Ramsey Nick F, van de Heuvel Martijn P, Kho Kuan H, Leijten Frans S S
Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Hospital of Utrecht, 3584CX Utrecht, The Netherlands.
IEEE Trans Neural Syst Rehabil Eng. 2006 Jun;14(2):214-7. doi: 10.1109/TNSRE.2006.875582.
One of the critical issues in brain-computer interface (BCI) research is how to translate a person's intention into brain signals for controlling computer programs. The motor system is currently the primary focus, where signals are obtained during imagined motor responses. However, cognitive brain systems are also attractive candidates, in that they may be more amenable to conscious control, yielding better regulation of magnitude and duration of localized brain activity. We report on a proof of principle study for the potential use of a higher cognitive system for BCI, namely the working memory (WM) system. We show that mental calculation reliably activates the WM network as measured with functional magnetic resonance imaging (fMRI). Moreover, activity in the dorsolateral prefrontal cortex (DLPFC) indicates that this region is active for the duration of mental processing. This supports the notion that DLPFC can be activated, and remains active, at will. Further confirmation is obtained from a patient with an implanted electrode grid for diagnostic purposes, in that gamma power within DLPFC increases during mental calculation and remains elevated for the duration thereof. These results indicate that cortical regions involved in higher cognitive functions may serve as a readily self-controllable input for BCI applications. It also shows that fMRI is an effective tool for identifying function-specific foci in individual subjects for subsequent placement of cortical electrodes. The fact that electrocorticographic (ECoG) signal confirmed the functional localization of fMRI provides a strong argument for incorporating fMRI in BCI research.
脑机接口（BCI）研究中的关键问题之一是如何将人的意图转化为脑信号以控制计算机程序。运动系统目前是主要关注点，在想象的运动反应过程中获取信号。然而，认知脑系统也是有吸引力的候选对象，因为它们可能更易于有意识控制，能更好地调节局部脑活动的幅度和持续时间。我们报告了一项关于BCI潜在使用更高认知系统（即工作记忆（WM）系统）的原理验证研究。我们表明，通过功能磁共振成像（fMRI）测量，心算可靠地激活了WM网络。此外，背外侧前额叶皮层（DLPFC）的活动表明，该区域在心理加工过程中持续活跃。这支持了DLPFC可以随意激活并保持活跃的观点。通过一名因诊断目的植入电极网格的患者获得了进一步的证实，即DLPFC内的伽马功率在心算期间增加并在整个过程中保持升高。这些结果表明，参与更高认知功能的皮层区域可能作为BCI应用中易于自我控制的输入。这也表明fMRI是识别个体受试者功能特异性焦点以便随后放置皮层电极的有效工具。皮层脑电图（ECoG）信号证实了fMRI的功能定位这一事实为将fMRI纳入BCI研究提供了有力论据。
