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bioRxiv · 10.1101/2024.09.16.612091

Functional MRI reveals regional changes of brain activity after five days of focal high-density theta burst stimulation (hdTBS) of the rat brain

Li, Q.·Hoffman, S.·Nguyen, H.·Carney, A.·Duan, Y.·Ma, Z.·Zhang, N.·Yang, Y.·Lu, H.
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Abstract

BackgroundThe therapeutic effects of transcranial magnetic stimulation (TMS) likely stem from neuroplasticity induced by repeated sessions over time. While animal models offer insights into TMS-induced plasticity, a rodent model that faithfully replicates prolonged TMS conditions in humans is still lacking. Objective/HypothesisDevelop a rat model that mimics the spatial and temporal patterns of TMS in humans. MethodsExperiments were conducted on two cohorts of healthy adult rats (N=33). In cohort 1, rats underwent surgical implantation of microelectrodes for motor evoked potential (MEP) recording. With a rodent-specific coil and the high-density theta burst stimulation (hdTBS) paradigm, under awake condition, rats received daily TMS at 100% motor threshold for five days (days 1-5) to the hindlimb motor cortex. Cortical excitability was measured by input-output (I-O) curves on Day 0 (pre-hdTBS baseline) and Day 6 (post-hdTBS). The second cohort received identical TMS and underwent fMRI to map cerebral blood volume (CBV) on Days 0 and 6. ResultsDaily hdTBS session for 5 days significantly up-shifted I-O curves only in the TMS group (N=9), not in the sham group (N=7), indicating enhanced cortical excitability. fMRI data showed that, compared to sham group (N=9), rats receiving hdTBS (N=8) had increased basal CBV in several brain regions proximal and distal to the stimulation site, suggesting enhanced basal metabolism. Conclusion(s)Daily hdTBS session for 5 days focally delivered to the motor cortex of naive rats significantly altered basal brain activity in a network of brain regions, opening a novel platform for further investigating TMS-induced plasticity.

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Li, Q., Hoffman, S., Nguyen, H., Carney, A., Duan, Y., Ma, Z., Zhang, N., Yang, Y., Lu, H.. 2024-09-16. Functional MRI reveals regional changes of brain activity after five days of focal high-density theta burst stimulation (hdTBS) of the rat brain. https://doi.org/10.1101/2024.09.16.612091

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