Characteristic neurobiological patterns differentiate paternal responsiveness in two Peromyscus species

Rodent paternal models provide unique opportunities to investigate the emergence of affiliative social behavior in mammals. Using biparental and uniparental Peromyscus species (californicus and maniculatus, respectively) we assessed paternal responsiveness by exposing males to biological offspring, unrelated conspecific pups, or familiar brothers following a 24-hour separation. The putative paternal circuit we investigated included brain areas involved in fear/anxiety [cingulate cortex (Cg), medial amygdala (MeA), paraventricular nucleus of the hypothalamus (PVN), and lateral septum (LS)], parental motivation [medial preoptic area (MPOA)], learning/behavioral plasticity (hippocampus), olfaction [pyriform cortex (PC)], and social rewards (nucleus accumbens). Paternal experience in californicus males reduced fos immunoreactivity (ir) in several fear/anxiety areas; additionally, all californicus groups exhibited decreased fos-ir in the PC. Enhanced arginine vasopressin (AVP) and oxytocin (OT)-ir cell bodies and fibers, as well as increased neuronal restructuring in the hippocampus, were also observed in californicus mice. Multidimensional scaling analyses revealed distinct brain activation profiles differentiating californicus biological fathers, pup-exposed virgins, and pup-naïve virgins. Specifically, associations among MPOA fos, CA1 fos, dentate gyrus GFAP, CA2 nestin-, and PVN OT-ir characterized biological fathers; LS fos-, Cg fos-, and AVP-ir characterized pup-exposed virgins, and PC-, PVN-, and MeA fos-ir characterized pup-naïve virgins. Thus, whereas fear/anxiety areas characterized pup-naïve males, neurobiological factors involved in more diverse functions such as learning, motivation, and nurturing responses characterized fatherhood in biparental californicus mice. Less distinct paternal-dependent activation patterns were observed in uniparental maniculatus mice. These data suggest that dual neurobiological circuits, leading to the inhibition of social-dependent anxiety as well as the activation of affiliative responses, characterize the transition from nonpaternal to paternal status in californicus mice.

Maternal care patterns and behavioral development of rhesus macaque abused infants in the first 6 months of life

We investigated the maternal care patterns of rhesus macaque mothers who physically abuse their infants, and compared their infants' behavior to that of nonabused infants. Parametric and multidimensional scaling analyses indicated that abusive mothers have a distinct parenting style characterized by high rates of rejection and contact-breaking from their infants. Compared to control infants, abused infants exhibited signs of delayed independence from their mothers including higher rates of distress calls and anxiety, lower rates of contact-breaking, and differences in play. Several aspects of the abused infants' behavior were correlated with rates of abuse received during the first month, or with other maternal behaviors. These findings provide a more comprehensive characterization of the parenting styles of abusive mothers and the early behavioral development of their infants than previously available. Detailed knowledge of the early experience of abused infants is crucial for understanding possible pathological alterations in behavior and neuroendocrine function later in life.