Woosang Cho

Complete Locked-in and Locked-in Patients: Command Following Assessment and Communication with Vibro-Tactile P300 and Motor Imagery Brain-Computer Interface Tools

Many patients with locked-in syndrome (LIS) or complete locked-in syndrome (CLIS) also need brain-computer interface (BCI) platforms that do not rely on visual stimuli and are easy to use. We investigate command following and communication functions of mindBEAGLE with 9 LIS, 3 CLIS patients and three healthy controls. This tests were done with vibro-tactile stimulation with 2 or 3 stimulators (VT2 and VT3 mode) and with motor imagery (MI) paradigms. In VT2 the stimulators are fixed on the left and right wrist and the participant has the task to count the stimuli on the target hand in order to elicit a P300 response. In VT3 mode an additional stimulator is placed as a distractor on the shoulder and the participant is counting stimuli either on the right or left hand. In motor imagery mode the participant is instructed to imagine left or right hand movement. VT3 and MI also allow the participant to answer yes and no questions. Healthy controls achieved a mean assessment accuracy of 100% in VT2, 93% in VT3, and 73% in MI modes. They were able to communicate with VT3 (86.7%) and MI (83.3%) after 2 training runs. The patients achieved a mean accuracy of 76.6% in VT2, 63.1% in VT3, and 58.2% in MI modes after 1–2 training runs. 9 out of 12 LIS patients could communicate by using the vibro-tactile P300 paradigms (answered on average 8 out of 10 questions correctly) and 3 out of 12 could communicate with the motor imagery paradigm (answered correctly 4,7 out of 5 questions). 2 out of the 3 CLIS patients could use the system to communicate with VT3 (90 and 70% accuracy). The results show that paradigms based on non-visual evoked potentials and motor imagery can be effective for these users. It is also the first study that showed EEG-based BCI communication with CLIS patients and was able to bring 9 out of 12 patients to communicate with higher accuracies than reported before. More importantly this was achieved within less than 15–20 min.

Paired Associative Stimulation using Brain-Computer Interfaces for Stroke Rehabilitation: A Pilot study

Conventional therapies do not provide paralyzed patients with closed-loop sensorimotor integration for motor rehabilitation. Paired associative stimulation (PAS) uses brain-computer interface (BCI) technology to monitor patients’ movement imagery in real-time, and utilizes the information to control functional electrical stimulation (FES) and bar feedback for complete sensorimotor closed loop. To realize this approach, we introduce the recoveriX system, a hardware and software platform for PAS. After 10 sessions of recoveriX training, one stroke patient partially regained control of dorsiflexion in her paretic wrist. A controlled group study is planned with a new version of the recoveriX system, which will use a new FES system and an avatar instead of bar feedback.

Brain-Computer Interfaces With Multi-Sensory Feedback for Stroke Rehabilitation: A Case Study

Conventional therapies do not provide paralyzed patients with closed-loop sensorimotor integration for motor rehabilitation. This work presents the recoveriX system, a hardware and software platform that combines a motor imagery (MI)-based brain-computer interface (BCI), functional electrical stimulation (FES), and visual feedback technologies for a complete sensorimotor closed-loop therapy system for poststroke rehabilitation. The proposed system was tested on two chronic stroke patients in a clinical environment. The patients were instructed to imagine the movement of either the left or right hand in random order. During these two MI tasks, two types of feedback were provided: a bar extending to the left or right side of a monitor as visual feedback and passive hand opening stimulated from FES as proprioceptive feedback. Both types of feedback relied on the BCI classification result achieved using common spatial patterns and a linear discriminant analysis classifier. After 10 sessions of recoveriX training, one patient partially regained control of wrist extension in her paretic wrist and the other patient increased the range of middle finger movement by 1 cm. A controlled group study is planned with a new version of the recoveriX system, which will have several improvements.

Validation of a Brain-Computer Interface (BCI) System Designed for Patients with Disorders of Consciousness (DOC): Regular and Sham Testing with Healthy Participants

Brain-computer interface (BCI) technology is increasingly used to research new methods to provide assessment and communication for patients diagnosed with a disorder of consciousness (DOC). As this technology advances, it could lead to tools that could support clinical diagnoses, provide communication to some persons who cannot otherwise communicate, and further impact families, friends, and carers. Hence, validation studies are needed to ensure that BCI systems that are intended for these patients operate as expected. This study aimed to validate different components of a hardware and software platform that is being used for research with patients with DOC called mindBEAGLE. This real-time EEG system uses four different paradigms for assessment and communication. We assessed regular and sham conditions with healthy participants and report on the resulting EEG data and BCI performance results.

