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Matilainen N, Kataja J, Laakso I. Predicting the hotspot location and motor threshold prior to transcranial magnetic stimulation using electric field modelling. Phys Med Biol 2023; 69:015012. [PMID: 37816371 DOI: 10.1088/1361-6560/ad0219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 10/10/2023] [Indexed: 10/12/2023]
Abstract
Objective.To investigate whether the motor threshold (MT) and the location of the motor hotspot in transcranial magnetic stimulation (TMS) can be predicted with computational models of the induced electric field.Approach.Individualized computational models were constructed from structural magnetic resonance images of ten healthy participants, and the induced electric fields were determined with the finite element method. The models were used to optimize the location and direction of the TMS coil on the scalp to produce the largest electric field at a predetermined cortical target location. The models were also used to predict how the MT changes as the magnetic coil is moved to various locations over the scalp. To validate the model predictions, the motor evoked potentials were measured from the first dorsal interosseous (FDI) muscle with TMS in the ten participants. Both computational and experimental methods were preregistered prior to the experiments.Main results.Computationally optimized hotspot locations were nearly as accurate as those obtained using manual hotspot search procedures. The mean Euclidean distance between the predicted and the measured hotspot locations was approximately 1.3 cm with a 0.8 cm bias towards the anterior direction. Exploratory analyses showed that the bias could be removed by changing the cortical target location that was used for the prediction. The results also indicated a statistically significant relationship (p< 0.001) between the calculated electric field and the MT measured at several locations on the scalp.Significance.The results show that the individual TMS hotspot can be located using computational analysis without stimulating the subject or patient even once. Adapting computational modelling would save time and effort in research and clinical use of TMS.
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Affiliation(s)
- Noora Matilainen
- Department of Electrical Engineering and Automation, Aalto University, Espoo, Finland
| | - Juhani Kataja
- Department of Electrical Engineering and Automation, Aalto University, Espoo, Finland
| | - Ilkka Laakso
- Department of Electrical Engineering and Automation, Aalto University, Espoo, Finland
- Aalto Neuroimaging, Aalto University, Espoo, Finland
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Pantovic M, Boss R, Noorda KJ, Premyanov MI, Aynlender DG, Wilkins EW, Boss S, Riley ZA, Poston B. The Influence of Different Inter-Trial Intervals on the Quantification of Intracortical Facilitation in the Primary Motor Cortex. Bioengineering (Basel) 2023; 10:1278. [PMID: 38002401 PMCID: PMC10669180 DOI: 10.3390/bioengineering10111278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 10/29/2023] [Accepted: 10/30/2023] [Indexed: 11/26/2023] Open
Abstract
Intracortical facilitation (ICF) is a paired-pulse transcranial magnetic stimulation (TMS) measurement used to quantify interneuron activity in the primary motor cortex (M1) in healthy populations and motor disorders. Due to the prevalence of the technique, most of the stimulation parameters to optimize ICF quantification have been established. However, the underappreciated methodological issue of the time between ICF trials (inter-trial interval; ITI) has been unstandardized, and different ITIs have never been compared in a paired-pulse TMS study. This is important because single-pulse TMS studies have found motor evoked potential (MEP) amplitude reductions over time during TMS trial blocks for short, but not long ITIs. The primary purpose was to determine the influence of different ITIs on the measurement of ICF. Twenty adults completed one experimental session that involved 4 separate ICF trial blocks with each utilizing a different ITI (4, 6, 8, and 10 s). Two-way ANOVAs indicated no significant ITI main effects for test MEP amplitudes, condition-test MEP amplitudes, and therefore ICF. Accordingly, all ITIs studied provided nearly identical ICF values when averaged over entire trial blocks. Therefore, it is recommended that ITIs of 4-6 s be utilized for ICF quantification to optimize participant comfort and experiment time efficiency.
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Affiliation(s)
- Milan Pantovic
- Health and Human Performance Department, Utah Tech University, St. George, UT 84770, USA;
| | - Rhett Boss
- School of Medicine, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA; (R.B.); (K.J.N.); (M.I.P.); (D.G.A.)
| | - Kevin J. Noorda
- School of Medicine, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA; (R.B.); (K.J.N.); (M.I.P.); (D.G.A.)
| | - Mario I. Premyanov
- School of Medicine, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA; (R.B.); (K.J.N.); (M.I.P.); (D.G.A.)
| | - Daniel G. Aynlender
- School of Medicine, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA; (R.B.); (K.J.N.); (M.I.P.); (D.G.A.)
| | - Erik W. Wilkins
- Department of Kinesiology and Nutrition Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA;
| | - Sage Boss
- School of Life Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA;
| | - Zachary A. Riley
- Department of Kinesiology, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA;
| | - Brach Poston
- Department of Kinesiology and Nutrition Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA;
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Rostami M, Zomorrodi R, Rostami R, Hosseinzadeh GA. Impact of methodological variability on EEG responses evoked by transcranial magnetic stimulation: a meta-analysis. Clin Neurophysiol 2022; 142:154-180. [DOI: 10.1016/j.clinph.2022.07.495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 07/12/2022] [Accepted: 07/15/2022] [Indexed: 12/01/2022]
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