Being able to consistently locate a cortical region and even a specific cell requires that each system used to collect data maintains a consistent relationship between the mouse's eye and the visual stimulus being presented. To achieve consistent placement of the mouse across systems, and address the challenge of finding and returning to the same cells from day to day, the engineering team designed a custom headframe that is affixed to the mouse’s skull in a standardized location. The headframe consists of a plastic head plate, or well, and a stainless steal clamp-plate that allows repeatable positioning of the animal on each experimental setup. The clamp plate fits perfectly into the placement tool, which in turn is secured to the stereotaxic arm of the surgery rig. Before attaching the head frame, the surgeons used a leveling protocol that was anatomically referenced, so that the headframe was consistently placed over the visual cortex. The cranial window was made within the well to expose the part of the brain that was to be imaged. This ensures an optimal position of the headframe to give visual access to the desirable cortical areas.
The headframe clamp enables cross-platform registration
A standardized clamping system on each experimental platform was made to match the head frame clamp plate and ensure reproducible placement of the head and eye position on all platforms. This cross platform registration is essential to put all the data into a common reference frame for downstream analysis.