One of the most astonishing things about becoming a mom was realizing, just a few minutes after my oldest child was born, that he knew the sound of my voice. I'd read that babies prefer their mothers' voices, but wasn't prepared to see what was clearly a look of recognition dawning on his face when he heard me say hello to him for the first time.
Although extensive research has documented the preference for - and emotional power of - one's mother's voice, the brain circuitry involved has been a mystery. A new Stanford study, publishing this week in the Proceedings of the National Academy of Sciences, changes that. The study shows that moms' voices get special treatment in a far wider variety of their children's brain areas than senior author Vinod Menon, PhD, and his team expected.
The researchers conducted MRI brain scans on children aged 7 to 12 while they listened to very brief clips taken from recordings of their biological mothers saying nonsense words. (Nonsense words were used to prevent the brain's language-processing centers from muddying the results.) The kids' brain responses were compared to what happened when they heard the same nonsense words said by women they had never met. In addition, the children's social communication abilities were assessed outside the scanner with a standard questionnaire answered by their parents.
Brain circuits turned on by the sound of Mom's voice handle emotions, rewards and more. From our press release about the findings:
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," Menon 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.
The findings are exciting on their own, and also leave the researchers with many more questions to explore. Do kids' brains respond similarly to the voices of their fathers or adoptive mothers? What might the discovery about social communication ability mean for children with communication disorders such as those seen in autism? How does the brain's response to one's mother's voice change in adolescence?
"Mom's voice is a big part of the soundtrack to childhood, but surprisingly little is known about how the brain organizes itself around this very important sound source for social, emotional and language learning," the study's first author, Dan Abrams, PhD, told me. The research team is eager to find out more.
Previously: Stanford study reveals why human voices are less rewarding for kids with autism, Stanford ingenuity + big data = new insight into the ADHD brain and Kids' brains reorganize as they learn new things, study shows
Photo of mother and daughter by Dave Parker