EVALUATION OF NON-INVASIVE OPTOGENETIC STIMULATION WITH TRANSCRANIAL FUNCTIONAL ULTRASOUND IMAGING

employs engineered viruses to genetically modify cells to express specific light-sensitive ion channels. The standard method for gene delivery in the brain involves invasive craniotomies that expose the brain and direct injections of viruses that invariably damage neural tissue along the syringe tract. A recently pro-posed alternative in which non-invasive optogenetics is performed with focused ultrasound (FUS)-mediated blood -brain barrier (BBB) openings has been found to non-invasively facilitate gene delivery for optogenetics in mice. Although gene delivery can be performed non-invasively, validating successful viral transduction and expression of encoded ion channels in target tissue typically involves similar invasive techniques, such as craniot-omies in longitudinal studies and/or postmortem histology. Functional ultrasound imaging (fUSi) is an emerging neuroimaging technique that can be used to transcranially detect changes in cerebral blood volume following introduction of a stimulus. In this study, we implemented a fully non-invasive combined FUS-fUSi technique for performing optogenetics in mice. FUS successfully delivered viruses encoding the red-shifted channelrhodopsin variant ChrimsonR in all treated subjects. fUSi successfully identified stimulus-evoked cerebral blood volume changes preferentially in brain regions expressing the light-sensitive ion channels. Improvements in cell-specific targeting of viral vectors and transcranial ultrasound imaging will make the combined technique a useful tool for neuroscience research in small animals. (E-mail: ek2191@columbia.edu) (c) 2022 World Federation for Ultrasound in Medicine & Biology. All rights reserved.

Automated summary

This study explores a fully non-invasive combined technique using focused ultrasound and functional ultrasound imaging for optogenetics in mice. It successfully delivers viral vectors encoding light-sensitive ion channels and detects stimulus-evoked cerebral blood volume changes. It can serve as a valuable tool for neuroscience research in small animals.