Predicting Modulation in Corticomotor Excitability and in Transcallosal Inhibition in Response to Anodal Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) has been widely explored as a neuromodulatory adjunct to modulate corticomotor excitability and improve motor behavior. However, issues with the effectiveness of tDCS have led to the exploration of empirical and experimental alternate electrode placements to enhance neuromodulatory effects. Here, we conducted a preliminary study to compare a novel electrode montage (which involved placing 13 cm2 electrodes anterior and posterior to the target location) to the traditionally used electrode montage (13 cm2 stimulating electrode over the target area and the 35 cm2 reference electrode over the contralateral orbit). We examined the effects of tDCS of the lower limb motor area (M1) by measuring the corticomotor excitability (CME) of the tibialis anterior muscle using transcranial magnetic stimulation in twenty healthy participants. We examined behavioral effects using a skilled motor control task performed with the ankle. We did not find one electrode montage to be superior to the other for changes in the CME or motor control. When the group was dichotomized into responders and non-responders (based on upregulation in CME), we found that the responders showed significant upregulation from baseline after tDCS for both montages. However, only the responders in the traditional montage group showed significant changes in motor control after tDCS. These results do not support the superiority of the new anterior–posterior montage over the traditional montage. Further work with a larger cohort and multiple cumulative sessions may be necessary to confirm our results.

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Voluntary movement reverses the effect of cathodal transcranial direct current stimulation (tDCS) on corticomotor excitability

Experimental Brain Research ◽

10.1007/s00221-017-5001-9 ◽

2017 ◽

Vol 235 (9) ◽

pp. 2653-2659 ◽

Cited By ~ 1

Author(s):

Esra Erkoc Ataoglu ◽

Hale Batur Caglayan ◽

Bülent Cengiz

Keyword(s):

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Voluntary Movement ◽

Corticomotor Excitability ◽

Direct Current Stimulation

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Combining transcranial direct current stimulation with aerobic exercise to optimize cortical priming in stroke

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2020-0677 ◽

2020 ◽

Author(s):

Anjali Sivaramakrishnan ◽

Sangeetha Madhavan

Keyword(s):

Reaction Time ◽

Aerobic Exercise ◽

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Lower Limb ◽

Synergistic Effects ◽

Short Interval ◽

Moderate Intensity ◽

Direct Current Stimulation ◽

Transcallosal Inhibition

Aerobic exercise (AE) and transcranial direct current stimulation (tDCS) are priming techniques that have been studied for their potential neuromodulatory effects on corticomotor excitability (CME), however the synergistic effects of AE and tDCS are not explored in stroke. Here we investigated the synergistic effects of AE and tDCS on CME, intracortical and transcallosal inhibition, and motor control for the lower limb in stroke. 26 stroke survivors participated in three sessions - tDCS, AE and AE + tDCS. AE included moderate intensity exercise and tDCS included 1 mA of anodal tDCS to the lower limb motor cortex with or without AE. Outcomes included measures of CME, short interval intracortical inhibition (SICI), ipsilateral silent period (iSP) (an index of transcallosal inhibition) for the tibialis anterior and ankle reaction time. Ipsilesional CME significantly decreased for AE compared to AE + tDCS and tDCS. No differences were noted in SICI, iSP measures or reaction time between all three sessions. Our findings suggest that a combination of exercise and tDCS, and tDCS demonstrate greater excitability of the ipsilesional hemisphere compared to exercise only, however these effects were specific to the descending corticomotor pathways. No additive priming effects of exercise and tDCS over tDCS was observed. Novelty: • An exercise and tDCS paradigm upregulated the descending motor pathways from the ipsilesional lower limb M1 compared to exercise. • Exercise or tDCS administered alone or in combination did not affect intracortical or transcallosal inhibition or reaction time.

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