使用闪光起始和偏移视觉诱发电位的脑机接口

Brain computer interface using flash onset and offset visual evoked potentials.

作者信息

Lee Po-Lei, Hsieh Jen-Chuen, Wu Chi-Hsun, Shyu Kuo-Kai, Wu Yu-Te

机构信息

Department of Electrical Engineering, National Central University, Taiwan; Institute of Biomedical Engineering, National Central University, Taiwan; Integrated Brain Research Laboratory, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan.

Integrated Brain Research Laboratory, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Institute of Neuroscience, School of Life Science, National Yang-Ming University, Taipei, Taiwan; Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.

出版信息

Clin Neurophysiol. 2008 Mar;119(3):605-616. doi: 10.1016/j.clinph.2007.11.013.

DOI:10.1016/j.clinph.2007.11.013

PMID:18164655

Abstract

OBJECTIVE

This paper presents a brain computer interface (BCI) actuated by flash onset and offset visual evoked potentials (FVEPs). Flashing stimuli, such as digits or letters, are displayed on a LCD screen for inducing onset and offset FVEPs when one stares at one of them. Subjects can shift their gaze at target flashing digits or letters to generate a string for communication purposes.

METHODS

By designing the flickering sequences with mutually independent flash onsets (or offsets) and employing the inherent property that onset (or offset) FVEPs are time-locked and phase-locked to flash onsets (or offsets) of gazed stimuli, segmented epochs based on the flash onsets (or offsets) of gazed stimuli will be enhanced after averaging whereas those based on the onsets (or offsets) of non-gazed stimuli will be suppressed after averaging. The amplitude difference between the N2 and P2 peaks of averaged onset FVEPs, denoted by Amp(onset), and that between the N1 and P1 peaks of averaged offset FVEPs, denoted by Amp(offset), are detected during experiments. The stimulus inducing the largest value of the sum Amp(onset)+Amp(offset) is identified as the gazed target and the representative digit or letter is sent out.

RESULTS

Five subjects participated in two experiments. In the first experiment, subjects were asked to gaze at 25 flickering stimuli one by one with each for a duration of 1min. The mean accuracy with 10-epoch averages was 97.4%. In the second task, subjects were instructed to generate a string '0287513694E' by staring at stimuli on a pseudo keypad comprising ten digits '0-9' and two letters 'B' and 'E'. The mean accuracy and information transfer rates were 92.18% and 33.65bits/min, respectively.

CONCLUSIONS

The onset and offset FVEP-based BCI has shown that high information transfer rate has been achieved.

SIGNIFICANCE

A novel FVEP-based BCI system is proposed as an efficient and reliable tool for disabled people to communicate with external environments.

摘要

目的

本文介绍一种由闪光起始和结束视觉诱发电位（FVEPs）驱动的脑机接口（BCI）。当人们盯着诸如数字或字母等闪烁刺激物时，这些刺激物会在液晶显示屏上显示，以诱发起始和结束FVEPs。受试者可以将目光转移到目标闪烁数字或字母上，以生成用于交流目的的字符串。

方法

通过设计具有相互独立闪光起始（或结束）的闪烁序列，并利用起始（或结束）FVEPs与注视刺激物的闪光起始（或结束）在时间上锁定且相位锁定的固有特性，基于注视刺激物的闪光起始（或结束）进行分段的时段在平均后会得到增强，而基于未注视刺激物的起始（或结束）进行分段的时段在平均后会被抑制。在实验过程中，检测平均起始FVEPs的N2和P2峰之间的幅度差，记为Amp（起始），以及平均结束FVEPs的N1和P1峰之间的幅度差，记为Amp（结束）。诱发Amp（起始）+Amp（结束）总和最大值的刺激物被识别为注视目标，并发送出代表性的数字或字母。

结果

五名受试者参与了两项实验。在第一个实验中，要求受试者逐个注视25个闪烁刺激物，每个刺激物持续1分钟。采用10个时段平均时的平均准确率为97.4%。在第二项任务中，要求受试者通过盯着包含十个数字“0 - 9”和两个字母“B”和“E”的虚拟键盘上的刺激物来生成字符串“0287513694E”。平均准确率和信息传输率分别为92.18%和33.65比特/分钟。