Chen Xiaogang, Hu Nan, Wang Yijun, Gao Xiaorong
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, 300192, China.
Rehabilitation Department, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, 510260, China.
Comput Biol Med. 2020 May;120:103729. doi: 10.1016/j.compbiomed.2020.103729. Epub 2020 Mar 25.
Digit symbol substitution test (DSST), which is a valid and sensitive tool to assess human cognitive dysfunction, has been widely used in clinical neuropsychology. Although several versions of DSST are currently available, most of the existing DSST versions rely on examinees' intact motor function. This limits their utility in severely motor-impaired individuals. A brain-computer interface (BCI) version of DSST was implemented in this study. Steady-state visual evoked potential (SSVEP) was adopted to build the BCI. Nine symbols in the proposed SSVEP BCI-based DSST were designed with clearly different shapes for decreasing measurement errors due to misidentified symbols. To reduce practice effect, furthermore, the digit-symbol pairs of each trial were different. A two-target SSVEP BCI was designed to judge whether the digit-symbol probe in the center of the user interface matched one of the nine digit-symbol pairs above the user interface. All 12 examinees were able to perform the tasks using the proposed SSVEP BCI-based DSST with 96.17 ± 4.18% averaged accuracy, which was comparable with that of computerized DSST. Furthermore, for examinees participating in both offline and online experiment, the accuracies of the online and offline experiments were comparable, supporting that the proposed BCI-DSST was reliable for repeatedly evaluating examinees' cognitive function over time. These results verified that the proposed SSVEP BCI-based DSST was feasible and effective for healthy subjects.
数字符号替换测验（DSST）是评估人类认知功能障碍的一种有效且灵敏的工具，已在临床神经心理学中广泛应用。尽管目前有多个版本的DSST，但现有的大多数DSST版本都依赖于受试者完整的运动功能。这限制了它们在严重运动功能受损个体中的效用。本研究实施了一种脑机接口（BCI）版本的DSST。采用稳态视觉诱发电位（SSVEP）来构建BCI。基于SSVEP BCI的DSST中设计的九个符号具有明显不同的形状，以减少因符号识别错误导致的测量误差。此外，为了减少练习效应，每个试验的数字 - 符号对都不同。设计了一种双目标SSVEP BCI，以判断用户界面中心的数字 - 符号探针是否与用户界面上方的九个数字 - 符号对之一匹配。所有12名受试者都能够使用所提出的基于SSVEP BCI的DSST执行任务，平均准确率为96.17 ± 4.18%，这与计算机化DSST的准确率相当。此外，对于同时参与离线和在线实验的受试者，在线和离线实验的准确率相当，这支持了所提出的BCI - DSST对于随时间重复评估受试者的认知功能是可靠的。这些结果证实了所提出的基于SSVEP BCI的DSST对健康受试者是可行且有效的。
