A walk on the dark side: TMS over the right inferior frontal gyrus (rIFG) disrupts behavioral responses to infant stimuli.

Infant signals, including infant sounds and facial expressions, play a critical role in eliciting parental proximity and care. Processing of infant signals in the adulthood brain is likely to recruit emotional empathy neural circuits, including the inferior frontal gyrus (IFG). Here, we used transcranial magnetic stimulation (TMS) to test the role of right IFG (rIFG) in behavioral responses to infant signals. Specifically, a group of nulliparous women were asked to perform a handgrip dynamometer task and an Approach-Avoidance Task (AAT) after receiving TMS over the right IFG or over a control site (vertex). Suppressing activity in the rIFG affected the modulation of handgrip force in response to infant crying. Moreover, the AAT showed that participants tend to avoid the sad infant face after Vertex stimulation, and this bias was counteracted by rIFG stimulation. Our results suggest a causal role of rIFG in sensitive responding towards sad infants and point to the rIFG as a critical node in the neural network underlying the innate releasing mechanism for feelings of love, affection and caring of sad infants.

Emotional maltreatment is associated with atypical responding to stimulation of endogenous oxytocin release through mechanically-delivered massage in males.

The neuropeptide oxytocin plays an important role in social behavior, parenting, and affectionate touch and there is some evidence that oxytocin release can be stimulated by massage or affectionate touch. We examined the effects of massage applied by a massage seat cover on salivary oxytocin levels in two exploratory studies using within-subject designs. In Study 1 massage effects on oxytocin levels were examined in a sample of N=20 healthy female participants. Effects of a 15-min massage session were compared to a control condition during which participants sat on a comfortable chair without a massage seat cover. Salivary oxytocin levels were measured at baseline and up to three hours after the session. We found that massage attenuated oxytocin decreases over time, indicating that massage stimulates oxytocin release. In Study 2, we examined whether effects of massage in N=46 healthy male participants depend on experiences of emotional maltreatment. In addition, we examined whether enhanced oxytocin levels after massage affect the use of excessive handgrip force in response to infant crying and laughter as measured with a handgrip dynamometer. Our findings show that massage results in elevated oxytocin levels compared to a control condition, but that the effects of massage are dependent on experiences of emotional maltreatment. Men with experiences of emotional maltreatment showed lower oxytocin levels, which did not increase after massage. Furthermore, we found that high oxytocin levels after massage were related to reduced handgrip force during exposure to infant crying and laughter, indicating that massage stimulates a sensitive response to infant signals by stimulating oxytocin release. Although massage did not affect oxytocin levels in individuals with experiences of maltreatment, it reduced the use of handgrip force in response to infant crying and laughter in these individuals. Our findings indicate that emotional maltreatment is associated with atypical responding to stimulation of endogenous oxytocin release.

Attachment in the brain: adult attachment representations predict amygdala and behavioral responses to infant crying.

Current research found that adult attachment representations influence neural, emotional, and behavioral responses to infant crying, thus validating the Berkeley Adult Attachment Interview with functional Magnetic Resonance Imaging. This study examined amygdala activation, feelings of irritation, and the use of excessive force as indicated by grip strength using a handgrip dynamometer during exposure to infant crying and scrambled control sounds in 21 women without children. Individuals with insecure attachment representations showed heightened amygdala activation when exposed to infant crying compared to individuals with secure attachment representations. In addition, insecure individuals experienced more irritation during infant crying and used more excessive force than individuals with a secure representation. Amygdala hyperactivity might be one of the mechanisms underlying the experience of negative emotions during exposure to infant crying in insecure individuals and might explain why insecure parents respond inconsistently to infant signals or reject their infants' attachment behavior.

No laughing matter: intranasal oxytocin administration changes functional brain connectivity during exposure to infant laughter.

Infant laughter is a rewarding experience. It activates neural reward circuits and promotes parental proximity and care, thus facilitating parent-infant attachment. The neuropeptide oxytocin might enhance the incentive salience of infant laughter by modulating neural circuits related to the perception of infant cues. In a randomized controlled trial with functional magnetic resonance imaging we investigated the influence of intranasally administered oxytocin on functional brain connectivity in response to infant laughter. Blood oxygenation level-dependent responses to infant laughter were measured in 22 nulliparous women who were administered oxytocin and 20 nulliparous women who were administered a placebo. Elevated oxytocin levels reduced activation in the amygdala during infant laughter and enhanced functional connectivity between the amygdala and the orbitofrontal cortex, the anterior cingulate, the hippocampus, the precuneus, the supramarginal gyri, and the middle temporal gyrus. Increased functional connectivity between the amygdala and regions involved in emotion regulation may reduce negative emotional arousal while enhancing the incentive salience of the infant laughter.

Oxytocin receptor gene and depressive symptoms associated with physiological reactivity to infant crying.

Both the oxytocin receptor (OXTR) gene and depressive symptoms have been associated with parenting behaviour. The OXTR GG genotype has been suggested to be related to more sensitive parenting, whereas depressive symptoms may affect sensitivity negatively. We examined the role of OXTR and the influence of depressive symptoms in explaining differences in physiological reactivity to infant crying. Heart rate responses of 40 healthy females without children (age 19-47 years, randomly selected half of twin pairs) were measured during the presentation of three episodes of infant cry sounds. Participants with the presumably more efficient variant of the oxytonergic system gene (OXTR GG) had more pronounced physiological reactivity to repeated cry sounds, except when they showed more symptoms of depression. Results were replicated in the second half of the twin sample. This is the first study to suggest effects of OXTR genotype on physiological reactivity to infant crying. Depressive symptoms may however suppress the effect of the OXTR GG genotype.