Exploring the fathering brain: insights from neural activation

Organisms require a great deal of behavioral plasticity to accomplish the tasks associated with reproduction. In addition to day-to-day activities, breeding animals must establish a territory, find a mate, find a place to raise offspring, mate and rear offspring. While organisms are breeding, they also have to behave appropriately to conflicting stimuli. For example, a parent may shift from being aggressive toward intruders to carefully tending young. A variety of studies have focused on how the brain changes at the beginning or end of the breeding season (Gozdowska et al., 2006; Hairston et al., 2003; Meitzen et al., 2009; Nakao et al., 2008; Paul et al., 2009), but less is known about how the brain, mediates behavioral plasticity during the breeding season. This is an unfortunate gap in our knowledge as the physiological and behavioral changes that occur within a single breeding cycle can be just as profound as those between the non-breeding and breeding seasons. Even less is known about neural mechanisms mediating behavioral plasticity in a species with paternal care, where the male is the sole provider of parental care, since most studies have focused on species with maternal or biparental care. To begin to understand how the brain mediates behavioral plasticity within a breeding season, we measured brain activation in male three-spined sticklebacks. First, we developed a method for quantifying brain activation by measuring the expression of an immediate early gene using whole mount in situ hybridization (WISH) (Chapter 1). The method uses mini mRNA probes that are capable of penetrating the whole brain; therefore, we have named this technique, mini-probe WISH (mpWISH). Second, we compared brain activation across the stickleback breeding cycle, which is marked by dramatic changes in behavior (Chapter 2). Finally, we quantified differences in behavior and brain activation in breeding males in response to ecologically relevant stimuli (Chapter 3). Collectively, these studies show that not only are behavior and neural activation context dependent in the stickleback but also specific brain areas are constitutively active at differing levels during the breeding cycle