Article summary with The effect of oxytocin and vasopressin administration on fathers’ neural responses to infant crying: A randomized controlled within-subject study by Witte et al. - 2022

What is the purpose of investigating the hormonal mechanisms implicated in neural models of infant cry perception during the first year of fatherhood?

Crying is a way for infants to communicate their need for parental care. Parents who respond sensitively to it stimulate positive child development. Parental responses to infant crying may be shaped by parents’ neural processing of infant cry sounds, but most studies have only looked at mothers. It is possible that fathers’ neural responses to infant crying are affected by hormonal levels.

Which hormones are especially interesting in studying paternal neural responses to infant cry sounds?

Oxytocin and vasopressin are hormones and neurotransmitters that have been associated with social behavior regulation, pair bonding, and parental caregiving.

• Oxytocin enhances the coding of social signals, in-group trust, empathy, and enhances positive parent-infant interactions. It exerts anxiolytic effects and attenuates endocrine and autonomic responses to stress.
• Vasopressin plays a role in social memory, encoding human facial expressions, defensive and territorial behaviors, and paternal caregiving.

Why do early childhood experiences need to be controlled for when studying the effects of oxytocin and vasopressin on paternal neural responses to infant cry sounds?

The prosocial effects of oxytocin and vasopressin may be moderated by early childhood experiences. Early childhood experiences alter gene expression. This results in individuals being less or more susceptible for the prosocial effects of hormonal administration. Previous research indicates that fathers with less negative childhood experiences experience larger prosocial effects from oxytocin and vasopressin.

What is the effect of oxytocin and vasopressin administration on neural responses to infant cry sounds in first-time fathers in the first year of parenthood?

The experiment showed the following results:

• Whole brain analyses revealed no significant effect of vasopressin or oxytocin administration on neural activation in response to infant cry sounds.
• Fathers showed neural activation in response to infant crying in several brain regions, including the cerebellum, posterior cingulate, supramarginal gyrus, angular gyrus, and the middle and superior temporal gyrus.
• Fathers’ early childhood experiences did not moderate the effects of oxytocin and vasopressin administration on neural responses to infant cry sounds.
• Oxytocin administration decreases amygdala activation, and may decrease feelings of anxiety or aversion to a crying infant.

How can a ceiling effect explain these results?

Previous studies suggested more efficient processing and increased motivation to end infant distress in parents compared to non-parents. The current study however looked at fathers in their first year of fatherhood. They may have had higher levels of neural reactivity in the brain areas that are related to mentalizing, emotion regulation, and empathy than non-parents. This ceiling effect may explain why no significant effect was found of oxytocin administration on the brain areas that in previous research were indeed affected.