| Summary: | Summary: Spatial navigation relies on visual landmarks as well as on self-motion information. In familiar environments, both place and grid cells maintain their firing fields in darkness, suggesting that they continuously receive information about locomotion speed required for path integration. Consistently, “speed cells” have been previously identified in the hippocampal formation and characterized in detail in the medial entorhinal cortex. Here we investigated speed-correlated firing in the hippocampus. We show that CA1 has speed cells that are stable across contexts, position in space, and time. Moreover, their speed-correlated firing occurs within theta cycles, independently of theta frequency. Interestingly, a physiological classification of cell types reveals that all CA1 speed cells are inhibitory. In fact, while speed modulates pyramidal cell activity, only the firing rate of interneurons can accurately predict locomotion speed on a sub-second timescale. These findings shed light on network models of navigation. : Neurons coding for locomotion speed are theoretically required to perform path integration. Góis and Tort show that in CA1, speed is encoded by inhibitory interneurons, but not pyramidal cells, shedding light on the network mechanisms of spatial navigation. Keywords: hippocampus, spatial navigation, CA1, neuronal coding, speed cells, place cells, path integration, rate coding, theta
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