Alcohol dependency is the most frequent addiction leading to a massive burden of both, patients health, and economy. Present therapeutic concepts suffer from limited efficacy, and thus new innovative therapies are needed. Neuroscientific studies have shown that prefrontal function in alcohol-dependent patients is impaired, leading to cognitive disturbances, and continuation of dependent behaviour. The results of pilot studies demonstrate that activation of prefrontal cortices via non-invasive brain stimulation improves cognitive performance in healthy subjects, and diminishes dependency-related behaviour in patients. The investigators aim to develop a stimulation protocol suited to induce a clinically relevant improvement of prefrontal functions in patients suffering from alcohol dependency. Therefore, the investigators will develop stimulation protocols which are able to modulate prefrontal activation for a much longer time course than those currently available, and will explore if the induced physiological alterations translate to respective cognitive improvements and reduction of addictive behaviour.