Motherhood Induces and Maintains Behavioral and Neural Plasticity across the Lifespan in the Rat

Abstract

Maternal behavior is multidimensional, encompassing many facets beyond the direct care of the young. Formerly unfamiliar activities are required of the mother. These include behaviors such as retrieving, grouping, crouching-over, and licking young, and protecting them against predators, together with enhancements in other behaviors, such as nest building, foraging, and aggression (inter/intra-species, predatory, etc.). When caring for young, the mother must strike a seemingly lose-lose bargain: leave the relative safety of the nest and her helpless offspring to forage for food and resources where predators await both mother and her vulnerable young, or remain entrenched and safe, thereby ensuring a slow and inexorable fate. Two predictions thus arise from this maternal cost-benefit ratio: first, there may be enhancements in behaviors on which the female relies, for example, predation and spatial ability, used for acquiring food and resources and for navigating her environment. Second, there may be reductions in the fear and anxiety inherent to the decision to leave the nest and to forage in an unforgiving environment where encounters with predators or reluctant/resistant prey await. There is overwhelming support for both hypotheses, with improvements in learning and memory accompanied by a diminution in stress responses and anxiety. The current review will examine the background for the phenomenon that is the maternal brain, and recent relevant data. In sum, the data indicate a remarkable set of changes that take place in the maternal (and, to a lesser extent, the paternal), brain, arguably, for the natural, simple but singular experience of reproduction.