1. Cataract progression associated with modifications in calcium signaling in human lens epithelia as studied by mechanical stimulationMarko Gosak, Dajana Gojić, Elena Spasovska, Marko Hawlina, Sofija Andjelić, 2021, original scientific article Keywords: human eye lens, lens epithelial cells, calcium signaling, mechanical stimulation, mechanical stimulation, calcium waves, paracrine signaling
Published in DKUM: 14.02.2025; Views: 0; Downloads: 2
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2. Wearable online freezing of gait detection and cueing systemJan Slemenšek, Jelka Geršak, Božidar Bratina, Vesna M. Van Midden, Zvezdan Pirtošek, Riko Šafarič, 2024, original scientific article Abstract: This paper presents a real-time wearable system designed to assist Parkinson’s disease patients experiencing freezing of gait episodes. The system utilizes advanced machine learning models, including convolutional and recurrent neural networks, enhanced with past sample data preprocessing to achieve high accuracy, efficiency, and robustness. By continuously monitoring gait patterns, the system provides timely interventions, improving mobility and reducing the impact of freezing episodes. This paper explores the implementation of a CNN+RNN+PS machine learning model on a microcontroller-based device. The device operates at a real-time processing rate of 40 Hz and is deployed in practical settings to provide ‘on demand’ vibratory stimulation to patients. This paper examines the system’s ability to operate with minimal latency, achieving an average detection delay of just 261 milliseconds and a freezing of gait detection accuracy of 95.1%. While patients received on-demand stimulation, the system’s effectiveness was assessed by decreasing the average duration of freezing of gait episodes by 45%. These preliminarily results underscore the potential of personalized, real-time feedback systems in enhancing the quality of life and rehabilitation outcomes for patients with movement disorders.
Keywords: Parkinson’s disease, freezing of gait, machine learning, real-time systems, wearable devices, on-demand stimulation
Published in DKUM: 31.01.2025; Views: 0; Downloads: 4
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3. Decoding firings of a large population of human motor units from high-density surface electromyogram in response to transcranial magnetic stimulationJakob Škarabot, Claudia Ammann, Thomas G. Balshaw, Matjaž Divjak, Filip Urh, Nina Murks, Guglielmo Foffani, Aleš Holobar, 2023, original scientific article Abstract: We describe a novel application of methodology for high-density surface electromyography (HDsEMG) decomposition to identify motor unit (MU) firings in response to transcranial magnetic stimulation (TMS). The method is based on the MU filter estimation from HDsEMG decomposition with convolution kernel compensation during voluntary isometric contractions and its application to contractions elicited by TMS. First, we simulated synthetic HDsEMG signals during voluntary contractions followed by simulated motor evoked potentials (MEPs) recruiting an increasing proportion of the motor pool. The estimation of MU filters from voluntary contractions and their application to elicited contractions resulted in high (>90%) precision and sensitivity of MU firings during MEPs. Subsequently, we conducted three experiments in humans. From HDsEMG recordings in first dorsal interosseous and tibialis anterior muscles, we demonstrated an increase in the number of identified MUs during MEPs evoked with increasing stimulation intensity, low variability in the MU firing latency and a proportion of MEP energy accounted for by decomposition similar to voluntary contractions. A negative relationship between the MU recruitment threshold and the number of identified MU firings was exhibited during the MEP recruitment curve, suggesting orderly MU recruitment. During isometric dorsiflexion we also showed a negative association between voluntary MU firing rate and the number of firings of the identified MUs during MEPs, suggesting a decrease in the probability of MU firing during MEPs with increased background MU firing rate. We demonstrate accurate identification of a large population of MU firings in a broad recruitment range in response to TMS via non-invasive HDsEMG recordings. KEY POINTS: Transcranial magnetic stimulation (TMS) of the scalp produces multiple descending volleys, exciting motor pools in a diffuse manner. The characteristics of a motor pool response to TMS have been previously investigated with intramuscular electromyography (EMG), but this is limited in its capacity to detect many motor units (MUs) that constitute a motor evoked potential (MEP) in response to TMS. By simulating synthetic signals with known MU firing patterns, and recording high-density EMG signals from two human muscles, we show the feasibility of identifying firings of many MUs that comprise a MEP. We demonstrate the identification of firings of a large population of MUs in the broad recruitment range, up to maximal MEP amplitude, with fewer required stimuli compared to intramuscular EMG recordings. The methodology demonstrates an emerging possibility to study responses to TMS on a level of individual MUs in a non-invasive manner.
Keywords: transcranial magnetic stimulation, TMS, electromyiograms
Published in DKUM: 10.04.2024; Views: 421; Downloads: 22
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4. Influence of transient response of platinum electrode on neural signals during stimulation of isolated swinish left vagus nervePolona Pečlin, Franci Vode, Andraž Mehle, Igor Grešovnik, Janez Rozman, 2012, original scientific article Abstract: The main aim of the work was to measure transient response characteristics of interface between platinum stimulating electrodes and isolated swinish left cervical vagus nerve (segment), when electrical stimulating pulses are appliedto preselected locations along the segment and elicited neural signals,also described as compound action potentials (CAPs), are recorded fromparticular compartments of the nerve. The stimulating system was manufactured as a silicone self-coiling spiral cuff (cuff) with embedded matrix of ninety-nine rectangular electrodes (0.5 mm in width and 2mm in length), made of 45 microm thick annealed platinum ribbon (99.99 % purity), and a geometric surface of 1 mm2. For electrical stimulation, a current quasitrapezoidal, asymmetric and biphasic pulses with frequency of 1 Hz, were used. To test an influence of stimulating pulses having different parameters and waveforms on elicited CAPs, various degree of imbalance between an electric charge (charge) injected in cathodic phase as well as charge injectedin anodic phase of a biphasic stimulating pulse, were deployed and compared. To identify the differences in elicited CAPs however, an integral ofthe CAP cathodic phase as well as integral of the CAP anodic phase of stimulating pulse, were calculated and compared. Results showed a strong component superimposed in the CAPs, considered as an ensemble artefact which greatly obscured the components of the CAPs, and various components did overlap. Results also showed that stimulating pulses, having preset certain degree of imbalance between charge injected in cathodic and charge injected inanodic phase, elicited a slight change in a positive waveform deflection of CAP manifested under a cathodic phase as well as slight change in a negative waveform deflection of CAP manifested under an anodic phase. (Abstract truncated at 2000 characters)
Keywords: electrical stimulation, platinum electrodes, left vagus nerve, electrochemistry, electrical charge
Published in DKUM: 16.03.2017; Views: 1405; Downloads: 122
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