Why BCIs work poorly with the patients who need them the most?

A major objective of Brain-Computer interfaces (BCI) is to restore communication and control in patients with severe motor impairments, like people with Locked-in syndrome. These patients are left only with limited eye and eyelid movements. However, they do not benefit from efficient BCI solutions, yet. Different signals can be used as commands for non-invasive BCI: mu and beta rhythm desynchronization, evoked potentials and slow cortical potentials. Whatever the signal, clinical studies show a dramatic loss of performance in severely impaired patients compared to healthy subjects. Interestingly, the control principle is always the same, namely the replacement of an impossible (overt) movement by a (covert) attentional command. Drawing from the premotor theory of attention, from neuroimaging findings about the functional anatomy of spatial attention, from clinical observations and from recent computational accounts of attention for both action and perception, we explore the hypothesis that these patients undergo negative plasticity that extends their impairment from overt to covert attentional processes.