American psychologist Harry Harlow is a controversial figure; his studies on maternal development, which danced a fine moral line, had a deep psychological effect on his monkey test subjects. While these experiments were considered highly unethical, they did lead to interesting findings on a mother’s importance in child development. Even among humans, young children placed in an orphanage or foster care often struggle with social relationships later in life. And a new study from the University of Rochester Medical Center (URMC) Department of Neuroscience sheds light on changes in the brain that may explain this phenomenon.
The researchers took data from a study that took place more than a decade earlier at the University of Pittsburgh. This study, which involved monkeys, was originally meant to observe the behaviors of newborns that were separated from their mothers and raised by another group of females. In this original study, it was found that monkeys who weren’t raised by their biological mothers differed in their social interactions. Monkeys, like humans, do not have fully developed brains at birth, and their brain development is at least in part dependent upon the nurturing of caregivers. While this original study was focused on the social outcome, the researchers from URMC were interested if there was any association between the absence of a primary caregiver and biological brain changes that explained this lasting social impairment.
The researchers focused on the amygdala, a region of the brain important for social and emotional development. Infancy is a critical stage for the amygdala’s development, since it features immature nerve cells that are more or less awaiting instructions. Through brain tissue preserved from the original study, the researchers identified a specific gene, tbr1, which was switched off in the amygdalae of monkeys that were raised without biological mothers. While tbr1 has been known to play a role in prenatal brain development, this marks the first time it’s been identified as playing a role in postnatal brain development.
Although the researchers don’t know what causes this gene to become inactive, they have speculated that it may be triggered at least in part by one’s environment. For example, no intense social and sensory cues could suppress tbr1’s expression. The researchers believe these findings show clear evidence that there are key parts of the brain in primates that continue developing in infancy, and that development could be helped (or hindered) by the infant’s environment.
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