First reproductive experience persistently affects spatial reference and working memory in the mother and these effects are not due to pregnancy or 'mothering' alone.

Abstract

Pregnancy and motherhood are life-altering events that result in a number of hormonal, neural and behavioral changes in the mother. Motherhood has been shown to influence spatial learning and memory performance of the mother. In turn new research has shown that reproductive experience (number of times pregnant and mothered) plays a significant role on spatial learning and memory performance. How long these changes persist after weaning and the role of pregnancy and/or mothering on these changes have yet to be fully investigated. The present study aimed to determine whether enhanced spatial working and/or reference memory in the mother is evident long after weaning and whether these effects are due, in part, to pregnancy or 'mothering' alone. Five groups of age-matched rats: multiparous, primiparous, nulliparous, pregnant-only and sensitized rats were tested approximately 1 month after weaning/pup-exposure, or 55 days after birth, on the spatial working/reference version of the radial arm maze. Results show that regardless of error type (reference or working memory errors), primiparous rats make fewer errors compared to multi- and nulli-parous rats, with a trend to enhanced memory compared to sensitized rats. In addition, pregnant-only rats completed the task on significantly fewer days than primiparous, multiparous, nulliparous and sensitized rats. Clearly the combination of first pregnancy and first mothering experience has a significant impact on hippocampus-dependent learning and memory performance in the mother.