2000). The brain’s output learn more channel is a certain signal in the EEG and the generation of this signal does not depend on the orientation of the eyes, but on the user’s intent (Sutton et al. 1965; Donchin 1981; Fabiani et al. 1987). This second group of BCIs seems to be more useful for ALS patients, who show damage in the output ways of peripheral nerves and muscles. The elements of a BCI There are four essential

parts of a BCI: (1) information input (i.e., recorded brain activity from the user), (2) signal processing (i.e., the components that translate raw information into output), (3) output (i.e., the commands administered Inhibitors,research,lifescience,medical by the BCI system), and (4) operating protocol that determines the timing of operation. These elements interact in order to produce the user’s intention. Signal acquisition is the measurement of the electrophysiological activity of the brain. This measurement is usually recorded via electrodes that can be either noninvasive (e.g., Inhibitors,research,lifescience,medical EEG) or invasive (i.e., intracortical). Moreover, BCIs can be categorized by whether they use evoked (e.g., EEG signals elicited by flashing letters) or spontaneous (e.g., EEG rhythms over cortex) inputs. Evoked inputs are generated by sensory stimulation provided by the BCI, while

spontaneous inputs do not depend on such stimulation. The most common type of input is EEG recorded from the scalp (Vidal Inhibitors,research,lifescience,medical 1977; Farwell and Donchin Inhibitors,research,lifescience,medical 1988; Pfurtscheller et al. 2000; Freeman et al. 2003). In this first part of BCI systems, the input is acquired by the electrodes, then amplified, digitalized, and sent to the BCI system for further analysis. Signal processing is the procedure to extract specific signal

features that reflect the user’s intent. In the signal processing stage, feature extraction process is carried out and the features are then converted, through translation algorithms, into commands that can operate and control devices (for Inhibitors,research,lifescience,medical a review see Norani et al. 2010). The output device is usually a computer screen and the output is the selection of targets (letters or icons) presented on it, performed by the BCI (see, for example, Farwell and Donchin 1988; Wolpaw et al. 1991; Perelmouter et al. 1999; Pfurtscheller et al. 2000). These targets are flashed or indicated in various ways. Other BCIs output includes moving a cursor on the screen, controlling a robotic arm, or controlling some other physiological very process. The operating protocol guides the BCI operations. It defines how the system is turned on and off, what kind of feedback is provided to the user, the sequence and the speed of interactions between user and system, and the speed with which the system implements commands (Wolpaw et al. 2002; Leuthardt et al. 2009). In most research protocols, the investigator sets these parameters and the users do not have on/off control, they just have to achieve very limited goals and tasks.