Tamara Matuz

A P300-based brain–computer interface for people with amyotrophic lateral sclerosis

OBJECTIVE The current study evaluates the efficacy of a P300-based brain-computer interface (BCI) communication device for individuals with advanced ALS. METHODS Participants attended to one cell of a N x N matrix while the N rows and N columns flashed randomly. Each cell of the matrix contained one character. Every flash of an attended character served as a rare event in an oddball sequence and elicited a P300 response. Classification coefficients derived using a stepwise linear discriminant function were applied to the data after each set of flashes. The character receiving the highest discriminant score was presented as feedback. RESULTS In Phase I, six participants used a 6 x 6 matrix on 12 separate days with a mean rate of 1.2 selections/min and mean online and offline accuracies of 62% and 82%, respectively. In Phase II, four participants used either a 6 x 6 or a 7 x 7 matrix to produce novel and spontaneous statements with a mean online rate of 2.1 selections/min and online accuracy of 79%. The amplitude and latency of the P300 remained stable over 40 weeks. CONCLUSIONS Participants could communicate with the P300-based BCI and performance was stable over many months. SIGNIFICANCE BCIs could provide an alternative communication and control technology in the daily lives of people severely disabled by ALS.

Depression and anxiety in individuals with amyotrophic lateral sclerosis : Epidemiology and management

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease with no curative treatment. Considering the devastating nature of the disease, a high prevalence of depression and anxiety in affected patients would be expected. A review of the literature shows prevalence rates for depression in ALS patients ranging from 0% to 44%, but studies using the structured interview according to DSM-IV criteria find highly consistent rates of 9–11%. Prevalence rates for anxiety in ALS range from 0% to 30%.Depression and anxiety appear to be not always properly addressed aspects of ALS, as there are only a few references in the literature about psychological and pharmacological interventions. Additionally, pharmacological antidepressant therapy is often not continuously monitored and its effectiveness remains unevaluated. A review of the literature and our own experiences show that there is a lack of psychological care and, to our knowledge, there is no specific psychological intervention method for ALS patients.Concerning pharmacological treatment of depression in patients with ALS, there is broad consensus among clinical experts that SSRIs and TCAs are helpful, but there have been no controlled clinical studies of these medications in ALS patients. TCAs can be prescribed if anticholinergic effects are desired simultaneously for treating pseudohypersalivation or insomnia. Anxiety is usually treated with anxiolytics, but again there have been no systematic studies of these drugs in patients with ALS.For psychological intervention we suggest a cognitive behavioural approach, which has to be integrated into an intervention programme that includes teaching of appropriate coping strategies and reappraisal skills and encourages engagement in activities that are still practicable and pleasant. We propose that the treatment of depression and anxiety should involve both cognitive behavioural therapy and pharmacological intervention. Pharmacological treatment should be strictly monitored for effectiveness. To date, no clinical trials are available that would allow us to recommend pharmacotherapy over psychotherapy or vice versa; however, evidence from other patient groups, such as elderly patients diagnosed with major depressive disorder, suggests that a combination of both therapies has the potential to also improve depression and anxiety in patients with ALS.

Coping with amyotrophic lateral sclerosis: an integrative view

Objectives To identify predictors of psychosocial adjustment to motor neurone disease. Methods A total of 27 individuals with a confirmed diagnosis of amyotrophic lateral sclerosis (ALS) participated in the study. The ALS functional rating scale mean score indicated a high physical impairment of the sample. Months since diagnosis varied between 4 and 129 (median 36). Adjustment outcomes were severity of depressive symptoms and individual quality of life (QoL). Predictors included social support, cognitive appraisal, coping strategies and illness parameters. Results Multiple regression analysis revealed that approximately 60% of the variance of depression and QoL were accounted for by social support, coping strategies and cognitive appraisal. The degree of physical impairment did not explain any variance of the adjustment outcomes. The best predictors for the severity of depressive symptoms were perceived social support and appraisal of coping potential (internal locus of control) and for individual QoL perceived social support. Conclusions The focus on medical issues in treatment of ALS is not sufficient. A palliative approach to ALS must equally imply advice with regards to adequate coping strategies, provide the adequate amount of disease- and support-related information at any one time, and encourage patients to seek social support. Sufficient medication and psychotherapy has to be provided for those patients who show depressive symptoms or disorder.

