||健常者への直流前庭電気刺激が主観的身体垂直に及ぼす影響 : 刺激極性と時間経過を要因とした検討
Influence of Galvanic Vestibular Stimulation on Subjective Postural Vertical in Healthy Subjects
本研究の目的は, 直流前庭電気刺激 (GVS)の剌激極性 (右・左)と時間経過 (Baseline・直後・10分後・20分後)によって主観的身体垂直 (SPV)の偏倚方向と程度に差が生じるかを検証することである. SPV測定計8回の平均値を傾斜方向性, 標準偏差値を動揺性として, 刺激極性と時間経過を 2要因とした反復測定分散分析を行った. 傾斜方向性は, 時間経過に主効果を認めた. 水準間の比較の結果, Baselineと直後, Baselineと10分後に有意な反時計回りへの偏倚を認めた. 動揺性について, 各要因に有意な差を認めなかった. 傾斜方向性はGVSによって刺激極性ごとに生じる陰極側の卵形嚢膜電位の発火と偏倚の方向が一致せず,左右どちらの刺激極性であっても反時計回りへ偏倚することが示唆された.また,剌激10分後に傾斜方向性が偏倚したことから, GVSによる後作用によってSPVの偏倚が持続する可能性が考えられた.
Background and Purpose: It has been reported that patients' perceptions of verticality can be biased due to brain damage. Although galvanic vestibular stimulation (GVS) could also modify the perception of verticality, the effects of GVS on the subjective postural vertical (SPV) are unclear. The aim of this study was to investigate whether SPV was biased by the polarity of GVS or by its time course in healthy subjects. Methods: Twenty healthy participants (27.0±3.0 years) were enrolled in the study. All participants gave their written informed consent. Bilateral bipolar GVS (with the anode on the left, or on the right) was administered for20 minutes on the first day. The subjects were asked to estimate their SPV before stimulation (Baseline), immediately after stimulation, and 10 and 20 minutes after stimulation. 0n the second day, they were administered GVS with the polarity reversed. For each of the eight trials, the mean of the participants reported SPV values was defined as the directional error. The standard deviation of these values was defined as the absolute error of the SPV values. A repeated measures analysis of variance was performed for each of the two factors. Results : Time after stimulation significantly influenced the reported directional error, but exerted no significant effect on absolute error. Post hoc analysis showed that the baseline SPV values differed significantly from those reported immediately after stimulation and 10 min after stimulation in the anticlockwise direction. Conclusion: This study demonstrates that GVS, regardless of polarity, biased SPV in the anticlockwise direction. A polarity effect was noted, however, since GVS produced an experience of linear acceleration towards the side of the cathode. SPV remained biased after 10 minutes by the aftereffect of GVS.
首都大学東京, 2016-03-25, 修士（理学療法学）