title: Is effect of transcranial direct current stimulation on visuomotor coordination dependent on task difficulty?
abstract: Transcranial direct current stimulation (tDCS), an emerging technique for non-invasive brain stimulation, is increasingly used to induce changes in cortical excitability and modulate motor behavior, especially for upper limbs. The purpose of this study was to investigate the effects of tDCS of the primary motor cortex on visuomotor coordination based on three levels of task difficulty in healthy subjects. Thirty-eight healthy participants underwent real tDCS or sham tDCS. Using a single-blind, sham-controlled crossover design, tDCS was applied to the primary motor cortex. For real tDCS conditions, tDCS intensity was 1 mA while stimulation was applied for 15 minutes. For the sham tDCS, electrodes were placed in the same position, but the stimulator was turned off after 5 seconds. Visuomotor tracking task, consisting of three levels (levels 1, 2, 3) of difficulty with higher level indicating greater difficulty, was performed before and after tDCS application. At level 2, real tDCS of the primary motor cortex improved the accurate index compared to the sham tDCS. However, at levels 1 and 3, the accurate index was not significantly increased after real tDCS compared to the sham tDCS. These findings suggest that tasks of moderate difficulty may improve visuomotor coordination in healthy subjects when tDCS is applied compared with easier or more difficult tasks.
authors: Department of Physical Therapy, Yeungnam University College,170, Daemyung-dong, Namgu, Daegu, 705-703, Republic of Korea.
authors: Yong Hyun
authors: YH
authors: Kwon
authors: Department of Physical Therapy, College of Rehabilitation Science, Daegu University, 15, Jilyang, Gyeongsan-si, Kyeongbuk, 712-714, Republic of Korea.
authors: Kyung Woo
authors: KW
authors: Kang
authors: Department of Physical Therapy, College of Health Science, Cheongju University, 298 Daeseong-ro, Cheongwon-gu, Cheongju-si, Chungbuk 363-764, Republic of Korea.
authors: Sung Min
authors: SM
authors: Son
authors: Department of Physical Therapy, College of Rehabilitation Science, Daegu University, 15, Jilyang, Gyeongsan-si, Kyeongbuk, 712-714, Republic of Korea.
authors: Na Kyung
authors: NK
authors: Lee
keywords: motor learning; neural regeneration; primary motor area; task difficulty; transcranial direct current stimulation; visuomotor coordination