How Transcranial Direct Current Stimulation Can Modulate Implicit Motor Sequence Learning and Consolidation: A Brief Review

Abstract

The purpose of this review is to investigate how transcranial direct current stimulation (tDCS) can modulate implicit motor sequence learning and consolidation. So far, most of the studies have focused on the modulating effect of tDCS for explicit motor learning. Here, we focus explicitly on implicit motor sequence learning and consolidation in order to improve our understanding about the potential of tDCS to affect this kind of unconscious learning. Specifically, we concentrate on studies with the serial reaction time task (SRTT), the classical paradigm for measuring implicit motor sequence learning. The influence of tDCS has been investigated for the primary motor cortex, the premotor cortex, the prefrontal cortex, and the cerebellum. The results indicate that tDCS above the primary motor cortex gives raise to the most consistent modulating effects for both implicit motor sequence learning and consolidation.

Keywords: implicit motor sequence learning; memory consolidation; non-invasive brain stimulation; serial reaction time task; transcranial direct current stimulation.

Figure 1

Prototypical performance trajectory in the SRTT (adapted from Meier and Cock, 2014). The x-axis depicts RTs across blocks (“S” sequenced block, “R” random block). General motor skill learning (RT difference between S 1 and S 10). Sequence-specific learning (i.e., disruption score calculated as RT difference between R 11 and the mean of S 10 and S 12). General motor skill consolidation (RT difference between S 12 of session 1 and S 1 of session 2). Sequence-specific consolidation (RT difference between the disruption scores of the two sessions).