In a nutshell: The experience of raising children is linked to life-long changes to the brain’s structure in mothers and fathers.

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The early years of parenthood alter the structure of the brain in both mothers and fathers. The thickness of the cortex – the outer layer of the brain known as the ‘grey matter’ – changes in different regions of the brain at different stages of child rearing. It can increase, as the brain develops, and decrease, in a process of fine-tuning.

Studies in rodents suggested that these changes might be permanent. But researchers knew very little about the lasting effects of parenthood on the human brain.

A team of Brain Function CoE researchers from Monash University, led by PhD student Edwina (Winnie) Orchard in Sharna Jamadar’s group, set out to answer this question. They examined the link between cortical thickness in older adults and the number of children a person has parented.

The researchers used data collected from 547 participants of a clinical trial called ASPREE-NEURO, which involved people aged 70 or above. Participants underwent brain scans and completed a health questionnaire. One of the questions asked how many children they had.

By analysing the brain scans of the participants, the researchers determined the thickness of the cortex in 34 regions of each brain hemisphere. They also calculated the average thickness across each hemisphere.

The researchers then compared these 70 measurements in participants with one or more children. They also compared the measurements between non-parents and parents with one child.

The researchers found that mothers with more children had thicker grey matter in the right parahippocampal gyrus, a brain region associated with memory. By contrast, cortical thickness decreased in regions associated with processing sensory information.

Compared with non-mothers, mothers with one child had thinner grey matter in the left dorsolateral prefrontal cortex. This region of the brain is involved in high-order cognitive functions including problem-solving and emotional regulation.

Compared with non-fathers, fathers with one child had thinner grey matter in the left anterior cingulate and thicker grey matter in the right temporal pole. These regions are involved in social cognition, including emotional regulation and empathy.

These findings suggest that parenthood causes life-long changes to the brain’s structure in both mothers and fathers. The researchers believe that these changes are related to the complexity of raising children – an ongoing experience that provides parents with rich sensory stimulation while requiring them to learn new skills and behaviours.

Next steps:
The researchers are now studying people within one year of having a baby, to understand how these changes in cortical thickness arise during early parenthood.

Orchard, E. R., Ward, P. G. D., Sforazzini, F., Storey, E., Egan, G. F., & Jamadar, S. D. (2020). Relationship between parenthood and cortical thickness in late adulthood. PLoS One, 15(7), e0236031. doi: 10.1371/journal.pone.0236031

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