Parenthood is as much a state of mind as it is simply looking after one’s off spring—at least that is the evidence from a study of marmoset fathers. Males of these small primates show substantial increases in dendritic spines and vasopressin receptors in the prefrontal cortex in response to fatherhood. Previous MRI studies have shown that human parents have activity related stimuli in response to their own children, so the Princeton researchers decided to investigate the changes further. Marmosets provided an ideal model because of the level of parental care provided by the males. “Rat fathers would be just as likely to eat their own babies”, explains Yevgenia A Kozorovitskiy (Psychology Department, Princeton University, NJ, USA), “but in marmosets the fathers are a great model of very involved fathers—a model of an ideal human father.” Directly after giving birth, marmoset females hand over their twins to the males, who will carry the off spring, in fact they off er nearly all parental care except for providing milk. The researchers found that, in male marmosets that had given parental care to their off spring the number of dendritic spines and vasopressin receptors in the prefrontal cortex were higher than in non-fathers (Nat Neurosci 2006; 9: 1094–95). “You might expect to see changes in areas responsible for maintaining hormonal balance, but to see it in such a high-level area involved in goal-directed behaviour was a real surprise”, Kozorovitskiy told The Lancet Neurology. “The fact that the prefrontal cortex is so highly responsive to endocrine and environmental infl uences is particularly important, since it mediates the highest levels of cognitive function”, says John Morrison (Mount Sinai School of Medicine, New York, USA). Given the similar endocrine responses to stress, reproduction, and childrearing of mammals, Morrison suggests that human beings would likely show similar adaptive changes in the prefrontal cortex in response to major parenthood and other fundamental transitions in life, such as puberty, menopause, and intense stress. Kozorovitskiy feels that the changes in the brain are likely brought about by interaction with young and hope to investigate what changes occur in nonparental care-givers. The researchers suspect that the changes in vasopressin receptors are in some way related to dopaminergic reward systems, and would also like to investigate the mechanisms behind these changes.
The Lancet Neurology