Non-invasive brain stimulation in neurorehabilitation: local and distant effects for motor recovery

Abstract

Non-invasive brain stimulation (NIBS) may enhance motor recovery after neurological injury through the causal induction of plasticity processes. Neurological injury, such as stroke, often results in serious long-term physical disabilities, and despite intensive therapy, a large majority of brain injury survivors fail to regain full motor function. Emerging research suggests that NIBS techniques, such as transcranial magnetic (TMS) and direct current (tDCS) stimulation, in association with customarily used neurorehabilitative treatments, may enhance motor recovery. This paper provides a general review on TMS and tDCS paradigms, the mechanisms by which they operate and the stimulation techniques used in neurorehabilitation, specifically stroke. TMS and tDCS influence regional neural activity underlying the stimulation location and also distant interconnected network activity throughout the brain. We discuss recent studies that document NIBS effects on global brain activity measured with various neuroimaging techniques, which help to characterize better strategies for more accurate NIBS stimulation. These rapidly growing areas of inquiry may hold potential for improving the effectiveness of NIBS-based interventions for clinical rehabilitation.

The Effect of Transcranial Direct Current Stimulation (tDCS) Electrode Size and Current Intensity on Motor Cortical Excitability: Evidence From Single and Repeated Sessions

“…When administered for several minutes or more, tDCS can produce changes in excitability that outlast the period of stimulation [3][4][5][6]. This is the principle behind the use of tDCS to examine brain functioning and as a potential treatment for neurological and psychiatric disorders [7][8][9].…”

Imaging human brain networks to improve the clinical efficacy of non-invasive brain stimulation

“…This has led to a dramatic increase in research applying NIBS in the clinical domain, with the goal of improving abnormal brain function in various conditions (Hummel et al, 2005;Hummel and Cohen, 2006;Passard et al, 2007;Floel, 2014;Liew et al, 2014). The rationale for the use of NIBS has been that if behavioral changes arising from a clinical condition occur due to altered activity within a given brain network, normalizing this activity with NIBS should lead to improved behavior.…”

“…Despite some encouraging results, symptomatic improvement following NIBS in such conditions has generally been modest, and often clinically insignificant (Kalu et al, 2012). Although several reviews have alluded to the effects of NIBS propagating to distant regions via axonal connectivity (Lefaucheur et al, 2014;Liew et al, 2014;Li et al, 2015), they have not considered the consequence of these aspects in the clinical domain. An often overlooked factor affecting the effectiveness of NIBS is the optimal targeting of underlying neural networks associated with the clinical condition (Fox et al, 2012).…”

Relationship Between Non-invasive Brain Stimulation-induced Plasticity and Capacity for Motor Learning

“…These effects of NIBS are believed to involve or augment the same mechanisms involved in the motor skill learning process, and are a key argument in utilizing NIBS in rehabilitation (e.g., in Stroke) [20].…”