Visual and auditory event-related potentials in sporadic amyotrophic lateral sclerosis

Auditory attention measured by EEG in neurological populations: systematic review of literature and meta-analysis

Sensorimotor synchronization strategies have been frequently used for gait rehabilitation in different neurological populations. Despite these positive effects on gait, attentional processes required to dynamically attend to the auditory stimuli needs elaboration. Here, we investigate auditory attention in neurological populations compared to healthy controls quantified by EEG recordings. Literature was systematically searched in databases PubMed and Web of Science. Inclusion criteria were investigation of auditory attention quantified by EEG recordings in neurological populations in cross-sectional studies. In total, 35 studies were included, including participants with Parkinson's disease (PD), stroke, Traumatic Brain Injury (TBI), Multiple Sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS). A meta-analysis was performed on P3 amplitude and latency separately to look at the differences between neurological populations and healthy controls in terms of P3 amplitude and latency. Overall, neurological populations showed impairments in auditory processing in terms of magnitude and delay compared to healthy controls. Consideration of individual auditory processes and thereafter selecting and/or designing the auditory structure during sensorimotor synchronization paradigms in neurological physical rehabilitation is recommended.

The Spectrum of Cognitive Dysfunction in Amyotrophic Lateral Sclerosis: An Update

Cognitive dysfunction is an important non-motor symptom in amyotrophic lateral sclerosis (ALS) that has a negative impact on survival and caregiver burden. It shows a wide spectrum ranging from subjective cognitive decline to frontotemporal dementia (FTD) and covers various cognitive domains, mainly executive/attention, language and verbal memory deficits. The frequency of cognitive impairment across the different ALS phenotypes ranges from 30% to 75%, with up to 45% fulfilling the criteria of FTD. Significant genetic, clinical, and pathological heterogeneity reflects deficits in various cognitive domains. Modern neuroimaging studies revealed frontotemporal degeneration and widespread involvement of limbic and white matter systems, with hypometabolism of the relevant areas. Morphological substrates are frontotemporal and hippocampal atrophy with synaptic loss, associated with TDP-43 and other co-pathologies, including tau deposition. Widespread functional disruptions of motor and extramotor networks, as well as of frontoparietal, frontostriatal and other connectivities, are markers for cognitive deficits in ALS. Cognitive reserve may moderate the effect of brain damage but is not protective against cognitive decline. The natural history of cognitive dysfunction in ALS and its relationship to FTD are not fully understood, although there is an overlap between the ALS variants and ALS-related frontotemporal syndromes, suggesting a differential vulnerability of motor and non-motor networks. An assessment of risks or the early detection of brain connectivity signatures before structural changes may be helpful in investigating the pathophysiological mechanisms of cognitive impairment in ALS, which might even serve as novel targets for effective disease-modifying therapies.

Functional Connectivity and Frequency Power Alterations during P300 Task as a Result of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is one of the most aggressive neurodegenerative diseases and is now recognized as a multisystem network disorder with impaired connectivity. Further research for the understanding of the nature of its cognitive affections is necessary to monitor and detect the disease, so this work provides insight into the neural alterations occurring in ALS patients during a cognitive task (P300 oddball paradigm) by measuring connectivity and the power and latency of the frequency-specific EEG activity of 12 ALS patients and 16 healthy subjects recorded during the use of a P300-based BCI to command a robotic arm. For ALS patients, in comparison to Controls, the results (p < 0.05) were: an increment in latency of the peak ERP in the Delta range (OZ) and Alpha range (PO7), and a decreased power in the Beta band among most electrodes; connectivity alterations among all bands, especially in the Alpha band between PO7 and the channels above the motor cortex. The evolution observed over months of an advanced-state patient backs up these findings. These results were used to compute connectivity- and power-based features to discriminate between ALS and Control groups using Support Vector Machine (SVM). Cross-validation achieved a 100% in specificity and 75% in sensitivity, with an overall 89% success.

Habituation of P300 in the Use of P300-based Brain-Computer Interface Spellers: Individuals With Amyotrophic Lateral Sclerosis Versus Age-Matched Controls

The P300-based brain-computer interface speller can provide motor independent communication to individuals with amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative disorder that affects the motor system. P300 amplitude stability is critical for operation of the P300 speller. The P300 has good long-term stability, but to our knowledge, short-term habituation in the P300 speller has not been studied. In the current study, 15 participants: 8 ALS patients and 7 age-matched healthy volunteers (HVs), used 2 versions of P300 spellers, Face speller and Flash speller, each for 30 minutes. The ALS group performed as well as the HVs in both spellers and HVs did better with the Face speller than Flash speller while the ALS group performed equally well in both spellers. Neither intra-run P300 habituation nor inter-run P300 habituation was found. The P300 speller could be a reliable communication device for individuals with ALS.

Signal-detection analysis of the WMS faces subtest: Results in amyotrophic lateral sclerosis patients

About 30% of patients with amyotrophic lateral sclerosis (ALS) suffer from cognitive impairment and 10-15% suffer from frontotemporal dementia (FTD). Due to the patients' reduced motor function, a neuropsychological assessment with a low motor demand can be an advantage when evaluating patients, aiding its application. The present work has studied the usefulness of the Faces subtest of the Wechsler Memory Scale in 42 patients with ALS and 42 healthy volunteers applying Holdnack's Two-High Threshold model. The ALS group performed significantly worse in immediate and delayed discriminability. With respect to the presence of cognitive impairment, it seemed to be independent of the indexes proposed by Holdnack and Delis. On the other hand, motor problems were associated with delayed recognition while behavior alterations were linked to problems with delayed discriminability. ALS patients do not express differences in the bias index, in line with other types of previously studied pathologies.

