Subcortical implantation of a passive microchip in rodents - an observational proof-of-concept study

The use of brain-computer interface (BCI) technologies is a rapidly developing area of interest in neurosurgery. Studies investigating the use of BCIs have primarily focused on surface electrodes; however, subcortically implanted microchips may provide novel, non-pharmacological approaches for managing nervous system disorders. Accessing subcortical regions without disrupting surrounding tissues remains a significant challenge. Accordingly, we conducted an observational, proof-of-concept study to evaluate the use of a modified BrainPath & REG; device to implant subcortical microchips in a rodent model. All animals survived the procedure and lived with a microchip in situ for one or three months with no apparent neurological effects. Histological examination revealed that implantation of a small chip was associated with some tissue damage, tract formation, and surrounding reactive changes. Gliosis and hemosiderin-laden macrophages were evident surrounding tract marks after one month and focal cystic cavitation consistent with infarcted tissue was evident after three months. While a more extensive cellular proliferation response was apparent one month after implantation of a large microchip, there was no significant collagen deposition suggestive of fibrosis. This study is the first demonstration of subcortical microchip implantation using a novel neurosurgical technique that may facilitate the development of BCI technologies for treatment of neurological disorders.