Is There a Future for Non-invasive Brain Stimulation as a Therapeutic Tool?

Abstract

Several techniques and protocols of non-invasive transcranial brain stimulation (NIBS), including transcranial magnetic and electrical stimuli, have been developed in the past decades. These techniques can induce long lasting changes in cortical excitability by promoting synaptic plasticity and thus may represent a therapeutic option in neuropsychiatric disorders. On the other hand, despite these techniques have become popular, the fragility and variability of the after effects are the major challenges that non-invasive transcranial brain stimulation currentlyfaces. Several factors may account for such a variability such as biological variations, measurement reproducibility, and the neuronal state of the stimulated area. One possible strategy, to reduce this variability is to monitor the neuronal state in real time using EEG and trigger TMS pulses only at pre-defined state. In addition, another strategy under study is to use the spaced application of multiple NIBS protocols within a session to improve the reliability and extend the duration of NIBS effects. Further studies, although time consuming, are required for improving the so far limited effect sizes of NIBS protocols for treatment of neurological or psychiatric disorders.

Transcutaneous spinal direct current stimulation increases corticospinal transmission and enhances voluntary motor output in humans

“…tDCS over the motor cortex has shown variable electrophysiological and behavioural effects and there is still no general consensus about its usefulness as a therapeutic technique for rehabilitation (Buch et al, 2017;Huang et al, 2017;Rothwell, 2016;Terranova et al, 2018). From the relatively few published studies on tsDCS in human participants a similar lack of consistency appears to be present at least in the case of electrophysiological measures such as MEPs and H-reflexes (Albuquerque et al, 2018;Bocci, Barloscio, et al, 2015;Bocci, Caleo, et al, 2015;Bocci, Marceglia, et al, 2015).…”

Interindividual Variability of Lower-Limb Motor Cortical Plasticity Induced by Theta Burst Stimulation

“…The inter-and intra-individual variability of cortical plasticity after TBS is a key issue of this tool (Hamada et al, 2013;Hinder et al, 2014;López-Alonso et al, 2014;Hordacre et al, 2017;Sasaki et al, 2018). The variability of the TBS-induced plasticity hinders its clinical applications as a potential therapy for neurological disorders (Terranova et al, 2019). Several factors contribute to the variation that occurs in response to TBS, such as biological factors including age, genetics, sex, and anatomy of the neural circuits (Suppa et al, 2016;Huang et al, 2017).…”

Frequency-specific transcranial neuromodulation of oscillatory alpha power alters and predicts human visuospatial attention performance

“…Instead, the regression equation takes the data of all participants into account and predicts the stimulation effect at different values of the covariate based on the regression equation (simple slope analysis). This form of analysis could be useful for various brain stimulation studies suffering from variable, weak or inconsistent stimulation effects [62,63,[72][73][74][75][64][65][66][67][68][69][70][71] or studies that want to elaborate on the association between the electrophysiological and the behavioral stimulation effect. Another advantage of mixed model analysis is that the omission of observations due to outlier removal, technical faults or data loss does not lead to exclusion of data on a subject level.…”