TY - JOUR
T1 - Design and Evaluation of a Rodent-Specific Transcranial Magnetic Stimulation Coil
T2 - An In Silico and In Vivo Validation Study
AU - Boonzaier, Julia
AU - Petrov, Petar I.
AU - Otte, Willem M.
AU - Smirnov, Nickolay
AU - Neggers, Sebastiaan F.W.
AU - Dijkhuizen, Rick M.
N1 - © 2019 The Authors. Neuromodulation: Technology at the Neural Interface published by Wiley Periodicals, Inc. on behalf of International Neuromodulation Society.
PY - 2020/4/1
Y1 - 2020/4/1
N2 - Background: Rodent models are fundamental in unraveling cellular and molecular mechanisms of transcranial magnetic stimulation (TMS)-induced effects on the brain. However, proper translation of human TMS protocols to animal models have been restricted by the lack of rodent-specific focal TMS coils. Objective: We aimed to improve TMS focalization in rodent brain with a novel small, cooled, and rodent-specific TMS coil. Methods: A rodent-specific 25-mm figure-of-eight TMS coil was developed. Stimulation focalization was simulated in silico for the rodent coil and a commercial human 50-mm figure-of-eight TMS coil. Both coils were also compared in vivo by electromyography measurements of brachialis motor evoked potential (MEP) responses to TMS at different brain sites in anesthetized rats (n = 6). Focalization was determined from the coils' level of stimulation laterality. Differences in MEPs were statistically analyzed with repeated-measures, within-subjects, ANOVA. Results: In silico simulation results deemed the human coil insufficient for unilateral stimulation of the rat motor cortex, whereas lateralized electrical field induction was projected attainable with the rodent coil. Cortical, in vivo MEP amplitude measurements from multiple points in each hemisphere, revealed unilateral activation of the contralateral brachialis muscle, in absence of ipsilateral brachialis activation, with both coils. Conclusion: Computer simulations motivated the design of a smaller rodent-specific TMS coil, but came short in explaining the capability of a larger commercial human coil to induce unilateral MEPs in vivo. Lateralized TMS, as demonstrated for both TMS coils, corroborates their use in translational rodent studies, to elucidate mechanisms of action of therapeutic TMS protocols.
AB - Background: Rodent models are fundamental in unraveling cellular and molecular mechanisms of transcranial magnetic stimulation (TMS)-induced effects on the brain. However, proper translation of human TMS protocols to animal models have been restricted by the lack of rodent-specific focal TMS coils. Objective: We aimed to improve TMS focalization in rodent brain with a novel small, cooled, and rodent-specific TMS coil. Methods: A rodent-specific 25-mm figure-of-eight TMS coil was developed. Stimulation focalization was simulated in silico for the rodent coil and a commercial human 50-mm figure-of-eight TMS coil. Both coils were also compared in vivo by electromyography measurements of brachialis motor evoked potential (MEP) responses to TMS at different brain sites in anesthetized rats (n = 6). Focalization was determined from the coils' level of stimulation laterality. Differences in MEPs were statistically analyzed with repeated-measures, within-subjects, ANOVA. Results: In silico simulation results deemed the human coil insufficient for unilateral stimulation of the rat motor cortex, whereas lateralized electrical field induction was projected attainable with the rodent coil. Cortical, in vivo MEP amplitude measurements from multiple points in each hemisphere, revealed unilateral activation of the contralateral brachialis muscle, in absence of ipsilateral brachialis activation, with both coils. Conclusion: Computer simulations motivated the design of a smaller rodent-specific TMS coil, but came short in explaining the capability of a larger commercial human coil to induce unilateral MEPs in vivo. Lateralized TMS, as demonstrated for both TMS coils, corroborates their use in translational rodent studies, to elucidate mechanisms of action of therapeutic TMS protocols.
KW - Electric fields
KW - finite element analysis
KW - motor evoked potential
KW - rats
KW - transcranial magnetic stimulation
UR - http://www.scopus.com/inward/record.url?scp=85084167095&partnerID=8YFLogxK
U2 - 10.1111/ner.13025
DO - 10.1111/ner.13025
M3 - Article
C2 - 31353780
AN - SCOPUS:85084167095
SN - 1094-7159
VL - 23
SP - 324
EP - 334
JO - Neuromodulation
JF - Neuromodulation
IS - 3
ER -