Brain–computer interfacing in disorders of consciousness

Abstract

Background: Recent neuroimaging research has strikingly demonstrated the existence of covert awareness in some patients with disorders of consciousness (DoC). These findings have highlighted the potential for the development of simple brain-computer interfaces (BCI) for the significant minority of behaviourally unresponsive patients who display consistent signs of covert awareness.Objectives: In this article, we review current EEG-based BCIs that hold potential for assessing and eventually assisting patients with DoC. We highlight key areas for further development that might eventually make their application feasible in this challenging patient group.Methods: We consider the major types of BCIs proposed in the literature, namely those based on the P3 potential, sensorimotor rhythms, steady state oscillations, and slow cortical potentials. In each case, we provide a brief overview of the relevant literature, and then consider their relative merits for BCI applications in DoC.Results: Over the last few decades, a range of BCI designs have been proposed and tested for enabling communication in fully conscious, paralysed patients. Though many of these have potential applicability for patients with DoC, they share some key challenges that need to be overcome, including limitations of stimulation modality, feedback, user training and consistency. Conclusion: Developing feasible BCIs for diagnostics and communication in DoCwill require parallel strands of enquiry. Preliminary exploratory research will need to specifically tailor cognitive tasks that can tap into the forms in which patients could potentially express volition. Alongside, future work will need to address the technical and practical challenges facing reliable implementation at the patient's bedside.

Stratification of unresponsive patients by an independently validated index of brain complexity

“…In this process, longitudinal TMS/EEG measurements also offer the fundamental readout to direct and titrate intervention toward the desired endpoint of PCI max  > PCI*. Finally, unresponsive patients in whom TMS/EEG already documents a core of high complexity should be selected for intensive interventions aimed at restoring responsiveness to the external environment, such as by increasing behavioral output through thalamic stimulation50 or by establishing communication through active paradigms or brain–machine interface 51, 52…”

Consciousness supporting networks

“…As soon as the patient was taken out of the MRI machine, no communication whatsoever was possible. Hence, portable and cheaper EEG-based equivalents [(e.g., 42,43,44)] have been developed for more routine clinical use [(for recent review see 45)]. Such brain computer interfaces (BCI) have already been used successfully in real clinical settings.…”

Disorders of consciousness after acquired brain injury: the state of the science

“…132 Most BCI systems have been developed for paralysed or LIS patients, but may not work in MCS because of fluctuations in vigilance and limitations in attention span. For example, a four-choice auditory oddball EEG-BCI paradigm, which had been validated in healthy controls and cognitively intact patients with LIS, revealed reliable command-following in a patient in MCS but could not be converted into a functional communication system.…”