Imaging population activity of head direction neurons in the presubiculum of freely behaving mice

The head direction (HD) system functions as the brain's compass, forming our inner representation of the external world. Single HD neurons increase their firing rate when the head of an animal is oriented in a specific direction. The HD signal is internally generated, driven by vestibular information and it is anchored to stable visual cues in the environment. How specific brain microcircuits combine the stable maintenance of the HD signal as well as flexibility upon reorientation is unknown. Our goal is to understand the dynamical structure of the head direction neural network in the presubiculum during stable maintenance and resetting by salient visual cues. For that purpose, we recorded population of HD neurons using 1-photon calcium imaging in freely behaving mice using a miniscope, a miniaturized microscope. To test if the population HD signal is cue controlled and stable during darkness, mice were placed inside a circular arena in which the location of a visual cue and the lighting condition were manipulated. Furthermore, HD resetting dynamics were investigated with the visual cue at an unexpected location after a period of darkness. Our results shed light on how HD cell population activity is shaped by multi-sensory integration in the presubiculum in freely behaving mice.