Communication and Control
Brain–computer interfaces have the potential to enable severely disabled individuals to communicate with other people and to control their environment. Communication functions consist mainly of sending/receiving emails, chatting, using VoIP phones and surfing the web. During the last 10 years, it has been proven in the labs that persons, even those suffering of severe disabilities, may interact with computers by only using their brain – in the extreme case using the brain channel as a single switch, just like a computer mouse.
There is also a commercial system that, in principle, allows BCI communication and control. Brain Actuated Technologies introduced “Cyberlink” in 1996, a system that records electrical signals from three electrodes integrated into a headband on the subject's forehead (Junker et al., 2002). Because of the location of the electrodes, users mainly use subtle facial muscles activity and eye movement for control, although the electrodes can also measure brain activity in the usual theta, alpha, and beta frequency bands. Recently OCZ Technology Inc. (San Jose, USA) acquired the company and is now commercializing the “Neural Impulse Actuator (NIA)”, the first consumer device that can be used for controlling standard video games without using mouse or joystick. OCZ is available since 2008 at a cost of about 300 USD.

BCI-driven spelling devices
In 1999, the Tübingen BCI group developed the Thought-Translation-Device (TTD; Birbaumer et al., 1999), a system that could be operated by patients suffering from ALS through the modulation of brain rhythms. Binary decisions made by the BCI were used to select letters in a procedure where the alphabet was iteratively split into halves. The achieved spelling rate was about 0.5 char/min. Since then, other groups have developed BCI-driven spelling devices based on the detection of voluntarily patterns of activity in the spontaneous EEG. These systems can operate synchronously (Birbaumer et al., 1999; Obermaier et al., 2003) or asynchronously (Millán, 2003; Millán et al., 2004a; Scherer et al., 2004; Müller and Blankertz, 2006; Williamson et al., 2009). Interestingly, one patient suffering from severe cerebral palsy could operate the Graz system at about 1 char/min. In the case of Millán's approach, trained subjects have taken 22.0 s on average to select a letter, including recovery from errors, with peak performances of 7.0 s per letter. Particularly relevant is the spelling system developed by the Berlin group in cooperation with the University of Glasgow, called Hex-o-Spell (Williamson et al., 2009), which illustrates how a normal BCI can be significantly improved by state-of-the-art HCI principles. The idea for Hex-o-Spell was taken from the Hex system which was designed for use on mobile devices augmented with accelerometers, where tilt control was used to maneuver through a hexagonal tessellation. The text entry system is controlled by the two mental states imagined right hand movement and imagined right foot movement. Expert subjects achieved typing speed of up to 7.5 char/min. A recent development in the field of HCI, inspired by a similar approach to Hex, is the Nomon selection system, based on the use of phase angle in clock-like displays (Broderick and MacKay, 2009). Still another speller designed upon efficient HCI principles is DASHER (Wills and MacKay, 2006).
Most BCI spelling devices, especially those actually used by disabled people, are based on the detection of potentials that are evoked by external stimuli rather than spontaneous mental states. The most prominent is the approach that elicits a P300 component (Donchin et al., 2000). In this approach, all characters are presented in a matrix, and the symbol which the user focuses her/his attention on can be predicted from the brain potentials that are evoked by random flashing of rows and columns. Similar P300-based spelling devices have since been extensively investigated and developed (e.g., Sellers et al., 2006; Nijboer et al., 2008; Silvoni et al., 2009).

BCI control of web browsers
The history of providing internet access to ALS patients dates back to 1999 when the TTD developed in Tübingen was used to operate a standard web browser. In a first implementation, called “Descartes” (Karim et al., 2006), the web window was shown for a certain amount of time (about 120 s), then a navigation screen would present the links from the current web page as leaves in a tree. A more advanced prototype, called “Nessi” (Bensch et al., 2007), allowed a more flexible selection of links thanks to a better user interface, again highlighting how BCI operation can be facilitated and improved by better HCI principles. More recently, this group has developed another browser based on P300 (Mugler et al., 2008). Theoretically, a browser with P300 control can enable selection from as many links as the elements in the P300 matrix (for a 6 × 6 matrix, 36), and the selection of a link could be completed in one step, although reliable recognition requires several iterations of the presentations of row/columns.

BCI and assistive technology
Brain–computer interface technology can be seen as a special Assistive technology in the area of Information and Communication Technologies (AT ICT), which is defined the Class 22 of ISO 9999:2007 (APs for communication and information):
“AT ICT products are understood to be devices for helping a person to receive, send, produce and/or process information in different forms. Included are, e.g., devices for seeing, hearing, reading, writing, telephoning, signalling and alarming, and information technology.”
A large variety of assistive technology is available today, providing the opportunity for nearly all people to access ICT. However, an individual with proper assistive technology has no guarantee of access. ICT products must be designed and created in ways that allow all users to access them, including those who need AT. It is for this reason that BCI must be combined with state-of-the-art AT ICT.
The standard user interface of a personal computer is powerful and flexible, but this flexibility is often a barrier to accessibility for many people with disabilities: many small icons, multiple open windows on a complex desktop, drag-and-drop, and so on. This kind of interface makes using a PC difficult and confusing for many people, like people with physical disabilities or first time users such as elderly people. A common approach to assisting people in using ICT is to add some assistive technology on top of the standard interface, such as text-to-speech or screen magnifiers. This approach has provided considerable benefit to specific user groups, but it does not remove the main limitation of standard user interfaces. The solution is then to design simpler user interfaces from scratch whose interaction principles and graphical appearance is uniform across applications. One of the few commercial state-of-the-art AT ICT products is “QualiWORLD” by QualiLife Inc. (Paradiso-Lugano, Switzerland).