Hemispheric lateralization is a fundamental organizing principle of nervous systems across taxonomic groups with bilateral symmetry. The mammalian hippocampus is lateralized anatomically, physiologically, and chemically; however, functional asymmetries are not yet well understood. Imaging studies in humans have implicated the left and right hippocampus in specialized processing associated with episodic memory and spatial navigation, respectively. However, it is not clear if different types of

more »

... put (i.e. external sensory input vs. self motion input) to the hippocampus are processed in each hemisphere. Immediate early gene (IEG) imaging in animals provides a measure of neuronal activity with a resolution at the level of single cells. To further understand functional lateralization of hippocampal processing, we compared interhemispheric expression of c-Fos in the dentate gyrus (DG), a structure involved in encoding new experiences, in mice that ran on a wheel, encoded a novel object, or remained in home cages. We found that wheel running induced the greatest amount of DG c-Fos expression in both hemispheres, with no difference in expression between the hemispheres. Object exploration resulted in left-lateralization of DG c-Fos expression, whereas control mice were not lateralized. This suggests that information regarding novel objects may be preferentially encoded by the left DG.