Brain-Computer Interfaces and Neurorehabilitation Roberta CARABALONA a , Paolo CASTIGLIONI a and Furio GRAMATICA a a Biomedical Technology Department, Santa Maria Nascente Research Hospital, Don Gnocchi Foundation, Milan, Italy Abstract. A brain-computer interface (BCI) directly uses brain-activity signals to allow users to operate the environment without any muscular activation. Thanks to this feature, BCI systems can be employed not only as assistive devices, but also as neurorehabilitation tools in clinical settings. However, several critical issues need to be addressed before using BCI in neurorehabilitation, issues ranging from signal acquisition and selection of the proper BCI paradigm to the evaluation of the affective state, cognitive load and system acceptability of the users. Here we discuss these issues, illustrating how a rehabilitation program can benefit from BCI sessions, and summarize the results obtained so far in this field. Also provided are experimental data concerning two important topics related to BCI usability in rehabilitation: the possibility of using dry electrodes for EEG acquisition, and the monitoring of psychophysiological effects during BCI tasks. Keywords. BCI, rehabilitation, technology acceptance, dry electrodes, affective computing Introduction A brain-computer interface (BCI) is a system that interprets brain signals generated by the user, allowing specific commands from the brain to be executed on an external device. Therefore such an interface would enable severely disabled people to interact with their environment without the need for any muscle activation. Indeed, BCI systems appear to be interesting new assistive devices for people with severe motor disabilities. However they differ from other human-machine interfaces in that the user must learn completely new skills in order to operate them. Years of experimentation have shown cortical plasticity even in adult brain, which still adapts to BCIs, thus the combination of rehabilitation and BCIs, both of which exploit cortical plasticity, could help people become “able” once again. For this reason, BCI systems appear promising rehabilitation tools. First, we provide an overview of BCI systems, from the historical and technical points of view, and then we move on to discuss the application of BCI in rehabilitation, where we focus on BCI usability in relation to user acceptance. In the final section we present experimental data concerning two important issues related to the applicability of BCI in rehabilitation procedures: i) the use of dry electrodes, a technology that has the potential to improve BCI system usability and comfort; ii) the monitoring of psychophysiological effects during BCI tasks, thus allowing the quantification of the “cognitive load” and “mental fatigue” of BCI rehabilitation sessions.