Electrophysiological correlates of neurodegeneration in motor and non-motor brain regions in amyotrophic lateral sclerosis-implications for brain-computer interfacing

OBJECTIVE

For patients with amyotrophic lateral sclerosis (ALS) who are suffering from severe communication or motor problems, brain-computer interfaces (BCIs) can improve the quality of life and patient autonomy. However, current BCI systems are not as widely used as their potential and patient demand would let assume. This underutilization is a result of technological as well as user-based limitations but also of the comparatively poor performance of currently existing BCIs in patients with late-stage ALS, particularly in the locked-in state.

APPROACH

Here we review a broad range of electrophysiological studies in ALS patients with the aim to identify electrophysiological correlates of ALS-related neurodegeneration in motor and non-motor brain regions in to better understand potential neurophysiological limitations of current BCI systems for ALS patients. To this end we analyze studies in ALS patients that investigated basic sensory evoked potentials, resting-state and task-based paradigms using electroencephalography or electrocorticography for basic research purposes as well as for brain-computer interfacing. Main results and significance. Our review underscores that, similarly to mounting evidence from neuroimaging and neuropathology, electrophysiological measures too indicate neurodegeneration in non-motor areas in ALS. Furthermore, we identify an unexpected gap of basic and advanced electrophysiological studies in late-stage ALS patients, particularly in the locked-in state. We propose a research strategy on how to fill this gap in order to improve the design and performance of future BCI systems for this patient group.

Evaluating Brain-Computer Interface Performance in an ALS Population: Checkerboard and Color Paradigms

The objective of this study was to investigate the performance of 3 brain-computer interface (BCI) paradigms in an amyotrophic lateral sclerosis (ALS) population (n = 11). Using a repeated-measures design, participants completed 3 BCI conditions: row/column (RCW), checkerboard (CBW), and gray-to-color (CBC). Based on previous studies, it is hypothesized that the CBC and CBW conditions will result in higher accuracy, information transfer rate, waveform amplitude, and user preference over the RCW condition. An offline dynamic stopping simulation will also increase information transfer rate. Higher mean accuracy was observed in the CBC condition (89.7%), followed by the CBW (84.3%) condition, and lowest in the RCW condition (78.7%); however, these differences did not reach statistical significance ( P = .062). Eight of the eleven participants preferred the CBC and the remaining three preferred the CBW conditions. The offline dynamic stopping simulation significantly increased information transfer rate ( P = .005) and decreased accuracy ( P < .000). The findings of this study suggest that color stimuli provide a modest improvement in performance and that participants prefer color stimuli over monochromatic stimuli. Given these findings, BCI paradigms that use color stimuli should be considered for individuals who have ALS.

Circadian course of the P300 ERP in patients with amyotrophic lateral sclerosis - implications for brain-computer interfaces (BCI)

Background

Accidents or neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) can lead to progressing, extensive, and complete paralysis leaving patients aware but unable to communicate (locked-in state). Brain-computer interfaces (BCI) based on electroencephalography represent an important approach to establish communication with these patients. The most common BCI for communication rely on the P300, a positive deflection arising in response to rare events. To foster broader application of BCIs for restoring lost function, also for end-users with impaired vision, we explored whether there were specific time windows during the day in which a P300 driven BCI should be preferably applied.

Methods

The present study investigated the influence of time of the day and modality (visual vs. auditory) on P300 amplitude and latency. A sample of 14 patients (end-users) with ALS and 14 healthy age matched volunteers participated in the study and P300 event-related potentials (ERP) were recorded at four different times (10, 12 am, 2, & 4 pm) during the day.

Results

Results indicated no differences in P300 amplitudes or latencies between groups (ALS patients v. healthy participants) or time of measurement. In the auditory condition, latencies were shorter and amplitudes smaller as compared to the visual condition.

Conclusion

Our findings suggest applicability of EEG/BCI sessions in patients with ALS throughout normal waking hours. Future studies using actual BCI systems are needed to generalize these findings with regard to BCI effectiveness/efficiency and other times of day.

Executive Dysfunctions and Event-Related Brain Potentials in Patients with Amyotrophic Lateral Sclerosis

A growing body of evidence implies psychological disturbances in amyotrophic lateral sclerosis (ALS). Specifically, executive dysfunctions occur in up to 50% of ALS patients. The recently shown presence of cytoplasmic aggregates (TDP-43) in ALS patients and in patients with behavioral variants of frontotemporal dementia suggests that these two disease entities form the extremes of a spectrum. The present study aimed at investigating behavioral and electrophysiological indices of conflict processing in patients with ALS. A non-verbal variant of the flanker task demanded two-choice responses to target stimuli that were surrounded by flanker stimuli which either primed the correct response or the alternative response (the latter case representing the conflict situation). Behavioral performance, event-related potentials (ERP), and lateralized readiness potentials (LRP) were analyzed in 21 ALS patients and 20 controls. In addition, relations between these measures and executive dysfunctions were examined. ALS patients performed the flanker task normally, indicating preserved conflict processing. In similar vein, ERP and LRP indices of conflict processing did not differ between groups. However, ALS patients showed enhanced posterior negative ERP waveform deflections, possibly indicating increased modulation of visual processing by frontoparietal networks in ALS. We also found that the presence of executive dysfunctions was associated with more error-prone behavior and enhanced LRP amplitudes in ALS patients, pointing to a prefrontal pathogenesis of executive dysfunctions and to a potential link between prefrontal and motor cortical functional dysregulation in ALS, respectively.

