Transparent neural interfaces: challenges and solutions of microengineered multimodal implants designed to measure intact neuronal populations using high-resolution electrophysiology and microscopy simultaneously

Abstract

The aim of this review is to present a comprehensive overview of the feasibility of using transparent neural interfaces in multimodal in vivo experiments on the central nervous system. Multimodal electrophysiological and neuroimaging approaches hold great potential for revealing the anatomical and functional connectivity of neuronal ensembles in the intact brain. Multimodal approaches are less time-consuming and require fewer experimental animals as researchers obtain denser, complex data during the combined experiments. Creating devices that provide high-resolution, artifact-free neural recordings while facilitating the interrogation or stimulation of underlying anatomical features is currently one of the greatest challenges in the field of neuroengineering. There are numerous articles highlighting the trade-offs between the design and development of transparent neural interfaces; however, a comprehensive overview of the efforts in material science and technology has not been reported. Our present work fills this gap in knowledge by introducing the latest micro- and nanoengineered solutions for fabricating substrate and conductive components. Here, the limitations and improvements in electrical, optical, and mechanical properties, the stability and longevity of the integrated features, and biocompatibility during in vivo use are discussed.

Integration of in vivo electrophysiology and optogenetics in rodents with PEDOT:PSS neural electrode array

“… 14 , 15 When this voltage signal combines with the small electrophysiological potential from the neural activity, results in contamination of the neural signals. 14 , 16 Additionally, opaque metal electrodes absorb most of the light for neuromodulation, preventing sufficient energy needed for optogenetics from reaching the brain tissue. This limited transmission of light is detrimental to the convergence of electrophysiology and optogenetics in that neural activity would not be activated with the light stimulation threshold.…”

Immunohistological responses in mice implanted with Parylene HT – ITO ECoG devices

“…One of the main reasons for unreliable electrical recordings in chronic experiments is the prolonged presence of ECoG devices resulting in neuroinflammatory responses that evoke glial scar formation, eventually isolating the device from the tissue ( Bérces et al, 2016 ; Kim et al, 2019 ). Therefore, the importance of investigating the performance of different neural interface materials can not be understated, a fact well recognized by the field ( Vomero et al, 2020 ; Fedor et al, 2022 ; Fekete et al, 2023 ). Several methods are available to probe the effects of device implantation.…”