Gerald Pichler

The auditory P300-based single-switch brain-computer interface

OBJECTIVE Within this work an auditory P300 brain-computer interface based on tone stream segregation, which allows for binary decisions, was developed and evaluated. METHODS AND MATERIALS Two tone streams consisting of short beep tones with infrequently appearing deviant tones at random positions were used as stimuli. This paradigm was evaluated in 10 healthy subjects and applied to 12 patients in a minimally conscious state (MCS) at clinics in Graz, Würzburg, Rome, and Liège. A stepwise linear discriminant analysis classifier with 10×10 cross-validation was used to detect the presence of any P300 and to investigate attentional modulation of the P300 amplitude. RESULTS The results for healthy subjects were promising and most classification results were better than random. In 8 of the 10 subjects, focused attention on at least one of the tone streams could be detected on a single-trial basis. By averaging 10 data segments, classification accuracies up to 90.6% could be reached. However, for MCS patients only a small number of classification results were above chance level and none of the results were sufficient for communication purposes. Nevertheless, signs of consciousness were detected in 9 of the 12 patients, not on a single-trial basis, but after averaging of all corresponding data segments and computing significant differences. These significant results, however, strongly varied across sessions and conditions. CONCLUSION This work shows the transition of a paradigm from healthy subjects to MCS patients. Promising results with healthy subjects are, however, no guarantee of good results with patients. Therefore, more investigations are required before any definite conclusions about the usability of this paradigm for MCS patients can be drawn. Nevertheless, this paradigm might offer an opportunity to support bedside clinical assessment of MCS patients and eventually, to provide them with a means of communication.

Acute small subcortical infarctions on diffusion weighted MRI: clinical presentation and aetiology

Objective: To determine the clinical presentation and aetiology of small subcortical infarctions as found on diffusion weighted magnetic resonance imaging (DWI). DWI is both sensitive and specific in the early detection of acute ischaemic brain lesions irrespective of pre-existing vascular damage. Methods: Ninety three patients were identified showing subcortical or brainstem DWI lesions <1.5 cm in diameter within a maximum of 7 days from the onset of stroke symptoms. The patients’ clinical status on admission was reviewed according to the Oxfordshire Community Stroke Project (OCSP). The results of procedures searching for cerebrovascular risk factors, large artery disease, and potential sources of cardiac embolism were included to determine stroke aetiology. Magnetic resonance imaging scans were also reviewed for concomitant changes that could support the aetiologic classification. Results: Only 41 (44.1%) patients presented clinically with a lacunar syndrome according to OCSP criteria. The nine (9.7%) patients who showed two or more DWI lesions in different vascular territories were also significantly more likely to have potential sources of cardiac embolism (5/9, 55.6% v 20/84, 23.8%). Hypertension was significantly more prevalent in the group of patients who showed a microangiopathy related imaging pattern, but this pattern did not exclude the presence of large artery disease or a possible cardioembolic source of stroke. Conclusion: Identification of small subcortical infarctions as the cause of stroke appears quite uncertain based on clinical characteristics only. DWI adds significant aetiologic information but does not obviate the search for other potentially causative mechanisms.

The auditory p300-based SSBCI: A door to minimally conscious patients?

In this study we report on the evaluation of a novel auditory single-switch BCI in nine patients diagnosed with MCS. The task included a simple and a complex oddball paradigm, the latter uses the tone stream segregation phenomenon. In all patients a significant difference between deviant and frequent tones could be observed in EEG. However, in some cases the deviant tones produce a significant negative peak and in some a very late positive peak. These preliminary findings are relevant in order to address future customization of this auditory ssBCI-based paradigm for unresponsive patients.

Detection of mental imagery and attempted movements in patients with disorders of consciousness using EEG

