The transition to human fatherhood involves increased brain activation to infant stimuli in regions involved with reward and motivation

Abstract

In species where males provide parental care, the transition to fatherhood involves a shift in life history strategy in the direction of increased parenting and decreased mating effort. In non-human mammals, the transition to parenthood involves an increase in the motivation to approach and care for offspring, which is mediated by changes in a neural system that includes the medial preoptic area and the mesolimbic dopamine system. Whether humans experience increased activity in this parental brain system with the transition to parenthood has not been established. Here, we use an effort-based decision-making task to longitudinally track changes in parenting and mating motivation, and functional MRI to track accompanying changes in brain function across the transition to first-time fatherhood in men and compare these changes with those found in a sample of non-father control males. Fathers were generally less willing than non-fathers to exert effort to view female stimuli; however, there were no apparent changes in motivation to engage with either infant or female stimuli across the transition to fatherhood. On the other hand, changes in brain activation were evident. In response to cues predicting infant pictures, new fathers showed a pre- to post-natal increase in activation of brain regions that are part of the mesolimbic dopamine system, and this change was not found in non-father male controls. Fathers, but not non-fathers, also showed increases in activation to infant stimuli in brain regions implicated in empathy, such as the anterior insula. While univariate analyses showed no significant change in the neural response to pictures of adult females among fathers, a multivariate brain signature that was previously found to classify pleasure responses to a wide range of stimuli revealed that fathers showed an increase in pleasure-related activity to infant stimuli, as well as a decrease in pleasure-related activity to female stimuli. Our findings suggest that human fathers experience neurofunctional changes that may adapt them to their new parental role.

Keywords: brain; fMRI; fathers; female; infant.