Midbrain Module

Abstract

Since decerebrate female rats with complete transections between diencephalon and mesencephalon do not perform lordosis (Figure 7–11; Kow et al., 1978), an output descending from the diencephalon or telencephalon must be required for mediating the behavior. Anterior to these complete transections, no source of axons other than the ventromedial nucleus of the hypothalamus has been shown to be necessary for lordosis (Chapter 7). Moreover, a common route of output from the diencephalon and mesencephalon, the medial forebrain bundle, does not carry descending ventromedial nucleus axons and is not required for lordosis (Modianos et al., 1976). Thus it appears that only output descending from neurons in and around the ventromedial nucleus of the hypothalamus is necessary for the behavior to occur. Presumably, these axons carry the estrogenic influences that mark control by the hormone over the behavior.