Journal article
Inter-individual and age-dependent variability in simulated electric fields induced by conventional transcranial electrical stimulation
Greifswald University Hospital1
Charité – Universitätsmedizin Berlin2
Copenhagen University Hospital Herlev and Gentofte3
Free University of Berlin4
Department of Health Technology, Technical University of Denmark5
Magnetic Resonance, Department of Health Technology, Technical University of Denmark6
Neurophysics, Magnetic Resonance, Department of Health Technology, Technical University of Denmark7
Variations in head and brain anatomy determine the strength and distribution of electrical fields in humans and may account for inconsistent behavioral and neurophysiological results in transcranial electrical stimulation (tES) studies. However, it is insufficiently understood which anatomical features contribute to the variability of the modelled electric fields, and if their impact varies across age groups.
In the present study, we tested the associations of global head anatomy, indexed by extra- and intra-cranial volumes, with electric field measures, comparing young and older adults. We modelled six “conventional” electrode montages typically used in tES studies using SimNIBS software in 40 individuals (20 young, 20 older adults; 20-35, 64-79 years).
We extracted individual electric field strengths and focality values for each montage to identify tissue volumes that account for variability of the induced electric fields in both groups. Linear mixed models explained most of the inter-individual variability of the overall induced field strength in the brain, but not of field focality.
Higher absolute head volume and relative volume of skin, skull and cerebrospinal fluid (CSF) were associated with lower overall electric field strengths. Additionally, we found interactions of age group with head volume and CSF, indicating that this relationship was mitigated in the older group. Our results demonstrate the importance to adjust brain stimulation not only according to brain atrophy, but also to additional parameters of head anatomy.
Future studies need to elucidate the mechanisms underlying individual variability of tES effects in young and older adults, and verify the usefulness of the proposed models in terms of neurophysiology and behavior in empirical studies.
Language: | English |
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Publisher: | Elsevier |
Year: | 2021 |
Pages: | 117413 |
ISSN: | 10538119 and 10959572 |
Types: | Journal article |
DOI: | 10.1016/j.neuroimage.2020.117413 |
ORCIDs: | 0000-0002-2839-4609 , 0000-0002-3466-8725 , 0000-0003-0906-592X and Thielscher, Axel |
Aging Biophysical modelling Non-invasive brain stimulation Older Adults Simulation Transcranial direct current
Adult Age Factors Aged Atrophy Biological Variation, Population Brain Cerebrospinal Fluid Computer Simulation Electricity Electrodes Electromagnetic Fields Female Head Humans Magnetic Resonance Imaging Male Middle Aged Neurosciences. Biological psychiatry. Neuropsychiatry Organ Size RC321-571 Skin Skull Transcranial Direct Current Stimulation Young Adult