Principles of Computer Numerical Controlled Machining Applied to Small Research Animal Microsurgical Procedures

Abstract

The palette of tools available for systems neuroscientists to measure and manipulate the brain during behavioral experiments has exploded in the last decade. Implementing these tools, from electrical to optical sensors require the removal of bone tissue without damage to the underlying brain tissue. This is typically a delicate procedure as the skulls of commonly used inbred mouse strains are very thin (~80-500 μm above the mice dorsal cortex). However, with increasing complexity, these microsurgical procedures have become art forms. It takes many months to become skilled at performing these operations. Automating some of the tissue removal processes would potentially enable more precise procedures to be performed. Here, we introduce the ‘Craniobot’, a microsurgery platform, assembled with off-the- shelf components, that combines automated skull surface profiling with a CNC milling machine to perform a variety of microsurgical procedures in mice. The Craniobot utilizes a low force contact sensor that can accurately measure the surface of the skull across the whole dorsal skull with a precision of 2.4 ± 8.5 µm and this information can be used to perform milling operations with comparable precision. We have used the Craniobot to perform skull thinning, small to large craniotomies, as well as drilling pilot holes for anchoring cranial implants. The system is implemented using open source and customizable machining practices, this approach can be expanded in the future to larger animal models, or for more complex procedures and a more comprehensive part of the pipeline of in vivo neuroscience.