| Description |
Intracortical microelectrode arrays create a direct interface between the brain and external devices. This “brain-machine interface†has found clinical application by allowing patients with tetraplegia to control computer cursors and robotic limbs. Unfortunately, use of intracortical microelectrode array technology is currently limited by its inconsistent ability to record neural signals over time. It is widely believed that the foreign body response (FBR) contributes to recording inconsistency. Most characterizations of the FBR to intracortical microelectrodes have been in the rat using devices with simple architecture, while the only device currently used in humans, the Utah Electrode Array (UEA), is much larger and more complex. In this work, we characterized the FBR to the UEA and found that, unlike with simpler devices, implantation of a UEA results in extensive vascular injury and loss of cortical tissue. We also sought to determine which features of the FBR correlated with recording inconsistency and found that biomarkers of astrogliosis, blood-brain barrier leakage, and tissue loss were associated with decreased recording performance. Next, since a significant portion of potential brain-machine interface recipients are aged, we applied similar methods in an aged cohort of rats in order to understand the effect of aging on the FBR and recording performance. We found that, surprisingly, recording performance was superior in the aged cohort. Astrogliosis was again associated with decreased recording performance in the aged cohort. Finally, we continued our development and validation of a finite element model of cytokine diffusion to assist in designing next-generation devices with a reduced FBR. Taken as a whole, this work provides meaningful insights into the mechanisms of inconsistent recording performance and discusses several promising avenues for overcoming them. |