P300-based brain-computer interface (BCI) event-related potentials (ERPs): People with amyotrophic lateral sclerosis (ALS) vs. age-matched controls

OBJECTIVE

Brain-computer interfaces (BCIs) aimed at restoring communication to people with severe neuromuscular disabilities often use event-related potentials (ERPs) in scalp-recorded EEG activity. Up to the present, most research and development in this area has been done in the laboratory with young healthy control subjects. In order to facilitate the development of BCI most useful to people with disabilities, the present study set out to: (1) determine whether people with amyotrophic lateral sclerosis (ALS) and healthy, age-matched volunteers (HVs) differ in the speed and accuracy of their ERP-based BCI use; (2) compare the ERP characteristics of these two groups; and (3) identify ERP-related factors that might enable improvement in BCI performance for people with disabilities.

METHODS

Sixteen EEG channels were recorded while people with ALS or healthy age-matched volunteers (HVs) used a P300-based BCI. The subjects with ALS had little or no remaining useful motor control (mean ALS Functional Rating Scale-Revised 9.4 (±9.5SD) (range 0-25)). Each subject attended to a target item as the items in a 6×6 visual matrix flashed. The BCI used a stepwise linear discriminant function (SWLDA) to determine the item the user wished to select (i.e., the target item). Offline analyses assessed the latencies, amplitudes, and locations of ERPs to the target and non-target items for people with ALS and age-matched control subjects.

RESULTS

BCI accuracy and communication rate did not differ significantly between ALS users and HVs. Although ERP morphology was similar for the two groups, their target ERPs differed significantly in the location and amplitude of the late positivity (P300), the amplitude of the early negativity (N200), and the latency of the late negativity (LN).

CONCLUSIONS

The differences in target ERP components between people with ALS and age-matched HVs are consistent with the growing recognition that ALS may affect cortical function. The development of BCIs for use by this population may begin with studies in HVs but also needs to include studies in people with ALS. Their differences in ERP components may affect the selection of electrode montages, and might also affect the selection of presentation parameters (e.g., matrix design, stimulation rate).

SIGNIFICANCE

P300-based BCI performance in people severely disabled by ALS is similar to that of age-matched control subjects. At the same time, their ERP components differ to some degree from those of controls. Attention to these differences could contribute to the development of BCIs useful to those with ALS and possibly to others with severe neuromuscular disabilities.

Uncinate fasciculus microstructure and verbal episodic memory in amyotrophic lateral sclerosis: a diffusion tensor imaging and neuropsychological study

The present study evaluates the integrity of uncinate fasciculus (UF) and the association between UF microstructure and verbal episodic memory (as one of the cognitive functions linked to UF) in non-demented patients with amyotrophic lateral sclerosis (ALS) using diffusion tensor imaging (DTI). We studied 21 patients with ALS and 11 healthy, demographically-comparable volunteers. Fractional anisotropy, apparent diffusion coefficient, axial and radial diffusivity were the DTI metrics examined. Episodic memory was evaluated with Babcock Story Recall Test and Rey Auditory Verbal Learning Test (RAVLT) for patients; measures of immediate and delayed recall and retention for both tests and sum of words recalled through five learning trials for RAVLT were considered. Patients with ALS showed significant bilateral reduction of axial diffusivity in the UF as compared to controls. Furthermore, there were several significant relations between various DTI metrics (mostly in left hemisphere) and memory measures (specifically for the RAVLT). UF microstructural changes may contribute to ALS-related memory impairment, with word-list learning performance relying more upon the integrity of frontal and temporal connections than memory components associated with story recall.

Epidural electrocorticography for monitoring of arousal in locked-in state

Electroencephalography (EEG) often fails to assess both the level (i.e., arousal) and the content (i.e., awareness) of pathologically altered consciousness in patients without motor responsiveness. This might be related to a decline of awareness, to episodes of low arousal and disturbed sleep patterns, and/or to distorting and attenuating effects of the skull and intermediate tissue on the recorded brain signals. Novel approaches are required to overcome these limitations. We introduced epidural electrocorticography (ECoG) for monitoring of cortical physiology in a late-stage amytrophic lateral sclerosis patient in completely locked-in state (CLIS). Despite long-term application for a period of six months, no implant-related complications occurred. Recordings from the left frontal cortex were sufficient to identify three arousal states. Spectral analysis of the intrinsic oscillatory activity enabled us to extract state-dependent dominant frequencies at <4, ~7 and ~20 Hz, representing sleep-like periods, and phases of low and elevated arousal, respectively. In the absence of other biomarkers, ECoG proved to be a reliable tool for monitoring circadian rhythmicity, i.e., avoiding interference with the patient when he was sleeping and exploiting time windows of responsiveness. Moreover, the effects of interventions addressing the patient's arousal, e.g., amantadine medication, could be evaluated objectively on the basis of physiological markers, even in the absence of behavioral parameters. Epidural ECoG constitutes a feasible trade-off between surgical risk and quality of recorded brain signals to gain information on the patient's present level of arousal. This approach enables us to optimize the timing of interactions and medical interventions, all of which should take place when the patient is in a phase of high arousal. Furthermore, avoiding low-responsiveness periods will facilitate measures to implement alternative communication pathways involving brain-computer interfaces (BCI).

