How many parents does a child need? (Image: Thinkstock)
Read aloud What difference does it make if a child grows up with just one or two parents? Many single mothers or fathers wonder if their child may lack something - because there is no second caregiver or because the profession simply leaves less time to look after the offspring. Canadian researchers have now investigated this question in mice - and actually found differences. In mouse infants born only with the mother, the brain subsequently produced fewer new brain cells in certain areas and behaved differently in tests. However, those who had two parents, father and mother or mother and co-mother, seemed to benefit from the more intensive care, but the boys were different from the females. Whether these results are transferable to humans is still unclear, the scientists emphasize. Setting the course for many aspects of our personality in early childhood is not new: "Early life experiences have profound effects on brain development, feelings, and behaviors that last throughout life, " explain Gloria Mak University of Calgary and her colleagues. Studies show that infants who are neglected or maltreated as infants are more susceptible to stress, depression, and other neuropsychological disorders as adults. Conversely, a childhood characterized by intense care and many positive experiences strengthens the subsequent social behavior, the ability to learn and also the resistance to stress. Brain scans also show that measurable differences in the shape and size of certain brain structures can occur.

Pure mother, with father or with co-mother

Whether such differences occur not only in blatant cases of neglect, but also in comparing alone educated versus double-supervised children, was so far unclear, as the researchers report. Mak and her colleagues therefore decided to investigate this in mice. For their study, they put pregnant mouse weasels just before the birth of the cubs in individual cages. Some remained alone until the release of their offspring - so they were almost single parents. Others shared a cage with the father of boys. A third group of females received a female, even non-pregnant co-mother set aside.

In order to be able to compare the effects of these rearing variants on the boys, the scientists subjected the offspring of all females at the age of eight weeks to different behavioral tests. Among other things, they examined the curiosity, the ability to learn, the social behavior and the anxiety behavior of the animals in various labyrinths, swimming tests and encounters with an unknown conspecific. As an indicator of neuronal development, researchers compared how many stem cells the mice had in certain regions of their brain. These cells can still produce new brain cells in adulthood, possibly affecting the function and volume of the mind. display

More pampering - more new brain cells

One difference was evident shortly after the birth of the mouse children: "The boys, raised by two parents or mother and co-mother, were licked and cleaned more often than those with only one mother, " Mak and her colleagues report. Although each animal had about the same care about the offspring, but at the nests with two caregivers, the boys got this attention from two sides and thus almost double the portion. Surprisingly, this infantile difference had very different effects on male and female boys, the researchers report. In the behavioral tests, the double-cared females showed better balance and coordination of movement and were more social. The males learned faster to avoid unpleasant stimuli out of the way.

At the level of brain cells, too, Mak and her colleagues clearly differed - and these were also gender-specific: females raised with two caregivers, as adults, produced twice as many stem cell neurons in the area of ​​the so-called bar, such as mother-only, The beam, also called Corpus Callosum, forms the bridge between the two hemispheres of the brain and is considered important for the coordination of movements, but also for social behavior, as the researchers explain. This may explain the differences observed in behavioral tests. The males had no differences in this brain area, but in another: the doubly cared for more stem cells in an area that supplies the hippocampus. This is considered important among other things for learning.

"Our study shows that care by two parents or mother and co-mother sustainably promotes cell growth in the brain and thus also has effects on the later behavior of the offspring, " the researchers state. Primary trigger is probably the more intensive care of children compared to single mothers. Surprisingly, however, Mak and her colleagues find out how different and gender-specific this effect is. Why this is the case now needs further investigation in further studies. And whether their results in the mouths are transferable to other mammals and humans has not yet been clarified.

Gloria Mak (University of Calgary) et al., PLoS ONE, doi: 10.1371 / journal.pone.0062701 - === Nadja Podbregar

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