An Overview of Noninvasive Brain Stimulation: Basic Principles and Clinical Applications

Abstract

The brain has the innate ability to undergo neuronal plasticity, which refers to changes in its structure and functions in response to continued changes in the environment. Although these concepts are well established in animal slice preparation models, their application to a large number of human subjects could only be achieved using noninvasive brain stimulation (NIBS) techniques. In this review, we discuss the mechanisms of plasticity induction using NIBS techniques including transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), random noise stimulation (RNS), transcranial ultrasound stimulation (TUS), vagus nerve stimulation (VNS), and galvanic vestibular stimulation (GVS). We briefly introduce these techniques, explain the stimulation parameters and potential clinical implications. Although their mechanisms are different, all these NIBS techniques can be used to induce plasticity at the systems level, to examine the neurophysiology of brain circuits and have potential therapeutic use in psychiatric and neurological disorders. TMS is the most established technique for the treatment of brain disorders, and repetitive TMS is an approved treatment for medication-resistant depression. Although the data on the clinical utility of the other modes of stimulation are more limited, the electrical stimulation techniques (tDCS, tACS, RNS, VNS, GVS) have the advantage of lower cost, portability, applicability at home, and can readily be combined with training or rehabilitation. Further research is needed to expand the clinical utility of NIBS and test the combination of different modes of NIBS to optimize neuromodulation induced clinical benefits.

In vivo low-intensity magnetic pulses durably alter neocortical neuron excitability and spontaneous activity

“…The LI-rTMS-induced inhibitory effects on neuronal excitability and firing is surprising in light of former studies using high-intensity rTMS. According to these reports, high-frequency magnetic stimulation (≥ 5 Hz) should increase cortical excitability (Bhattacharya et al, 2021; Cirillo et al, 2017; Huang et al, 2005), potentiate excitatory synaptic transmission and/or upregulate the expression of neurochemical markers of synaptic plasticity (Cirillo et al, 2017; Gersner et al, 2011; Lenz et al, 2015; Vlachos et al, 2012).…”

“…Finally, most previous studies used magnetic fields at least ten times stronger than the one used in our study. High-intensity, high-frequency stimulation protocols require regular pauses to allow the coil to cool – resulting in short periods (a few seconds) of stimulation separated by pauses without stimulation (see Bhattacharya et al, 2021; Cirillo et al, 2017 for reviews), an intermittent pattern in contrast to our continuous 10 Hz. Theta-burst stimulation, for example, induces opposite effects if applied continuously versus intermittently (Huang et al, 2005).…”

“…Repetitive transcranial magnetic stimulation (rTMS) is a promising tool for the treatment of neurological and psychiatric diseases. However, a better understanding of the cellular mechanisms underlying rTMS effects is needed to optimize current treatment protocols, whose outcomes remain variable (Bhattacharya et al, 2021; Cirillo et al, 2017; Rossini et al, 2015). Clinical application of magnetic stimulation delivers repeated high-intensity (0.5–2 Tesla, T) magnetic pulses to a targeted cortical area to induce an electric field that activates cortical neurons and initiates activity-dependent plasticity (Bhattacharya et al, 2021; Cirillo et al, 2017).…”

“…However, a better understanding of the cellular mechanisms underlying rTMS effects is needed to optimize current treatment protocols, whose outcomes remain variable (Bhattacharya et al, 2021; Cirillo et al, 2017; Rossini et al, 2015). Clinical application of magnetic stimulation delivers repeated high-intensity (0.5–2 Tesla, T) magnetic pulses to a targeted cortical area to induce an electric field that activates cortical neurons and initiates activity-dependent plasticity (Bhattacharya et al, 2021; Cirillo et al, 2017). Such plasticity is confirmed in rodents, where high-intensity magnetic stimulation in vitro induces synaptic plasticity in hippocampal networks (Lenz and Vlachos, 2016; Vlachos et al, 2012) and modulates neocortical inhibitory interneurons (Hoppenrath et al, 2016; Mix et al, 2015).…”

Stimulationsverfahren zur Behandlung von Demenzen

“…Da davon auszugehen ist, dass Erinnerungen durch eine Veränderung der Synapsenstärke kodiert werden, gilt die LTP weithin als ein wichtiger zellulärer Mechanismus der Gedächtnisbildung. Aus diesem Grund stellen NIBS-Verfahren insbesondere bei der Alzheimer-Demenz (AD) einen vielversprechenden Ansatz dar [7].…”