Four infant face categories: own happy (OH), own sad (OS), unknown happy (UH), and unknown sad (US) face images. The pictures were taken approximately 7 months postpartum (age of infant: 6.6 ± 0.3 months) and shown to mothers in the scanner 11 months postpartum. The mean interval between the stimulus acquisition and scanning was 4.9 ± 0.5 months. For each 6-minute functional run, 10 unique images from each face category were pseudorandomly presented with a stimulus duration of 2 seconds, each followed by a black screen for a variable interstimulus interval of 2 to 6 seconds.