Nonlinear interaction between stimulation intensity and initial brain state: Evidence for the facilitatory/suppressive range model of online TMS effects. (18th January 2021)

• Record Type: Journal Article
• Authors: Silvanto, Juha; Cattaneo, Zaira
• Is Part Of: Neuroscience letters. Volume 742(2021)
• Publication Date: 2021-01-18
• Subjects: Brain stimulation -- State-dependency -- Visual cortex; Neurology -- Periodicals; Neurology -- Periodicals; Research -- Periodicals; Neurologie -- Périodiques; Neuroanatomie -- Périodiques; Neuropharmacologie -- Périodiques; Neurophysiologie -- Périodiques; Neurology; Periodicals; Electronic journals; 617.48
• DOI: 10.1016/j.neulet.2020.135538
• Languages: English
• ISSNs: 0304-3940

Abstract

Highlights: It is not known how stimulation intensity interacts with state-dependent TMS effects. This was studied by using priming to modulate visual cortical excitability states. While high intensity TMS impaired primed trials, low intensity induced facilitation. Thus stimulation intensity and brain state interacted in nonlinear manner. Provides evidence for existence for facilitatory/suppressive ranges of TMS effects. Abstract: The effects of online Transcranial Magnetic Stimulation (TMS) can qualitatively vary as a function of brain state. For example, TMS intensities which normally impair performance can have a facilitatory effect if the targeted neuronal representations are in a suppressed state. These phenomena have been explained in terms of the existence of distinct facilitatory and suppressive ranges as a function of TMS intensity which are shifted by changes in neural excitability. We tested this model by applying TMS at a low (60 % of phosphene threshold) or high (120 % of phosphene threshold) intensity during a priming paradigm. Our results show that state-dependent TMS effects vary qualitatively as a function of TMS intensity. Whereas the application of TMS at 120 % of participants' phosphene threshold impaired performance on fully congruent trials (in effect, reducing the benefit of priming), TMS applied at a lower intensity (60 % of phosphene threshold), facilitated performance on congruent trials. These results demonstrate that behavioral effects of TMS reflect a nonlinear interaction between initial activation state and TMS intensity. They also provide support for the existence of facilitatory/suppressive ranges of TMS effects which shift when neural excitability changes.