When do you first leave the nest? Early in development infants of many species experience important transitionssuch as learning when to leave the protective presence of their mother to start exploring the wider world. Neuroscientists have now pinpointed molecular events occurring in the brain during that turning point.
Based on animal studies, the findings may shed light on the strength of attachments in many speciesincluding the conundrum of why human children form strong attachments to even abusive caregivers.
"This is one of the few times we know what causes this type of early transition," said psychologist Gordon A. Barr, Ph.D., of The Children's Hospital of Philadelphia, co-author of a study that appeared online Sept. 27 in Nature Neuroscience. Barr performed the studies in rats with a longtime collaborator, neuroscientist Regina M. Sullivan, Ph.D., of the Nathan Kline Institute and New York University Langone Medical Center.
The youngest rats, called pups, first experience the mother's presence with both positive and negative stimuli. Even if the mother does something unpleasant, like stepping on or biting a pup, the baby rat stays close by the mother, something called preference learning. "From an evolutionary standpoint, this makes sense," said Barr. "The dependent baby has a better chance of survival if it doesn't stray from the mother's side."
However, at about ten days of age, the rat pups experience a transition to so-called aversion learning, in which they learn to avoid unpleasant stimuli. Said Barr, "Once an animal is better able to move around, it needs to be able to escape from stressful situations, again in the interests of its survival." The maturing rat learns a type of safe behavior while away from parental protection.
For neuroscientists, one puzzle has been how to understand the underlying biological events in the changeover from preference learning to aversion learning. In a series of s
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Children's Hospital of Philadelphia