How do individuals become competent parents/caregivers?
For some animals, they are just born that way. Whether or not they are the biological parents, these animals are willing (although probably not fully capable) to care for young conspecifics (i.e., members of its own species). What about those that are not spontaneously parental? How do they become parental? My lab is interested in determining just that by studying our animal model, prairie voles (Microtus ochrogaster). We also are interested in determining whether the experiences that are important for animals influence postpartum maternal care in women.
The animal model we use to study how non-parental animals become competent parents is the prairie vole (Microtus ochrogaster). Prairie voles are ideal for the study of attachment because of their human-like social system. Adult male and female prairie voles form monogamous bonds and both are involved in caring for their offspring once they become parents (Lonstein & De Vries 1999). As virgin (i.e., parentally and sexually naïve) adults, however, their reactions to pups differ depending on whether they are male or female. Most virgin males are willing to care for pups throughout their lifetime, while virgin female prairie voles tend to be infanticidal, meaning they react aggressively towards pups (Lonstein & De Vries, 1999). My lab is interested in the events and physiological changes that cause infanticidal animals to become parental, thereby protecting their future offspring.
Why study infanticide?
Although the nature of this behavior is distressing, infanticide still warrants studying. Most consider the care of young to be a natural, even instinctive response. While an accurate description for some, other animals must undergo certain experiences that typically are related to reproduction before they are able to rear young successfully. Such a requirement suggests that species have evolved safeguards to ensure the survival of the offspring and species. As a result, my research proposes that the absence of these protective experiences/events deny mothers necessary, preparatory changes and puts offspring at risk of harm. My research using infanticidal animals is conducted to offer a biological perspective to aggression against neonates in an attempt to contribute to the prevention of child abuse and neglect.
What does it mean to be infanticidal?
Greater insight is needed to understand (and experimentally modify) the motivation underlying infanticide. To begin to determine what drives an animal to react aggressively to neonates, we are looking at the emotional states and activity levels of infanticidal and parental prairie voles. Likewise, we are interested in determining whether early neonatal experiences influence social behaviors (including parental behaviors) in adulthood.
Can reproductive experiences determine level of parental responsiveness?
Our research was first to show that the likelihood that female voles will respond maternally to pups (i.e., parental responsiveness) does not change during pregnancy (Hayes & de Vries, 2007). In fact, infanticidal females do not display maternal behaviors until delivery. When pups are delivered via caesarian section at the end of pregnancy, infanticidal female voles fail to display maternal behaviors (Hayes & de Vries, 2007). Additionally, if sensory nerves from the birth canal are severed before delivery, infanticidal females do not become maternal (Hayes, Ortiz, et al., in revision). We hypothesized that sensory information from the cervix triggers a cascade of physiological events that eventually lead to maternal care. Currently, we are examining how parturition triggers maternal care by focusing on 1) the relay of sensory information during delivery from the pelvic area to the brain and 2) how that signaling alters the oxytocinergic system in the brain (see below).
Is the "parental" brain different from an "infanticidal" one?
For infanticidal female prairie voles, maternal care is seen at delivery (Hayes & de Vries, 2007). As a result, chemical systems in the brain that are elevated at the time of delivery are likely candidates for triggering the onset of maternal behaviors. One such hormone is oxytocin. Oxytocin is a small peptide that is produced in the brain and is most known for its roles in delivery (induces uterine contractions), lactation (triggers milk letdown), and facilitation of social attachment (e.g., maternal and romantic bonds). In female rats, oxytocin peptide levels increase dramatically at the end of pregnancy (Jirikowski et al., 1989), while oxytocin receptor binding increases progressively across pregnancy (Bealer et al., 2006). We are interested in determining whether there is a difference in oxytocin signaling in the brains of infanticidal and maternal females.
There are many parallels between rodents and humans in regard to maternal behaviors. For example, the type of parental care a mother (human or rat) received as a neonate heavily determines how she will care for her offspring (Bentley et al., 1999; Francis et al., 1999). Another factor that influences the quality of care is the mother's mental health. Similar to rats and voles, depression in human mothers is associated with inferior care (and abuse). A related public health issue is the long-term negative effects of maternal depression on the emotional, cognitive, and physical development of children (Hay et al., 2001; Halligan et al., 2007; Buss et al., 2007).
Our clinical research seeks to determine whether certain procedures commonly used during delivery (i.e., cesarean delivery and the administration of epidural anesthesia) affect mothers' mental health after delivery and, subsequently, her ability to care for her baby. A better understanding of how delivery predicts postpartum mental health will allow medical practitioners and expectant mothers to more effectively design birth plans that maximize mothers' postpartum well-being. Additionally, understanding how obstetric interventions affect women and their postpartum functioning will have meaningful implications for our healthcare system (e.g., costs associated with obstetric procedures in low-risk deliveries and disease burden of children).
Can reproductive experience determine quality of maternal care?
Although expected to be happy, women commonly experience emotional distress after delivering their babies. With the routine use of various obstetric procedures during delivery (e.g., epidural and cesarean delivery), it is important to determine whether the common appearance of depression after delivery may be related to increased use of obstetric interventions. Findings from our animal studies illustrate the importance of certain physiological events for females entering motherhood (Hayes & de Vries, 2007; Le Neindre et al., 1979). With regard to humans, it is important to determine whether individual obstetric procedures or some combination of these procedures may preclude important physiological changes that protect against postpartum mental distress. Through a collaboration with Maureen Perry-Jenkins (Developmental Psychologist), Sally Powers (Developmental Psychopathologist), JuliAnna Smith (Statistician) and Susan Balaban (Clinical Graduate Student) in the Psychology Department at UMass, we examined the relationship between delivery (i.e., pelvic sensory signaling) and maternal depression. We found that women who experienced pelvic signaling during delivery reported fewer depressive symptoms by the end of the first postpartum year than those who were less likely to have received any sensory input (Hayes et al., 2010).
1. We are designing studies to determine the specific obstetric exerience(s) that is associated with less depressive symptomatology and the relationship between pelvic signaling and maternal sensitivity.
2. Using the dataset from our preliminary study, we are examining whether breastfeeding lessens the negative effects of obstetric intervention on postpartum depressive symptomatology. Our preliminary analyses suggest that breastfeeding does indeed help.
Stay tuned for exciting updates!!!
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