This work is supported by the European ICT Programme Project FP7-224631. This paper only reflects the authors’ views and funding agencies are not liable for any use that may be made of the information contained herein. 1That is, people with different degrees of stabilized motor disability as a consequence of traumatic lesions (spinal cord injury), cerebrovascular diseases (stroke), or degenerative neuromuscular diseases (muscular dystrophies and motor neuron disorders such as amyotrophic lateral sclerosis and spinal muscular atrophies) that are characterized by a progressive loss of muscular activity. In all these cases, however, cognitive functions are spared to a large, if not complete, extent.
2Besides electrical activity, neural activity also produces other types of signals, such as magnetic and metabolic, that can be also measured non-invasively. Magnetic fields can be recorded with magnetoencephalography (MEG), while brain metabolic activity – reflected in changes in blood flow – can be observed with positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and optical imaging (NIRS). Unfortunately, such alternative techniques require sophisticated equipment that can be operated only in special facilities. Moreover, techniques for measuring blood flow have long latencies and thus are less appropriate for interaction.
3Clearly, all these issues (from standardization to esthetics) are relevant to any kind of BCI, regardless of the kind of brain signal in use.