“…In non-invasive BMIs, six types of brain signals have been tested: 1. sensori-motor rhythms (SMR,(8)(9)(10)(11)(12)(13)(14)(15) Hz, also termed rolandic alpha or mu-rhythm depending on the context) (McFarland et al, 1993(McFarland et al, , 2006Pfurtscheller et al, 2006;Soekadar et al, 2011a, in press-a), 2. slow cortical potentials (SCP) (Birbaumer et al, 1999), 3. event-related potentials (ERPs) (Farwell and Donchin, 1988) and 4. steady-state visually or auditory evoked potentials (SSVEP/SSAEP) (Sakurada et al, 2013), 5. blood-oxygenation level dependent (BOLD)-contrast imaging using functional MRI (Weiskopf et al, 2003), and 6. concentration changes of oxy/deoxy hemoglobin using functional near-infrared spectroscopy (fNIRS; Sitaram et al, 2009;Mihara et al, 2013;Rea et al, 2014). Implantable BMIs, in contrast, require surgical implantation of epidural, subdural, or intracortical electrode arrays.…”