Different Frontal Involvement in ALS and PLS Revealed by Stroop Event-Related Potentials and Reaction Times

BACKGROUND

A growing body of evidence suggests a link between cognitive and pathological changes in amyotrophic lateral sclerosis (ALS) and in frontotemporal lobar degeneration (FTLD). Cognitive deficits have been investigated much less extensively in primary lateral sclerosis (PLS) than in ALS.

OBJECTIVE

To investigate bioelectrical activity to Stroop test, assessing frontal function, in ALS, PLS, and control groups.

METHODS

Thirty-two non-demented ALS patients, 10 non-demented PLS patients, and 27 healthy subjects were included. Twenty-nine electroencephalography channels with binaural reference were recorded during covert Stroop task performance, involving mental discrimination of the stimuli and not vocal or motor response. Group effects on event-related potentials (ERPs) latency were analyzed using statistical multivariate analysis. Topographic analysis was performed using low-resolution brain electromagnetic tomography (LORETA).

RESULTS

Amyotrophic lateral sclerosis patients committed more errors in the execution of the task but they were not slower, whereas PLS patients did not show reduced accuracy, despite a slowing of reaction times (RTs). The main ERP components were delayed in ALS, but not in PLS, compared with controls. Moreover, RTs speed but not ERP latency correlated with clinical scores. ALS had decreased frontotemporal activity in the P2, P3, and N4 time windows compared to controls.

CONCLUSION

These findings suggest a different pattern of psychophysiological involvement in ALS compared with PLS. The former is increasingly recognized to be a multisystems disorder, with a spectrum of executive and behavioral impairments reflecting frontotemporal dysfunction. The latter seems to mainly involve the motor system, with largely spared cognitive functions. Moreover, our results suggest that the covert version of the Stroop task used in the present study, may be useful to assess cognitive state in the very advanced stage of the disease, when other cognitive tasks are not applicable.

Psychophysiological correlates of coping and quality of life in patients with ALS

OBJECTIVE

Self-regulation models of coping suggest that patients with chronic diseases reporting low quality of life (QoL), an indicator of failed coping efforts, should show facilitated access to disease related words. Here we investigated whether a reduced N400 amplitude within an incongruent, i.e. unpredictable disease-related context would be a correlate of this facilitated access.

METHODS

ERPs were recorded in N=18 patients with amyotrophic lateral sclerosis (ALS) and N=20 age-matched healthy controls during reading of sentences, ending either with congruent or incongruent words. Incongruent and congruent words were disease related or disease unrelated. Mean N400 amplitudes were analyzed with mixed models.

RESULTS

Generally, incongruent words elicited a more negative N400 amplitude than congruent words in all groups and conditions, i.e. an N400 effect. In patients with high QoL this N400 effect did not differ between disease related and unrelated words. In patients with low QoL, however, the N400 effect was significantly smaller for disease related than for disease unrelated words. In healthy controls N400 amplitudes showed no such interaction between congruence, disease relatedness and QoL. Results remained stable when controlling for disease severity, duration and depression.

CONCLUSION

The N400 indicates increased accessibility to disease related information in ALS patients with low QoL. The increased access may imply a constantly activated disease related context which is linked to low QoL.

SIGNIFICANCE

N400 modulation by disease related information may serve as a psychophysiological correlate of coping and the patient's QoL.

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.

Magnetic resonance imaging in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disorder which is incurable to date. As there are many ongoing studies with therapeutic candidates, it is of major interest to develop biomarkers not only to facilitate early diagnosis but also as a monitoring tool to predict disease progression and to enable correct randomization of patients in clinical trials. Magnetic resonance imaging (MRI) has made substantial progress over the last three decades and is a practical, noninvasive method to gain insights into the pathology of the disease. Disease-specific MRI changes therefore represent potential biomarkers for ALS. In this paper we give an overview of structural and functional MRI alterations in ALS with the focus on task-free resting-state investigations to detect cortical network failures.

The use of P300-based BCIs in amyotrophic lateral sclerosis: from augmentative and alternative communication to cognitive assessment

The use of augmentative and alternative communication (AAC) tools in patients with amyotrophic lateral sclerosis (ALS), as effective means to compensate for the progressive loss of verbal and gestural communication, has been deeply investigated in the recent literature. The development of advanced AAC systems, such as eye-tracking (ET) and brain-computer interface (BCI) devices, allowed to bypass the important motor difficulties present in ALS patients. In particular, BCIs could be used in moderate to severe stages of the disease, since they do not require preserved ocular-motor ability, which is necessary for ET applications. Furthermore, some studies have proved the reliability of BCIs, regardless of the severity of the disease and the level of physical decline. However, the use of BCI in ALS patients still shows some limitations, related to both technical and neuropsychological issues. In particular, a range of cognitive deficits in most ALS patients have been observed. At the moment, no effective verbal-motor free measures are available for the evaluation of ALS patients' cognitive integrity; BCIs could offer a new possibility to administer cognitive tasks without the need of verbal or motor responses, as highlighted by preliminary studies in this field. In this review, we outline the essential features of BCIs systems, considering advantages and challenges of these tools with regard to ALS patients and the main applications developed in this field. We then outline the main findings with regard to cognitive deficits observed in ALS and some preliminary attempts to evaluate them by means of BCIs. The definition of specific cognitive profiles could help to draw flexible approaches tailored on patients' needs. It could improve BCIs efficacy and reduce patients' efforts. Finally, we handle the open question, represented by the use of BCIs with totally locked in patients, who seem unable to reliably learn to use such tool.

