is motor learning mediated by tdcs intensity? j. f. daphnie leenus 1,2, koen cuypers 1-3, femke e....
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Is motor learning mediated by tDCS intensity?
J. F. Daphnie Leenus1,2, Koen Cuypers1-3, Femke E. van den Berg3, Michael A. Nitsche4, Herbert Thijs5,Nicole Wenderoth 3,6, Raf Meesen1-3
Introduction
Previous research demonstrated that a single
session of anodal tDCS over the primary motor
cortex (M1) was able to ameliorates motor
learning
Numerous different parameter settings are used
in tDCS studies (electrode size and placement,
stimulation intensity etc..)
This study was conducted to unveal the
correlation between current intensity and motor
learning in healthy subjects
Materials and methods
Subjects
13 Healthy subjects (7M: 6F, mean age 19.92 +/-
1.12 years) were included
11 subjects were right-handed and 2 were left-
handed
Study design
TMS Hotspot finding
Stimulation was applied on the hotspot of FDI
muscle for each subject as determined by TMS
tDCS stimulation
Experimental design Double-blind cross-over design Interval between sessions: 1 week 2 sessions: tDCS or SHAM-tDCS applied
during the motor training
Stimulation parameters: Duration: 20 min Constant current Intensities: 1mA ,1.5mA Sham: Received current for first 26sec Electrode size:
Anode: 25cm2,current density
0.04mA/cm2 for 1mA
0.06mA/cm2 for 1.5mA
Cathode: 50cm2, current density
0.02mA/cm2 for 1mA
0.03mA/cm2 for 1.5mA tDCS
Stimulation location: Anode: Hotspot FDI Cathode: contralateral supraorbital region
Motor training: Sequence task
Complete as many correct sequences as fast as
possible 1 block = 30 sec performance + 30 sec rest PRE (3 blocks) – TRAINING (26 blocks) – POST
(3 blocks) The sequences were [4 2 1 3 4 2 3 2] and [2 4 3
1 2 3 2 4] (1 = index finger, 2 = middle finger, 3 =
ring finger and 4 = little finger) No feedback was provided Compound measurement of performance = %
correct sequences/mean intertab interval (ITI)
Results
The percentage of correct sequences/mean ITI
improved in both sham and stimulation conditions
(p < .0001)
During motor learning, a significant INTENSITY X
TIME interaction was reported
Slope analysis: the slope was significantly steeper
at 1.5mA. Indicating, an increased motor
performance rate as compared to 1mA and SHAM
At post-intervention (30 min later), a paired t-test
revealed a significant improvement in motor
performance at 1.5mA compared with Sham
condition
Discussion
Healthy subjects were able to learn the sequence
task and the motor learning improved with the
stimulation The motor learning increased with the increase in
the stimulation intensity A remarkable long-term effect of tDCS was
observed during the post-intervention (30min after
the stimulation) Previous studies has explained about the ability of
single session tDCS in cortical excitability. This is
the first study explaining the intensity-dependent
motor learning effects of tDCS In contrast with other studies conducted in healthy
subjects, we found no significant differences at 1mA
stimulation and sham condition We suggest that increasing the sample size and the
current intensity (for example: 2mA) might lead to
increased effects between conditions
References
1. Hummel,F. et al. (2005) Effects of non-invasive cortical
stimulation on skilled motor function in chronic stroke. Brain
128, 490-499
2. Fregni,F. et al. (2006) Noninvasive cortical stimulation with
transcranial direct current stimulation in Parkinson's disease.
Mov Disord. 21, 1693-1702
3. Nitsche,M.A. et al. (2005) Modulating parameters of excitability
during and after transcranial direct current stimulation of the
human motor cortex. J. Physiol 568, 291-303
Correspondence
Please contact :
Prof.Dr.Raf Meesen
J. F .Daphnie Leenus, Dra