Background and objectives: Infant facial expressions provide an important cue to elicit emotional and behavioral responses from a caregiver. Recent fMRI studies have demonstrated that differences in sex and parental status have an influence on brain responses to the stimuli related to infants. The purpose of the present study was to investigate the relationship between brain responses to infant emotional faces and individual differences in motivational tendencies in nulliparous women. We used fMRI with an event-related design to measure neural responses and utilized the Behavioral Inhibition System (BIS) / Behavioral Approach System (BAS) scales to determine individual differences in motivational tendencies. We highlighted two brain regions: the dorsal anterior cingulate cortex (dACC) and the orbitofrontal cortex (OFC), both of which are thought to be associated with empathic processing or reward, or both.
Methods: Fifty-five healthy nulliparous female volunteers (age M = 20.2, SD = 0.4) participated in this study. All subjects were right-handed and had normal or corrected-to-normal vision. They completed the BIS / BAS scales before the fMRI scanning. During the fMRI scanning, the subjects were presented with 72 photographs of infant faces (24 happy, 24 sad, and 24 neutral) one-by-one in pseudo-randomized order and asked to rate each face based on how positive or negative it was.
Results: We carried out correlation analyses of the relationships between (1) the BIS/BAS scores and the activity of the dACC, and (2) the BIS/BAS scores and the activity of the OFC. The BIS scores were positively correlated with the activity of the dACC while viewing sad infant faces, and were positively correlated with the activity of the OFC while viewing happy infant faces. No correlations were found between the BAS scores and the activity of the dACC or the OFC. These results indicate that in the nulliparous women, the BIS scores (not the BAS scores) are well correlated with the activity of either the dACC or the OFC depending on the emotional valence of stimuli.
Katsuko Niwano, Ayahito Ito, Motoko Tanabe, Yosuke Sato, Toshikatsu Fujii