Mothers with major depression show reduced neural activation in response to the cries of their babies compared with nondepressed mothers, according to a new study published online in Social Cognitive and Affective Neuroscience.

"Mothers who are depressed respond differently to their crying babies than do non-depressed moms," Heidemarie K. Laurent, PhD, from the University of Wyoming, Laramie, a coauthor of the study, said in a statement.

"In fact, we have shown in brain scans that their reaction is much more muted than the robust brain activity seen in non-depressed mothers."An infant’s cry of distress sets in motion a cascade of emotional and behavioral responses in the caregiver that cements their bond and, ultimately, serves the survival of the species.

However, deviations from this sequence occur, notably in cases of parental psychopathology, Dr. Laurent and coauthor Jennifer C. Ablow, PhD, from the University of Oregon, Eugene, write.

"An infant crying is normal, but how mothers respond can affect a child’s development," said Dr. Ablow.

Lack of Response Dr. Ablow has studied the relationship between behavior and physiologic responses, such as heart rate and respiration, of depressed and nondepressed mothers in response to the crying of their babies. In this study, she and Dr. Laurent investigated whether there were any depression-related differences in each mother's neural response to her own infant’s distress cues.

Using functional magnetic resonance imaging (fMRI), they scrutinized the brains of 11 mothers diagnosed with major depressive disorder and 11 mothers with no diagnosed psychopathology. Each mother was exposed to her own 18-month-old infant’s cry as well as to an unfamiliar infant’s cry and control sound.

They found that in the nondepressed mothers, brain responses to the sound of their own babies’ cries were seen on both sides of the brain’s lateral paralimbic areas and core limbic subcortical regions, including the striatum, thalamus, and midbrain, but in the depressed mothers, no response to their babies’ cries was seen.

In addition, nondepressed mothers activated much more strongly than depressed mothers in a subcortical cluster involving the striatum — specifically the caudate and nucleus accumbens — and the medial thalamus. These areas are closely associated with the processing of rewards and motivation.

"It looks as though depressed mothers are not responding in a more negative way than nondepressed mothers, which has been one hypothesis. What we saw was really more of a lack of responding in a positive way," said Dr. Laurent.

"It was interesting to see that the nondepressed mothers were able to respond to this cry sound as a positive cue. Their response was consistent with wanting to approach their infants. Depressed mothers were really lacking in that response," she added.

Long-term Effect: The study also showed that mothers who self-reported that they were more depressed at the time of their fMRI sessions displayed diminished prefrontal brain activity, particularly in the anterior cingulate cortex, when hearing their babies' cries.

"This brain region is associated with the abilities to evaluate information and to plan and regulate a response to emotional cues," Dr. Laurent said. The authors note that the important message from this study is that depression can exert long-lasting effects on mother-child relationships by blunting the mother’s response to her infant’s emotional cues.

"A mother who is able to process and act upon relevant information will have more sensitive interactions with her infant, which, in turn, will allow the infant to develop its own regulation capacities," said Dr. Ablow.

"Some mothers are unable to respond optimally to their infants’ emotional cues. A mother’s emotional response requires a coordination of multiple cortical and subcortical systems of the brain. How that plays out has not been well known," she noted.

Dr. Laurent added that the findings may suggest new implications for treating depression symptoms in mothers. "Some of these prefrontal problems may be changed more easily by addressing current symptoms, but there may be deeper, longer-lasting deficits at the motivational levels of the brain that will take more time to overcome," she said.

In a future study, the researchers plan to follow women from the prenatal period through their first year of motherhood to see how these brain responses shape mother-infant relationships during this crucial period of an infant’s development.