Hänselmann Siegfried, Schneiders Matthias, Weidner Norbert, Rupp Rüdiger
Heidelberg University Hospital, Spinal Cord Injury Center, Schlierbacher Landstrasse 200a, 69118, Heidelberg, Germany.
J Neuroeng Rehabil. 2015 Aug 25;12:71. doi: 10.1186/s12984-015-0063-z.
For the translation of noninvasive motor imagery (MI)-based brain-computer interfaces (BCIs) from the lab environment to end users at their homes, their handling must be improved. As a key component, the number of electroencephalogram (EEG)-recording electrodes has to be kept at a minimum. However, due to inter-individual anatomical and physiological variations, reducing the number of electrodes bares the risk of electrode misplacement, which will directly translate into a limited BCI performance of end users. The aim of the study is to evaluate the use of focal transcranial magnetic stimulation (TMS) as an easy tool to individually optimize electrode positioning for a MI-based BCI. For this, the area of MI-induced mu-rhythm modulation was compared with the motor hand representation area in respect to their localization and to the control performance of a MI-based BCI.
Focal TMS was applied to map the motor hand areas and a 48-channel high-resolution EEG was used to localize MI-induced mu-rhythm modulations in 11 able-bodied, right-handed subjects (5 male, age: 23-31). The online BCI performances of the study participants were assessed with a single next-neighbor Laplace channel consecutively placed over the motor hand area and over the area of the strongest mu-modulation.
For most subjects, a consistent deviation between the position of the mu-modulation center and the corresponding motor hand areas well above the localization error could be observed in mediolateral and to a lesser degree in anterior-posterior direction. On an individual level, the MI-induced mu-rhythm modulation was at average found 1.6 cm (standard deviation (SD) = 1.30 cm) lateral and 0.31 cm anterior (SD = 1.39 cm) to the motor hand area and enabled a significantly better online BCI performance than the motor hand areas.
On an individual level a trend towards a consistent average spatial distance between motor hand area and mu-rhythm modulation center was found indicating that TMS may be used as a simple tool for quick individual optimization of EEG-recording electrode positions of MI-based BCIs. The study results indicate that motor hand areas of the primary motor cortex determined by TMS are not the main generators of the cortical mu-rhythm.
为了将基于非侵入性运动想象(MI)的脑机接口(BCI)从实验室环境推广到家庭终端用户,必须改进其操作方式。作为关键组件,脑电图(EEG)记录电极的数量必须保持在最低限度。然而,由于个体间解剖学和生理学的差异,减少电极数量存在电极放置错误的风险,这将直接导致终端用户的BCI性能受限。本研究的目的是评估使用局灶性经颅磁刺激(TMS)作为一种简单工具,为基于MI的BCI单独优化电极定位。为此,将MI诱发的μ节律调制区域与运动手代表区在定位以及基于MI的BCI控制性能方面进行了比较。
对11名身体健康的右利手受试者(5名男性,年龄:23 - 31岁)应用局灶性TMS来绘制运动手区域,并使用48通道高分辨率EEG来定位MI诱发的μ节律调制。研究参与者的在线BCI性能通过依次放置在运动手区域和最强μ调制区域上方的单个最近邻拉普拉斯通道进行评估。
对于大多数受试者,在内外侧方向上可以观察到μ调制中心位置与相应运动手区域之间存在一致的偏差,且远高于定位误差,在前后方向上偏差较小。在个体水平上,平均发现MI诱发的μ节律调制位于运动手区域外侧1.6厘米(标准差(SD) = 1.30厘米)和前方0.31厘米(SD = 1.39厘米)处,并且与运动手区域相比,能实现显著更好的在线BCI性能。
在个体水平上,发现运动手区域与μ节律调制中心之间存在一致的平均空间距离趋势,这表明TMS可作为一种简单工具,用于快速单独优化基于MI的BCI的EEG记录电极位置。研究结果表明,由TMS确定的初级运动皮层的运动手区域不是皮层μ节律的主要产生源。