Influence of gamma transcranial alternating current stimulation frequency and intensity on motor cortex excitability in young and older adults

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dc.contributor.authorCirillo, J.
dc.contributor.authorHand, B.J.
dc.contributor.authorLiao, W.-Y.
dc.contributor.authorOpie, G.M.
dc.contributor.authorSasaki, R.
dc.contributor.authorSemmler, J.
dc.date.issued2025
dc.description.abstractGamma transcranial alternating current stimulation (tACS) over primary motor cortex (M1) has been shown to reduce gamma-aminobutyric acid (GABA)-mediated inhibition during stimulation. However, the effectiveness of gamma tACS may be influenced by various factors, such as stimulation frequency, current intensity, and age. The aim of this study was to examine whether corticomotor excitability and GABA-mediated inhibition is influenced by gamma tACS when applied at different frequencies and intensities over M1 of young and older adults. Electromyographic recordings were obtained from the right hand first dorsal interosseous muscle of 18 young and 17 older adults. Motor-evoked potential (MEP) amplitudes elicited by single- and pairedpulse transcranial magnetic stimulation were used to examine corticomotor excitability and short-interval intracortical inhibition (SICI) during gamma and sham tACS. Gamma tACS was applied at three frequencies (60 Hz, 75 Hz, and 90 Hz) and three current intensities (1.0 mA, 1.5 mA, and 2.0 mA). Corticomotor excitability during tACS was not altered by the different gamma frequencies and intensities in young and older adults. Modulation of SICI during gamma tACS was both frequency- and intensity- dependent, with more inhibition than sham for 75 Hz and at 1.5–2.0 mA, but neither was influenced by age. These findings contrast with previous studies, showing that reduced SICI during gamma tACS is not a consistent outcome. Further investigation that includes a greater range of frequencies and intensities is needed to identify the optimal dose for modulating human M1 excitability and intracortical inhibition with gamma tACS
dc.description.statementofresponsibilityJohn Cirillo, Brodie J. Hand, Wei-Yeh Liao, George M. Opie, Ryoki Sasaki, and John G. Semmler
dc.identifier.citationJournal of Neurophysiology, 2025; 134(2):619-627
dc.identifier.doi10.1152/jn.00147.2025
dc.identifier.issn0022-3077
dc.identifier.issn1522-1598
dc.identifier.orcidCirillo, J. [0000-0002-3404-6408]
dc.identifier.orcidHand, B.J. [0000-0002-9778-343X]
dc.identifier.orcidLiao, W.-Y. [0000-0002-8912-9796]
dc.identifier.orcidOpie, G.M. [0000-0001-7771-7569]
dc.identifier.orcidSemmler, J. [0000-0003-0260-8047]
dc.identifier.urihttps://hdl.handle.net/2440/147790
dc.language.isoen
dc.publisherAmerican Physiological Society
dc.relation.granthttp://purl.org/au-research/grants/arc/DE230100022
dc.relation.granthttp://purl.org/au-research/grants/arc/DP200202009
dc.rights© 2025 The Authors. Licensed under Creative Commons Attribution CC-BY 4.0. Published by the American Physiological Society
dc.source.urihttps://doi.org/10.1152/jn.00147.2025
dc.subjectaging; inhibition; motor cortex; transcranial alternating current stimulation; transcranial magnetic stimulation
dc.subject.meshMuscle, Skeletal
dc.subject.meshMotor Cortex
dc.subject.meshHumans
dc.subject.meshElectromyography
dc.subject.meshEvoked Potentials, Motor
dc.subject.meshAging
dc.subject.meshNeural Inhibition
dc.subject.meshAdult
dc.subject.meshAged
dc.subject.meshMiddle Aged
dc.subject.meshFemale
dc.subject.meshMale
dc.subject.meshTranscranial Magnetic Stimulation
dc.subject.meshYoung Adult
dc.subject.meshTranscranial Direct Current Stimulation
dc.subject.meshCortical Excitability
dc.titleInfluence of gamma transcranial alternating current stimulation frequency and intensity on motor cortex excitability in young and older adults
dc.typeJournal article
pubs.publication-statusPublished online

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