MRI-guided robotic arm drives optogenetic fMRI with concurrent Ca ²⁺ recording

Abstract

Optical fiber-mediated optogenetic activation and neuronal Ca ²⁺ recording in combination with fMRI provide a multi-modal fMRI platform. Here, we developed an MRI-guided robotic arm (MgRA) as a flexible positioning system with high precision to real-time assist optical fiber brain intervention for multi-modal animal fMRI. Besides the ex vivo precision evaluation, we present the highly reliable brain activity patterns in the projected basal forebrain regions upon MgRA-driven optogenetic stimulation in the lateral hypothalamus. Also, we show the step-wise optical fiber targeting thalamic nuclei and map the region-specific functional connectivity with whole-brain fMRI accompanied by simultaneous calcium recordings to specify its circuit-specificity. The MgRA also guides the real-time microinjection to specific deep brain nuclei, which is demonstrated by an Mn-enhanced MRI method. The MgRA represents a clear advantage over the standard stereotaxic-based fiber implantation and opens a broad avenue to investigate the circuit-specific functional brain mapping with the multi-modal fMRI platform.

Abstract

Fiber optic implantation in deep areas of the rodent’s brain for MRI combined with optogenetics is challenging. Here the authors use an MRI-guided robotic arm as the navigation method for accurate fiber optic placement and precise microinjection during multi-modal fMRI, optogenetics and calcium recordings.