Severe motor disability affects functional cortical integration in the context of brain-computer interface (BCI) use

The purpose of this study was to investigate cortical interaction between brain regions in people with and without severe motor disability during brain-computer interface (BCI) operation through coherence analysis. Eighteen subjects, including six patients with cerebral palsy (CP) and three patients with amyotrophic lateral sclerosis (ALS), participated. The results showed (1) the existence of BCI performance difference caused by severe motor disability; (2) different coherence patterns between participants with and without severe motor disability during BCI operation and (3) effects of motor disability on cortical connections varying in the brain regions for the different frequency bands, indicating reduced cortical differentiation and specialisation. Participants with severe neuromuscular impairments, as compared with the able-bodied group, recruited more cortical regions to compensate for the difficulties caused by their motor disability, reflecting a less efficient operating strategy for the BCI task. This study demonstrated that coherence analysis can be applied to examine the ways cortical networks cooperate with each other during BCI tasks.

PRACTITIONER SUMMARY

Few studies have investigated the electrophysiological underpinnings of differences in BCI performance. This study contributes by assessing neuronal synchrony among brain regions. Our findings revealed that severe motor disability causes more cortical areas to be recruited to perform the BCI task, indicating reduced cortical differentiation and specialisation.

Listen, You are Writing! Speeding up Online Spelling with a Dynamic Auditory BCI

Representing an intuitive spelling interface for brain-computer interfaces (BCI) in the auditory domain is not straight-forward. In consequence, all existing approaches based on event-related potentials (ERP) rely at least partially on a visual representation of the interface. This online study introduces an auditory spelling interface that eliminates the necessity for such a visualization. In up to two sessions, a group of healthy subjects (N = 21) was asked to use a text entry application, utilizing the spatial cues of the AMUSE paradigm (Auditory Multi-class Spatial ERP). The speller relies on the auditory sense both for stimulation and the core feedback. Without prior BCI experience, 76% of the participants were able to write a full sentence during the first session. By exploiting the advantages of a newly introduced dynamic stopping method, a maximum writing speed of 1.41 char/min (7.55 bits/min) could be reached during the second session (average: 0.94 char/min, 5.26 bits/min). For the first time, the presented work shows that an auditory BCI can reach performances similar to state-of-the-art visual BCIs based on covert attention. These results represent an important step toward a purely auditory BCI.

Brain Painting: First Evaluation of a New Brain-Computer Interface Application with ALS-Patients and Healthy Volunteers

Brain-computer interfaces (BCIs) enable paralyzed patients to communicate; however, up to date, no creative expression was possible. The current study investigated the accuracy and user-friendliness of P300-Brain Painting, a new BCI application developed to paint pictures using brain activity only. Two different versions of the P300-Brain Painting application were tested: A colored matrix tested by a group of ALS-patients (n = 3) and healthy participants (n = 10), and a black and white matrix tested by healthy participants (n = 10). The three ALS-patients achieved high accuracies; two of them reaching above 89% accuracy. In healthy subjects, a comparison between the P300-Brain Painting application (colored matrix) and the P300-Spelling application revealed significantly lower accuracy and P300 amplitudes for the P300-Brain Painting application. This drop in accuracy and P300 amplitudes was not found when comparing the P300-Spelling application to an adapted, black and white matrix of the P300-Brain Painting application. By employing a black and white matrix, the accuracy of the P300-Brain Painting application was significantly enhanced and reached the accuracy of the P300-Spelling application. ALS-patients greatly enjoyed P300-Brain Painting and were able to use the application with the same accuracy as healthy subjects. P300-Brain Painting enables paralyzed patients to express themselves creatively and to participate in the prolific society through exhibitions.

The influence of psychological state and motivation on brain-computer interface performance in patients with amyotrophic lateral sclerosis - a longitudinal study

The current study investigated the effects of psychological well-being measured as quality of life (QoL), depression, current mood and motivation on brain–computer interface (BCI) performance in amyotrophic lateral sclerosis (ALS). Six participants with most advanced ALS were trained either for a block of 20 sessions with a BCI based on sensorimotor rhythms (SMR) or a block of 10 sessions with a BCI based on event-related potentials, or both. Questionnaires assessed QoL and severity of depressive symptoms before each training block and mood and motivation before each training session. The SMR-BCI required more training than the P300-BCI. The information transfer rate was higher with the P300-BCI (3.25 bits/min) than with the SMR-BCI (1.16 bits/min). Mood and motivation were related to the number of BCI sessions. Motivational factors, specifically challenge and mastery confidence, were positively related to BCI performance (controlled for the number of sessions) in tow participants, while incompetence fear was negatively related with performance in one participant. BCI performance was not related to motivational factors in three other participants nor to mood in any of the six participants. We conclude that motivational factors may be related to BCI performance in individual subjects and suggest that motivational factors and well-being should be assessed in standard BCI protocols. We also recommend using P300-based BCI as first choice in severely paralyzed patients who present with a P300 evoked potential.

