Functional MRI mapping the optogenetic activation of the lateral hypothalamus driven by an MRI-guided robotic arm (MgRA)
Yi Chen1,2, Pais Roldán Patricia1,2, Xuming Chen1, Michael Frosz3, and Xin Yu1,4

1Research Group of Translational Neuroimaging and Neural Control, High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 2Graduate Training Centre of Neuroscience, University of Tuebingen, Tuebingen, Germany, 3The Max Planck Institute for the Science of Light, Erlangen, Germany, 4The Werner Reichardt Centre for Integrative Neuroscience, University of Tuebingen, Tuebingen, Germany


A multiple degree-of-freedom robotic controlling system was developed to guide the fiber optic targeting lateral hypothalamus in the rat brain inside the high field (14.1T) MRI scanner. Optogenetic activation of the LH leads to highly reliable functional fMRI activation patterns in the LH and its projecting regions including LPO, MPA, MPOL and StA across animals. The MgRA provides a MR-compatible brain intervention strategy to target deep brain nuclei for optogenetic activation or calcium recordings with high precision and flexibility.

Target Audience

Scientists who are interested in small animal fMRI with cutting-edge techniques.


Lateral hypothalamus (LH) is comprised of highly heterogeneous neuronal populations and diverse projections1, 2. Cell-specific optogenetic activation and GCaMP-mediated calcium imaging of LH neurons has been applied to reveal the circuit specific behavioral modulation in rodents 1, 3. However, it remains challenging to target different groups of LH neurons with high flexibility for optogenetic activation and calcium recordings in combination with whole brain fMRI mapping to study the LH-specific brain network modulation. Here, an MRI-guided robotic arm (MgRA) with high precision for fiber optic positioning was developed to drive brain intervention inside the MRI scanner so as to map the BOLD-fMRI functional patterns upon optogenetic activation of LH neurons.


Using an MgRA-guided optical fiber (~200um), neural activity was optogenetically evoked on a region of LH expressing AVV5.CaMKII.ChR2.eYFP of male Sprague-Dawley rats under alpha-chloralose anesthesia. Fig. 1a shows the MgRA positioning system developed in the 14.1T horizontal MR scanner with 12cm inner diameter gradient. An MRI compatible camera allows visual guidance of the fiber towards the target craniotomy at the iso-center of the horizontal bore magnet. It is noteworthy that MRI anatomical images allowed for detection of the potential collateral damage during fiber insertion (Fig.1c). Fiber tip location in LH was confirmed by MRI anatomical images acquired with 2D rapid acquisition with relaxation enhancement sequence: TR, 1200ms, TE, 7.5ms, 1.92cmX1.68cm FOV, 128X112 matrix, 150X150um in-plane resolution, 600um thickness. The optical fiber(~200um) delivered blue light pulses (473nm) at 5Hz, 20ms width with 15s duration for the fMRI block design. fMRI scans with block design were performed using 3D Echo planar imaging sequence: TR, 1.5s, TE,11.5ms, 2.24X1.92X1.92cm3 FOV, 56X48X48 matrix, 400X400X400 um3 spatial resolution. The detailed surgical procedures for optogenetic fMRI were described previously4. MRI data analysis was performed using Analysis of Functional NeuroImages software(NIH, Bethesda).


Blue light pulses (473nm) delivered to the LH triggered the optogenetically driven BOLD signal, which was located not only at the LH region close to the tip of the optical fiber, but also in the lateral preoptic area (LPO), medial preoptic area (MPA), medial preoptic nucleus, lateral part (MPOL) and Strial part of the preoptic area (StA) (Fig. 2b). These widespread changes in BOLD activity were reliably detected in 5 different rats with similar spatial patterns by coregistering the brain atlas to individual rat functional map (Fig. 2b). Quantitative analysis showed robust BOLD signals from the LH and the preoptic area(PA) with optogenetic activation (Fig. 2c, d).


Optogenetic activation of the LH can be directly driven by MgRA system to produce highly reliable activation patterns in LH and the projected regions including LPO, MPA, MPOL and StA across different animals. This work makes it possible to further target different LH neuronal populations and decipher the cell-type specific functional projections in future studies.


We thank Mr. Shanyi Yu for building up the first prototype of the robotic arm and Mr. Johannes Boldt for helping to improve the MgRA system. We thank Mr. Jan Kevin Schlüsener for technical support. This work is supported by the Max-Planck-Society and the China Scholarship Council (PhD fellowship to Yi Chen).


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2. G. D. Stuber, and R. A. Wise, 'Lateral Hypothalamic Circuits for Feeding and Reward', Nat Neurosci, 19 (2016), 198-205.

3. J. H. Jennings, R. L. Ung, S. L. Resendez, A. M. Stamatakis, J. G. Taylor, J. Huang, K. Veleta, P. A. Kantak, M. Aita, K. Shilling-Scrivo, C. Ramakrishnan, K. Deisseroth, S. Otte, and G. D. Stuber, 'Visualizing Hypothalamic Network Dynamics for Appetitive and Consummatory Behaviors', Cell, 160 (2015), 516-27.

4. X. Yu, Y. He, M. Wang, H. Merkle, S. J. Dodd, A. C. Silva, and A. P. Koretsky, 'Sensory and Optogenetically Driven Single-Vessel Fmri', Nat Methods, 13 (2016), 337-40.


Fig. 1. Robotic arm setup and in vivo evaluation. a. View of robotic arm in MRI scanner. b. Camera monitored fiber position above the craniotomy on rat skull. b, The snapshot of the fiber optic (tip with 589nm wavelength laser light, yellow arrow) positioned above the burr hole (green arrow) on the skull of an anesthetized rat with the fiber-driving piece. c, Potential collateral damage from the choroid plexus when fiber was lowered to pass through the lateral ventricles, seen as a dark signal below the hippocampus. Step size was 300um.

Fig. 2. Optogenetic excitation of lateral hypothalamic cells drives positive BOLD. a, Top: Anatomical image shows fiber optic location. Fluorescence image illustrates ChR2-eYFP expression. Bottom: Anatomical image shows fiber optic and virus injection trace. b, Top: Average fMRI map of brain-wide activity during light stimulation. Average evoked BOLD map and 5 individual rat in PA and LH (Bottom). c, Time courses for the ipsilateral LH and PA (n =5 animals). Error bars represent mean±SD, across 5 animals. d, Average time courses for both LH and PA. 1. MPOL; 2. MPA; 3. LPO; 4. LH; FT: fiber tip; PA: preoptic area.

Proc. Intl. Soc. Mag. Reson. Med. 26 (2018)