Real-Time Feature Extraction From Electrocochleography With Impedance Measurements During Cochlear Implantation Using Linear State-Space Models.

Electrocochleography (ECochG) is increasingly used to monitor the inner ear function of cochlear implant (CI) patients during surgery. Current ECochG-based trauma detection shows low sensitivity and specificity and depends on visual analysis by experts. Trauma detection could be improved by including electric impedance data recorded simultaneously with the ECochG. However, combined recordings are rarely used because the impedance measurements produce artifacts in the ECochG. In this study, we propose a framework for automated real-time analysis of intraoperative ECochG signals using Autonomous Linear State-Space Models (ALSSMs). We developed ALSSM based algorithms for noise reduction, artifact removal, and feature extraction in ECochG. Feature extraction includes local amplitude and phase estimations and a confidence metric over the presence of a physiological response in a recording. We tested the algorithms in a controlled sensitivity analysis using simulations and validated them with real patient data recorded during surgeries. The results from simulation data show that the ALSSM method provides improved accuracy in the amplitude estimation together with a more robust confidence metric of ECochG signals compared to the state-of-the-art methods based on the fast Fourier transform (FFT). Tests with patient data showed promising clinical applicability and consistency with the findings from the simulations. We showed that ALSSMs are a valid tool for real-time analysis of ECochG recordings. Removal of artifacts using ALSSMs enables simultaneous recording of ECochG and impedance data. The proposed feature extraction method provides the means to automate the assessment of ECochG. Further validation of the algorithms in clinical data is needed

Electrocochleography in Cochlear Implant Recipients: Correlating Maximum Response With Residual Hearing.

OBJECTIVES Electrocochleography (ECochG) is increasingly recognized as a biomarker for assessing inner ear function in cochlear implant patients. This study aimed to objectively determine intraoperative cochlear microphonic (CM) amplitude patterns and correlate them with residual hearing in cochlear implant recipients, addressing the limitations in current ECochG analysis that often depends on subjective visual assessment and overlook the intracochlear measurement location. DESIGN In this prospective study, we investigated intraoperative pure-tone ECochG following complete electrode insertion in 31 patients. We used our previously published objective analysis method to determine the maximum CM amplitude and the associated electrode position for each electrode array. Using computed tomography, we identified electrode placement and determined the corresponding tonotopic frequency using Greenwood's function. Based on this, we calculated the tonotopic shift, that is, the difference between the stimulation frequency and the estimated frequency of the electrode with the maximum CM amplitude. We evaluated the association between CM amplitude, tonotopic shift, and preoperative hearing thresholds using linear regression analysis. RESULTS CM amplitudes showed high variance, with values ranging from -1.479 to 4.495 dBµV. We found a statistically significant negative correlation () between maximum CM amplitudes and preoperative hearing thresholds. In addition, a significant association () between the tonotopic shift and preoperative hearing thresholds was observed. Tonotopic shifts of the maximum CM amplitudes occurred predominantly toward the basal direction. CONCLUSIONS The combination of objective signal analysis and the consideration of intracochlear measurement locations enhances the understanding of cochlear health and overcomes the obstacles of current ECochG analysis. We could show the link between intraoperative CM amplitudes, their spatial distributions, and preoperative hearing thresholds. Consequently, our findings enable automated analysis and bear the potential to enhance specificity of ECochG, reinforcing its role as an objective biomarker for cochlear health

Probing the roles of orientation and multiscale gas distributions in shaping the obscuration of active galactic nuclei through cosmic time

The origin of obscuration in active galactic nuclei (AGNs) is still an open debate. In particular, it is unclear what drives the relative contributions to the line-of-sight column densities from galaxy-scale and torus-linked obscuration. The latter source is expected to play a significant role in Unification Models, while the former is thought to be rele v ant in both Unification and Evolutionary models. In this work, we make use of a combination of cosmological semi-analytic models and semi-empirical prescriptions for the properties of galaxies and AGN, to study AGN obscuration. We consider a detailed object-by-object modelling of AGN evolution, including different AGN light curves (LCs), gas density profiles, and also AGN feedback-induced gas cavities. Irrespective of our assumptions on specific AGN LC or galaxy gas fractions, we find that, on the strict assumption of an exponential profile for the gas component, galaxy-scale obscuration alone can hardly reproduce the fraction of log ( N H /cm −2 ) ≥24 sources at least at z  3. This requires an additional torus component with a thickness that decreases with luminosity to match the data. The torus should be present in all evolutionary stages of a visible AGN to be ef fecti ve, although galaxy-scale gas obscuration may be sufficient to reproduce the obscured fraction with 22 < log ( N H /cm −2 ) < 24 (Compton-thin, CTN) if we assume extremely compact gas disc components. The claimed drop of CTN fractions with increasing luminosity does not appear to be a consequence of AGN feedback, but rather of gas reservoirs becoming more compact with decreasing stellar mass

Effects of a Deca Iron Triathlon on body composition: a case study

We investigated energy balance and change of body composition in one athlete in a multistage triathlon, the World Challenge Deca Iron Triathlon 2006, where athletes had to perform one Ironman triathlon of 3.8 km swimming, 180 km cycling and 42.195 km running per day for ten consecutive days. In one well-experienced male ultra-endurance triathlete, we measured body mass, skinfold thicknesses and perimeters of extremities, in order to calculate skeletal muscle mass, fat mass and percentage of body fat. Energy intake was measured by analysis of nutrition, and energy expenditure was calculated using a portable heart rate monitor. This was performed to quantify energy deficit. In addition, bio-impedance measurements were performed to determine fluid metabolism. The athlete finished the race in 128 hours, 22 minutes and 42 seconds in 3rd position. Body mass decreased by 1 kilogram, skeletal muscle mass decreased by 0.9 kilograms and calculated fat mass decreased by 0.8 kilograms. Total body water increased by 2.8 liters. Total energy expenditure for the Deca Iron was 89,112 kilocalories and a total energy deficit of 11,480 kilocalories resulted. We presume that energy deficit was covered by consumption of adipose subcutaneous tissue as well as skeletal muscle mass; the degradation of muscle mass seems to lead to hypoproteinemic edemas

Calculus of the Ideas Immanent in Nervous Activity [23],

This paper reviews differential implementations of threshold logic gates, detailing two classes of solutions: capacitive (switched capacitor and floating gate), and conductance/current. 1