University of California Los Angeles
Abstract:The hippocampus gets inputs from all nearly all sensory modalities. However, hippocampal place cells are mostly studied only in the context of the distal visual cues or path integration. While many place cells rotate with the rotation of surrounding visual cues, hippocampal activity is thought to have no directional selectivity during two-dimensional random foraging, i.e. it is uninfluenced by the head direction of the rat with respect to the distal visual cues. Further, hippocampal neurons also show a robust temporal code, termed theta phase precession. The contribution of multisensory cues to theta rhythm and to phase precession is unknown. These questions are difficult to address in the real world since multisensory cues are difficult to control and measure, let alone precisely manipulate. Hence, we measured the spiking activity of ensembles of neurons from the hippocampus in a multisensory virtual reality while rats performed a variety of tasks. The results reveal both cooperative and competitive interaction between multisensory stimuli in governing hippocampal spatio-temporal selectivity and directional tuning. We suggest that the building blocks of hippocampal neural activity, termed hippocampal motifs, are internally generated. The motifs are combined by multisensory cues to generate a diversity of hippocampal activity patterns under different conditions, including the place-selectivity, distance-selectivity and head directional selectivity.