Amygdala and affective responses to infant pictures: Comparing depressed and non-depressed mothers and non-mothers.

In many mammalian species, new mothers show heightened positive responsiveness to infants and their cues when they give birth. As is evident from non-human and human studies, the amygdala is a brain region implicated in both the maternal and affective neural circuitry, and is involved in processing socioemotionally salient stimuli. In humans, infants are socially salient stimuli to women, and mothers in particular. Neuroimaging studies investigating the maternal response to infant cues have identified infant-related amygdala function as an important factor in maternal anxiety/depression, in the quality of mothering and in individual differences in the motivation to mother. The present study investigated the effects of maternal status and depression on the subjective affective response and amygdala responsiveness to unfamiliar infants using functional magnetic resonance imaging. Smiling infant pictures were used in a 2 × 2 design comparing four groups of women: mothers and non-mothers, with and without depression (total of 101 women: postpartum depression [PPD] = 32, non-PPD = 25, major depression [MDD] = 15, non-MDD = 29). We undertook an anatomically defined region of interest analysis of the amygdala response for a priori defined group comparisons. We found that mothers rated infants more positively than non-mothers and non-mothers rated non-infant stimuli (scenery) more positively than mothers. In the amygdala, we found that depression elevated response to smiling unfamiliar infants in mothers but had no effect in non-mothers. Within the depressed groups, mothers (PPD) showed an elevated amygdala response to unfamiliar smiling infants compared to depressed non-mothers. Hence, our results indicate that women with PPD show an enhanced amygdala response to affectively positive infant pictures but not to affectively positive (but non-salient) pictures of scenery. Women with depression outside of the postpartum period show no change in amygdala responsiveness to either stimulus categories.

Exploring the morphological and emotional correlates of infant cuteness.

Ethologists have observed that "baby schema" or infant cuteness is an adaptive protective mechanism ensuring the young's survival. Past efforts to quantify cuteness have been restricted to line measurement techniques. We developed a novel data-driven approach to quantify infant cuteness into a single metric. Using the Psychomorph program, we delineated facial elements of 72 infant pictures using 206 facial points and identified the facial components that were significantly related to subjective cuteness perceptions of the faces. 108 nulliparous females rated the pictures on cuteness and emotional dimensions. We found that cuter infants have larger cephalic curvature compared to a smaller chin, a big smile, and round chubby features among others. We also investigated the relationship between cuteness and emotional responses. Our results show that a greater degree of cuteness elicits both increased positive emotional responses and decreased negative emotional responses. Cuter infants also elicited greater feelings of alertness, interest, and the need to respond. In fact, the participants' emotional responses were predictive of both data-driven scores and subjective perceptions of cuteness.

Postpartum depression and brain response to infants: Differential amygdala response and connectivity.

Recent evidence suggests that postpartum depression is associated with reduced amygdala (AMY) response to negative stimuli. However, given the anhedonic features of PPD, it is important to consider mothers' brain response specifically to positive infant and to other positive stimuli. Mothers with (n = 28) and without (n = 17) clinically determined PPD (n = 28) viewed smiling pictures of infants (Own and Other), and positive non-infant stimuli (Non-Infant). First, we examined group differences in AMY response across conditions. Next, psychophysiological interaction was used to examine group differences in AMY connectivity across conditions. Connectivity estimates were then correlated with measures of maternal mood and anxiety. PPD mothers, compared to non-PPD mothers, showed overall increased AMY response across conditions in the right AMY. Despite this, PPD mothers demonstrated decreased bilateral AMY-right insular cortex (IC) connectivity as compared to non-PPD mothers when they view Own-Other infants. Furthermore, decreasing AMY-IC connectivity was associated with increasing symptoms of depression and anxiety. These differences were evident only for infant stimuli and did not apply to all positively valenced stimuli. Thus, PPD mothers show altered brain response and connectivity in regions strongly implicated in the processing of socially and emotionally relevant stimuli, as well as interoception and the evaluation of subjective emotional experience.

Maternal affect and quality of parenting experiences are related to amygdala response to infant faces.

We examined how individual differences in mood and anxiety in the early postpartum period are related to brain response to infant stimuli during fMRI, with particular focus on regions implicated in both maternal behavior and mood/anxiety, that is, the subgenual anterior cingulate cortex (sgACC) and the amygdala. At approximately 3 months postpartum, 22 mothers completed an affect-rating task (ART) during fMRI, where their affective response to infant stimuli was explicitly probed. Mothers viewed/rated four infant face conditions: own positive (OP), own negative (ON), unfamiliar positive (UP), and unfamiliar negative (UN). Mood and anxiety were measured by the Edinburgh Postnatal Depression Scale (EDPS) and the State-Trait Anxiety Inventory-Trait Version (STAI-T); maternal factors related to parental stress and attachment were also assessed. Brain-imaging data underwent a random-effects analysis, and cluster-based statistical thresholding was applied to the following contrasts: OP-UP, ON-UN, OP-ON, and UP-UN. Our main finding was that poorer quality of maternal experience was significantly related to reduced amygdala response to OP compared to UP infant faces. Our results suggest that, in human mothers, infant-related amygdala function may be an important factor in maternal anxiety/mood, in quality of mothering, and in individual differences in the motivation to mother. We are very grateful to the staff at the Imaging Research Center of the Brain-Body Institute for their contributions to this project. This work was supported by an Ontario Mental Health Foundation operating grant awarded to Alison Fleming and a postdoctoral fellowship awarded to Jennifer Barrett.