Applications for the Self-Control of Slow Cortical Potentials It is well established that biofeedback and operant learning procedures can be used to enable humans to gain voluntary control over bodily functions such as heart rate, blood pressure, or muscle tension. Similarly, individuals can acquire control over their brain activity. In a typical training paradigm, visual feedback of slow cortical potential shifts is provided online on a computer monitor, and the desired changes of cortical behavior are reinforced. The efficacy of this approach has been demonstrated in numerous studies by Birbaumer and colleagues. The present paper presents two applications of slow cortical potential self-control. 1) Epilepsy patients show an increased brain potential negativity both before and during a seizure. A feedback paradigm has been used, teaching patients to produce positive potential shifts. A recent long-term study in 41 epileptic patients has demonstrated that the frequency of seizures can be reduced if patients are able to control their cortical potentials in the absence of feedback. 2) In recent years, self-control of slow cortical potentials has been applied to communication, creating a direct interface between brain and computer in completely paralyzed individuals. Birbaumer and co-workers developed a ‘Thought Translation Device’ (TTD) using self-regulation of slow cortical potentials to generate a binary signal. This response can be used to choose letters and words from a selection menu. Thus the TTD has enabled three completely paralyzed patients diagnosed with amyotrophic lateral sclerosis to communicate solely with their brain potentials.