Comparing effects of 1 mA M1 a-tDCS and c-tDCS
It was hypothesized in the current study that 1 mA M1 a-tDCS compared to
1 mA M1 c-tDCS had more effects on online and offline motor learning.
The findings of the current study were consisting with this hypothesis
and even indicated disturbing effects of 1 mA c-tDCS as compared to 1 mA
a-tDCS on motor learning. In this regard, there is evidence that
applying M1 a-tDCS leads to an increase in excitability of the region
through modulation of NMDA receptors, GABA receptors, BDNF, and
calcium-dependent mechanisms (Liebetanz et al. , 2002; Nitscheet al. , 2003; Stagg et al. , 2009). It appears that anodal
stimulation leads to a reduction in the activation threshold and
ultimately increases the opening of voltage-dependent ion channels
(Pellicciari et al. , 2013). By depolarizing the postsynaptic
membrane and increasing the presynaptic firing frequency, it strengthens
synaptic connections and improves learning (Pellicciari et al. ,
2013). On the other hand, cathodal stimulation at 1 mA leads to
decreased neuronal excitability due to an increase in the activation
threshold (Pellicciari et al. , 2013). Additionally, reducing
presynaptic activity and hyperpolarization in the postsynaptic membrane
weaken synaptic connections (Pellicciari et al. , 2013). The
results of the current study also indicated that M1 1 mA a-tDCs as
compared to M1 1 mA c-tDCS induces more online and offline motor
learning.