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Babies’ brains process emotional tone of voice even while asleep

Filed in
  • Infants
  • Cognitive Development
  • stress

By Lynn Celmer  |  Apr 02, 2013
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Being exposed to arguing parents is associated with the way babies' brains process emotional tone of voice, according to a newly published study by University of Oregon researchers.

UO doctoral student Alice Graham, working with her faculty advisers Phil Fisher and Jennifer Pfeifer, found that infants respond to angry tone of voice, even when they're asleep. The study appears in Psychological Science, a journal of the Association for Psychological Science.

Babies' brains are highly plastic, allowing them to develop in response to the environments and encounters they experience. But this plasticity comes with a certain degree of vulnerability — research has shown that severe stress, such as maltreatment or institutionalization, can have a significant, negative impact on child development.

Graham and colleagues wondered what the impact of more moderate stressors could have on infants. "We were interested in whether a common source of early stress in children's lives — conflict between parents — is associated with how infants' brains function," Graham said.

Graham and colleagues turned to advances in functional magnetic resonance image (fMRI) scanning to answer this question. Twenty infants, ranging in age from 6 to 12 months, came into the lab at their regular bedtime. While asleep in the scanner, they were presented with nonsense sentences spoken in very angry, mildly angry, happy and neutral tones of voice by a male adult.

"Even during sleep, infants showed distinct patterns of brain activity depending on the emotional tone of voice we presented," Graham said.

The researchers found that infants from high-conflict homes showed greater reactivity to very angry tone of voice in brain areas linked to stress and emotion regulation, such as the anterior cingulate cortex, caudate, thalamus and hypothalamus.

Previous research with animals has shown that these brain areas play an important role in the impact of early life stress on development — the results of this new study suggest that the same might be true for human infants.

According to the researchers, the findings show that babies are not oblivious parental conflicts, and exposure to them may influence the way babies' brains process emotion and stress.