Chapter 2 - Neural Substrates Involved in the Onset of Maternal Responsiveness and Selectivity in Sheep

Abstract

This chapter reviews the data on the neural and neurochemical mechanisms of maternal responsiveness and selectivity characteristics of maternal behavior, and considers the possible relations between the neural networks controlling these two facets of maternal attachment in precocial species. Thus, it first introduces the main physiological and sensory determinants of maternal responsiveness and selectivity and, second, the different neural substrates that mediate these responses. Across mammalian species, sheep are unique in showing maternal care together with a specialized form of rapid learning producing recognition of individual young. These two behavioral processes, which lead to maternal attachment, are synchronized at parturition by VCS induced by the expulsion of the neonate, although the mechanisms controlling these two processes differ. At a physiological level, oxitocin (OT), supported by the opioid peptides and CRH, is the key factor for maternal responsiveness, while its role in lamb olfactory memory is not determined yet. At the neural level, the control of maternal responsiveness is mainly hypothalamic (PVN, MPOA, and BNST) and has little in common with the circuitry involved in selectivity that mainly concerns olfactory processing regions (MOB, CoA, MeA, and frontal cortices) and the cholinergic and noradrenergic systems. Finally, the chapter examines how previous maternal experience provided by interacting with the young during the first parental cycle results in changes in the underlying neural mechanisms controlling maternal care.