SATURDAY, Feb. 26, 2011 (HealthDay News) -- Armed with brain scans, researchers have discovered bawling babies trigger a far more muted response in the brains of depressed mothers than in mothers who aren't depressed.
Contrary to a previous theory, "it looks as though depressed mothers are not responding in a more negative way than non-depressed mothers. What we saw was really more of a lack of responding in a positive way," said study lead author Heidemarie K. Laurent in a news release from the University of Oregon.
Laurent is an assistant professor at the University of Wyoming, but she worked on the study as a postdoctoral researcher at the University of Oregon.
The study, which appears online in the journal Social Cognitive and Affective Neuroscience, is the first to examine how the brains of depressed women responded to the crying of babies.
In total, the researchers studied the brains of 22 women using functional magnetic resonance imaging, which measures brain activity through blood flow changes. The women were all first-time mothers with 18-month-old babies.
When the babies cried, the brains of the mothers who weren't depressed lit up in the areas connected to reward and motivation. "In this context, it was interesting to see that the non-depressed mothers were able to respond to this cry sound as a positive cue," Laurent said. "Their response was consistent with wanting to approach their infants. Depressed mothers were really lacking in that response. "
The key message from the study, the researchers noted, was that depression can have a long-lasting impact on mother-infant relationships by dampening the brain's response to a baby's emotional cues.
According to Laurent, the research -- and the levels of activity in the brain -- suggests the challenges of treating depression in mothers. "Some of these prefrontal problems may be changed more easily by addressing current symptoms," Laurent said in the release, "but there may be deeper, longer-lasting deficits at the motivational levels of the brain that will take more time to overcome."
Visit the U.S. National Library of Medicine for more on depression.