The Optically Guided and Pre-assembled Implantation Cranial Window Reveals Cortical Spatial Representations during Navigation

Head-mounted miniaturized microscopes have provided new capabilities for neuroscience by enabling neural imaging in freely behaving animals. The long-term application of these microscopes, however, is contingent upon specific and reliable cranial window designs. Here, we introduce optically guided and pre-assembled implantation (OGPI), a standardized cranial window technique designed for head-mounted miniaturized microscope imaging. OGPI employs a cost-effective, minimalist design and offers robust compatibility with miniaturized microscopes. This integrated method ensures precise implantation and supports chronic large-scale neural imaging in freely behaving animals for periods exceeding 8 months. The OGPI method is adaptable, supporting both semiautomated operation for enhanced throughput and manual operation for standard laboratory settings. Through behavioral assessments, we further demonstrate that animals with OGPI cranial windows exhibit preserved locomotor and spatial cognitive abilities. Leveraging this chronic window, we performed large-scale cortical imaging in mice engaged in a Y-maze navigation task. We found that the neurons' tuning position, path, and acceleration were distributed in a "salt-and-pepper" pattern across multiple cortices. A subpopulation of neurons exhibiting conjunctive tuning to both spatial information and linear acceleration was identified, suggesting that the acceleration-tuned neurons required for the generation and updating of the spatial signal exist in the cortex. Further, population-level analyses of spatial representation in the cortex were conducted. A decoder and a classifier based on cortical activity accurately predicted the animal's position and path. Altogether, our results establish OGPI as an enabling platform and a key methodological advancement for chronic imaging in freely behaving animals and reveal a widespread representation of spatial information in the cortex.