Voroslakos, M. | bioRxiv Science

bioRxiv2022

flexLiTE: flexible micro-LED integrated optoelectrodesfor minimally-invasive chronic deep-brain study

Understanding complex neuronal circuitry and its functions of a living organism requires a specialized tool which is capable of recording a large ensemble of neuronal signals at single cell resolution and modulating neuronal activities selectively in the target region of brains with high spatiotemporal resolution, while sustaining long-term chronic operation without significant tissue degeneration or device shifts. We hereby present an ultra-flexible, minimally-invasive, Michigan-type neural probe for chronic opto-electrophysiology studies: flexLiTE (flexible micro-LED integrated optoelectrodes). flexLiTE incorporates monolithically integrated, soma-sized inorganic micro-LEDs (12 individually operated) and 32 recording electrodes. Both stimulation and recording modalities were achieved by stacking two modules on a flexible substrate: one with micro-LEDs for neuromodulation and the other with recording sites, resulting in a 115 m-wide,12 m-thick, 10 mm-long optoelectrode. From prototype devices, we demonstrated the reliable operation of flexLiTEs for recording and modulation of hippocampal neurons in a freely moving mice for over [~]8 month.

bioengineering↗

bioRxiv2022

Brain-implanted conductors amplify radiofrequency fields in rodents: advantages and risks

Over the past few decades, daily exposure to radiofrequency (RF) fields has been increasing due to the rapid development of wireless and medical imaging technologies. Under extreme circumstances, exposure to very strong RF energy can lead to heating of body tissue, even resulting in tissue injury. The presence of implanted devices, moreover, can amplify RF effects on surrounding tissue. Therefore, it is important to understand the interactions of RF fields with tissue in the presence of implants, in order to establish appropriate wireless safety protocols, and also to extend the benefits of medical imaging to increasing numbers of people with implanted medical devices. This study explored the neurological effects of RF exposure in rodents implanted with neuronal recording electrodes. We exposed freely moving and anesthetized rats and mice to 950 MHz RF energy while monitoring their brain activity, temperature, and behavior. We found that RF exposure could induce fast onset firing of single neurons without heat injury. In addition, brain implants enhanced the effect of RF stimulation resulting in reversible behavioral changes. Using an optical temperature measurement system, we found greater than tenfold increase in brain temperature in the vicinity of the implant. On the one hand, our results underline the importance of careful safety assessment for brain implanted devices, but on the other hand, we also show that metal implants may be used for neurostimulation if brain temperature can be kept within safe limits.

neuroscience↗