Transcranial magnetic stimulation set-up for small animals

Jaakko O Nieminen; Alexey S Pospelov; Lari M Koponen; Pauliina Yrjölä; Anastasia Shulga; Stanislav Khirug; Claudio Rivera

doi:10.3389/fnins.2022.935268

Transcranial magnetic stimulation set-up for small animals

Front Neurosci. 2022 Nov 10:16:935268. doi: 10.3389/fnins.2022.935268. eCollection 2022.

Authors

Jaakko O Nieminen^{1

2

3}, Alexey S Pospelov^{4

5

6}, Lari M Koponen¹, Pauliina Yrjölä^{2

5

6}, Anastasia Shulga^{2

7}, Stanislav Khirug⁶, Claudio Rivera^{6

8}

Affiliations

¹ Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland.
² BioMag Laboratory, HUS Medical Imaging Centre, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
³ Biomedical Imaging Unit, A.I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland.
⁴ Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland.
⁵ Department of Clinical Neurophysiology, BABA Center, Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
⁶ Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.
⁷ Department of Physical and Rehabilitation Medicine, Helsinki University Hospital, Helsinki, Finland.
⁸ INMED (INSERM U1249), Aix-Marseille Université, Marseille, France.

Abstract

Transcranial magnetic stimulation (TMS) is widely applied on humans for research and clinical purposes. TMS studies on small animals, e.g., rodents, can provide valuable knowledge of the underlying neurophysiological mechanisms. Administering TMS on small animals is, however, prone to technical difficulties, mainly due to their small head size. In this study, we aimed to develop an energy-efficient coil and a compatible experimental set-up for administering TMS on rodents. We applied a convex optimization process to develop a minimum-energy coil for TMS on rats. As the coil windings of the optimized coil extend to a wide region, we designed and manufactured a holder on which the rat lies upside down, with its head supported by the coil. We used the set-up to record TMS-electromyography, with electromyography recorded from limb muscles with intramuscular electrodes. The upside-down placement of the rat allowed the operator to easily navigate the TMS without the coil blocking their field of view. With this paradigm, we obtained consistent motor evoked potentials from all tested animals.

Keywords: TMS; coil; electromyography; holder; rat; transcranial magnetic stimulation.