Hemiparetic Stroke Rehabilitation Using Avatar and Electrical Stimulation Basedon Non-invasive Brain Computer Interface

Brain computer interfaces (BCIs) have been employed in rehabilitation training for post-stroke patients. Patients in the chronic stage, and/or with severe paresis, are particularly challenging for conventional rehabilitation. We present results from two such patients who participated in BCI training with first-person avatar feedback. Five assessments were conducted to assess any behavioural changes after the intervention, including the upper extremity Fugl-Meyer assessment (UE-FMA) and 9 hole-peg test (9HPT). Patient 1 (P1) increased his UE-FMA score from 25 to 46 points after the intervention. He could not perform the 9HPT in the first session. After the 18th session, he was able to perform the 9HPT and reduced the time from 10 min 22 sec to 2 min 53 sec. Patient 2 (P2) increased her UE-FMA from 17 to 28 points after the intervention. She could not perform the 9HPT throughout the training session. However, she managed to complete the test in 17 min 17 sec during the post-assessment session. These results show that the feasibility of this BCI approach with chronic patients with severe paresis, and further support the growing consensus that these types of tools might develop into a new paradigm for rehabilitation tool for stroke patients. However, the results are from only two chronic stroke patients. This approach should be further validated in broader randomized controlled studies involving more patients.

Feasibility of Brain-Computer Interface Triggered Functional Electrical Stimulation and Avatar for Motor Improvement in Chronic Stroke Patients

We present the feasibility of a complete rehabilitation system based on brain computer interface (BCI) triggered functional electrical stimulation (FES) and avatar mirroring to improve the function of the paretic limbs. The system was tested on two chronic stroke patients with 25 BCI training sessions over 13 weeks. The Upper-Extremity Fugl-Meyer Assessment (FMA-UE) and the Modified Ashworth Scale (MAS) were improved in both patients, however, one patient showed more improvement than the other, for whom the longer time since the stroke (31 years vs. 4 years), no residual motor function in the paretic wrist, and poor BCI performance may have limited recovery. Randomized controlled studies are necessary to show the effectiveness of the BCI-FES-avatar system with a larger sample size and matched parameters between test and control groups.

Assessing command-following and communication with vibro-tactile P300 brain-computer interface tools in patients with unresponsive wakefulness syndrome

Persons diagnosed with disorders of consciousness (DOC) typically suffer from motor disablities, and thus assessing their spared cognitive abilities can be difficult. Recent research from several groups has shown that non-invasive brain-computer interface (BCI) technology can provide assessments of these patients cognitive function that can supplement information provided through conventional behavioral assessment methods. In rare cases, BCIs may provide a binary communication mechanism. Here, we present results from a vibrotactile BCI assessment aiming at detecting command-following and communication in 12 unresponsive wakefulness syndrome (UWS) patients. Two different paradigms were administered at least once for every patient: (i) VT2 with two vibro-tactile stimulators fixed on the patients left and right wrists and (ii) VT3 with three vibro-tactile stimulators fixed on both wrists and on the back. The patients were instructed to mentally count either the stimuli on the left or right wrist, which may elicit a robust P300 for the target wrist only. The EEG data from −100 to +600 ms around each stimulus were extracted and sub-divided into 8 data segments. This data was classified with linear discriminant analysis (using a 10 × 10 cross validation) and used to calibrate a BCI to assess command following and YES/NO communication abilities. The grand average VT2 accuracy across all patients was 38.3%, and the VT3 accuracy was 26.3%. Two patients achieved VT3 accuracy ≥80% and went through communication testing. One of these patients answered 4 out of 5 questions correctly in session 1, whereas the other patient answered 6/10 and 7/10 questions correctly in sessions 2 and 4. In 6 other patients, the VT2 or VT3 accuracy was above the significance threshold of 23% for at least one run, while in 4 patients, the accuracy was always below this threshold. The study highlights the importance of repeating EEG assessments to increase the chance of detecting command-following in patients with severe brain injury. Furthermore, the study shows that BCI technology can test command following in chronic UWS patients and can allow some of these patients to answer YES/NO questions.

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

Detection 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.

MindBEAGLE — A new system for the assessment and communication with patients with disorders of consciousness and complete locked-in syndrom

Patients with disorders of consciousness (DOC) cannot reply to questions or clinical assessments using voluntary motor control, and therefore it is very difficult to assess their cognitive capabilities and conscious awareness. Patients who are locked-in (LIS) are instead fully conscious, and they can communicate with their preserved eye movements. However, when the residual oculomotor activity is also lost (e.g., patients with amyotrophic lateral sclerosis disease of very long duration), the locked-in status becomes complete (CLIS). In CLIS patients, detection of conscious awareness may become very challenging, similarly to the subjects with DOC. mindBEAGLE has a physiological testing battery that uses auditory, vibro-tactile and motor imagery paradigms and brain-computer interface (BCI) technology to assess these patients and even provide communication for some of them. The current study presents results from 5 DOC and 3 LIS patients. The auditory evoked potential (AEP) assessement led to classification accuracies between 0 and 90 %, the vibro-tactile P300 paradigms led to 0 % to 100 % accuracy and the motor imagery paradigms led to accuracies up to 83.3 %. Three of the eight patients could succcessfully establish communication with the mindBEAGLE system. The results show that an assessment battery with auditory, vibro-tactile and motor imagery paradigms is able to identify cognitive functions of DOC and LIS patients. Patients showed substantial fluctuations in EEG measures, assessment results and communication reliability across different days and runs. Therefore, it is important to have a system available that can quickly and easily determine the status of a patient. Successful communication with these patients is also important.