Boris Kotchoubey

A spelling device for the paralysed.

When Jean-Dominique Bauby suffered from a cortico-subcortical stroke that led to complete paralysis with totally intact sensory and cognitive functions, he described his experience in The Diving-Bell and the Butterfly as “something like a giant invisible diving-bell holds my whole body prisoner”. This horrifying condition also occurs as a consequence of a progressive neurological disease, amyotrophic lateral sclerosis, which involves progressive degeneration of all the motor neurons of the somatic motor system. These ‘locked-in’ patients ultimately become unable to express themselves and to communicate even their most basic wishes or desires, as they can no longer control their muscles to activate communication devices. We have developed a new means of communication for the completely paralysed that uses slow cortical potentials (SCPs) of the electro-encephalogram to drive an electronic spelling device.

The thought translation device (TTD) for completely paralyzed patients

The thought translation device trains locked-in patients to self-regulate slow cortical potentials (SCPs) of their electroencephalogram (EEG). After operant learning of SCP self-control, patients select letters, words or pictograms in a computerized language support program. Results of five respirated, locked-in-patients are described, demonstrating the usefulness of the thought translation device as an alternative communication channel in motivated totally paralyzed patients with amyotrophic lateral sclerosis.

Brain-computer communication: unlocking the locked in.

With the increasing efficiency of life-support systems and better intensive care, more patients survive severe injuries of the brain and spinal cord. Many of these patients experience locked-in syndrome: The active mind is locked in a paralyzed body. Consequently, communication is extremely restricted or impossible. A muscle-independent communication channel overcomes this problem and is realized through a brain-computer interface, a direct connection between brain and computer. The number of technically elaborated brain-computer interfaces is in contrast with the number of systems used in the daily life of locked-in patients. It is hypothesized that a profound knowledge and consideration of psychological principles are necessary to make brain-computer interfaces feasible for locked-in patients.

The thought translation device: a neurophysiological approach to communication in total motor paralysis

Abstract A thought translation device (TTD) for brain-computer communication is described. Three patients diagnosed with amyotrophic lateral sclerosis (ALS), with total motor paralysis, were trained for several months. In order to enable such patients to communicate without any motor activity, a technique was developed where subjects learn to control their slow cortical potentials (SCP) in a 2-s rhythm, producing either cortical negativity or positivity according to the task requirement. SCP differences between a baseline interval and an active control interval are transformed into vertical or horizontal cursor movements on a computer screen. Learning SCP self regulation followed an operant-conditioning paradigm with individualized shaping procedures. After prolonged training over more than 100 sessions, all patients achieved self-control, leading to a 70–80% accuracy for two patients. The learned cortical skill enabled the patients to select letters or words in a language-supporting program (LSP) developed for inter-personal communication. The results demonstrate that the fast and stable SCP self-control can be achieved with operant training and without mediation of any muscle activity. The acquired skill allows communication even in total locked-in states.

Modification of slow cortical potentials in patients with refractory epilepsy: a controlled outcome study.

Summary:  Purpose: To compare self‐regulation of low‐frequency EEG components (slow cortical potentials, SCPs) with other methods of seizure control for patients with drug‐refractory partial epilepsy and to separate the real anticonvulsive effect from placebo effects.

Psychobiology of altered states of Consciousness

The article reviews the current knowledge regarding altered states of consciousness (ASC) (a) occurring spontaneously, (b) evoked by physical and physiological stimulation, (c) induced by psychological means, and (d) caused by diseases. The emphasis is laid on psychological and neurobiological approaches. The phenomenological analysis of the multiple ASC resulted in 4 dimensions by which they can be characterized: activation, awareness span, self-awareness, and sensory dynamics. The neurophysiological approach revealed that the different states of consciousness are mainly brought about by a compromised brain structure, transient changes in brain dynamics (disconnectivity), and neurochemical and metabolic processes. Besides these severe alterations, environmental stimuli, mental practices, and techniques of self-control can also temporarily alter brain functioning and conscious experience.

