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ABSTRACT: Background
Recent studies have shown that neurophysiological outcomes of transcranial direct current stimulation (TDCS) are influenced by current flow in brain regions between the electrodes, and in particular the orientation of current flow relative to the cortical surface.Objective
We asked whether the directional effects of TDCS on physiological measures in the motor system would also be observed on motor behaviours.Methods
We applied TDCS during the practice of a ballistic movement task to test whether it affected learning or the retention of learning 48?h later. TDCS electrodes were oriented perpendicular to the central sulcus and two current orientations were used (posterior-anterior, TDCSPA; and anterior-posterior, TDCSAP). Transcranial magnetic stimulation (TMS) was used to assess whether changes in corticospinal excitability reflected any behavioural changes.Results
Directional TDCSAP impaired the retention of learning on the ballistic movement task compared to TDCSPA and a sham condition. Although TDCSPA had no effect on learning or retention, it blocked the typical increase in corticospinal excitability after a period of motor practice.Conclusions
Our results extend on previous reports of TDCS producing directionally specific changes in neurophysiological outcomes by showing that current direction through a cortical target also impacts upon behavioural outcomes. In addition, changes in corticospinal excitability after a period of motor practice are not causally linked to behavioural learning.
SUBMITTER: Hannah R
PROVIDER: S-EPMC6491497 | biostudies-literature | 2019 May - Jun
REPOSITORIES: biostudies-literature
Brain stimulation 20190128 3
<h4>Background</h4>Recent studies have shown that neurophysiological outcomes of transcranial direct current stimulation (TDCS) are influenced by current flow in brain regions between the electrodes, and in particular the orientation of current flow relative to the cortical surface.<h4>Objective</h4>We asked whether the directional effects of TDCS on physiological measures in the motor system would also be observed on motor behaviours.<h4>Methods</h4>We applied TDCS during the practice of a ball ...[more]