Immunohistochemical study on the distribution of insulin-like growth factor-binding protein 4 in the central nervous system of SOD1(G93A) transgenic mice as an in vivo model of amyotrophic lateral sclerosis

In the present study, we used the SOD1(G93A) mutant transgenic mice as an in vivo model of amyotrophic lateral sclerosis (ALS) and performed immunohistochemical studies to investigate the changes of insulin-like growth factor-binding protein 4 (IGFBP4) in the central nervous system. Decreased expression of IGFBP4 was obvious in the cerebral cortex, hippocampus, cerebellar cortex and inferior olive of SOD1(G93A) transgenic mice. In the cerebral cortex, there was a significant decrease in IGFBP4 immunoreactivity in the pyramidal cells. In the hippocampal formation, IGFBP4 immunoreactivity was also decreased in the pyramidal cells of CA1-3 areas and the granule cells of dentate gyrus. In the cerebellar cortex, IGFBP4 immunoreactivity was prominent in the granular layer in wtSOD1 transgenic mice, compared to that in SOD1(G93A) transgenic mice. IGFBP4 immunoreactivity was decreased in the inferior olive of SOD1(G93A) transgenic mice. This study, showing decreased IGFBP4 in different brain regions of SOD1(G93A) transgenic mice, may provide clues to understanding the differential susceptibility of neural structures in ALS, suggesting a role of IGFBP4 in an abnormality of cognitive and/or motor function in ALS. The mechanisms and functional implications of these decreases require elucidation.

Brain-computer interface research at the University of South Florida Cognitive Psychophysiology Laboratory: the P300 Speller

We describe current efforts to implement and improve P300-BCI communication tools. The P300 Speller first described by Farwell and Donchin (in 1988) adapted the so-called oddball paradigm (OP) as the operating principle of the brain-computer interface (BCI) and was the first P300-BCI. The system operated by briefly intensifying each row and column of a matrix and the attended row and column elicited a P300 response. This paradigm has been the benchmark in P300-BCI systems, and in the past few years the P300 Speller paradigm has been solidified as a promising communication tool. While promising, we have found that some people who have amyotrophic lateral sclerosis (ALS) would be better suited with a system that has a limited number of choices, particularly if the 6 x 6 matrix is difficult to use. Therefore, we used the OP to implement a four-choice system using the commands: Yes, No, Pass, and End; we also used three presentation modes: auditory, visual, and auditory and visual. We summarize results from both paradigms and also discuss obstacles we have identified while working with the ALS population outside of the laboratory environment.

Cognitive impairment and neurophysiological correlates in MS

Cognitive impairment in multiple sclerosis (MS) has received considerable interest over the last decades. Heterogeneous patterns of cognitive dysfunction have been reported in literature in relation to the subtype of the disease and the severity of specific cognitive domains affected. Event related potentials (ERPs), especially P300, have been employed to evaluate the cognitive decline in MS and neurophysiological findings agree with data obtained by neuropsychological testing. The objectivity, the reliability and the easy administration are the main features of ERP technique but more specific attention and memory tasks are needed to enhance the clinical value of the methodology. Moreover, ERP recording has the advantage of being feasible even in severe disabled patients. Finally, longitudinal ERP studies are required to investigate the natural course of cognitive dysfunction in MS, to estimate the prognostic value of subclinical defects in different clinical form of the disease and to evaluate clinical benefits of therapeutic and rehabilitative interventions.

A P300-based brain–computer interface: Initial tests by ALS patients

OBJECTIVE

The current study evaluates the effectiveness of a brain-computer interface (BCI) system that operates by detecting a P300 elicited by one of four randomly presented stimuli (i.e. YES, NO, PASS, END).

METHODS

Two groups of participants were tested. The first group included three amyotrophic lateral sclerosis (ALS) patients that varied in degree of disability, but all retained the ability to communicate; the second group included three non-ALS controls. Each participant participated in ten experimental sessions during a period of approximately 6 weeks. During each run the participant's task was to attend to one stimulus and disregard the other three. Stimuli were presented auditorily, visually, or in both modes.

RESULTS

Two of the 3 ALS patient's classification rates were equal to those achieved by the non-ALS participants. Waveform morphology varied as a function of the presentation mode, but not in a similar pattern for each participant.

CONCLUSIONS

The event-related potentials elicited by the target stimuli could be discriminated from the non-target stimuli for the non-ALS and the ALS groups. Future studies will begin to examine online classification.

SIGNIFICANCE

The results of offline classification suggest that a P300-based BCI can serve as a non-muscular communication device in both ALS, and non-ALS control groups.

Only subtle cognitive deficits in non-bulbar amyotrophic lateral sclerosis patients

Neuropsychological investigations of amyotrophic sclerosis (ALS) patients revealed considerable discrepancies regarding neurocognitive functions. Some, but not all studies have suggested executive dysfunctioning and memory impairment, and there is a wide range of applied neuropsychological tests and results. In this study, we investigated the neuropsychological performance of 15 non-bulbar ALS patients, 14 patients with neuromuscular symptoms, and 15 healthy controls. To avoid confounding effects of motor disability, performance was assessed using exclusively motor-free tests of frontal lobe functioning (specific memory functions, conditional-associative learning, attention, and executive functions). ALS patients exhibited poorer performance in two conditions (semantic and alternating condition, respectively) of the Verbal Fluency Test, suggesting a subtle executive deficit. No deficits were found in tests of memory, conditional-associative learning, or attention. Assessed mood status was not related to neuropsychological performance. Verbal memory (CVLT) and verbal fluency (lexical condition) were positively associated with duration of disease. Our results support the view that there are only subtle cognitive deficits in ALS patients and we assume a possible effect of practice on cognitive tasks following reduced daily motor activity.

