PMC7503177_01
Cerebellar lesion detection (
A &
B), its functional connectivity map (
C) and MRI-guided transcranial magnetic stimulation delivery (
D). Average blood oxygen level-dependent (BOLD) signal time-series were extracted from voxels within a binarized lesion-mask that overlapped with the right crus II (
1A &
1B). This was used as the model predictor in a general linear model to determine the brain regions that temporally correlated with the lesion-mask using FSL-FEAT
. The resultant seed-to-voxel connectivity map (z-thresholded at 4) was used to identify the best connectivity of the seed with voxels in the pre-supplementary motor area (pre-SMA; MNI x=3; y=13; z=58;
1C). Six-hundred pulses were delivered as triplet bursts at theta frequency and 90% of the resting motor threshold (50 Hz; 2s on; 8s off) using a MagPro X100 (MagVenture, Denmark) device under MR-guided neuronavigation using the Brainsight stereotaxic system (Rogue Research, Montreal, Canada) with a figure-of-eight coil held with the handle in line with the sagittal plane, pointing toward the occiput to stimulate the pre-SMA site (
1D).
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f1
MRI revealed a wedge-shaped lesion in the right posterior cerebellum, suggestive of a chronic infarct in the posterior inferior cerebellar artery territory ( Figure-1A). MR-angiogram revealed no focal narrowing of intracranial and extracranial vessels. FMRIB Software Library (FSL version-5.0.10) . Figure 1 describes how we obtained a seed-to-voxel connectivity map to identify the best connectivity of the cerebellar lesion-seed with voxels in the pre-supplementary motor area (pre-SMA; MNI x=3; y=13; z=58) - a commonly used site for neuromodulation in OCD . We augmented escitalopram with rTMS, administered as intermittent theta-burst stimulation (iTBS) to the pre-SMA coordinates ( Figure-1D).
Rank-two ellipse seriation-based visualization of correlation matrix before (
A) and after (
B) rTMS treatment. The dotted-black boxes denote the cerebellar network and other connected networks, where the green boxes show the inter-network overlap. Thus, we see that the overlapped region in (
2A) has now transitioned to three different overlapped areas in (
2B), which shows the increase in the overlap between modular networks after treatment. Cerebellar nodes are denoted in black, cortical nodes in blue and subcortical nodes in green. The lesion node (right crus II) and the region of neuro-stimulation are given in red; R2E= Rank-two ellipse.
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f2
We analyzed the two 91 x 91 matrices using the Rank-two ellipse (R2E) seriation technique for node clustering  ( Figure 2).