Another kind of ‘BOLD Response’: answering multiple-choice questions via online decoded single-trial brain signals

Abstract

Abstract:The term 'locked-in' syndrome (LIS) describes a medical condition in which persons concerned are severely paralyzed and at the same time fully conscious and awake. The resulting anarthria makes it impossible for these patients to naturally communicate, which results in diagnostic as well as serious practical and ethical problems. Therefore, developing alternative, muscle-independent communication means is of prime importance. Such communication means can be realized via brain-computer interfaces (BCIs) circumventing the muscular system by using brain signals associated with preserved cognitive, sensory, and emotional brain functions. Primarily, BCIs based on electrophysiological measures have been developed and applied with remarkable success. Recently, also blood flow-based neuroimaging methods, such as functional magnetic resonance imaging (fMRI) and functional near-infrared spectroscopy (fNIRS), have been explored in this context.After reviewing recent literature on the development of especially hemodynamically based BCIs, we introduce a highly reliable and easy-to-apply communication procedure that enables untrained participants to motor-independently and relatively effortlessly answer multiple-choice questions based on intentionally generated single-trial fMRI signals that can be decoded online. Our technique takes advantage of the participants' capability to voluntarily influence certain spatio-temporal aspects of the blood oxygenation level-dependent (BOLD) signal: source location (by using different mental tasks), signal onset and offset. We show that healthy participants are capable of hemodynamically encoding at least four distinct information units on a single-trial level without extensive pretraining and with little effort. Moreover, realtime data analysis based on simple multi-filter correlations allows for automated answer decoding with a high accuracy (94.9%) demonstrating the robustness of the presented method. Following our 'proof of concept', the next step will involve clinical trials with LIS patients, undertaken in close collaboration with their relatives and caretakers in order to elaborate individually tailored communication protocols.� Corresponding author. As our procedure can be easily transferred to MRI-equipped clinical sites, it may constitute a simple and effective possibility for online detection of residual consciousness and for LIS patients to communicate basic thoughts and needs in case no other alternative communication means are available (yet) -especially in the acute phase of the LIS. Future research may focus on further increasing the efficiency and accuracy of fMRI-based BCIs by implementing sophisticated data analysis methods (e.g., multivariate and independent component analysis) and neurofeedback training techniques. Finally, the presented BCI approach could be transferred to portable fNIRS systems as only this would enable hemodynamically based communication in daily life situations.

From unresponsive wakefulness to minimally conscious PLUS and functional locked-in syndromes: recent advances in our understanding of disorders of consciousness

“…In conclusion, some patients who awaken from their coma may fail to show any behavioural sign of awareness (i.e., they are considered to be vegetative or-as we prefer-unresponsive [11]), or they may remain unable to communicate (i.e., are in a minimally conscious state- [68] or evoked potential brain computer interfaces will be used to address important clinical and ethical questions such as feeling of pain and discomfort [69]. These novel technological means will undoubtedly further improve the existing nosology and clinical care of these challenging patients with disorders of consciousness.…”

Coma and consciousness: Paradigms (re)framed by neuroimaging

“…As we have here briefly discussed a yet to be determined minority of patients who are currently considered to be -vegetative‖ or unresponsive, show fMRI or EEG/ERP based signs of consciousness that are inaccessible to clinicians' motor-response dependent behavioral assessment. These ever improving technological means are changing the existing clinical boundaries and will permit some -non-communicative‖ and locked-in (Bruno et al, 2009b;Gosseries et al, 2009;Laureys et al, 2005) patients to correspond their thoughts and wishes and control their environment via non-motor pathways. It is clear from this overview that our understanding of consciousness and disorders of consciousness after coma is currently witnessing a significant paradigm shift (Laureys and Boly, 2008;Owen et al, 2009).…”

La neuro-imagerie : un outil diagnostique des états de conscience altérée

“…Ces études illustrent le pouvoir pronostique potentiel de ces paradigmes actifs en IRMf. Toujours grâce à l'IRMf, Sorger et al [28] ont mis au point un autre exemple de communication à choix multiples : deux tâches d'imagerie mentale (imagerie motrice et calcul mental) sont utilisées comme réponses aux questions posées aux participants. Chacune des quatre réponses correspond à une tâche d'imagerie mentale et à une fenêtre de temps spécifique.…”