EVIDENCE OF SPATIAL PERIODIC FIRING IN THE SUBICULUM OF MICE

Abstract

AbstractThe subiculum (SUB) is a region located at the core of the hippocampal formation. The SUB receives inputs from grid cells located in the medial entorhinal cortex (MEC) and from place cells in the CA1 area. Moreover, this structure mediates the output from the hippocampus to cortical and sub-cortical areas involved in the processing of different types of information. Despite the potential relevance of the SUB, its role in memory and spatial coding remains poorly studied. Previous work described a heterogeneous population of SUB spatial neurons, with evidence of its role in coding the geometry of the environment and spatial navigation in darkness. With the aim of understanding further the properties of spatial coding in the SUB, we implanted mice with microdrives carrying tetrodes to target CA1 and the SUB. Apart from the classical place cells described before, we discovered a fraction of SUB pyramidal neurons that generated spatial periodic firing. SUB spatial neurons presented lower spatial resolution and spatial stability than CA1 place cells. The role of spatial periodic neurons in the SUB might be relevant in several computations through the interaction of this region with CA1, the pre-parasubiculum and the MEC.Significance StatementSpatial information coding and memory formation relies in a complex circuit that involves the hippocampal formation and multiple spatial neuron types. We found for the first-time evidence of pyramidal neurons showing grid and periodic firing in the SUB. Our data support the idea that the SUB might be involved in complex spatial information processing beyond the integration of CA1 unit inputs.