How brain-computer interface technology may improve the diagnosis of the disorders of consciousness: A comparative study

ObjectiveClinical assessment of consciousness relies on behavioural assessments, which have several limitations. Hence, disorder of consciousness (DOC) patients are often misdiagnosed. In this work, we aimed to compare the repetitive assessment of consciousness performed with a clinical behavioural and a Brain-Computer Interface (BCI) approach. Materials and methodsFor 7 weeks, sixteen DOC patients participated in weekly evaluations using both the Coma Recovery Scale-Revised (CRS-R) and a vibrotactile P300 BCI paradigm. To use the BCI, patients had to perform an active mental task that required detecting specific stimuli while ignoring other stimuli. We analysed the reliability and the efficacy in the detection of command following resulting from the two methodologies. ResultsOver repetitive administrations, the BCI paradigm detected command following before the CRS-R in seven patients. Four clinically unresponsive patients consistently showed command following during the BCI assessments. ConclusionBrain-Computer Interface active paradigms might contribute to the evaluation of the level of consciousness, increasing the diagnostic precision of the clinical bedside approach. SignificanceThe integration of different diagnostic methods leads to a better knowledge and care for the DOC

EEG-based Brain-Computer Interfaces for people with Disorders of Consciousness: Features and applications. A systematic review

Background: Disorders of Consciousness (DoC) are clinical conditions following a severe acquired brain injury (ABI) characterized by absent or reduced awareness, known as coma, Vegetative State (VS)/Unresponsive Wakefulness Syndrome (VS/UWS), and Minimally Conscious State (MCS). Misdiagnosis rate between VS/UWS and MCS is attested around 40% due to the clinical and behavioral fluctuations of the patients during bedside consciousness assessments. Given the large body of evidence that some patients with DoC possess "covert" awareness, revealed by neuroimaging and neurophysiological techniques, they are candidates for intervention with brain-computer interfaces (BCIs). Objectives: The aims of the present work are (i) to describe the characteristics of BCI systems based on electroencephalography (EEG) performed on DoC patients, in terms of control signals adopted to control the system, characteristics of the paradigm implemented, classification algorithms and applications (ii) to evaluate the performance of DoC patients with BCI. Methods: The search was conducted on Pubmed, Web of Science, Scopus and Google Scholar. The PRISMA guidelines were followed in order to collect papers published in english, testing a BCI and including at least one DoC patient. Results: Among the 527 papers identified with the first run of the search, 27 papers were included in the systematic review. Characteristics of the sample of participants, behavioral assessment, control signals employed to control the BCI, the classification algorithms, the characteristics of the paradigm, the applications and performance of BCI were the data extracted from the study. Control signals employed to operate the BCI were: P300 (N = 19), P300 and Steady-State Visual Evoked Potentials (SSVEP; hybrid system, N = 4), sensorimotor rhythms (SMRs; N = 5) and brain rhythms elicited by an emotional task (N = 1), while assessment, communication, prognosis, and rehabilitation were the possible applications of BCI in DoC patients. Conclusion: Despite the BCI is a promising tool in the management of DoC patients, supporting diagnosis and prognosis evaluation, results are still preliminary, and no definitive conclusions may be drawn; even though neurophysiological methods, such as BCI, are more sensitive to covert cognition, it is suggested to adopt a multimodal approach and a repeated assessment strategy

Komunikacja w grupie pacjentów z zaburzeniami świadomości – wnioskiz projektu InteRDoCTor

Thanks to recent advances in health care an increased number of patients may recover from  severe brain injuries, but some of them are still assessed as non-responsive. Reliance on behavioural measures in communication with DoC patients seems be too prone to errors. There is need for solutions providing more objective attempts of bidirectional communication (intentional questions/commands and adequate related responses) in patients with DoC using significant processed by the patient stimuli and novel technologies (EEG-, fMRI-, BCI-based, etc.) based on recent scientific and clinical evidences. Such communication may be fulfilled even in the absence of behavior.This article aims at assessment the extent to which current possibilities in the area of devices for extended communication has been exploited, including own experiences within InteRDoCTor project.Dzięki najnowszym osiągnięciom w opiece zdrowotnej coraz większa liczba pacjentów może powrócić do zdrowia z poważnych urazów mózgu, lecz część z nich jest ciągle diagnozowana jako niereagujący na bodźce. Poleganie jedy-nie na miarach behawioralnych w komunikacji z pacjentami z zaburzeniami świadomości wydaje się zbyt podatne na błędy. Istnieje zapotrzebowanie na rozwiązania zapewniające bardziej obiektywne próby komunikacji dwukierunkowej (celowe pytania/polecenia i odpowiadające im reakcje)u pacjentów z zaburzeniami świadomości, z wykorzystaniem bodźców znaczących dla pacjenta i przetwarzanych przez niego oraz nowych technologii (opartych na EEG, fMRI, BCI, itd.) w oparciu o najnowsze dowody naukowe i kliniczne. Ww. komunikacja może być realizowana nawet w przypadku braku obserwowalnych zmian zachowania pacjenta.Artykuł ma na celu ocenę, w jakim zakresie wykorzystuje się możliwości w tym obszarze, w tym w oparciu o doświadczenia własne z projektu InteRDoCTor

