THE HIPPOCAMPAL FORMATION AND SPATIAL PROCESSING

A major event in the field of spatial cognition and its neurobiological bases has been the discovery of a population of hippocampal neurons, the properties of which reflect unambiguously the encoding of the animal’s location in the environment. They were christened “place-cells” by O’Keefe and Dostrovski who discovered them in 1971. Despite some debates about the precise meaning of place-cell firing properties, and also about the involvement of such cells in non spatial processing, this finding has given a strong impetus to research in the domain of the brain substrates of spatial cognition. A few years later, O’Keefe and Nadel (1978) proposed that the hippocampus represented the neural substrate of cognitive maps. As already discussed in Chapter 1, the integration of findings about brain functioning and spatial behavior into a unified theory strengthened the impact of the initial discovery, giving rise to a growing interest in rodents’ hippocampus and spatial memory. Some years earlier, the observation by Scoville and Milner (1957) of the dramatic temporally graded amnesia produced in H.M. by bilateral lesions to the hippocampus and related temporal lobe structures had a comparable general impact in the field of human memory. This chapter is aimed at giving an overview of studies which allow us to better understand the role played by the hippocampus and associated structures. Studies of the effects of lesions on traditional learning tasks, exploratory behavior and spatial problem solving tests, are presented in the first two sections. The other sections are devoted to electrophysiological studies.