Increasing human leg motor cortex excitability by transcranial high frequency random noise stimulation

Abstract

Purpose: Transcranial random noise stimulation (tRNS) can increase the excitability of hand area of the primary motor cortex (M1). The aim of this study was to compare the efficacy of tRNS and transcranial direct current stimulation (tDCS) on the leg motor cortex. Method: Ten healthy subjects received anodal, cathodal tDCS, tRNS and sham stimulation for 10 min using 2 mA intensity during separate experimental sessions. Single pulse transcranial magnetic stimulation (TMS) induced motor evoked potential (MEP) measurements were used to assess motor cortical excitability changes after the stimulation. Results: Similar to the hand area, we found that both tRNS and anodal tDCS induced an increase of the amplitude of the MEPs. Anodal tDCS induced a constant gradual increase of corticospinal excitability until 60 min post-stimulation, whereas the effect of tRNS was immediate with a duration of 40 min following stimulation. The cathodal tDCS induced decrease in MEP amplitude did not reach statistical significance. Conclusion: Our results suggest that although the leg area has a deeper position in the cortex compared to the hand area, it can be reached by weak transcranial currents. Both anodal tDCS and tRNS had comparable effect on cortical excitability.

Cerebellar Transcranial Direct Current Stimulation Improves Maximum Isometric Force Production during Isometric Barbell Squats

“…A large cathode was used to maintain the current density of the reference electrode at a low level, as such a reference electrode was demonstrated to be functionally ineffective without compromising the effectiveness of tDCS regarding the stimulation electrode [39,40]. The anatomical landmark for bilateral M1 (leg area) was determined according to previous studies which based their peak coordinates on Transcranial magnetic stimulation (TMS)-measurements [41][42][43]. For anodal tDCS of M1, we placed the anode 1 cm behind the vertex (Cz) on the mid-sagittal line to cover both leg motor cortices.…”

Recurrence quantification analysis of surface electromyogram supports alterations in motor unit recruitment strategies by anodal transcranial direct current stimulation

“…A 45-second rest period was provided between each trial to minimize any potential effects of fatigue. After completing the target-matching experiment, the subject underwent either anodal tDCS (2 mA, 10 minutes, 0.125 mA/cm 2 ) (Laczo et al, 2014;Wiethoff et al, 2014) or the control condition depending on their group allocation. All procedures were exactly identical between the two conditions (i.e., groups), except that no stimulation was provided to the subjects in the control condition (see Figure 1a).…”

A Case Report on Red Ear Syndrome with Tinnitus Successfully Treated with Transcranial Random Noise Stimulation

“…It is hypothesized that by the random changes in polarity homeostatic counteracting processes influencing the neuronal ion channels in the electrical field are avoided thus inhibiting adaption processes of the neuronal cell membrane and the resulting back shift to "resting state"-levels (24). High frequency tRNS (101 -640 Hz) exerts excitatory cortical effects of the motor cortex (26) and the auditory cortex (27), whereas low frequency tRNS (0.1 -100 Hz) seems to exert no significant effects on motor cortical areas (25). However, clinical effects of low-frequency tRNS applied to the auditory cortex have been shown in chronic tinnitus (28).…”