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Saha R, Faramarzi S, Bloom R, Benally OJ, Wu K, di Girolamo A, Tonini D, Keirstead SA, Low WC, Netoff T, Wang JP. Strength-frequency curve for micromagnetic neurostimulation through excitatory postsynaptic potentials (EPSPs) on rat hippocampal neurons and numerical modeling of magnetic microcoil (μcoil). J Neural Eng 2022; 19. [PMID: 35030549 DOI: 10.1088/1741-2552/ac4baf] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 01/14/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The objective of this study was to measure the effect of micromagnetic stimulation (μMS) on hippocampal neurons, by using single microcoil (μcoil) prototype, Magnetic Pen (MagPen). MagPen will be used to stimulate the CA3 magnetically and excitatory post synaptic potential (EPSP) measurements will be made from the CA1. The threshold for μMS as a function of stimulation frequency of the current driving the µcoil will be demonstrated. Finally, the optimal stimulation frequency of the current driving the μcoil to minimize power will be estimated. APPROACH A biocompatible prototype, MagPen was built, and customized such that it is easy to adjust the orientation of the μcoil over the hippocampal tissue in an in vitro setting. Finite element modeling (FEM) of the μcoil was performed to estimate the spatial profiles of the magnetic flux density (in T) and the induced electric fields (in V/m). The induced electric field profiles generated at different values of current applied to the µcoil whether can elicit a neuron response was validated by numerical modeling. The modeling settings were replicated in experiments on rat hippocampal neurons. MAIN RESULTS The preferred orientation of MagPen over the Schaffer Collateral fibers was demonstrated such that they elicit a neuron response. The recorded EPSPs from CA1 due to μMS at CA3 were validated by applying tetrodotoxin (TTX). Finally, it was interpreted through numerical analysis that increasing frequency of the current driving the μcoil, led to a decrease in the current amplitude threshold for μMS. SIGNIFICANCE This work reports that μMS can be used to evoke population EPSPs in the CA1 of hippocampus. It demonstrates the strength-frequency curve for µMS and its unique features related to orientation dependence of the µcoils, spatial selectivity and distance dependence. Finally, the challenges related to µMS experiments were studied including ways to overcome them.
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Affiliation(s)
- Renata Saha
- Electrical and Computer Engineering, University of Minnesota Twin Cities, 200 Union Street SE, Kenneth Keller Hall, Rm 6-147D, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Sadegh Faramarzi
- Department of Biomedical Engineering, University of Minnesota Twin Cities, Nils Hasselmo Hall,, 312 Church St SE,, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Robert Bloom
- Department of Electrical and Computer Engineering, University of Minnesota, 200 Union Street SE, 4-174 Keller Hall, Minneapolis, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Onri J Benally
- Department of Electrical and Computer Engineering, University of Minnesota Twin Cities, 200 Union Street SE,, Kenneth Keller Hall, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Kai Wu
- Electrical and Computer Engineering, University of Minnesota Twin Cities, 200 Union Street SE, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Arturo di Girolamo
- Department of Electrical and Computer Engineering, University of Minnesota Twin Cities, 200 Union Street SE, Kenneth Keller Hall, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Denis Tonini
- Department of Electrical and Computer Engineering, University of Minnesota Twin Cities, 200 Union Street SE,, Kenneth Keller Hall, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Susan A Keirstead
- Department of Integrative Biology & Physiology, University of Minnesota Twin Cities, Stem Cell Institute, LRB/MTRF 2873B (Campus Delivery Code), 2001 6th St SE, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Walter C Low
- Department of Neurosurgery, University of Minnesota Twin Cities, LRB/MTRF 2873J (Campus Delivery Code), 2001 6th St SE, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Theoden Netoff
- Department of Biomedical Engineering, University of Minnesota Twin Cities, 312 Church Street SE, 7-105 Nils Hasselmo Hall, Minneapolis, Minnesota, 55455, UNITED STATES
| | - Jian-Ping Wang
- Department of Electrical and Computer Engineering, University of Minnesota Twin Cities, 200 Union Street SE, Kenneth Keller Hall, Minneapolis, Minnesota, 55455, UNITED STATES
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