Further development of an EEG based communication device for patients with disorders of consciousness (DoC) could benefit from addressing the following gaps in knowledge—first, an evaluation of different types of motor imagery; second, an evaluation of passive feet movement as a mean of an initial classifier setup; and third, rapid delivery of biased feedback. To that end we investigated whether complex and/or familiar mental imagery, passive, and attempted feet movement can be reliably detected in patients with DoC using EEG recordings, aiming to provide them with a means of communication. Six patients in a minimally conscious state (MCS) took part in this study. The patients were verbally instructed to perform different mental imagery tasks (sport, navigation), as well as attempted feet movements, to induce distinctive event-related (de)synchronization (ERD/S) patterns in the EEG. Offline classification accuracies above chance level were reached in all three tasks (i.e., attempted feet, sport, and navigation), with motor tasks yielding significant (p < 0.05) results more often than navigation (sport: 10 out of 18 sessions; attempted feet: 7 out of 14 sessions; navigation: 4 out of 12 sessions). The passive feet movements, evaluated in one patient, yielded mixed results: whereas time-frequency analysis revealed task-related EEG changes over neurophysiological plausible cortical areas, the classification results were not significant enough (p < 0.05) to setup an initial classifier for the detection of attempted movements. Concluding, the results presented in this study are consistent with the current state of the art in similar studies, to which we contributed by comparing different types of mental tasks, notably complex motor imagery and attempted feet movements, within patients. Furthermore, we explored new venues, such as an evaluation of passive feet movement as a mean of an initial classifier setup, and rapid delivery of biased feedback.

An exploratory intervention study suggests clinical benefits of training in chronic stroke to be paralleled by changes in brain activity using repeated fMRI

Purpose Previous studies demonstrated changes in sensorimotor network activation over time after stroke that have been interpreted as partly compensatory. Locomotor and balance trainings may improve both mobility and cognition even in chronic stroke and thereby impact on cerebral activation patterns. We here aimed at testing these assumptions in an exploratory study to inform subsequent larger intervention studies. Patients and methods Eight patients (73.3±4.4 years) with a chronic lacunar stroke (mean interval 3.7 years after the acute event with a range from 2 to 4 years) and residual leg paresis leading to gait disturbance received a guided 5-week training focusing on mobility, endurance, and coordination. Before and afterward, they underwent clinical, neuropsychological, and gait assessments and brain MRI at 3 T including a functional ankle movement paradigm. Sixteen healthy controls (HCs; 68.8±5.4 years) followed the same protocol without intervention. Results After training, patients had improved in mobility, memory, and delayed recall of memory. While cerebral activations in HC remained completely unaltered, patients showed increased activations in the right precentral gyrus, the right and left superior frontal gyri, and the right frontal lobe, with bipedal ankle movements after training. Conclusion In this exploratory study of chronic stroke, we found not only significant effects of physical training on mobility but also distinct aspects of cognition already with a small number of highly selected patients. These improvements were paralleled by alterations in cerebral activity possibly reflecting neuronal plasticity. Larger studies including randomization are needed.

Towards using fNIRS recordings of mental arithmetic for the detection of residual cognitive activity in patients with disorders of consciousness (DOC)

Background: Recently, fNIRS has been proposed as a promising approach for awareness detection, and a possible method to establish basic communication in patients with disorders of consciousness (DOC). Aim: Using fNIRS, the present study evaluated the applicability of auditory presented mental‐arithmetic tasks in this respect. Methods: We investigated the applicability of active attention to serial subtractions for awareness detection in ten healthy controls (HC, 21–32 y/o), by comparing the measured patterns to patterns induced by self‐performance of the same task. Furthermore, we examined the suitability of ignoring the given task as additional control signal to implement a two‐class brain‐computer interface (BCI) paradigm. Finally, we compared our findings in HC with recordings in one DOC patient (78 y/o). Results and conclusion: Results of the HC revealed no differences between the self‐performance and the attention condition, making the attention task suitable for awareness detection. However, there was no general difference between the ignore and attend condition, making the tasks less suitable for BCI control. Despite inconsistent correlations between the patient data and the HC group, single runs of the patient recordings revealed task‐synchronous patterns – however, we cannot conclude whether the measured activation derives from instruction based task performance and thus awareness. HIGHLIGHTSWe used fNIRS to investigate brain responses in healthy controls and one patient in minimally conscious state.A variation of auditory presented mental arithmetic tasks was used.10 healthy participants showed typical fNIRS responses during a serial subtraction task.The patient did not show clearly reproducible fNIRS responses over three sessions.The patient showed typical activation patterns in individual channels.

Improved concept and first results of an auditory single-switch BCI for the future use in disorders of consciousness patients

A promising approach to establish basic communication for disorders of consciousness (DOC) patients, is the application of Brain-Computer Interface (BCI) systems, especially the use of single-switch BCIs (ssBCIs). Recently we proposed the concept of a novel auditory ssBCI paradigm and presented first classification results. In this study we report on the evaluation of four different modifications of the original paradigm with the intention to increase the suitability. Therefore we investigated different sound types and the inclusion of additional spatial information. Finally, the classification investigation with the most encouraging modifications shows an enhancement compared to our original paradigm, within healthy subjects, implicating better results for the future use in DOC patients.

