Anodal Transcranial Direct Current Stimulation Enhances Procedural Consolidation

Abstract

The primary motor cortex (M1) area recruitment enlarges while learning a finger tapping sequence. Also M1 excitability increases during procedural consolidation. Our aim was to investigate whether increasing M1 excitability by anodal transcranial DC stimulation (AtDCS) when procedural consolidation occurs was able to induce an early consolidation improvement. Forty-seven right-handed healthy participants were trained in a nine-element serial finger tapping task (SFTT) executed with the left hand. Random series blocks were interspersed with training series blocks. Anodal or sham tDCS was administered over the right M1 after the end of the training session. After stimulation, the motor skills of both trained and a new untrained sequential series blocks were tested again. For each block, performance was estimated as the median execution time of correct series. Early consolidation of the trained series, assessed by the performance difference between the first block after and the last block before stimulation normalized by the random, was enhanced by anodal and not by sham tDCS. Stimulation did not affect random series execution. No stimulation effect was found on the on-line learning of the trained and new untrained series. Our results suggest that AtDCS applied on M1 soon after training improves early consolidation of procedural learning. Our data highlight the importance of neuromodulation procedures for understanding learning processes and support their use in the motor rehabilitation setting, focusing on the timing of the application.

Effects of tDCS on motor learning and memory formation: A consensus and critical position paper

“…The effects of anodal tDCS on online sequence learning have been a particular area of interest (Amadi, Allman, Johansen-Berg, & Stagg, 2015;Ambrus et al, 2016;Cuypers et al, 2013;Kang & Paik, 2011;Kantak, Mummidisetty, & Stinear, 2012;Karok & Witney, 2013; M. F. Kuo et al, 2008;Nitsche et al, 2010;Nitsche et al, 2003;Reis et al, 2015;Reis et al, 2009;Stagg, Jayaram, et al, 2011;Tecchio et al, 2010;Vines, Cerruti, & Schlaug, 2008;Wade & Hammond, 2015). In an initial study, Nitsche and colleagues (2003) showed that anodal tDCS applied over M1 concurrently with training improved online implicit learning of a motor sequence, while stimulation applied to PMd, DMPFC and DLPFC did not .…”

Does transcranial direct current stimulation enhance cognitive and motor functions in the ageing brain? A systematic review and meta- analysis

“…As Horvath and colleagues note , even seemingly innocuous activities performed during stimulation, such as reading, talking or texting, may interfere with tDCS effects. There is clearly a need for further research to determine whether applying tDCS prior to, during, or even after (Tecchio et al, 2010) task practice leads to the greatest task performance benefits.…”

Optimizing Transcranial Direct Current Stimulation Protocols to Promote Long-Term Learning

“…Therefore, it is conceivable that tDCS, with its putative effects on cortical excitability (which may operate via glial-neuron interactions rather than neural stimulation directly), could enhance neural replay and therefore enhance consolidation. Though a direct demonstration is lacking, several studies have applied tDCS during waking rest at time periods when replay is thought to occur (Javadi and Cheng 2013;Sandrini et al 2014;Tecchio et al 2010) and subsequently demonstrated greater consolidation. Similarly, the application of slow-oscillating tDCS during slow-wave sleep has been shown to enhance declarative memory (reviewed in Barham et al 2016).…”

“…For example, stimulation immediately after, but not during, training of a finger-tapping task enhanced subsequent performance 30 min later, presumably by facilitating early consolidation of procedural memory (Tecchio et al 2010). Similarly, reactivation of a previously learned word list hours or a day later led to better retention if stimulation was administered directly during this reactivation/reconsolidation period (Javadi and Cheng 2013;Sandrini et al 2014).…”