Immunohistochemical study on the distribution of phosphorylated extracellular signal-regulated kinase (ERK) in the central nervous system of SOD1G93A transgenic mice

In the present study, we performed immunohistochemical studies to investigate the changes of phosphorylated extracellular signal-regulated kinases (pERK) in the central nervous system of SOD1(G93A) transgenic mice. In symptomatic transgenic mice, pERK-immunoreactive astrocytes were detected in the spinal cord, brainstem, central gray and cerebellar nuclei. In contrast to symptomatic mice, no pERK-immunoreactive astrocytes were observed in any brain region of wtSOD1 and presymptomatic mice, and the number and intensity of stained neurons were not different at the age of 8 weeks and 13 weeks. Interestingly, region-specific alterations in pERK immunoreactivity were observed in the hippocampal region and cerebellum. These results provide the first evidence that pERK-immunoreactive astrocytes were found in the CNS of SOD1(G93A) transgenic mice after clinical symptoms, showing a possible consequence of the pathological process of ALS. This study has also demonstrated that pERK increases in the hippocampus and cerebellum, suggesting a role of pERK in an abnormality of cognitive and/or motor function in ALS, respectively. However, the mechanisms underlying the increased immunoreactivity for pERK and the functional implications require elucidation.

Neuropsychophysiological findings in a case of long-standing overt ventriculomegaly (LOVA)

Long-standing overt ventriculomegaly in adults (LOVA) is a clinical entity characterized by chronic hydrocephalus with infant onset, slow evolution and clinical disturbances during adulthood. Few cases are reported in literature describing the evident contrast between the severity of hydrocephalus and the relatively spared neurological functioning and cognitive aspects. The authors describe a 59-year-old man with congenital hydrocephalus complaining of persistent gait impairment. Neurological examination showed a mild paraparesis, severe higher cortical function impairment but relatively sparing of daily living activity. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a very remarkable ventriculomegaly compressing the brain cortex but sparing the cerebellum and the brainstem. Brain Single Photon Emission Computer Tomography (SPECT) showed a prevalent cerebellar perfusion as well. Neuropsychological testing was consistent with severe cognitive deterioration and attention disorders. Language and praxis functions seemed to be preserved. Auditory oddball ERPs (P300) showed morphological abnormalities especially of late components. This case report demonstrates in vivo the level of adaptation to which human brain can reach under chronic mechanic stress conditions. The striking poor cerebral parenchyma representation and the relatively spared language and praxic abilities account for a functional reorganization of residual structures due to the neural plasticity.

Decreased expression of calretinin in the cerebral cortex and hippocampus of SOD1G93A transgenic mice

In the present study, we investigated the changes of calretinin (CR) expression in the central nervous system of SOD1G93A transgenic mice as an in vivo model of amyotrophic lateral sclerosis (ALS). In wild-type SOD1 (wtSOD1) transgenic mice, many CR-immunoreactive neurons were found in all cortical regions. In the cerebral cortex of SOD1G93A transgenic mice, the number and staining intensity of CR-positive neurons were decreased. In the hippocampal formation, layer-specific alterations in the staining intensity of CR-immunoreactive neurons were observed in the CA1-3 areas and dentate gyrus. In wtSOD1 transgenic mice, CR-immunoreactive neurons with long processes were found in the stratum oriens and stratum radiatum of CA1-3 areas, and heavily stained band-like molecular layer was prominent in the dentate gyrus. CR immunoreactivity was decreased in each layer of CA1-3 areas and dentate gyrus of SOD1G93A transgenic mice. The first demonstration of decreased immunoreactivity for CR in the cerebral cortex and hippocampus of SOD1G93A transgenic mice may provide insights into the pathogenesis of motor neuron degeneration in human ALS although further quantitative studies are needed.

A Device for the Detection of Cognitive Brain Functions in Completely Paralyzed or Unresponsive Patients

Unresponsive patients with remaining cognitive abilities may be able to communicate with a brain-computer interface (BCI) such as the Thought Translation Device (TTD). Before initiating TTD learning, which may imply considerable effort, it is important to classify the patients' state of awareness and their remaining cognitive abilities. A tool for detection of cognitive activity (DCA) in the completely paralyzed was developed and integrated into the TTD which is a psychophysiological system for direct brain communication. In the present version, DCA entails five event-related brain-potential (ERP) experiments and investigates the capability of a patient to discriminate, e.g., between semantically related and unrelated concepts and categories. ERPs serve as an indicator of the patients' cortical information processing. Data from five severely brain-injured patients in persistent vegetative state diagnosed as unresponsive and five healthy controls are presented to illustrate the methodology. Two patients showing the highest responsiveness were selected for TTD training. The DCA integrated in the TTD allows screening of cognitive abilities and direct brain communication in the patients' home.

