Here's an interesting study just out:
This is the first study to show a distinction between breast and formula feeding mothers in brain activity in response to their babies' cries. Medical News Today reports:
The breastfeeding mothers surveyed for the study showed greater responses to their infant's cry in brain regions related to caregiving behavior and empathy than mothers who relied upon formula as the baby's main food source. This is the first paper to examine the underlying neurobiological mechanisms as a function of breastfeeding, and to connect brain activity with maternal behaviors among human mothers.
The authors concluded, "Results suggest links between breastfeeding and greater response to infant cues in brain regions implicated in maternal–infant bonding and empathy during the early postpartum. Such brain activations may facilitate greater maternal sensitivity as infants enter their social world."
This was a small study - just 17 moms - but it sets the stage for more investigation into the neurological mechanisms involved in breastfeeding.