Decades of research have shown that children prefer their mother's voices: In one classic study, 1-day-old babies sucked harder on a pacifier when they heard the sound of their mom's voice, as opposed to the voices of other women. However, the mechanism behind this preference had never been defined.

The research published in Proceedings of the National Academy of Sciences shows that the children's brains are far more engaged by their mother's voice than by voices of women they do not know.

Brain regions that respond more strongly to the mother's voice extend beyond auditory areas to include those involved in emotion and reward processing, social functions, detection of what is personally relevant and face recognition.

The study examined 24 children ages 7 to 12. All had IQs of at least 80, none had any developmental disorders, and all were being raised by their biological mothers. Parents answered a standard questionnaire about their child's ability to interact and relate with others. And before the brain scans, each child's mother was recorded saying three nonsense words.

"In this age range, where most children have good language skills, we didn't want to use words that had meaning because that would have engaged a whole different set of circuitry in the brain," said the senior author.

Two mothers whose children were not being studied, and who had never met any of the children in the study, were also recorded saying the three nonsense words. These recordings were used as controls.

The children's brains were scanned via magnetic resonance imaging while they listened to short clips of the nonsense-word recordings, some produced by their own mother and some by the control mothers. Even from very short clips, less than a second long, the children could identify their own mothers' voices with greater than 97 percent accuracy.

The brain regions that were more engaged by the voices of the children's own mothers than by the control voices included auditory regions, such as the primary auditory cortex; regions of the brain that handle emotions, such as the amygdala; brain regions that detect and assign value to rewarding stimuli, such as the mesolimbic reward pathway and medial prefrontal cortex; regions that process information about the self, including the default mode network; and areas involved in perceiving and processing the sight of faces.

"The extent of the regions that were engaged was really quite surprising," senior author said.

Children whose brains showed a stronger degree of connection between all these regions when hearing their mom's voice also had the strongest social communication ability, suggesting that increased brain connectivity between the regions is a neural fingerprint for greater social communication abilities in children.

http://med.stanford.edu/news/all-news/2016/05/moms-voice-activates-different-regions-in-children-brains.html