Limiting iron availability confers neuroprotection from chronic mild carbon monoxide exposure in the developing auditory system of the rat

Iron deficiency and chronic mild carbon monoxide (CO) exposure are nutritional and environmental problems that can be experienced simultaneously. We examined the effects of chronic mild CO exposure and iron availability on auditory development in the rat. We propose that chronic mild CO exposure creates an oxidative stress condition that impairs the spiral ganglion neurons. The CO-exposed rat pups had decreased neurofilament proteins and increased copper, zinc-superoxide dismutase (SOD1) in the spiral ganglion neurons. We conclude that the increased amount of SOD1 causes an increase in hydrogen peroxide production that allows the Fenton reaction to occur. This reaction uses both iron and hydrogen peroxide to generate hydroxyl radicals and leads to the development of oxidative stress that impairs neuronal integrity. However, rat pups with decreased iron and CO exposure (ARIDCO) exhibited in their cochlea an up-regulation of transferrin, whereas their expression of neurofilament proteins and SOD1 were similar to control. Consequently, reduced iron availability and the normal expression of SOD1 do not promote oxidative stress in the cochlea. By using basal c-Fos expression as a marker for cellular activation we found a significant reduction in c-Fos expression in the central nucleus of the inferior colliculus in iron-adequate rat pups exposed to CO. By contrast, rather than being reduced, c-Fos expression in the ARIDCO group is the same as for controls. We conclude that the cochlea of rat pups with normal iron availability is selectively affected by mild CO exposure, causing a chronic oxidative stress, whereas limiting iron availability ameliorates the effect caused by mild CO exposure by averting conditions that facilitate oxidative stress.

Assessment of cognitive functions in severely paralysed and severely brain-damaged patients: neuropsychological and electrophysiological methods

A systematic neuropsychological assessment technique is described for use with severely physically disabled individuals, possibly with combined motor and cognitive disorders. Target neurological conditions may be, e.g., an incomplete locked-in state, a minimally conscious state, or severe combinations of paralysis, agnosia, and apraxia. Neuropsychological assessment in these patients is difficult, because standard neuropsychological tests require fast motor responses, which can be manual, verbal, or both. To assess the cognitive status of patients with residual motor function, tests have been applied that can be answered by a binary (yes/no) signal and whose outcomes were not based on reaction times. Further, a battery of neurophysiological examination procedures based on event-related brain potentials has been developed. These procedures can be performed directly at a patient's bedside (at home or in a hospital) and applied for assessment of cognitive functions even in patients without residual motor function.

Enhanced expression of erythropoietin in the central nervous system of SOD1G93A transgenic mice

In the present study, we investigated the changes of erythropoietin (Epo) expression in the central nervous system (CNS) of SOD1(G93A) transgenic mice as an in vivo model of amyotrophic lateral sclerosis (ALS). In wild-type SOD1 (wtSOD1) transgenic mice, little immunoreactivity was found in all cortical regions. In the cerebral cortex of symptomatic SOD1(G93A) transgenic mice, there was a significant increase in Epo immunoreactivity. In the hippocampal formation, layer-specific alterations in the staining intensity were observed in the CA1-3 areas and dentate gyrus. Epo immunoreactivity was significantly increased in the midbrain, cerebellar cortex and brainstem of SOD1(G93A) transgenic mice. On the contrary, Epo immunoreactivity was moderately stained in the spinal cord and was not different between wtSOD1 and SOD1(G93A) transgenic mice at the age of 8 weeks, 13 weeks and 18 weeks. In the staining of Epo receptor (EpoR), the changing pattern was similar with that of Epo in the spinal cord and hippocampal formation in wtSOD1 and SOD1(G93A) transgenic mice. Although further studies of functional features of Epo in ALS are needed, the first demonstration of increased immunoreactivity for Epo in the CNS of SOD1(G93A) transgenic mice may provide initial insights into the development of interventional strategies to alleviate motor neuron degeneration in human ALS.

Immunohistochemical study on the distribution of insulin-like growth factor I (IGF-I) receptor in the central nervous system of SOD1G93A mutant transgenic mice

In the present study, we used the SOD1(G93A) mutant transgenic mice as an in vivo model of ALS and performed immunohistochemical studies to investigate the changes of insulin-like growth factor I (IGF-I) receptor in the central nervous system. IGF-I receptor-immunoreactive astrocytes were detected in the spinal cord, brainstem, central gray and cerebellar nuclei of SOD1(G93A) transgenic mice. In contrast to transgenic mice, no IGF-I receptor-immunoreactive astrocytes were observed in any brain region of wtSOD1 transgenic mice although a few moderately stained neurons were observed. In the hippocampal formation of SOD1(G93A) transgenic mice, IGF-I receptor immunoreactivity was increased in the pyramidal cells of the CA1-3 regions and granule cells of the dentate gyrus. The present study provides the first evidence that IGF-I receptor immunoreactivity was increased in reactive astrocytes in the central nervous system of SOD(G93A) transgenic mice, suggesting that reactive astrocytes may play an important role in the pathogenesis and progress of ALS. The mechanisms underlying the increased immunoreactivity for IGF-I receptor, and the functional implications of these increases, require elucidation.

Cognitive processing in completely paralyzed patients with amyotrophic lateral sclerosis

Cognitive functions have never been studied before in completely paralyzed patients, probably due to the lack of the appropriate method. In this study, three male patients in the last stage of amyotrophic lateral sclerosis (ALS) are examined. They were totally locked-in, i.e., incapable of any voluntary response including eye movements. Given this complete lack of motor expression, the method of event-related brain potentials (ERPs) was used. The ERP recording was carried out at the patients' bedside. In one patient indications of preserved cognitive abilities including adequate language comprehension were obtained. The data of the second patient also demonstrate a high degree of intactness of complex cognitive functions, but some ERP phenomena were consistently abnormal, which may be interpreted as a consequence of disease-related degenerative processes. In the third patient no electrocortical response which might indicate higher cortical processing was found. This first ERP study of totally paralyzed patients shows that some of them can possess high, perhaps even normal, information processing capacity after a long period of severe immobility and artificial ventilation.