NEURAL ENCODING OF THE EXTERNAL WORLD IN FREELY MOVING MICE USING MINIATURIZED TWO-PHOTON MICROSCOPY

Understanding cognition and behavior requires measuring neuronal activity during complex tasks performed under naturalistic conditions. Two-photon (2P) microscopy has revolutionized systems neuroscience by enabling high-resolution, cell-type-specific recordings from large neuronal populations in awake animals. However, conventional 2P approaches rely on head fixation, limiting the range of behaviors that can be studied and reducing ecological validity. A recent technological advance developed by the Moser lab (Kavli Institute, Trondheim) overcomes this limitation by enabling 2P imaging of genetically identified neurons across multiple brain regions in freely moving mice.

Sensory systems must integrate external stimuli with self-generated signals to guide behavior, a particularly critical challenge in vision, where self-motion strongly modulates sensory input. Head movements alter visual input, requiring the brain to distinguish environmental changes from those caused by the animal’s own actions. While classical studies of the primary visual cortex (V1) relied on head-fixed preparations, recent evidence indicates that head movements significantly influence V1 neuronal activity. Here, we investigated how V1 neurons encode egocentric versus allocentric visual information in freely moving mice. Using head-mounted 2P microscopy, we recorded activity from genetically identified neuronal populations in V1 during visual stimulation combined with spontaneous head movements. Head orientation was monitored using an inertial measurement unit, and eye position was tracked with a head-mounted camera. This multimodal approach allowed us to dissociate visually driven responses from self-motion-related activity, providing insight into how V1 integrates sensory and motor signals during natural behavior.