Does Transcranial Direct Current Stimulation Affect the Learning of a Fine Sequential Hand Motor Skill with Motor Imagery?

Abstract

Learning a fine sequential hand motor skill, like playing the piano or learning to type, improves not only due to physical practice, but also due to motor imagery. Previous studies revealed that transcranial direct current stimulation (tDCS) and motor imagery independently affect motor learning. In the present study, we investigated whether tDCS combined with motor imagery above the primary motor cortex influences sequence-specific learning. Four groups of participants were involved: an anodal, cathodal, sham stimulation, and a control group (without stimulation). A modified discrete sequence production (DSP) task was employed: the Go/NoGo DSP task. After a sequence of spatial cues, a response sequence had to be either executed, imagined, or withheld. This task allows to estimate both non-specific learning and sequence-specific learning effects by comparing the execution of unfamiliar sequences, familiar imagined, familiar withheld, and familiar executed sequences in a test phase. Results showed that the effects of anodal tDCS were already developing during the practice phase, while no effects of tDCS on sequence-specific learning were visible during the test phase. Results clearly showed that motor imagery itself influences sequence learning, but we also revealed that tDCS does not increase the influence of motor imagery on sequence learning.

Keywords:

• Motor imagery
• motor learning
• transcranial direct current stimulation (tDCS)
• Go/NoGo DSP task

Acknowledgments

This work was supported by a grant from the National Science Centre in Poland, UMO-2015/17/N/HS6/00661. All authors disclose any sources of conflict of interest. The authors want to thank all the participants who took part in this study.

Appendix

Sequences of five key presses used in the experiment:

6 structures of the sequence, 4 version

1-a, 2-s, 3-d, 4-f

1-;, 2-l, 3-k, 4-j

Structure 1

Version_1: Left hand: a s f d s (12432) Right hand: ; l j k l (12432)

Version_2: Left hand: s d a f d (23143 Right hand: (23143)

Version_3: Left hand: d f s a f (34214) Right hand: (34214)

Version_4: Left hand: f a d s a (41321) Right hand: (41321)

Structure 2

Version_1: Left hand: a d f s d (13423) Right hand: (13423)

Version_2: Left hand: (24134) Right hand: (24134)

Version_3: Left hand: (31241) Right hand: (31241)

Version_4: Left hand: (42312) Right hand: (42312)

Structure 3

Version_1: Left hand: a f s a d (14213) Right hand: (14213)

Version_2: Left hand: (21324) Right hand: (21324)

Version_3: Left hand: (32431) Right hand: (32431)

Version_4: Left hand: (43142 Right hand: (43142)

Structure 4

Version_1: Left hand: a d s f a (13241) Right hand: (13241)

Version_2: Left hand: (24312) Right hand: (24312)

Version_3: Left hand: (31423) Right hand: (31423)

Version_4: Left hand: (42134) Right hand: (42134)

Structure 5

Version_1: Left hand: a f d a s (14312) Right hand: (14312)

Version_2: Left hand: (21423) Right hand: (21423)

Version_3: Left hand: (32134) Right hand: (32134)

Version_4: Left hand: (43241) Right hand: (43241)

Structure 6

Version_1: Left hand: a f d a s (21431) Right hand: (21431)

Version_2: Left hand: (32142) Right hand: (32142)

Version_3: Left hand: (43213) Right hand: (43213)

Version_4: Left hand: (14324) Right hand: (14324)