scholarly journals Differential Modulation of Corticospinal Excitability by Different Current Densities of Anodal Transcranial Direct Current Stimulation

PLoS ONE ◽  
2013 ◽  
Vol 8 (8) ◽  
pp. e72254 ◽  
Author(s):  
Andisheh Bastani ◽  
Shapour Jaberzadeh
Keyword(s):  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Corticospinal Excitability ◽  
Differential Modulation ◽  
Direct Current Stimulation ◽  
Current Densities

Acute Changes in Motor Cortical Excitability During Slow Oscillatory and Constant Anodal Transcranial Direct Current Stimulation

2009 ◽  
Vol 102 (4) ◽  
pp. 2303-2311 ◽  
Author(s):  
Til Ole Bergmann ◽  
Sergiu Groppa ◽  
Markus Seeger ◽  
Matthias Mölle ◽  
Lisa Marshall ◽  
...  
Keyword(s):  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Corticospinal Excitability ◽  
Slow Oscillation ◽  
Facilitatory Effect ◽  
Endogenous Rhythms ◽  
Direct Current Stimulation ◽  
On Line

Transcranial oscillatory current stimulation has recently emerged as a noninvasive technique that can interact with ongoing endogenous rhythms of the human brain. Yet, there is still little knowledge on how time-varied exogenous currents acutely modulate cortical excitability. In ten healthy individuals we used on-line single-pulse transcranial magnetic stimulation (TMS) to search for systematic shifts in corticospinal excitability during anodal sleeplike 0.8-Hz slow oscillatory transcranial direct current stimulation (so-tDCS). In separate sessions, we repeatedly applied 30-s trials (two blocks at 20 min) of either anodal so-tDCS or constant tDCS (c-tDCS) to the primary motor hand area during quiet wakefulness. Simultaneously and time-locked to different phase angles of the slow oscillation, motor-evoked potentials (MEPs) as an index of corticospinal excitability were obtained in the contralateral hand muscles 10, 20, and 30 s after the onset of tDCS. MEPs were also measured off-line before, between, and after both stimulation blocks to detect any lasting excitability shifts. Both tDCS modes increased MEP amplitudes during stimulation with an attenuation of the facilitatory effect toward the end of a 30-s tDCS trial. No phase-locking of corticospinal excitability to the exogenous oscillation was observed during so-tDCS. Off-line TMS revealed that both c-tDCS and so-tDCS resulted in a lasting excitability increase. The individual magnitude of MEP facilitation during the first tDCS trials predicted the lasting MEP facilitation found after tDCS. We conclude that sleep slow oscillation-like excitability changes cannot be actively imposed on the awake cortex with so-tDCS, but phase-independent on-line as well as off-line facilitation can reliably be induced.

scholarly journals Anodal transcranial direct current stimulation increases corticospinal excitability, while performance is unchanged

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254888
Author(s):  
Mathias Kristiansen ◽  
Mikkel Jacobi Thomsen ◽  
Jens Nørgaard ◽  
Jon Aaes ◽  
Dennis Knudsen ◽  
...  
Keyword(s):  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Perceived Exertion ◽  
Motor Evoked Potentials ◽  
Time Trial ◽  
Corticospinal Excitability ◽  
Afferent Feedback ◽  
Sham Stimulation ◽  
Direct Current Stimulation ◽  
Rpe Clamp

Anodal transcranial direct current stimulation (a-tDCS) has been shown to improve bicycle time to fatigue (TTF) tasks at 70–80% of VO2max and downregulate rate of perceived exertion (RPE). This study aimed to investigate the effect of a-tDCS on a RPE-clamp test, a 250-kJ time trial (TT) and motor evoked potentials (MEP). Twenty participants volunteered for three trials; control, sham stimulation and a-tDCS. Transcranial magnetic stimulation was used to determine the corticospinal excitability for 12 participants pre and post sham stimulation and a-tDCS. The a-tDCS protocol consisted of 13 minutes of stimulation (2 mA) with the anode placed above the Cz. The RPE-clamp test consisted of 5 minutes ergometer bicycling at an RPE of 13 on the Borg scale, and the TT consisted of a 250 kJ (∼10 km) long bicycle ergometer test. During each test, power output, heart rate and oxygen consumption was measured, while RPE was evaluated. MEPs increased significantly by 36% (±36%) post a-tDCS, with 8.8% (±31%) post sham stimulation (p = 0.037). No significant changes were found for any parameter at the RPE-clamp or TT. The lack of improvement may be due to RPE being more controlled by afferent feedback during TT tests than during TTF tests. Based on the results of the present study, it is concluded that a-tDCS applied over Cz, does not enhance self-paced cycling performance.

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