Lifting the degeneracy of optical fiber neural interfaces for optogenetics and electrophysiology by using axialtrodes

Optogenetics and electrophysiology are powerful methods in neuroscience for precise spatiotemporal control and recording of neural activity. Conventional flat optical fibers, commonly used in deep brain regions, can only interface with limited tissue volume at their distal end. However, depth-resolved neuromodulation and recordings are crucial for decoding neuronal connections across various brain domains. In this work, we address this limitation by introducing an axialtrode developed using soft polymers integrated with multiple metal electrodes via a scalable thermal drawing process. We employ the developed fiber-based neural interface, controllably angled-cleaved, for multisite optogenetics and electrophysiology at different brain regions. Its suppressed inflammatory responses indicate improved biocompatibility compared to conventional fibers. This concept can be adapted to any fiber material and application where depth-resolved stimulation and electrical recordings are important, bringing the community a step closer to understanding complex neuronal dynamics.