Interaction of photoperiod and testes development is associated with paternal care in Microtus pennsylvanicus (meadow voles)

Tales from the life and lab of a female social neuroscientist

This narrative review charts my unconventional path to becoming a social neuroscientist and describes my research findings - some baffling, some serendipitous, some pivotal - in the field of neuropeptide biology. I trace my childhood as a Bell Labs "brat" to my adolescence as a soccer-playing party girl, to my early days as a graduate student, when I first encountered oxytocin and vasopressin. These two molecules instantly captivated - and held - my attention and imagination. For more than 25 years, a core goal of my research program has been to better understand how these neuropeptides regulate social functioning across a range of species (e.g., meadow voles, mice, squirrel monkeys, rhesus monkeys, and humans), and to translate fundamental insights from this work to guide development of novel pharmacotherapies to treat social impairments in clinical populations. I also discuss my experience of being a woman and a mother in STEM, and identify the important people and events which helped shape my career and the scientist I am today.

Neuropeptide Regulation of Social Attachment: The Prairie Vole Model

Social attachments are ubiquitous among humans and integral to human health. Although great efforts have been made to elucidate the neural underpinnings regulating social attachments, we still know relatively little about the neuronal and neurochemical regulation of social attachments. As a laboratory animal research model, the socially monogamous prairie vole (Microtus ochrogaster) displays behaviors paralleling human social attachments and thus has provided unique insights into the neural regulation of social behaviors. Research in prairie voles has particularly highlighted the significance of neuropeptidergic regulation of social behaviors, especially of the roles of oxytocin (OT) and vasopressin (AVP). This article aims to review these findings. We begin by discussing the role of the OT and AVP systems in regulating social behaviors relevant to social attachments, and thereafter restrict our discussion to studies in prairie voles. Specifically, we discuss the role of OT and AVP in adult mate attachments, biparental care, social isolation, and social buffering as informed by studies utilizing the prairie vole model. Not only do these studies offer insight into social attachments in humans, but they also point to dysregulated mechanisms in several mental disorders. We conclude by discussing these implications for human health. © 2017 American Physiological Society. Compr Physiol 7:81-104, 2017.

Modeling dad: animal models of paternal behavior

In humans, paternal behaviors have a strong influence on the emotional and social development of children. Fathers, more frequently than mothers, leave the family nucleus, and/or become abusive, leading to offspring that are more likely to grow under stressful conditions and greater susceptibility to abnormal health and social outcomes. Literature on parental behaviors, human or animal, has primarily focused on the interactions between mothers and offspring, with little research directed at understanding paternal behavior. In animal studies, experimenters correlate paternal behaviors with those seen in rodent or primate mothers, often under situations in which behaviors such as nest protection, huddling, pup grooming, and retrieval are artificially induced. In humans, the majority of the studies have looked at paralleling hormonal changes in fathers with those occurring in mothers, or observed paternal behaviors in populations with specific anthropological backgrounds. These studies reveal commonalities in parental behaviors and their underlying neural circuits. However, this work highlights the possibility that paternal behavior has components that are strictly masculine with unique neurobiological mechanisms. This review summarizes this information and provides a current view of a topic that needs further exploration.

Same-sex social behavior in meadow voles: Multiple and rapid formation of attachments

Adult meadow voles (Microtus pennsylvanicus) are solitary in the spring-summer reproductive season, but during winter months, females and males are socially tolerant and aggregate in groups. This behavioral difference is triggered by day length: female meadow voles housed in short, winter-like day lengths form same-sex partner preferences, whereas those housed in long, summer-like day lengths are less social. The present study demonstrates that same-sex social attachments in short day lengths are not exclusive; females formed concurrent attachments with more than one individual, and with non-kin as well as siblings. Partner preferences between females were established within one day of cohousing and did not intensify with greater durations of cohabitation. Males also formed same-sex social attachments, but unlike female affiliative behavior, male partner preferences were not significantly affected by day length. These data are discussed in the context of field behavior and the physiological mechanisms supporting social behavior in voles.

Can knowledge of developmental processes illuminate the evolution of parental care?

There are two levels of investigation for elucidating the evolution of parental behavior. The macro level focuses on how parental behavior can evolve as an aspect of reproduction. The micro level focuses on how species variations in parental behavior evolve. Recently, modern evolutionary biology has turned to developmental biology as a source for information about how trait variability (the substrate upon which natural selection and other evolutionary mechanisms can operate) can emerge during development (called "evo-devo"). Application of this evo-devo approach to the phenomenon of parental behavior requires identification of those mechanisms that produce variations in developmental pathways leading to parental behavior. It is these variations that provide the phenotypes for the potential evolution of different parental behavior systems. Variations in rodent maternal behavior affect the development of the HPA and HPG axes in their offspring. These mechanisms are examined to reveal how such developmental variations could underlie the evolution of biparental behavior. Knowledge of the developmental mechanisms responsible for species variations in mammalian parental behavior systems may provide insight into those mechanisms that may have been involved in the evolution of parental behavior itself.