Communication in patients with disorders of consciousness – lessons learned From InteRDoCTor project

Thanks to recent advances in health care an increased number of patients may recover from  severe brain injuries, but some of them are still assessed as non-responsive. Reliance on behavioural measures in communication with DoC patients seems be too prone to errors. There is need for solutions providing more objective attempts of bidirectional communication (intentional questions/commands and adequate related responses) in patients with DoC using significant processed by the patient stimuli and novel technologies (EEG-, fMRI-, BCI-based, etc.) based on recent scientific and clinical evidences. Such communication may be fulfilled even in the absence of behavior. This article aims at assessment the extent to which current possibilities in the area of devices for extended communication has been exploited, including own experiences within InteRDoCTor project.Dzięki najnowszym osiągnięciom w opiece zdrowotnej coraz większa liczba pacjentów może powrócić do zdrowia z poważnych urazów mózgu, lecz część z nich jest ciągle diagnozowana jako niereagujący na bodźce. Poleganie jedy-nie na miarach behawioralnych w komunikacji z pacjentami z zaburzeniami świadomości wydaje się zbyt podatne na błędy. Istnieje zapotrzebowanie na rozwiązania zapewniające bardziej obiektywne próby komunikacji dwukierunkowej (celowe pytania/polecenia i odpowiadające im reakcje)u pacjentów z zaburzeniami świadomości, z wykorzystaniem bodźców znaczących dla pacjenta i przetwarzanych przez niego oraz nowych technologii (opartych na EEG, fMRI, BCI, itd.) w oparciu o najnowsze dowody naukowe i kliniczne. Ww. komunikacja może być realizowana nawet w przypadku braku obserwowalnych zmian zachowania pacjenta. Artykuł ma na celu ocenę, w jakim zakresie wykorzystuje się możliwości w tym obszarze, w tym w oparciu o doświadczenia własne z projektu InteRDoCTor

BCI performance and brain metabolism profile in severely brain-injured patients without response to command at bedside

peer reviewedDetection and interpretation of signs of "covert command following" in patients with disorders of consciousness (DOC) remains a challenge for clinicians. In this study, we used a tactile P3-based BCI in 12 patients without behavioral command following, attempting to establish "covert command following." These results were then confronted to cerebral metabolism preservation as measured with glucose PET (FDG-PET). One patient showed "covert command following" (i.e., above-threshold BCI performance) during the active tactile paradigm. This patient also showed a higher cerebral glucose metabolism within the language network (presumably required for command following) when compared with the other patients without "covert command-following" but having a cerebral glucose metabolism indicative of minimally conscious state. Our results suggest that the P3-based BCI might probe "covert command following" in patients without behavioral response to command and therefore could be a valuable addition in the clinical assessment of patients with DOC

A P300 Based Cognitive Assessment Battery for Severely Motor-impaired and Overtly Non-responsive Patients

Diagnosing disorders of consciousness (DOC) is notoriously difficult, with estimates of misdiagnosis rates as high as 40%. Moreover, recent studies have demonstrated that patients who do not show signs of volitional motor responses can exhibit preserved command following detected by functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Although these patients clearly retain some cognitive abilities, lack of consistent motor responses makes administration of standard neuropsychological tests impossible. Consequently, the extent of their cognitive function is unknown. In the current study, we developed and validated a P300b event related potential (ERP) neuropsychological battery in healthy participants to assess components of executive function without requiring motor output. First, participants were instructed to attend to a target auditory stimulus. P300b responses to attended relative to unattended stimuli were used as a neural proxy for detecting command following. To assess working memory capacity we adapted a digit span test to use a similar P300b response mechanism. Finally, reasoning was assessed by adapting a verbal reasoning task in the same manner. At the group level, and in a large majority of participants at the single-participant level, accurate performance could be detected using the P300b ERP, validating the potential utility of the battery. Additionally, the normalized magnitude of the P300b predicted individual differences in performance, but only when a suitable level of variability between participants was present. A post hoc Monte Carlo analysis was conducted to examine the necessary time required to conduct the battery as well as the interaction between time and performance in determining statistically significant performance. At 100% accuracy, a mean time of five minutes was required to achieve a significant result, with time increasing as a function of decreasing performance. These results demonstrate that covert control of attention, as measured by the P300b ERP, can be used to assess command following, working memory and reasoning abilities with a high degree of reliabilit

Decoding Mental States after Severe Brain Injury

Some patients with disorders of consciousness retain sensory and cognitive abilities that are not apparent from their outward behaviour. It is crucial to identify and characterise these covert abilities for diagnosis, prognosis, and medical ethics. This thesis uses neuroimaging techniques to investigate cognitive preservation and awareness in patients who are behaviourally non-responsive due to acquired brain injuries. In the first chapter, a large sample of healthy volunteers, including experienced athletes and musicians, imagined actions of varying complexity and familiarity. Motor imagery involving certain complex, familiar actions correlated with a more robust sensorimotor rhythm. In the second chapter, several patients with disorders of consciousness participated in multiple experiments based on neural responses to mental imagery, including one task featuring complex, familiar imagined actions. Although the patients did not generate enhanced sensorimotor rhythms for the complex, familiar motor imagery, the detection of covert cognition was more sensitive owing to the multi-modal nature of the assessment. In the final empirical chapter, a sample of healthy volunteers and a heterogeneous cohort of patients with disorders of consciousness completed a novel oddball task based on tactile stimulation. Critically, this task delineated an attentional hierarchy in the patient sample, and patients with the ability to follow commands were differentiated from those unable to do so by event-related potential evidence of attentional orienting. Due to the heterogeneity of aetiology and pathology in the disorders of consciousness, these patients vary in their suitability for neuroimaging, the preservation of neural structures, and the cognitive resources available to them. Assessments of several perceptual and cognitive abilities supported by spatially-distinct brain regions and indexed by multiple neural signatures are therefore required to accurately characterise a patient’s abilities and probable subjective experience

Electrophysiological investigations of brain function in coma, vegetative and minimally conscious patients.

Electroencephalographic activity in the context of disorders of consciousness is a swiss knife like tool that can evaluate different aspects of cognitive residual function, detect consciousness and provide a mean to communicate with the outside world without using muscular channels. Standard recordings in the neurological department offer a first global view of the electrogenesis of a patient and can spot abnormal epileptiform activity and therefore guide treatment. Although visual patterns have a prognosis value, they are not sufficient to provide a diagnosis between vegetative state/unresponsive wakefulness syndrome (VS/UWS) and minimally conscious state (MCS) patients. Quantitative electroencephalography (qEEG) processes the data and retrieves features, not visible on the raw traces, which can then be classified. Current results using qEEG show that MCS can be differentiated from VS/UWS patients at the group level. Event Related Potentials (ERP) are triggered by varying stimuli and reflect the time course of information processing related to the stimuli from low-level peripheral receptive structures to high-order associative cortices. It is hence possible to assess auditory, visual, or emotive pathways. Different stimuli elicit positive or negative components with different time signatures. The presence of these components when observed in passive paradigms is usually a sign of good prognosis but it cannot differentiate VS/UWS and MCS patients. Recently, researchers have developed active paradigms showing that the amplitude of the component is modulated when the subject's attention is focused on a task during stimulus presentation. Hence significant differences between ERPs of a patient in a passive compared to an active paradigm can be a proof of consciousness. An EEG-based brain-computer interface (BCI) can then be tested to provide the patient with a communication tool. BCIs have considerably improved the past two decades. However they are not easily adaptable to comatose patients as they can have visual or auditory impairments or different lesions affecting their EEG signal. Future progress will require large databases of resting state-EEG and ERPs experiment of patients of different etiologies. This will allow the identification of specific patterns related to the diagnostic of consciousness. Standardized procedures in the use of BCIs will also be needed to find the most suited technique for each individual patient.Peer reviewe

BRAIN COMPUTER INTERFACE (BCI) ON ATTENTION: A SCOPING REVIEW

Technological innovations are now an integral part of healthcare. Brain-computer interface (BCI) is a novel technological intervention system that is useful in restoring function to people disabled by neurological disorders such as attention deficit hyperactivity disorder (ADHD), amyotrophic lateral sclerosis (ALS), cerebral palsy, stroke, or spinal cord injury. This paper surveys the literature concerning the effectiveness of BCI on attention in subjects under various conditions. The findings of this scoping review are that studies have been made on ADHD, ALS, ASD subjects, and subjects recovering from brain and spinal cord injuries. BCI based neurofeedback training is seen to be effective in improving attention in these subjects. Some studies have also been made on healthy subjects.BCI based neurofeedback training promises neurocognitive improvement and EEG changes in the elderly. Different cognitive assessments have been tried on healthy adults.   From this review, it is evident that hardly any research has been done on using BCI for enhancing attention in post-stroke subjects. So there arises the necessity for making a study on the effects of BCI based attention training in post-stroke subjects, as attention is the key for learning motor skills that get impaired following a stroke. Currently, many researches are underway to determine the effects of a BCI based training program for the enhancement of attention in post-stroke subjects