Infrared neural stimulation and inhibition using an implantable silicon photonic microdevice

Brain is one of the most temperature sensitive organs.Besides the fundamental role of temperature in cellular metabolism,thermal response of neuronal populations is also significant during the evolution of various neurodegenerative diseases.For such critical environmental factor,thorough mapping of cellular response to variations in temperature is desired in the living brain.So far,limited efforts have been made to create complex devices that are able to modulate temperature,and concurrently record multiple features of the stimulated region.In our work,the in vivo application of a multimodal photonic neural probe is demonstrated.Optical,thermal,and electrophysiological functions are monolithically integrated in a single device.The system facilitates spatial and temporal control of temperature distribution at high precision in the deep brain tissue through an embedded infrared waveguide,while it provides recording of the artefact-free electrical response of individual cells at multiple locations along the probe shaft.Spatial distribution of the optically induced temperature changes is evaluated through in vitro measurements and a validated multi-physical model.The operation of the multimodal microdevice is demonstrated in the rat neocortex and in the hippocampus to increase or suppress firing rate of stimulated neurons in a reversible manner using continuous wave infrared light(λ=1550 nm).Our approach is envisioned to be a promising candidate as an advanced experimental toolset to reveal thermally evoked responses in the deep neural tissue.

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

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,artifactfree 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.