Estrogen and Progesterone

Estrogen and progesterone are among the many hormones the maternal brain is abundant in. The increase of these hormones during pregnancy and their decrease at delivery are responsible for switching on maternal behavior. Endorphins and oxytocin, feel-good hormones, are also key to the activation of maternal instinct. The act of suckling will release endorphins and oxytocin to promote maternal bond between mother and child.

The expression of maternal behavior begins during pregnancy and continues well after parturition. Several regions of the brain are involved in this. Playing a role in the establishment of maternal behavior is the pituitary gland through its release of several hormones necessary for maternal stimulation. The hippocampus, which manages memory and learning, gets ramped up during pregnancy so that appropriate care can be provided to the young for their survival. Motivational behaviors of the mother are regulated by the nucleus accumbens, as this area is part of the pleasure center and plays an integral part in rewards for maternal behavior. A mother's positive response to her infant and their emotional attachment can be traced to the prefrontal cortex. The cingulated cortex, which regulates emotions, is also responsible for ensuring proper attention and care is given to the offspring, while the hypothalamus governs the maternal responsiveness.

The demands of motherhood mean that certain skills and behaviors must be enhanced. In rodent mothers, one such behavior is her foraging skills. This is necessary as it allows her to forage faster without fear of leaving the nest; otherwise she and her children would starve. She also becomes faster at catching prey and her spatial learning and memory is boosted. Remembering the location of a food supply and the ability to quickly access it will ensure a hasty return to her offspring. Lastly, boldness is increased. She has less fear and anxiety when leaving the nest to forage for food.

Ronald J. Gandelman of Rutgers conducted an experiment in which mother mice could choose whether or not to adopt pups. Consistently, she would continue to receive them until her cage was filled with the foster pups. This is most likely due to the release of endorphins, which act like an opiate drug in the mother when the pups suckle. So, the mother will take on more and more pups to get the reward of endorphins more often.

The hormonal changes due to pregnancy and birth result in enhanced spatial relation skills. These skills are used to locate an object. Navigating and searching out food quickly lessens the extent to which her pups are alone in the nest, as well as the amount of time they are without food. The changes in the brain that improve these skills are necessary for the mother's survival and the survival of her vulnerable young.

A reduction in fear and anxiety levels in mother rats is also a necessary aspect of offspring survival. This is important, because without it she wouldn't be able to leave the security of the nest and confront the challenges that face her out in the environment.

Research has shown that pregnancy and child care lead to structural changes in the mother's brain. This is particularly true in a part of the hypothalamus called the medial preoptic area (mPOA). Neuron cell bodies in this area actually increase in volume. The number and length of dendrites increase as well. Since the amount of nerve signals in the hippocampus is increased during pregnancy, the amount of surface area needed to receive them is also increased. This is accomplished by dendritic spines increasing their density and strengthening neuronal connections. However, not