Differential Effects of Unihemispheric Concurrent Dual-site and Conventional Primary Motor Cortex Transcranial Direct Current Stimulation on Motor Sequence Learning in Healthy Individuals: A Randomized Sham-Controlled Study

Abstract

Introduction: Based on the literature, unihemispheric concurrent dual-site anodal transcranial Direct Current Stimulation (a-tDCSUHCDS) of primary Motor cortex (M1) and Dorsolateral Prefrontal Cortex (DLPFC) would be more efficient than conventional a-tDCS of M1 to induce larger and longer-lasting M1 corticospinal excitability. The main objective of the present study was to compare the effects of a-tDCSUHCDS and conventional M1 a-tDCS on the extent and durability of the motor sequence acquisition in healthy individuals. Methods: In this randomized sham-controlled study, healthy volunteers were randomly divided into three groups: experimental (a-tDCSUHCDS), control (M1 a-tDCS), and sham stimulation groups. The participants practiced serial response time task over three consecutive days when they simultaneously received a-tDCS. Using the skill measure, we assessed motor learning up to 4 weeks after the completion of experimental conditions. Results: Data analysis revealed that all groups exhibited the improved trend over the training course (P<0.001). There were no significant differences in skill acquisition among groups at post-intervention (P>0.05), while a significant improvement was observed between experimental and sham group at the retention time (P<0.05). Moreover, there were no significant differences between the control and two other groups with regard to the retention time (P>0.05). Conclusion: These results revealed a significant increase in the skill acquisition by a-tDCSUHCDS technique with regard to retention issue, which could be a valuable finding in neuro-rehabilitation field.

The Effect of Transcranial Direct Current Stimulation on Relapse, Anxiety, and Depression in Patients With Opioid Dependence Under Methadone Maintenance Treatment: A Pilot Study

“…Transcranial Direct Current Stimulation (tDCS) usually involves the use of a weak and direct electric current (e.g. 1 to 2 mA) through two or more electrodes which are placed on the scalp (Talimkhani et al, 2019). The connection of two electrodes with different poles (usually an anode and a cathode) in different parts of the skull surface, leads to the stimulation of the lower neurons.…”

“…Transcranial Direct Current Stimulation (tDCS) is one of the techniques of brain stimulation which involves the use of a weak direct electric current (e.g., 1 to 2 mA) through two or more electrodes, usually an anode and a cathode, on the scalp (Talimkhani et al, 2019). This stimulation acts as a noninvasive, inexpensive, and safe method for altering the resting potential of cortical neural cells.…”

Using high-definition transcranial direct current stimulation to investigate the role of the dorsolateral prefrontal cortex in explicit sequence learning

“…For instance, whether stimulation is applied during task performance or entirely before is an important consideration as some of the excitatory effects of anodal tDCS and null effects of cathodal tDCS have been observed with online protocols [27]. Further, the body of work on the effects of DLPFC stimulation on implicit sequence learning and consolidation is also chiefly reliant on studies that used an online tDCS approach [34–37]. In the current study, we employed offline stimulation.…”

“…Generally speaking, however, to this point results of these studies using tDCS to investigate the DLPFC during learning have been mixed. Notably, the majority of these investigations use the traditional 2-pad stimulation technique [32–34,36,37], which involves applying greater amounts of electrical current to larger cortical areas, thereby delivering diffuse stimulation to the brain, and in turn, what is likely a more distributed impact on brain activity.…”

Transcranial direct current stimulation does not improve performance in a whole-body movement task

“…Minor movements occur in the wrist, hands, fingers, feet and toes, and typically only involve movements with one goal. Positive effects of tDCS have been found in studies looking at; motor adaptation (Weightman, Brittain, Punt, Niall & Jenkinson, 2020), throwing tasks (Jackson et al 2019), serial reaction time finger tapping tasks (Ehsani, Bakhtiary, Jaberzadeh, Talimkhani & Hajihsani 2016;Talimkhani et al 2019) and balance tasks (Kaminski et al 2016;Zandvliet, Meskers, Kwakkel & van Wegen 2018). Additionally, similar positive effects have been found in patients suffering from neurological injuries and illnesses, such as in stroke (Rocha et al, 2016;Allman et al, 2016) and Parkinson's disease (Kami, Sadler, Nantel and Carlsen, 2018).…”