Full activation pattern mapping by simultaneous deep brain stimulation and fMRI with graphene fiber electrodes

Abstract

Simultaneous deep brain stimulation (DBS) and functional magnetic resonance imaging (fMRI) constitutes a powerful tool for elucidating brain functional connectivity, and exploring neuromodulatory mechanisms of DBS therapies. Previous DBS-fMRI studies could not provide full activation pattern maps due to poor MRI compatibility of the DBS electrodes, which caused obstruction of large brain areas on MRI scans. Here, we fabricate graphene fiber (GF) electrodes with high charge-injection-capacity and little-to-no MRI artifact at 9.4T. DBS-fMRI with GF electrodes at the subthalamic nucleus (STN) in Parkinsonian rats reveal robust blood-oxygenation-level-dependent responses along the basal ganglia-thalamocortical network in a frequency-dependent manner, with responses from some regions not previously detectable. This full map indicates that STN-DBS modulates both motor and non-motor pathways, possibly through orthodromic and antidromic signal propagation. With the capability for full, unbiased activation pattern mapping, DBS-fMRI using GF electrodes can provide important insights into DBS therapeutic mechanisms in various neurological disorders.

Subthalamic Nucleus Deep Brain Stimulation Modulates 2 Distinct Neurocircuits

“…For these reasons, previous DBS-fMRI studies were predominantly performed in animals. 13,15 The majority of human studies have been carried out using 1.5T MRI and suffer from small sample sizes and low reliability. [16][17][18][19] However, recent advances in 3T MRI-compatible DBS technology, which can now be safely applied to humans, [20][21][22] has provided an unprecedented opportunity for exploring specific but subtle changes in brain circuitry induced by DBS.…”

“…These techniques are not ideal for revealing distributed, large‐scale network activity across the whole brain. Concurrent DBS–functional magnetic resonance imaging (fMRI) may provide a more comprehensive picture of stimulation‐induced changes in brain networks 13 . One drawback that has hindered its use is the potential risk it poses to the brain, namely brain damage induced by electrode displacement or heating, 14 especially in the high‐field MRI environment.…”

“…One drawback that has hindered its use is the potential risk it poses to the brain, namely brain damage induced by electrode displacement or heating, 14 especially in the high‐field MRI environment. For these reasons, previous DBS‐fMRI studies were predominantly performed in animals 13,15 . The majority of human studies have been carried out using 1.5T MRI and suffer from small sample sizes and low reliability 16–19 .…”

An FMRI-compatible System for Targeted Electrical Stimulation

“…Correspondingly, we observed a DBS-STN induced change in BOLD response in neocortex, but not in the cerebral target site for the implanted electrode and stimulation, so possible effects of DBS at stimulation site remain unknown. However, no stimulator system used in fMRI examinations, including ours, can overcome the di culties with metallic susceptibility artefacts proximate to electrodes and leads, but future advances in carbon electrodes might (19).…”

Advances in Carbon-Based Microfiber Electrodes for Neural Interfacing

“…Using a four-channel electrode array, they were able to record SU spikes with high SNRs in an acute study from rat motor cortex. Zhao et al (2020) used graphene fibers fabricated with a different technique for neural stimulation. In this work, their fibers were prepared through a one-step dimensionally confined hydrothermal process using suspensions of graphene oxide.…”