Individual differences in neuroanatomy and neurophysiology predict effects of transcranial alternating current stimulation

Theodore P. Zanto; Kevin T. Jones; Avery E. Ostrand; Wan-Yu Hsu; Richard Campusano; Adam Gazzaley

Brain Stimulation (Sep 2021)

Individual differences in neuroanatomy and neurophysiology predict effects of transcranial alternating current stimulation

Theodore P. Zanto,
Kevin T. Jones,
Avery E. Ostrand,
Wan-Yu Hsu,
Richard Campusano,
Adam Gazzaley

Affiliations

Theodore P. Zanto: Department of Neurology, University of California-San Francisco, San Francisco, CA, USA; Neuroscape, University of California-San Francisco, San Francisco, CA, USA; Corresponding author. Department of Neurology, 675 Nelson Rising Lane, San Francisco, CA, 94158, USA.
Kevin T. Jones: Department of Neurology, University of California-San Francisco, San Francisco, CA, USA; Neuroscape, University of California-San Francisco, San Francisco, CA, USA
Avery E. Ostrand: Department of Neurology, University of California-San Francisco, San Francisco, CA, USA; Neuroscape, University of California-San Francisco, San Francisco, CA, USA
Wan-Yu Hsu: Department of Neurology, University of California-San Francisco, San Francisco, CA, USA
Richard Campusano: Department of Neurology, University of California-San Francisco, San Francisco, CA, USA; Neuroscape, University of California-San Francisco, San Francisco, CA, USA
Adam Gazzaley: Department of Neurology, University of California-San Francisco, San Francisco, CA, USA; Neuroscape, University of California-San Francisco, San Francisco, CA, USA; Departments of Physiology and Psychiatry, University of California-San Francisco, San Francisco, CA, USA

Journal volume & issue: Vol. 14, no. 5
pp. 1317 – 1329

Abstract

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Background: Noninvasive transcranial electrical stimulation (tES) research has been plagued with inconsistent effects. Recent work has suggested neuroanatomical and neurophysiological variability may alter tES efficacy. However, direct evidence is limited. Objective: We have previously replicated effects of transcranial alternating current stimulation (tACS) on improving multitasking ability in young adults. Here, we attempt to assess whether these stimulation parameters have comparable effects in older adults (aged 60–80 years), which is a population known to have greater variability in neuroanatomy and neurophysiology. It is hypothesized that this variability in neuroanatomy and neurophysiology will be predictive of tACS efficacy. Methods: We conducted a pre-registered study where tACS was applied above the prefrontal cortex (between electrodes F3-F4) while participants were engaged in multitasking. Participants were randomized to receive either 6-Hz (theta) tACS for 26.67 min daily for three days (80 min total; Long Exposure Theta group), 6-Hz tACS for 5.33 min daily (16-min total; Short Exposure Theta group), or 1-Hz tACS for 26.67 min (80 min total; Control group). To account for neuroanatomy, magnetic resonance imaging data was used to form individualized models of the tACS-induced electric field (EF) within the brain. To account for neurophysiology, electroencephalography data was used to identify individual peak theta frequency. Results: Results indicated that only in the Long Theta group, performance change was correlated with modeled EF and peak theta frequency. Together, modeled EF and peak theta frequency accounted for 54%–65% of the variance in tACS-related performance improvements, which sustained for a month. Conclusion: These results demonstrate the importance of individual differences in neuroanatomy and neurophysiology in tACS research and help account for inconsistent effects across studies.

Published in Brain Stimulation

ISSN: 1935-861X (Print); 1876-4754 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Medicine: Internal medicine: Neurosciences. Biological psychiatry. Neuropsychiatry
Website: https://www.journals.elsevier.com/brain-stimulation

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