Low prevalence of colonization with multidrug-resistant gram-negative bacteria in long-term care facilities in Graz, Austria

HighlightsColonization by multi‐drug resistant Gram negatives 8.7% in LTCFs in Graz, Austria.Urinary catheter, chronic wounds, gastrostomy risk factors for MRGN colonization.No difference in 6‐month mortality between colonized and non‐colonized patients. Background: Residents in long‐term care facilities (LTCFs) are increasingly found to be an important reservoir of multidrug‐resistant gram‐negative (MRGN) bacteria. Aims: We aimed to determine colonization by MRGN bacteria over 6 months in LTCFs and geriatric wards in Graz, Austria, and to evaluate risk factors for such colonization. Methods: During August 2015, we conducted a point‐prevalence survey at LTCFs and geriatric wards of the Geriatric Health Centers of the City of Graz. Inguinal and perianal swabs were taken from 137 patients and screened for MRGN using standard procedures. Six months after the initial investigation all colonized patients were sampled again and use of antibiotics, hospital admissions, and mortality was registered. Genetic relatedness of MRGN bacteria was evaluated. Results: We detected 12 patients harboring MRGN isolates (prevalence, 8.7%). Overall inguinal colonization was 5.1%. After 6 months, only 2 out of 12 patients were still colonized. Presence of a urinary catheter was associated with a higher risk of MRGN colonization (odds ratio [OR], 17.5; 95% CI, 1.6‐192). Chronic wounds and gastrostomy were also risk factors of MRGN colonization (OR, 10.7; 95% CI, 1.6‐69.3 and OR, 18.3; 95% CI, 2.4‐139.4, respectively). There was no difference in mortality between colonized and noncolonized patients. Conclusions: Prevalence of colonization with MRGN bacteria was low in patients in LTCFs and geriatric wards in Graz, Austria.

Evaluation einer antibiotikafreien Dekontamination

Neben den zunehmenden Problemen mit Gram-negativen Pathogenen in Krankenanstalten spielen auch die Gram-positiven Bakterien weiterhin eine wesentliche Rolle. Eine Kolonisation mit MRSA (Methicillin-resistentem S. aureus) erhöht das Risiko einer postoperativen Wundinfektion und im Fall einer Sepsis auch die Mortalität. Die aktuelle Datenlage zeigt einen kausalen Zusammenhang zwischen MRSA-Kolonisationen und nosokomialen MRSA-Infektionen, die wiederum mit verlängertem stationären Aufenthalt und erhöhten Kosten assoziiert sind. Vor allem im amerikanischen Sprachraum ist eine Patienten-Dekontamination aus einer Kombination von Chlorhexidin und Mupirocin bereits weit verbreitet, wobei weltweit zunehmend Erkenntnisse über Resistenzen gegenüber beiden Wirkstoffen bekannt werden. In der vorliegenden Studie untersuchten wir daher mit Octenidin, einem Wirksto , der in Europa vor allem in der Wundund Schleimhautantisepsis im Einsatz ist, eine Alternative zum oben genannten Standardprotokoll. In früheren Studien wurde Octenidin als besonders breit wirksame und gut verträgliche Substanz mit einem ausgeprägten Remanenze ekt beschrieben. Erstes Ziel unserer interventionellen Kohortenstudie war, die MRSA-Prävalenz in unserem Haus in den Abteilungen „Medizinische Geriatrie“ und „Wachkomastation“ zu erheben, um nachfolgend die MRSA-Träger mit handelsüblich erhältlichen octenidinbasierten Produkten zu dekontaminieren. Das Screening erfolgte an einem einzigen Tag an allen 126 zu diesem Tag stationär be ndlichen Patienten mittels Abstrich der 1. Nasenvorhöfe, 2. Achseln und Leisten und, falls vorhanden, 3. der Wunde, 4. des Tracheostomas, 5. der PEG-Sonde und 6. jeder anderen Kathetereintrittstelle. Zu unserer Überraschung konnten wir 25 MRSA-positive Patienten identi zieren (das entspricht 19,8% unserer Bewohner in den beiden Abteilungen), wobei sich auf den Wachkomastationen eine signi kant höhere Rate zeigte (38% vs. 11%; p<0,0004). Im Detail wurden die Erreger an folgenden Lokalisationen gefunden: