Probing command following in patients with disorders of consciousness using a brain–computer interface

Lulé, Dorothée; Noirhomme, Quentin; Kleih, Sonja C.; Chatelle, Camille; Halder, Sebastian; Demertzi, Athena; Bruno, Marie-Aurélie; Gosseries, Olivia; Vanhaudenhuyse, Audrey; Schnakers, Caroline; Thonnard, Marie; Soddu, Andrea; Kübler, Andrea; Laureys, Steven

doi:10.1016/j.clinph.2012.04.030

“…The fact that a scanner is needed limits its use to a hospital setting and precludes application in patients with metal implants or in critical condition in intensive care. Active command paradigms combined with EEG [45][46][47] or electromyography [48] are more wieldy solutions, which have already permitted the detection of voluntary brain function in patients with VS/UWS and enabled functional communication with patients with complete locked-in syndrome (i.e., fully conscious but completely paralyzed including eye movement [49]). …”

Section: Detection Of Awareness In Disorders Of Consciousnessmentioning

confidence: 99%

Functional neuroanatomy of disorders of consciousness

Perri

¹

,

Stender

²

,

Laureys

³

et al. 2014

Epilepsy & Behavior

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. Our understanding of the mechanisms of loss and recovery of consciousness, following severe brain injury or during anesthesia, is changing rapidly. Recent neuroimaging studies have shown that patients with chronic disorders of consciousness and subjects undergoing general anesthesia present a complex dysfunctionality in the architecture of brain connectivity. At present, the global hallmark of impaired consciousness appears to be a multifaceted dysfunctional connectivity pattern with both within-network loss of connectivity in a widespread frontoparietal network and between-network hyperconnectivity involving other regions such as the insula and ventral tegmental area. Despite ongoing efforts, the mechanisms underlying the emergence of consciousness after severe brain injury are not thoroughly understood. Important questions remain unanswered: What triggers the connectivity impairment leading to disorders of consciousness? Why do some patients recover from coma, while others with apparently similar brain injuries do not? Understanding these mechanisms could lead to a better comprehension of brain function and, hopefully, lead to new therapeutic strategies in this challenging patient population.This article is part of a Special Issue entitled Epilepsy and Consciousness.

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“…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.…”

Section: Discussionmentioning

confidence: 99%

Consciousness supporting networks

Demertzi¹,

Soddu²,

Laureys³

2013

Current Opinion in Neurobiology

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. Author's personal copy In most cases authors Consciousness supporting networksAthena Demertzi, Andrea Soddu and Steven LaureysFunctional neuroimaging shows that patients with disorders of consciousness exhibit disrupted system-level functional connectivity. Unresponsive/''vegetative state'' patients preserve wakefulness networks of brainstem and basal forebrain but the cerebral networks accounting for external perceptual awareness and internal self-related mentation are disrupted. Specifically, the 'external awareness' network encompassing lateral fronto-temporo-parietal cortices bilaterally, and the 'internal awareness' network including midline anterior cingulate/mesiofrontal and posterior cingulate/ precuneal cortices, are functionally disconnected. By contrast, patients in minimally conscious state 'minus', who show nonreflex behaviors, are characterized by right-lateralized recovery of the external awareness network. Similarly, patients who evolve to minimally conscious state 'plus' and respond to commands recover the dominant left-lateralized language network. Now, the use of active experimental paradigms targeting at detecting motor-independent signs of awareness or even establishing communication with these patients, challenge these two clinical boundaries. Such advances are naturally accompanied by legitimate neuroscientific and ethical queries demanding our attention on the medical implementations of this new knowledge. What is 'minimally conscious'?At present there is no generally accepted definition of consciousness [1]. As clinicians, we will reduce the complexity of this term and define consciousness operationally, separating two main components: wakefulness and awareness [2]. Wakefulness has been shown to critically depend upon the functional integrity of subcortical arousal systems over 50 years ago [(e.g., see 3)]. The level of wakefulness can be estimated by simple behavioral criteria based on eye opening ranging from absent, over stimulus-induced to spontaneous sustained eye opening.For instance, every night when falling asleep, we experience a decrease of the level of wakefulness up to the point we lose awareness of our environment. Awareness is more difficult to define and more challenging to assess behaviorally [4]. We have recently proposed to reduce the phenomenological complexity of awareness into two further components: external awareness, namely everything we perceive through our senses (what we see, hear, feel, smell and taste), and internal awareness or stimulusindependent thoughts. Interestingly, the switch between the external and internal milieu was found not only to characterize overt...

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“…While nine of the fourteen healthy subjects achieved spelling accuracy above 70%, the patient's performance was poor. An auditory four-choice P300-speller BCI was proposed by Lulé et al and was tested in two patients with LIS [40]. One of the two patients showed an offline accuracy higher than chance level but neither of them showed an online performance higher than 70%.…”

Section: Discussionmentioning

confidence: 99%

An independent SSVEP-based brain–computer interface in locked-in syndrome

Lesenfants

¹

,

Habbal

²

,

Lugo

³

et al. 2014

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Objective. Steady-state visually evoked potential (SSVEP)-based brain-computer interfaces (BCIs) allow healthy subjects to communicate. However, their dependence on gaze control prevents their use with severely disabled patients. Gaze-independent SSVEP-BCIs have been designed but have shown a drop in accuracy and have not been tested in brain-injured patients. In the present paper, we propose a novel independent SSVEP-BCI based on covert attention with an improved classification rate. We study the influence of feature extraction algorithms and the number of harmonics. Finally, we test online communication on healthy volunteers and patients with locked-in syndrome (LIS). Approach. Twenty-four healthy subjects and six LIS patients participated in this study. An independent covert two-class SSVEP paradigm was used with a newly developed portable light emitting diode-based 'interlaced squares' stimulation pattern. Main results. Mean offline and online accuracies on healthy subjects were respectively 85 ± 2% and 74 ± 13%, with eight out of twelve subjects succeeding to communicate efficiently with 80 ± 9% accuracy. Two out of six LIS patients reached an offline accuracy above the chance level, illustrating a response to a command. One out of four LIS patients could communicate online. Significance. We have demonstrated the feasibility of online communication with a covert SSVEP paradigm that is truly independent of all neuromuscular functions. The potential clinical use of the presented BCI system as a diagnostic (i.e., detecting command-following) and communication tool for severely brain-injured patients will need to be further explored.

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Probing command following in patients with disorders of consciousness using a brain–computer interface

Cited by 167 publications

References 53 publications

Functional neuroanatomy of disorders of consciousness

Functional neuroanatomy of disorders of consciousness

Consciousness supporting networks

An independent SSVEP-based brain–computer interface in locked-in syndrome

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