impairs the neural basis of attachment at the transition to adolescence and advocate the need for relationship-focused early interventions.

Child brain exhibits a multi-rhythmic response to attachment cues

Research on the human parental brain implicated brain networks involved in simulation, mentalization and emotion processing and indicated that stimuli of own parent-child interaction elicit greater integration among networks supporting attachment. Here, we examined children's neural activation while viewing own parent-child interactions and asked whether similar networks activate when children are exposed to attachment stimuli. Sixty-five 11-year-old children underwent magnetoencephalography (MEG) while observing own vs unfamiliar mother-child interaction. Own mother-child interactions elicited a greater neural response across distributed brain areas including alpha suppression in posterior regions, theta enhancement in the fusiform gyrus and beta- and gamma-band oscillations across a wide cluster in the right temporal cortex, comprising the superior temporal sulcus/superior temporal gyrus and insula. Theta and gamma activations were associated with the degree of mother-child social synchrony in the home ecology. Findings from this exploratory study are the first to show activations in children that are similar to previous findings in parents and comparable associations between social synchrony and gamma oscillations in temporal regions. Results indicate that attachment stimuli elicit a strong neural response in children that spreads across a wide range of oscillations, underscoring the considerable neural resources allocated to this fundamental, survival-related cue.