BME Lecture Series: Biological Response to Neural Implants Using SV-OCA & TPLSM

Abstract: Penetrating electrodes used to record from cortical neurons in neural prostheses are showing significant promise in allowing patients to move artificial limbs with their thoughts. However, electrodes permanently implanted tend to degrade rapidly over time, reducing long-term usefulness. With support from DARPA, our division (Division of Biomedical Physics) within the Office of Science and Engineering Laboratories (OSEL) is leading a research program that aims to better understand the causes of degraded neural electrode performance. Led by Dr. Cristin Welle, two avenues are being explored. First, in collaboration with OSEL’s Division of Biology, Chemistry, and Material Science, we have developed an accelerated aging platform to investigate issues with the electrode material itself. Second, we have applied a battery of methodological approaches to study the biological response to implanted electrodes, including electrophysiology, immunohistochemistry, behavioral testing, two-photo laser scanning microscopy (TPLSM), and optical coherence tomography (OCT) imaging. The optical imaging methods, in particular, show potential to reveal microscopic tissue changes in the region immediately surrounding an electrode or electrode array.  Hammer will describe FDA research projects that involve in-vivo optical imaging of implanted neural electrodes in the motor cortex of transgenic and wild-type mice. TPLSM of transgenic mice with sparse neuron labeling has revealed specific mechanical stress on the dendrites, as well as acute varicosity formation within the superficial dendritic tuft immediately following insertion. Speckle-variance optical coherence angiography (SV-OCA) was used to complement the TPLSM findings to explore vascular remodeling with intrinsic contrast.