2001b) and this is a problematic issue for patients with completely locked-in syndrome. This kind of communication system is categorized as dependent BCI, because it depends

on muscular control of gaze direction. Slow cortical potentials (SCP) SCPs are slow voltage changes generated in the cortex. Users can learn to control SCPs, although it requires a long training. Several studies showed that SCPs originating from central Inhibitors,research,lifescience,medical and frontal regions could be brought under voluntary operant control after training (Lutzenberger et al. 1993) and the importance of the anterior brain systems for the control of these functions has been further confirmed. As a matter of fact, patients Inhibitors,research,lifescience,medical with prefrontal dysfunction show extreme difficulties in learning SCP control, even if other cognitive functions are preserved (Lutzenberger et al. 1980; Birbaumer et al. 1986; Schneider et al. 1992). It is suggested that also patient with ALS are unable to voluntarily control local cortical excitation, because of the involvement of motor and premotor cortical systems in this disease. Mu rhythm (sensorymotor rhythms SMR) Mu rhythm refers to 8–12 Hz EEG activity

that Inhibitors,research,lifescience,medical can be recorded over primary motor and somatosensory cortex when awake SB939 cost subjects are not engaged in processing sensory input or producing motor output (Niedermeyer 2004). It is usually accompanied by 18–26 Hz beta-rhythms. SMR are associated Inhibitors,research,lifescience,medical with cortical areas most directly connected to the brain’s motor output pathways. Movement or preparation of movement is associated with a decrease in mu and beta rhythms, labeled “event-related desynchronization” (ERD), while relaxation is accompanied by a rhythm increase or “event-related synchronization” (ERS) (Pfurtscheller 1999; Pfurtscheller et al. 2000). Notably, these rhythm changes occur

also with motor imagery (i.e., mental representation of a movement) and do not require effective movement (Pfurtscheller and Neuper 1997; McFarland et al. 2000). Therefore, they may be used in independent BCI systems, which Inhibitors,research,lifescience,medical can be successfully adopted by paralyzed patients. P300 P300 evoked potentials are the best studied Thymidine kinase ERPs and they can be used as control signal in BCI systems. In the next paragraph, P300-based BCI will be extensively treated. P300-based BCI systems P300 event-related potentials The P300 event-related potential is one possible EEG-based BCI control signal. These signals include both spontaneous electrical activity of the cerebral network and the cortical response to external or internal events. Event-related potentials are defined as brain activity that is elicited in response to events (Figs. 2 and ​and3;3; Donchin et al. 2000). ERPs can be distinguished in exogenous and endogenous. The former are the result of early and automatic processing of stimuli, whereas the latter correspond to later and more conscious processing of stimuli (Kubler et al. 2001b).