Modulation of mu rhythm desynchronization during motor imagery by transcranial direct current stimulation.
BACKGROUND
The mu event-related desynchronization (ERD) is supposed to reflect motor preparation and appear during motor imagery. The aim of this study is to examine the modulation of ERD with transcranial direct current stimulation (tDCS).


METHODS
Six healthy subjects were asked to imagine their right hand grasping something after receiving a visual cue. Electroencephalograms (EEGs) were recorded near the left M1. ERD of the mu rhythm (mu ERD) by right hand motor imagery was measured. tDCS (10 min, 1 mA) was used to modulate the cortical excitability of M1. Anodal, cathodal, and sham tDCS were tested in each subject with a randomized sequence on different days. Each condition was separated from the preceding one by more than 1 week in the same subject. Before and after tDCS, mu ERD was assessed. The motor thresholds (MT) of the left M1 were also measured with transcranial magnetic stimulation.


RESULTS
Mu ERD significantly increased after anodal stimulation, whereas it significantly decreased after cathodal stimulation. There was a significant correlation between mu ERD and MT.


CONCLUSIONS
Opposing effects on mu ERD based on the orientation of the stimulation suggest that mu ERD is affected by cortical excitability.
Matsumoto
Jun
J
School of Fundamental Science and Technology, Graduate School of Keio University, Kanagawa, Japan.
Fujiwara
Toshiyuki
T
Takahashi
Osamu
O
Liu
Meigen
M
Kimura
Akio
A
Ushiba
Junichi
J
D000328:Adult; D001921:Brain / Q000502:physiology*; D003344:Cortical Synchronization; D003463:Cues; D004558:Electric Stimulation / Q000379:methods*; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor; D007839:Functional Laterality; D006225:Hand / Q000502:physiology; D006801:Humans; D007092:Imagination / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology; D009483:Neuropsychological Tests; D010507:Periodicity; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology