Oliver Bichsel

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Bichsel

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Oliver

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0000-0002-1026-5753

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Publications 1 - 10 of 14

Neurofeedback-enabled beta power control with a fully implanted DBS system in patients with Parkinson’s disease
Rohr-Fukuma, Manabu; Stieglitz, Lennart H.; Bujan, Bartosz; et al. (2023)
medRxiv
Parkinsonian motor symptoms are linked to pathologically increased beta oscillations in the basal ganglia. Studies with externalised deep brain stimulation electrodes showed that Parkinson patients were able to rapidly gain control over these pathological basal ganglia signals through neurofeedback. Studies with fully implanted deep brain stimulation systems duplicating these promising results are required to grant transferability to daily application. In this study, seven patients with idiopathic Parkinson’s disease and one with familial Parkinson’s disease were included. In a postoperative setting, beta oscillations from the subthalamic nucleus were recorded with a fully implanted deep brain stimulation system and converted to a real-time visual feedback signal. Participants were instructed to perform bidirectional neurofeedback tasks with the aim to modulate these oscillations. While receiving regular medication and deep brain stimulation, participants were able to significantly improve their neurofeedback ability and achieved a significant decrease of subthalamic beta power (median reduction of 31% in the final neurofeedback block). We could demonstrate that a fully implanted deep brain stimulation system can provide visual neurofeedback enabling patients with Parkinson’s disease to rapidly control pathological subthalamic beta oscillations.
Functionally separated networks for self-paced and externally-cued motor execution in Parkinson's disease: Evidence from deep brain recordings in humans
Bichsel, Oliver; Gassert, Roger; Stieglitz, Lennart; et al. (2018)
NeuroImage
The modulatory effect of self-paced and cued motor execution on subthalamic beta-bursts in Parkinson's disease: Evidence from deep brain recordings in humans
Bichsel, Oliver; Stieglitz, Lennart; Oertel, Markus; et al. (2022)
Neurobiology of Disease
Deep brain stimulation (DBS) electrodes provide an unparalleled window to record and investigate neuronal activity right at the core of pathological brain circuits. In Parkinson's disease (PD), basal ganglia beta-oscillatory activity (13–35 Hz) seems to play an outstanding role. Conventional DBS, which globally suppresses beta-activity, does not meet the requirements of a targeted treatment approach given the intricate interplay of physiological and pathological effects of beta-frequencies. Here, we wanted to characterise the local field potential (LFP) in the subthalamic nucleus (STN) in terms of beta-burst prevalence, amplitude and length between movement and rest as well as during self-paced as compared to goal-directed motor control. Our electrophysiological recordings from externalised DBS-electrodes in nine patients with PD showed a marked decrease in beta-burst durations and prevalence during movement as compared to rest as well as shorter and less frequent beta-bursts during cued as compared to self-paced movements. These results underline the importance of beta-burst modulation in movement generation and are in line with the clinical observation that cued motor control is better preserved than self-paced movements. Furthermore, our findings motivate the use of adaptive DBS based on beta-bursts, which selectively trim longer beta-bursts, as it is more suitable and efficient over a range of motor behaviours than conventional DBS.
Lower limb motor effects of DBS neurofeedback in Parkinson’s disease assessed through IMU-based UPDRS movement quality metrics
Salzmann, Lena; Bichsel, Oliver; Rohr-Fukuma, Manabu; et al. (2025)
Scientific Reports
Parkinson’s disease (PD) is characterized by progressive motor impairments, including lower limb dysfunction, leading to reduced mobility and increased fall risk. To counteract these deficits, neurofeedback based on deep brain stimulation (DBS) electrodes has been proposed as a novel approach to mitigate motor symptoms via modulation of abnormal beta-oscillations in the subthalamic nucleus. However, its potential to improve motor symptoms has yet to be fully established. This study examined whether a single session of DBS-based neurofeedback could have a short term effect on movement quality, quantified through inertial measurement unit recordings. Ten PD patients performed two standardized motor tasks, foot stomping and hand pronation-supination, from the Unified Parkinson’s Disease Rating Scale. Movement quality metrics from inertial measurement units were extracted and compared before and after neurofeedback-induced beta-power downregulation. Beta-power was successfully reduced by -12.42% on average, and the reduction was associated with significant improvements in lower limb movement quality metrics—acceleration magnitude (p = 0.037), movement speed (steps per second: p = 0.010; mean peak velocity: p = 0.002), and reduced halts (p = 0.020)—with a strong coupling between beta reduction and speed gain (Spearman rho = 0.976, p < 0.001). No significant improvements were observed in upper limb movements. These findings indicate that neurofeedback-driven downregulation of beta-power produces measurable enhancements in lower limb movement quality, captured through wearable sensor metrics. Future work should assess whether these improvements translate into lasting functional benefits and validate the clinical relevance of these metrics.
