The first and arguably the most impactful social interaction experienced in life is the interaction of the child with its parents. In mammals, including humans, the quality of parental care is key to the survival of offspring. In the lab of 2013 BBRF Young Investigator Ioana Carcea, M.D., Ph.D., of the Brain Health Institute of Rutgers University, experiments are in progress to determine the neural circuitry and brain signaling processes that underlie the kind of parental behavior that increases chances that offspring will not only survive but flourish.

One of the lab's three experimental foci concerns how adults can, via social cues, learn from other adults about how to properly care for their newborns. In a paper published in the journal Nature, Dr. Carcea and colleagues including senior author Robert Froemke, Ph.D., report on experiments in which they observed unschooled "virgin" female mice learn from experienced mothers about care of the mothers' newborns. The researchers recorded the activity of neurons as this vital activity was going on.

Interestingly, virgin female mice initially ignore newly born mice in their vicinity, including the ultrasonic distress calls emitted by pups that become isolated. These sounds are well within range of the mouse auditory system; they are simply ignored by female mice with no mothering experience.

Within several days of co-housing with experienced mothers and their litters, virgin females do begin to perform functions that normal mothers perform, including the retrieval of wayward pups to the nest. But how do they learn to do this? And what happens in the brain when they do?

Dr. Carcea's team built a system that enabled them to continuously monitor cages containing virgin females and experienced females and their newborns. An overhead camera, able to use infrared sensing to "see" at night, was synchronized with ultrasonic audio recording and neural recording devices, which supplied data that could be correlated and analyzed in detail offline.

As noted by the team, the hormone oxytocin is an important signal for maternal behavior, and in mammals, is released from the brain's hypothalamus in coordination with childbirth and lactation. Oxytocin release is also known to help the brain mark salient events—including, the team hypothesized, the salience of learned social information bearing on raising newborns.

The team's neural recordings from the paraventricular nucleus (PVN) of the hypothalamus revealed that oxytocin-releasing neurons were activated in virgin females as they were enlisted in maternal care by experienced mothers—who shepherded virgins into the nest and demonstrated the "how-to" of pup retrieval.

Virgins were seen to visually observe maternal retrieval of the pups, and the team concluded that this in turn activated PVN oxytocin neurons and promoted the learning of parenting behavior in the virgins.

"This social learning depended on visual input" the team noted. "We identified direct projections from visual layers of superior colliculus onto PVN oxytocin neurons." The superior colliculus is a midbrain structure that integrates visual, auditory, and other spatial information to initiate orienting movements of the eyes and head toward relevant objects in space.

Oxytocin served to amplify neural representations of cues from pups, the team noted. Its release may indicate salience not only in response to visual cues but also auditory ones such as distress calls, perhaps involving the left auditory cortex, in behaviors that are important for learned aspects of maternal care.

Learning how to care for newborns—even by females who are not pregnant and have not had prior offspring—likely has a species benefit, serving generally to improve maternal care, and "could occur throughout early life in animals living communally," the team noted. "Socially transmitted parental behavioral would then be useful for helping to ensure the survival and success of offspring," not only in mice but in other social mammals including humans.

The flip side of these observations can be seen in a large body of brain and behavior research, by BBRF grantees and others, dedicated to understanding what goes wrong when the proper cues are not given or are not learned, or when, in certain cases, offspring are subjected to traumas including neglect or other forms of abuse. This, too, is part of the story of life, and understanding how the brain responds when circumstances go awry are informed by observations such as those of Dr. Carcea's team which probe brain processes at the interface of nurture and lived experience.