Muscarinic acetylcholine receptors modulate HCN channel properties in vestibular ganglion neurons

Vestibular efferent neurons play an important role in shaping vestibular afferent excitability and accordingly, on the information encoded by their spike patterns. Efferent-modulation is linked to muscarinic signaling cascades that affect ion channel conductances, most notably low-voltage gated potassium channels such as KCNQ. Here we tested and found that muscarinic signaling cascades also modulate hyperpolarization-activated cyclic-nucleotide gated channels (HCN). HCN channels play a key role in controlling spike-timing regularity and a non-chemical form of transmission between type I hair cells and vestibular afferents. The impact of cholinergic efferent input on HCN channels was assessed using voltage-clamp methods, which measure currents in the disassociated cell bodies of vestibular ganglion neurons (VGN). Membrane properties in VGN were characterized before and after administration of the muscarinic acetylcholine receptor (mAChR) agonist Oxotremorine-M (Oxo-M). We found that Oxo-M shifted the voltage-activation range of HCN channels in the positive direction by 4.1 +/- 1.1 mV, which more than doubled the available current when held near rest at -60 mV (a 184 +/- 90.1% increase, n=19). This effect was not blocked by pre-treating the cells with a KCNQ channel blocker, linopirdine, which suggests that this effect is not dependent on KCNQ currents. We also found that HCN channel properties in the baseline condition and sensitivity to mAChR activation depended on cell size and firing patterns. Large-bodied neurons with onset firing patterns had the most depolarized activation range and least sensitivity to mAChR activation. Together, our results highlight the complex and dynamic regulation of HCN channels in VGN.

Exploring Channel Properties to Improve Singing Voice Detection with Convolutional Neural Networks

Singing voice detection is still a challenging task because the voice can be obscured by instruments having the same frequency band, and even the same timbre, produced by mimicking the mechanism of human singing. Because of the poor adaptability and complexity of feature engineering, there is a recent trend towards feature learning in which deep neural networks play the roles of feature extraction and classification. In this paper, we present two methods to explore the channel properties in the convolution neural network to improve the performance of singing voice detection by feature learning. First, channel attention learning is presented to measure the importance of a feature, in which two attention mechanisms are exploited, i.e., the scaled dot-product and squeeze-and-excitation. This method focuses on learning the importance of the feature map so that the neurons can place more attention on the more important feature maps. Second, the multi-scale representations are fed to the input channels, aiming at adding more information in terms of scale. Generally, different songs need different scales of a spectrogram to be represented, and multi-scale representations ensure the network can choose the best one for the task. In the experimental stage, we proved the effectiveness of the two methods based on three public datasets, with the accuracy performance increasing by up to 2.13 percent compared to its already high initial level.

Evaluation of a New Observationally Based Channel Parameterization for the National Water Model

Accurate representation of channel properties is important for forecasting in hydrologic models, as it affects height, celerity, and attenuation of flood waves. Yet, considerable uncertainty in the parameterization of channel geometry and hydraulic roughness (Manning’s n) exists within the NOAA National Water Model (NWM), due largely to data scarcity: only ~2,800 out of the 2.7 million river reach segments in the NWM have measured channel properties. In this study, we seek to improve channel representativeness by updating channel geometry and roughness parameters using a large, previously unpublished hydraulic geometry (HyG) dataset of approximately 48,000 gages. We begin with a Sobol’ sensitivity analysis of channel geometry parameters for 12 small semi-natural basins across the continental U.S., which reveals an outsized sensitivity of simulated flow to Manning’s n relative to channel geometry parameters. We then develop and evaluate a set of regression-based regionalizations of channel parameters estimated using the HyG dataset. Finally, we compare the model output generated from updated channel parameter sets to observations and the current NWM v2.1 parameterization. We find that, while the NWM land surface model holds the most influence over flow given its control over total volume, the updated channel parameterization leads to improvements in simulated streamflow performance relative to observed flows, with a statistically significant mean R2 increase from 0.479 to 0.494 across approximately 7,400 gage locations. HyG-based channel geometry and roughness provide a substantial overall improvement in channel representation over the default parameterization, updating the previous set value for most reaches of Manning’s n = 0.060 to a new range between 0.006 and 0.537 (median 0.077). This research provides a more representative, observationally based channel parameter dataset for the NWM routing module, as well as new insight into the influence of the routing module within the overall modeling framework.

