Maternal care, infant fear memory retention, and the moderating role of variations in separation‐induced ultrasonic vocalizations

Individual differences in parental care predict variations in offspring anxiety across species. Here, we examined whether between‐ and within‐litter variations in maternal licking (a measure of rodent maternal care) predict infant rats’ retention of an aversive association (a predictor of later anxiety‐like behavior) and whether the relationship between maternal licking and infant fear memory is moderated by variations in infants’ solicitation of maternal care. Unique marks were drawn on each pup, coded for fading, and touched up daily across the first week of life. Mark fading was used as an index of maternal licking where greater fading suggested more maternal licking the previous day. Separation‐induced ultrasonic vocalizations (USVs) were recorded to measure individual differences in solicitation of maternal care. Infants were fear conditioned at postnatal day (P) 17 and tested for fear of the conditioned stimulus (CS) 1 week later. Across litters, mark fading negatively predicted CS‐elicited fear at test for male, but not female, offspring. This relationship was moderated by number of USVs emitted at P1, such that mark fading only predicted CS‐elicited fear for males that emitted a low number of USVs. These results suggest that offspring solicitation may moderate the relationship between maternal care and fear/anxiety.