Interaction between territoriality, spatial environment, and hippocampal neurogenesis in male side-blotched lizards.

Abstract

Differences in an animal's spatial environment can have dramatic effects on the hippocampus, an area of the brain involved with spatial processing. Animals in spatially impoverished environments have decreased hippocampal attributes. However, we do not know if differences in the spatial environment differentially interact with territorial status, which also covaries with hippocampal attributes. Here, we asked whether territoriality and differential spatial-area use interact to generate different effects on cortical attributes (reptilian hippocampal homologue) in lizards. We compared medial and dorsal cortical attributes between territorial and nonterritorial morphotypes of side-blotched lizards, Uta stansburiana, in larger versus smaller (i.e., spatially impoverished) enclosures. We found that territorial males had increased neurogenesis rates in their medial cortices in larger enclosures when compared with their siblings in smaller enclosures; nonterritorial males had low levels of neurogenesis regardless of enclosure size. Enclosure size had no significant effect on cortical volumes or the total number of neurons in either cortical region. These results suggest that territorial morphotypes may be more sensitive to changes in the spatial environment, thus leading to increases in regulation of neurogenesis in the face of increased spatial processing and physical activity demands.