Deep brain electrical neurofeedback allows Parkinson patients to control pathological oscillations and quicken movements
Bichsel, Oliver; Stieglitz, Lennart H.; Oertel, Markus F.; et al. (2021)
Scientific Reports
Parkinsonian motor symptoms are linked to pathologically increased beta-oscillations in the basal ganglia. While pharmacological treatment and deep brain stimulation (DBS) reduce these pathological oscillations concomitantly with improving motor performance, we set out to explore neurofeedback as an endogenous modulatory method. We implemented real-time processing of pathological subthalamic beta oscillations through implanted DBS electrodes to provide deep brain electrical neurofeedback. Patients volitionally controlled ongoing beta-oscillatory activity by visual neurofeedback within minutes of training. During a single one-hour training session, the reduction of beta-oscillatory activity became gradually stronger and we observed improved motor performance. Lastly, endogenous control over deep brain activity was possible even after removing visual neurofeedback, suggesting that neurofeedback-acquired strategies were retained in the short-term. Moreover, we observed motor improvement when the learnt mental strategies were applied 2 days later without neurofeedback. Further training of deep brain neurofeedback might provide therapeutic benefits for Parkinson patients by improving symptom control using strategies optimized through neurofeedback.
UNDERSTANDING AND NEUROFEEDBACK-MODULATING DEEP BRAIN OSCILLATIONS IN PATIENTS WITH PARKINSON’S DISEASE
Bichsel, Oliver (2022)
Continuous and Unconstrained Tremor Monitoring in Parkinson's Disease Using Supervised Machine Learning and Wearable Sensors
Rodriguez, Fernando; Krauss, Philipp; Kluckert, Jonas; et al. (2024)
Parkinson's Disease
Background: Accurately assessing the severity and frequency of fluctuating motor symptoms is important at all stages of Parkinson’s disease management. Contrarily to time-consuming clinical testing or patient self-reporting with uncertain reliability, recordings with wearable sensors show promise as a tool for continuously and objectively assessing PD symptoms. While wearables-based clinical assessments during standardised and scripted tasks have been successfully implemented, assessments during unconstrained activity remain a challenge. Methods: We developed and implemented a supervised machine learning algorithm, trained and tested on tremor scores. We evaluated the algorithm on a 67-hour database comprising sensor data and clinical tremor scores for 24 Parkinson patients at four extremities for periods of about 3 hours. A random 25% subset of the labelled samples was used as test data, the remainder as training data. Based on features extracted from the sensor data, a Support Vector Machine was trained to predict tremor severity. Due to the inherent imbalance in tremor scores, we applied dataset rebalancing techniques. Results: Our classifier demonstrated robust performance in detecting tremor events with a sensitivity of 0.90 on the test-portion of the resampled dataset. The overall classification accuracy was high at 0.88. Conclusion: We implemented an accurate classifier for tremor monitoring in free-living environments that can be trained even with modestly sized and imbalanced datasets. This advancement offers significant clinical value in continuously monitoring Parkinson’s disease symptoms beyond the hospital setting, paving the way for personalized management of PD, timely therapeutic adjustments, and improved patient quality of life.
Air travel with pneumocephalus: a systematic review
Bichsel, Oliver; Hauck, Annalisa; Oertel, Markus (2022)
Acta Neurochirurgica
Introduction Concerns arise when patients with pneumocephalus engage in air travel. How hypobaric cabin pressure affects intracranial air is largely unclear. A widespread concern is that the intracranial volume could relevantly expand during flight and lead to elevated intracranial pressure. The aim of this systematic review was to identify and summarise models and case reports with confirmed pre-flight pneumocephalus. Methods The terms (pneumocephalus OR intracranial air) AND (flying OR fly OR travel OR air transport OR aircraft) were used to search the database PubMed on 30 November 2021. This search returned 144 results. To be included, a paper needed to fulfil each of the following criteria: (i) peer-reviewed publication of case reports, surveys, simulations or laboratory experiments that focussed on air travel with pre-existing pneumocephalus; (ii) available in full text. Results Thirteen studies met the inclusion criteria after title or abstract screening. We additionally identified five more articles when reviewing the references. A notion that repeatedly surfaced is that any air contained within the neurocranium increases in volume at higher altitude, much like any extracranial gas, potentially resulting in tension pneumocephalus or increased intracranial pressure. Discussion Relatively conservative thresholds for patients flying with pneumocephalus are suggested based on models where the intracranial air equilibrates with cabin pressure, although intracranial air in a confined space would be surrounded by the intracranial pressure. There is a discrepancy between the models and case presentations in that we found no reports of permanent or transient decompensation secondary to a pre-existing pneumocephalus during air travel. Nevertheless, the quality of examination varies and clinicians might tend to refrain from reporting adverse events. We identified a persistent extracranial to intracranial fistulous process in multiple cases with newly diagnosed pneumocephalus after flight. Finally, we summarised management principles to avoid complications from pneumocephalus during air travel and argue that a patient-specific understanding of the pathophysiology and time course of the pneumocephalus are potentially more important than its volume.
Neurofeedback for precision rehabilitation of Parkinson’s patients
Salzmann, Lena; Bichsel, Oliver; Ravi, Deepak Kumar; et al. (2023)
Brain Stimulation
Parkinson’s disease (PD) is the second most common neurodegenerative disease in the elderly population. It is caused by a progressive loss of dopaminergic neurons in the basal ganglia, leading to impaired motor function. Deep Brain Stimulation (DBS) is a possible treatment for PD, but its success differs significantly among patients. As an adjunct personalized therapeutic approach, we study how the DBS electrode can be alternatively used to provide closed-loop neurofeedback in PD patients. Local field potentials (LFPs) from the subthalamic nucleus are recorded, and a digitally processed version of these signals is visually presented to the patients. Observing their neural oscillations in real-time allows patients to develop a mental strategy to actively regulate their pathological brain activity. We hypothesized that a decrease in pathological brain activity could have a positive short-term influence on motor performance. Preliminary results from a pilot study in 8 patients confirm that down-regulation of pathological beta-activity via DBS-neurofeedback is feasible and possible from the first training session on. Effects of beta-power down-regulation on lower limb motor performance are currently under investigation. Additionally, further neural markers associated with gait features will be identified in an exploratory study with Parkinson’s patients and healthy controls involving electroencephalography and DBS-LFP recordings. We expect that personalization by selecting the most appropriate neural biomarker for closed-loop neurofeedback may result in enhanced motor performance. Within a prospective sham-controlled clinical trial, we also investigate the feasibility of personalized closed-loop neurofeedback with a focus on gait rehabilitation in Parkinson’s patients via multi-session neurofeedback training. Beyond demonstrating a proof-of-concept for novel methods of precision sensory-motor rehabilitation, positive results in this project may inspire novel treatments by providing an understanding of neural activity during gait as well as the mechanisms of personalized neurofeedback.
Direct subthalamic nucleus stimulation influences speech and voice quality in Parkinson's disease patients
Bobin, Marine; Sulzer, Neil; Bründler, Gina; et al. (2024)
Brain Stimulation
Background: DBS of the subthalamic nucleus (STN) considerably ameliorates cardinal motor symptoms in PD. Reported STN-DBS effects on secondary dysarthric (speech) and dysphonic symptoms (voice), as originating from vocal tract motor dysfunctions, are however inconsistent with rather deleterious outcomes based on post-surgical assessments. Objective: To parametrically and intra-operatively investigate the effects of deep brain stimulation (DBS) on perceptual and acoustic speech and voice quality in Parkinson's disease (PD) patients. Methods: We performed an assessment of instantaneous intra-operative speech and voice quality changes in PD patients (n = 38) elicited by direct STN stimulations with variations of central stimulation features (depth, laterality, and intensity), separately for each hemisphere. Results: First, perceptual assessments across several raters revealed that certain speech and voice symptoms could be improved with STN-DBS, but this seems largely restricted to right STN-DBS. Second, computer-based acoustic analyses of speech and voice features revealed that both left and right STN-DBS could improve dysarthric speech symptoms, but only right STN-DBS can considerably improve dysphonic symptoms, with left STN-DBS being restricted to only affect voice intensity features. Third, several subareas according to stimulation depth and laterality could be identified in the motoric STN proper and close to the associative STN with optimal (and partly suboptimal) stimulation outcomes. Fourth, low-to-medium stimulation intensities showed the most optimal and balanced effects compared to high intensities. Conclusions: STN-DBS can considerably improve both speech and voice quality based on a carefully arranged stimulation regimen along central stimulation features.

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Oliver Bichsel

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