The study, published in the current issue of NeuroImage, explored what happens in the brain when mothers are shown pictures of their babies, as well as images of unfamiliar infants. While all the photos increased the amount of activity in a part of the brain associated with emotion, the images of the mothers' own infants generally increased activity even more, suggesting that this brain region may be involved in maternal attachment.
Motivations for the study originated from a lack of reliable knowledge about positive emotions, says Jack Nitschke, a neuroscientist and assistant professor of psychiatry and psychology at UW-Madison. "We know that depression and anxiety are not accompanied solely by an increase in negative emotions, but also by a decrease in positive ones," says Nitschke, lead author of the paper. "Yet we know much more about negative emotions than about positive emotions."
Earlier studies have examined the effects of certain positive experiences on brain activity. But Nitschke notes that many of them are limited either in the scope of emotions elicited or in the reliability of the stimuli such as pictures, tastes or sounds to produce a positive emotional response. For example, while a picture of an ice cream cone may be pleasing to many people, those who are dieting or have an eating disorder may respond less favorably, says the Wisconsin neuroscientist.
To improve and expand upon previous studies, Nitschke and his colleagues wanted to use stimuli that evoke powerful feelings of positive emotion, such as warmth, joy and fulfillment.
"There's one stimulus that's universally positive: baby faces," says Nitschke. "Just looking at them gets most people, particularly new moms, feeling all warm and happy."
Contact: Jack Nitschke
University of Wisconsin-Madison