Fabrication of Implantable Capsule-Type Channel Sounders for the High-Accuracy Measurement of the Signal Loss of Out-Body to In-Body Channels

This paper proposes a channel sounder to measure the channel properties of an implantable device that transmits data from inside to outside the human body. The proposed channel sounder measures the receiving power of a signal transmitted from outside the human body. The channel sounder is equipped with a Bluetooth module that enables the wireless transmission of the receiving power outside the human body. Wireless transmission enables the channel measurement by isolating the transmitter and receiver inside the channel sounder. Using the proposed channel sounder, the channel properties can be measured without any interference between the transmitter and the receiver.

Modeling Macroscopic Currents of Ion Channels

Ion-channel functions are often studied by the current-voltage relation, which is commonly fitted by the Boltzmann equation, a powerful model widely used nowadays. However, the Boltzmann model is restricted to a two-state ion-permeation process. Here we present an improved model that comprises a flexible number of states and incorporates both the single-channel conductance and the open-channel probability. Employing the channel properties derived from the single-channel recording experiments, the proposed model is able to describe various current-voltage relations, especially the reversal ion-permeation curves showing the inward- and outward-rectifications. We demonstrate the applicability of the proposed model using the published patch-clamp data of BK and MthK potassium channels, and discuss the similarity of the two channels based on the model studies.

Tripolarizated MIMO: Experimental Analysis and Modeling of Channel Properties in Both Indoor and Outdoor Scenarios

The tripolarized MIMO system can provide one more degree of freedom and have a more compacted size over a dual-polarized MIMO system, which is attractive for high-capacity wireless communication systems. In this paper, we analyze and model channel properties for tripolarized MIMO systems based on experimental channel measurements in typical indoor and outdoor scenarios. Firstly, channel measurement campaigns in the laboratory and the Urban Micro (UMi) scenarios on sub-6 GHz bands are presented. Then, based on measured data, path loss, delay spread (DS), and cross-polarization discrimination (XPD) for 9 polarization combinations are analyzed and modeled in a statistical way. Statistical results of these channel properties are also given. It is observed that channel properties of both large-scale fading and small-scale fading depend strongly on the polarization direction. Furthermore, we evaluate the performance of tripolarized MIMO systems by analyzing the Demmel condition number and channel capacity gain (CG). For both the indoor and the outdoor scenarios, it is found that colocated tripolarized antenna can bring a nearly threefold CG with respect to the unipolarized one. These results can give good insights into the design and evaluation of tripolarized MIMO systems.

A Method of Implementing a 4 × 4 Correlation Matrix for Evaluating the Uplink Channel Properties of MIMO Over-the-Air Apparatus

This paper presents a method of implementing a 4 × 4 correlation matrix for evaluating the uplink channel properties of multiple-input multiple-output (MIMO) antennas using an over-the-air measurement system. First, the implementation model used to determine the correlation coefficients between the signals received at the base station (BS) antennas via the uplink channel is described. Then, a methodology is introduced to achieve a 4 × 4 correlation matrix for a BS MIMO antenna based on Jakes’ model by setting the initial phases of the secondary wave sources in the two-dimensional channel model. The performance of the uplink channel for a four-element MIMO terminal array antenna is evaluated using a two-dimensional bidirectional fading emulator. The results show that the measured correlation coefficients between the signals received via the uplink channel at the BS antennas using the proposed method are in good agreement with the BS correlation characteristics calculated using Monte Carlo simulation and the theoretical formula, thereby confirming the effectiveness of the proposed method.

H1153Y-KCNH2 Mutation Identified in a Sudden Arrhythmic Death Syndrome Case Alters Channel Gating

Long QT syndrome is one of the most common hereditary channelopathies inducing fatal arrhythmias and sudden cardiac death. We identified in a sudden arrhythmic death syndrome case a C-term KCNH2 mutation (c.3457C > T; p.His1153Tyr) classified as variant of unknown significance and functional impact. Heterologous expression in HEK293 cells combined with western-blot, flow-cytometry, immunocytochemical and microscope analyses shows no modification of channel trafficking to the cell membrane. Electrophysiological studies reveal that the mutation causes a loss of HERG channel function through an alteration of channel biophysical properties that reduces the current density leading to LQT2. These results provide the first functional evidence for H1153Y-KCNH2 mutation-induced abnormal channel properties. They concur with previous biophysical and clinical presentations of a survived patient with another variant that is G1036D. Therefore, the present report importantly highlights the potential severity of variants that may have useful implications for treatment, surveillance, and follow-up of LQT2 patients.