Hippocampal neurophysiology across species

Comparative research in neuroscience can contribute to the understanding of general principles underlying brain function; it can also provide testable hypotheses that direct future research. This chapter provides a comparative review of the neurophysiology of the hippocampal formation across mammals. Over the last 40 years, the vast majority of findings on hippocampal electrophysiology were based on research from a single animal model-the rat. Yet, while rat hippocampal studies provided one of the richest datasets in systems neuroscience, the paradigms generated based on rat data were, until recently, largely untested in other mammals-and at least some of the ideas have been questioned by the few studies that were conducted in other species. Here we will summarize the data available from different mammalian species regarding hippocampal neurophysiology, focusing on similarities and differences across species-including functional implications. We will limit our discussion to two aspects: spatial cell types in the hippocampal formation and hippocampal oscillations. We will conclude by highlighting some of the major gaps in the available comparative data and by raising a call to arms to conduct further comparative research on the hippocampal formation.