Alternative communication systems for people with severe motor disabilities: a survey <s> Synchronous BCI <s> With the development of brain-computer interface (BCI) technology, researchers are now attempting to put current BCI techniques into practical application. This paper presents an environmental controller using a BCI technique based on steady-state visual evoked potential. The system is composed of a stimulator, a digital signal processor, and a trainable infrared remote-controller. The attractive features of this system include noninvasive signal recording, little training requirement, and a high information transfer rate. Our test results have shown that this system can distinguish at least 48 targets and provide a transfer rate up to 68 b/min. The system has been applied to the control of an electric apparatus successfully. <s> BIB001 </s> Alternative communication systems for people with severe motor disabilities: a survey <s> Synchronous BCI <s> Abstract Objective This study aimed to describe the use of the P300 event-related potential as a control signal in a brain computer interface (BCI) for healthy and paralysed participants. Methods The experimental device used the P300 wave to control the movement of an object on a graphical interface. Visual stimuli, consisting of four arrows (up, right, down, left) were randomly presented in peripheral positions on the screen. Participants were instructed to recognize only the arrow indicating a specific direction for an object to move. P300 epochs, synchronized with the stimulus, were analyzed on-line via Independent Component Analysis (ICA) with subsequent feature extraction and classification by using a neural network. Results We tested the reliability and the performance of the system in real-time. The system needed a short training period to allow task completion and reached good performance. Nonetheless, severely impaired patients had lower performance than healthy participants. Conclusions The proposed system is effective for use with healthy participants, whereas further research is needed before it can be used with locked-in syndrome patients. Significance The P300-based BCI described can reliably control, in ‘real time’, the motion of a cursor on a graphical interface, and no time-consuming training is needed in order to test possible applications for motor-impaired patients. <s> BIB002 </s> Alternative communication systems for people with severe motor disabilities: a survey <s> Synchronous BCI <s> We describe a study designed to assess properties of a P300 brain–computer interface (BCI). The BCI presents the user with a matrix containing letters and numbers. The user attends to a character to be communicated and the rows and columns of the matrix briefly intensify. Each time the attended character is intensified it serves as a rare event in an oddball sequence and it elicits a P300 response. The BCI works by detecting which character elicited a P300 response. We manipulated the size of the character matrix (either 3 � 3o r 6� 6) and the duration of the inter stimulus interval (ISI) between intensifications (either 175 or 350 ms). Online accuracy was highest for the 3 � 3 matrix 175-ms ISI condition, while bit rate was highest for the 6 � 6 matrix 175-ms ISI condition. Average accuracy in the best condition for each subject was 88%. P300 amplitude was significantly greater for the attended stimulus and for the 6 � 6 matrix. This work demonstrates that matrix size and ISI are important variables to consider when optimizing a BCI system for individual users and that a P300-BCI can be used for effective communication. # 2006 Elsevier B.V. All rights reserved. <s> BIB003 </s> Alternative communication systems for people with severe motor disabilities: a survey <s> Synchronous BCI <s> To address the issue of system simplicity and subject applicability, a brain controlled HCI system derived from steady state visual evoked potential (SSVEP) based brain computer interface (BCI) is proposed in this paper. Aiming at an external input device for personal computer, key issues of hardware and software design for better performance and user-friendly interface are introduced systematically. With proper parameter customization for each individual, an average information transfer rate of 46bits/min was achieved in the operation of dialing a phone number. With encouraging online performance and advantages of system simplicity, the proposed HCI using SSVEP-based BCI technology is promising for a substitute of standard computer input device for both health and disabled computer users. <s> BIB004 </s> Alternative communication systems for people with severe motor disabilities: a survey <s> Synchronous BCI <s> An EEG-based brain–computer system can be used to control external devices such as computers, wheelchairs or Virtual Environments. One of the most important applications is a spelling device to aid severely disabled individuals with communication, for example people disabled by amyotrophic lateral sclerosis (ALS). P300-based BCI systems are optimal for spelling characters with high speed and accuracy, as compared to other BCI paradigms such as motor imagery. In this study, 100 subjects tested a P300based BCI system to spell a 5-character word with only 5 min of training. EEG data were acquired while the subject looked at a 36-character matrix to spell the word WATER. Two different versions of the P300 speller were used: (i) the row/column speller (RC) that flashes an entire column or row of characters and (ii) a single character speller (SC) that flashes each character individually. The subjects were free to decide which version to test. Nineteen subjects opted to test both versions. The BCI system classifier was trained on the data collected for the word WATER. During the real-time phase of the experiment, the subject spelled the word LUCAS, and was provided with the classifier selection accuracy after each of the five letters. Additionally, subjects filled out a questionnaire about age, sex, education, sleep duration, working duration, cigarette consumption, coffee consumption, and level of disturbance that the flashing characters produced. 