Usability and Workload of Access Technology for People With Severe Motor Impairment: A Comparison of Brain-Computer Interfacing and Eye Tracking

Background. Eye trackers are widely used among people with amyotrophic lateral sclerosis, and their benefits to quality of life have been previously shown. On the contrary, Brain-computer interfaces (BCIs) are still quite a novel technology, which also serves as an access technology for people with severe motor impairment. Objective. To compare a visual P300-based BCI and an eye tracker in terms of information transfer rate (ITR), usability, and cognitive workload in users with motor impairments. Methods. Each participant performed 3 spelling tasks, over 4 total sessions, using an Internet browser, which was controlled by a spelling interface that was suitable for use with either the BCI or the eye tracker. At the end of each session, participants evaluated usability and cognitive workload of the system. Results. ITR and System Usability Scale (SUS) score were higher for the eye tracker (Wilcoxon signed-rank test: ITR T = 9, P = .016; SUS T = 12.50, P = .035). Cognitive workload was higher for the BCI (T = 4; P = .003). Conclusions. Although BCIs could be potentially useful for people with severe physical disabilities, we showed that the usability of BCIs based on the visual P300 remains inferior to eye tracking. We suggest that future research on visual BCIs should use eye tracking–based control as a comparison to evaluate performance or focus on nonvisual paradigms for persons who have lost gaze control.

A telepresence robotic system operated with a P300-based brain-computer interface: Initial tests with ALS patients

Brain-computer interfaces (BCIs) open a new valuable communication channel for people with severe neurological or motor degenerative diseases, such as ALS patients. On the other hand, the ability to teleoperate robots in a remote scenario provides a physical entity embodied in a real environment ready to perceive, explore, and interact. The combination of both functionalities provides a system with benefits for ALS patients in the context of neurorehabilitation or maintainment of the neural activity. This paper reports a BCI telepresence system which offers navigation, exploration and bidirectional communication, only controlled by brain activity; and an initial study of applicability with ALS patients. The results show the feasibility of this technology in real patients.

Auditory habituation in the fetus and neonate: an fMEG study.

Habituation--the most basic form of learning--is used to evaluate central nervous system (CNS) maturation and to detect abnormalities in fetal brain development. In the current study, habituation, stimulus specificity and dishabituation of auditory evoked responses were measured in fetuses and newborns using fetal magnetoencephalography (fMEG). An auditory habituation paradigm consisting of 100 trains of five 500 Hz tones, one 750 Hz tone (dishabituator) and two more 500 Hz tones, respectively, were presented to 41 fetuses (gestational age 30-39 weeks) and 22 newborns or babies (age 6-89 days). A response decrement between the first and fifth tones (habituation), an increment between the fifth tone and the dishabituator (stimulus specificity) and an increment between the fifth (last tone before the dishabituator) and seventh tones (first tone after the dishabituator) (dishabituation) were expected. Fetuses showed weak responses to the first tone. However, a significant response decrement between the second and fifth tones (habituation) and a significant increment between the fifth tone and the dishabituator (stimulus specificity) were found. No significant difference was found for dishabituation nor was a developmental trend found at the group level. From the neonatal data, significant values for stimulus specificity were found. Sensory fatigue or adaptation was ruled out as a reason for the response decrement due to the strong reactions to the dishabituator. Taken together, the current study used fMEG to directly show fetal habituation and provides evidence of fetal learning in the last trimester of pregnancy.

