Abstract
Chronic in vivo imaging and electrophysiology are important for better understanding of neural functions and circuits. We introduce the new cranial window using soft, penetrable, elastic, and transparent, silicone-based polydimethylsiloxane (PDMS) as a substitute for the skull and dura in both rats and mice. The PDMS can be readily tailored to any size and shape to cover large brain area. Clear and healthy cortical vasculatures were observed up to 15 weeks post-implantation. Real-time hemodynamic responses were successfully monitored during sensory stimulation. Furthermore, the PDMS window allowed for easy insertion of microelectrodes and micropipettes into the cortical tissue for electrophysiological recording and chemical injection at any location without causing any fluid leakage. Longitudinal two-photon microscopic imaging of Cx3Cr1+/− GFP transgenic mice was comparable with imaging via a conventional glass-type cranial window, even immediately following direct intracortical injection. This cranial window will facilitate direct probing and mapping for long-term brain studies.
Highlights
Chronic in vivo imaging and electrophysiology are important for better understanding of neural functions and circuits
To better utilize the recent advances in neuroscience techniques to study the wide brain network[1,2,3,4,5], an ideal cranial window should have the following properties: 1) high optical clarity and a wide-field of view for longitudinal morphological and functional imaging and optogenetic stimulation, 2) simple fabrication process for any size and design of window, and 3) easy accessibility for the introduction of pharmacological drugs, dyes, and viruses at desired locations as well as for electrophysiological recording to be performed at any position within the cranial window
To overcome the limitations of conventional cranial window approaches, we propose a novel and simple cranial window technique using a brain cover based on soft, flexible, elastic, clear, and biocompatible PDMS
Summary
Flexible and simple cranial window for chronic functional in vivo imaging. A silicone-based organic polymer film comprising PDMS is highly flexible and can float on water due to its light weight and hydrophobic nature (Fig. 1A and Supplementary Fig. S1). With our open-skull wide-view PDMS cranial window, we were was able to i) maintain animals at healthy conditions up to 15 weeks after the surgical implantation, ii) insert multiple microelectrodes and micropipettes for electrophysiological recording and chemical injection at any location, and iii) obtain longitudinal functional imaging with high clarity and 2p imaging with deep tissue penetration. These observations meet the highly ideal criteria for using a chronic cranial window to study system neuroscience. We expect that the large-scale soft cranial window techniques presented here, when combined with other modern neurotechnologies, such as optogenetics, will contribute to the elucidation of brain function and circuitry
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