72.8% (N = 81) of the subjects were able to spell with 100% accuracy in the RC paradigm and 55.3% (N = 38) of the subjects spelled with 100% accuracy in the SC paradigm. Less than 3% of the subjects did not spell any character correctly. People who slept less than 8 h performed significantly better than other subjects. Sex, education, working duration, and cigarette and coffee consumption were not statistically related to differences in accuracy. The disturbance of the flashing characters was rated with a median score of 1 on a scale from 1 to 5 (1, not disturbing; 5, highly disturbing). This study shows that high spelling accuracy can be achieved with the P300 BCI system using approximately 5 min of training data for a large number of non-disabled subjects, and that the RC paradigm is superior to the SC paradigm. 89% of the 81 RC subjects were able to spell with accuracy 80–100%. A similar study using a motor imagery BCI with 99 subjects showed that only 19% of the subjects were able to achieve accuracy of 80–100%. These large differences in accuracy suggest that with limited amounts of training data the P300-based BCI is superior to the motor imagery BCI. Overall, these results are very encouraging and a similar study should be conducted with subjects who have ALS to determine if their accuracy levels are similar. <s> BIB005
In this type of interface, EEG signals used are not created in a spontaneous way by the user but are synchronised on stimulations sent by the interface. These stimulations are generally visual and more rarely auditory, and EEG signals are generally called evoked potential. Among the evoked potentials, those which are generally used to build a BCI are the SSVEP and P300. The wave P300 corresponds to a short positive deflection of the EEG signal which appears 300 ms after a rare and awaited stimulation within a great number of stimulations  . A well known experimental design used to obtain this P300, is referred to as the oddball paradigm  . A communication interface based on this paradigm, which makes it possible to select letters of the alphabet to spell words, is called P300 speller  . This P300 speller is generally formed by a 6 × 6 matrix containing 36 items (letters, numbers or characters) which it is possible to select. The experimental procedure consists in flashing successively each line and each column in a random way. The selection of one item is carried out by the detection of the P300 which will appear in response to an awaited stimulation which is the flashing of the line or the column containing the desired choice. These awaited stimulations are rare (2) since they appear in a random way among the succession of the flashing of each line and each column of the matrix (12: 6 lines and 6 columns). The detection of the P300 is generally made by carrying out averages on a great number of stimulations, because these waves have very low amplitudes if one compares them with sensorimotor rhythms for example. Another difficulty to detect these P300 quickly lies in the fact that they are not as well localized as sensorimotor rhythms on the cortex, it exists indeed several cortical centres of the wave P300  . The minimum number of electrodes to be used in the case of an interface containing P300 will be thus a priori higher than that necessary for a BCI based on sensorimotor rhythms. In spite of the difficulty of measurement and analysis of the P300, many BCI based on this type of wave were made, P300 speller being most known BIB002 BIB003 . The major advantage of this type of interface lies in the absence of training necessary to the subject to control EEG signals since those are stimulated by the interface. Nevertheless, offline analysis of training session is generally needed in order to optimize the algorithms used to process the P300 which enormously vary from one person to another but also on the same subject according to its state of tiredness. The adaptation effort is thus deferred subject towards the software. Performances records in term of speed thus could be carried out on P300 speller BIB005 . In best case, the time needed to select a choice is of the same order of magnitude as that necessary to a subject having to move a cursor on a precise place of the screen with a mouse. These results let consider the possibility of fast information transmission through BCI systems. Nevertheless studies on the reproducibility and the reliability of these types of communication systems must be done, because the significant effort of concentration that is requested from the user involves rather quickly a tiredness of this one. Recently a commercial BCI became available: the Intendix ®  is a typing device that uses visual evoked potentials running over a non-dedicated personal computer. The other evoked potential often used for BCI is the visual evoked potential and in particular the SSVEP. This evoked potential is recorded on the visual cortex in the occipital lobe. Contrary to P300, this evoked potential being better localised on the cortex, only 2 or 3 electrodes are necessary. The stimulation which allows the appearance of a SSVEP is induced by a flickering at a frequency higher than 6 Hz present on the target which the subject must gaze BIB001 . It is thus possible to build an interface containing different items which one associates different frequencies of flickering; the detection of item is carried out by a spectral analysis of the EEG signals which must reveal the frequency of the target that the subject gazed. The number of target may be from 4 to 48, the range of the frequencies usable from 6 to 24 Hz and the resolution given for these SSVEP is of 0.2 Hz BIB001 . The use of SSVEP makes it possible to obtain information transfer rate of 46bits/min with an accuracy of 95% BIB004 . Just like P300 speller, this type of interface requires an increased concentration of the subject, which lets predict a significant tiredness for the user.