Habituation of visual evoked responses in neonates and fetuses: A MEG study

In this study we aimed to develop a habituation paradigm that allows the investigation of response decrement and response recovery and examine its applicability for measuring the habituation of the visually evoked responses (VERs) in neonatal and fetal magnetoencephalographic recordings. Two paradigms, one with a long and one with a short inter-train interval (ITI), were developed and tested in separate studies. Both paradigms consisted of a train of four light flashes; each train being followed by a 500Hz burst tone. Healthy pregnant women underwent two prenatal measurements and returned with their babies for a neonatal investigation. The amplitudes of the neonatal VERs in the long-ITI condition showed within-train response decrement. An increased response to the auditory dishabituator was found confirming response recovery. In the short-ITI condition, neonatal amplitude decrement could not be demonstrated while response recovery was present. In both ITI conditions, the response rate of the cortical responses was much lower in the fetuses than in the neonates. Fetal VERs in the long-ITI condition indicate amplitude decline from the first to the second flash with no further decrease. The long-ITI paradigm might be useful to investigate habituation of the VERs in neonates and fetuses, although the latter requires precaution.

Brain-computer interface and semantic classical conditioning of communication in paralysis.

We propose a classical semantic conditioning procedure to allow basic yes-no communication in the completely locked-in state as an alternative to instrumental-operant learning of brain responses, which is the common approach in brain-computer interface research. More precisely, it was intended to establish cortical responses to the trueness of a statement irrespective of the particular constituent words and letters or sounds of the words. As unconditioned stimulus short aversive stimuli consisting of 1-ms electrical pulses were used. True and false statements were presented acoustically and only the true statements were immediately followed by electrical stimuli. 15 healthy participants and one locked-in ALS patient underwent the experiment. Three different classifiers were employed in order to differentiate between the two cortical responses by means of electroencephalographic recordings. The offline analysis revealed that semantic classical conditioning can be applied successfully to enable basic communication using a non-muscular channel.

Prediction of P300 BCI Aptitude in Severe Motor Impairment

Brain-computer interfaces (BCIs) provide a non-muscular communication channel for persons with severe motor impairments. Previous studies have shown that the aptitude with which a BCI can be controlled varies from person to person. A reliable predictor of performance could facilitate selection of a suitable BCI paradigm. Eleven severely motor impaired participants performed three sessions of a P300 BCI web browsing task. Before each session auditory oddball data were collected to predict the BCI aptitude of the participants exhibited in the current session. We found a strong relationship of early positive and negative potentials around 200 ms (elicited with the auditory oddball task) with performance. The amplitude of the P2 (r  =  −0.77) and of the N2 (r  =  −0.86) had the strongest correlations. Aptitude prediction using an auditory oddball was successful. The finding that the N2 amplitude is a stronger predictor of performance than P3 amplitude was reproduced after initially showing this effect with a healthy sample of BCI users. This will reduce strain on the end-users by minimizing the time needed to find suitable paradigms and inspire new approaches to improve performance.

Auditory habituation to simple tones: reduced evidence for habituation in children compared to adults

Habituation—the response decrement to repetitively presented stimulation—is a basic cognitive capability and suited to investigate development and integrity of the human brain. To evaluate the developmental process of auditory habituation, the current study used magnetoencephalography (MEG) to investigate auditory habituation, dishabituation and stimulus specificity in children and adults and compared the results between age groups. Twenty-nine children (Mage = 9.69 years, SD ± 0.47) and 14 adults (Mage = 29.29 years, SD ± 3.47) participated in the study and passively listened to a habituation paradigm consisting of 100 trains of tones which were composed of five 500 Hz tones, one 750 Hz tone (dishabituator) and another two 500 Hz tones, respectively while focusing their attention on a silent movie. Adults showed the expected habituation and stimulus specificity within-trains while no response decrement was found between trains. Sensory adaptation or fatigue as a source for response decrement in adults is unlikely due to the strong reaction to the dishabituator (stimulus specificity) and strong mismatch negativity (MMN) responses. However, in children neither habituation nor dishabituation or stimulus specificity could be found within-trains, response decrement was found across trains. It can be speculated that the differences between children and adults are linked to differences in stimulus processing due to attentional processes. This study shows developmental differences in task-related brain activation and discusses the possible influence of broader concepts such as attention, which should be taken into account when comparing performance in an identical task between age groups.