Adrenal steroids and plasticity of hippocampal neurons: toward an understanding of underlying cellular and molecular mechanisms.

Abstract

The hippocampal formation of the mammalian brain and its homologue in birds are involved in spatial information processing as well as in aspects of learning and memory (Sherry et al., 1989; Krebs et al., 1989; Eichenbaum and Otto, 1992), and the size of the hippocampus is sometimes an index of the degree to which an animal is involved in such behavior. For example, the volume of the hippocampal complex relative to brain and body size is significantly greater in bird species that store food than in species that do not (Krebs et al., 1989). Furthermore, in two species of kangaroo rat, differences in foraging behavior in terms of use of environmental space positively correlate with hippocampal size (Jacobs and Spencer, 1991), and in mice, hippocampal size correlates positively with maze performance (Crusio and Schwegler, 1991; Crusio et al., 1990). Thus the hippocampus varies in size according to the importance of spatial memory for the species, but it is not known thus far whether it is malleable in the course of an individual animal's life. The hippocampus is also a brain structure with many intriguing histological and neurochemical properties, including sensitivity to a variety of hormones