A Brain-Computer Interface Controlled Auditory Event-Related Potential (P300) Spelling System for Locked-In Patients

Using brain–computer interfaces (BCI) humans can select letters or other targets on a computer screen without any muscular involvement. An intensively investigated kind of BCI is based on the recording of visual event‐related brain potentials (ERP). However, some severely paralyzed patients who need a BCI for communication have impaired vision or lack control of gaze movement, thus making a BCI depending on visual input no longer feasible. In an effort to render the ERP–BCI usable for this group of patients, the ERP–BCI was adapted to auditory stimulation. Letters of the alphabet were assigned to cells in a 5 × 5 matrix. Rows of the matrix were coded with numbers 1 to 5, and columns with numbers 6 to 10, and the numbers were presented auditorily. To select a letter, users had to first select the row and then the column containing the desired letter. Four severely paralyzed patients in the end‐stage of a neurodegenerative disease were examined. All patients performed above chance level. Spelling accuracy was significantly lower with the auditory system as compared with a similar visual system. Patients reported difficulties in concentrating on the task when presented with the auditory system. In future studies, the auditory ERP–BCI should be adjusted by taking into consideration specific features of severely paralyzed patients, such as reduced attention span. This adjustment in combination with more intensive training will show whether an auditory ERP–BCI can become an option for visually impaired patients.

Predicting coma and other low responsive patients outcome using event-related brain potentials: A meta-analysis

OBJECTIVE A meta-analysis was performed to estimate the predictive power (odd ratio, OR) for awakening of auditory event-related potential (ERP) components in low responsive patients with stroke or hemorrhage, trauma, anoxic, post-operative, and metabolic encephalopathy etiologies. METHODS We reviewed MEDLINE and analyzed citations for retrieved articles. Logistic regressions were applied on patient samples (Glasgow Coma Scale <12) across and for separate etiologies. RESULTS For stroke and hemorrhage the ORs with 95% confidence intervals were: 2.05 [1.12-3.75] (N100), 4.47 [1.92-10.44] (MMN), 10.29 [2.00-52.79] (P300), for trauma: 1.63 [0.70-3.80] (N100), 4.72 [1.35-16.44] (MMN), 12.89 [4.82-34.43] (P300), anoxic: 8.03 [2.83-22.75] (N100), 15.50 [4.27-56.26] (MMN), 5.93 [2.38-14.77] (P300), post-operative: 10.66 [1.98-57.50] (N100), metabolic encephalopathy: 2.12 [0.34-13.13] (N100), 3.60 [0.28-46.36] (MMN), 7.71 [0.75-79.77] (P300), and all etiologies: 2.85 [1.91-4.27] (N100), 6.53 [3.55-12.01] (MMN), and 8.79 [4.88-15.83] (P300). Based on six N100 studies (N=548 patients), five MMN studies (N=470), and six P300 studies (N=313), the N100, MMN, or P300, when present, significantly predicted awakening, P300 and MMN being significantly better predictors than N100. CONCLUSIONS The MMN and P300 appear to be reliable predictors of awakening. SIGNIFICANCE The prognostic assessment of low responsive patients with auditory ERP should take into account both MMN and P300.

Event-related potentials, cognition, and behavior: a biological approach.

The prevailing cognitive-psychological accounts of event-related brain potentials (ERPs) assume that ERP components manifest information processing operations leading from stimulus to response. Since this view encounters numerous difficulties already analyzed in previous studies, an alternative view is presented here that regards cortical control of behavior as a repetitive sensorimotor cycle consisting of two phases: (i) feedforward anticipation and (ii) feedback cortical performance. This view allows us to interpret in an integrative manner numerous data obtained from very different domains of ERP studies: from biophysics of ERP waves to their relationship to the processing of language, in which verbal behavior is viewed as likewise controlled by the same two basic control processes: feedforward (hypothesis building) and feedback (hypothesis checking). The proposed approach is intentionally simplified, explaining numerous effects on the basis of few assumptions and relating several levels of analysis: neurophysiology, macroelectrical processes (i.e. ERPs), cognition and behavior. It can, therefore, be regarded as a first approximation to a general theory of ERPs.

Brain–computer interfaces for communication with nonresponsive patients

A substantial number of patients who survive severe brain injury progress to a nonresponsive state of wakeful unawareness, referred to as a vegetative state (VS). They appear to be awake, but show no signs of awareness of themselves, or of their environment in repeated clinical examinations. However, recent neuroimaging research demonstrates that some VS patients can respond to commands by willfully modulating their brain activity according to instruction. Brain–computer interfaces (BCIs) may allow such patients to circumvent the barriers imposed by their behavioral limitations and communicate with the outside world. However, although such devices would undoubtedly improve the quality of life for some patients and their families, developing BCI systems for behaviorally nonresponsive patients presents substantial technical and clinical challenges. Here we review the state of the art of BCI research across noninvasive neuroimaging technologies, and propose how such systems should be developed further to provide fully fledged communication systems for behaviorally nonresponsive populations. Ann Neurol 2012;72:312–323