Threshold Curves Research Articles

FRAX-based assessment and intervention threshold curves for osteoporosis evaluation in Ecuador

IntroductionFRAX has been validated and adapted to different countries, covering almost 80% of the world's population, including Ecuador where it was adapted in 2009. The purpose of this study is to elaborate evaluation and intervention curves based on FRAX Ecuador. MethodsUsing the FRAX Ecuador model, we calculated the probability of a major osteoporotic fracture and a female hip fracture without any risk factor and without the inclusion of BMD. The probabilities were calculated in 5-year intervals from 40 to 90 years. The probabilities of major fractures and hip fractures were calculated in 3 different scenarios: 1. History of previous fracture without the inclusion of BMD, 2. T score −2.5 SD without other clinical risk factors, 3. T score −1.5 SD without other clinical risk factors. ResultsIn women without risk factors, the probability of a major osteoporotic fracture increased with age from 0.4% at 40 years to 7.3% at 90 years. The probability of hip fracture increased with age from 0% at 40 years to 3.6% at 90 years. The probability of a major osteoporotic fracture increased in women with a T score of −2.5 SD from 0.9% at 40 years to 5.5% at 90 years; with a T-score of −1.5 SD, from 0.6% at 40 years to 3.9% at 90 years. ConclusionData shows the importance of applying tools such as FRAX, specific for each country and also the creation of evaluation and intervention curves that allow discerning according to each patient the need for the use of resources such as DXA and specific treatments.

A hydrology-process based method for correlating debris flow density to rainfall parameters and its application on debris flow prediction

Antecedent effective rainfall (Ar) and rainfall intensity (I) play an important role in the formation process of debris flow. Establishing Ar-I threshold curve of debris flow is hence of great importance for early warning purpose. However, conventional statistical models require sufficient observation data, which is not feasible for developing countries without adequate field observation stations. To this end, a hydrology-process based method is proposed to construct the Ar-I threshold. In this model, debris flow is considered as a soil-water mixture composed of solid and water, the loose solid sources contributing to debris flow is provided by the rainfall-induced shallow landslide, and the water is from rainfall-induced runoff. A necessity of having the characteristics of debris flow is that the density of water-soil mixture should approximate to the density of debris flow ranging from 1.2 to 2.3 g/cm3. The value of 1.2 and 2.3 g/cm3, which represent lower and upper borders of the density of debris flow, is used as the threshold for predicting debris flow. The task of the model is to find out the rainfall parameters that correlate with the border value of density and use the searched data of rainfall parameters to fit corresponding curves. Verification of the proposed threshold was conducted based on field observation data of Jiangjia Gully located in Yunnan Province, China, which indicates the false negative and false positive rates of the threshold are 26.7% and 15%, respectively. The precision of the threshold is evaluated as 82.6% by the Receiver Operator Characteristics method, which can provide a solution for debris flow early warning.

Optimum roughage proportion in barley-based feedlot cattle diets: total tract nutrient digestibility, rumination, ruminal acidosis, short-chain fatty absorption, and gastrointestinal tract barrier function.

Cattle need physically effective fiber to promote rumination and maintain rumen health, but economics favor the use of low-roughage feedlot diets. The study investigated the optimum barley silage proportion in barley-based finishing diets. Apparent total-tract digestibility (4-d total fecal collection), chewing behavior (6-d video recording), ruminal pH (6-d indwelling pH recording), and fermentation (1 day, sampling 0, 3, 6, 12, and 18 h postfeeding), short-chain fatty acid (SCFA) absorption (washed reticulo-rumen technique), gastrointestinal tract barrier function (marker infusion), and blood variables (catheters) were measured. Eight ruminally fistulated crossbred beef heifers (653 ± 44.2 kg; mean starting body weight [BW] ± SD) were used in a replicated 4 × 4 Latin square design with 28-d periods. Dietary treatments were 0%, 4%, 8%, and 12% of dietary dry matter (DM) as barley silage, with diets containing 80%, 76%, 72%, and 68% barley grain, respectively. Increasing silage proportion decreased dietary starch content from 49.0% to 43.1% DM, while neutral detergent content increased from 22.7% to 25.1% DM. Silage proportion had no effect on DM intake, but apparent DM digestibility decreased quadratically (86.0%, 82.1%, 81.1%, 79.5% for the four diets, respectively; P < 0.001). Although, silage proportion had no effect on eating activity, rumination time increased quadratically (246, 289, 302, 316 min/d; P = 0.04). Increased silage proportion increased minimum (5.07, 5.27, 5.29, 5.41; quadratic, P = 0.011) and mean (5.61, 5.87, 5.93, 5.95; quadratic, P = 0.007) ruminal pH, and there was a quadratic (P ≤ 0.047) decrease in duration and area under the pH acidosis threshold curves of 5.8, 5.5, and 5.2. Although increasing silage proportion decreased ruminal acidosis, it was not completely eliminated even with a diet containing 12% silage DM. SCFA concentration in ruminal fluid was not affected by diet, but silage proportion quadratically (P ≤ 0.088) increased ruminal acetate:propionate. There was no effect of diet on absolute or fractional rates of absorption of acetate, propionate, butyrate or total SCFA, and no effect on gastrointestinal barrier function or blood measurements. In conclusion, responses to roughage level were mostly quadratic with greatest improvements in acidosis variables between 0% and 4% barley silage, with incremental improvements with further increases in silage levels. The study showed a trade-off between maximizing digestibility and energy intake to promote animal performance and minimizing the risk of acidosis.

Generating pseudo-capillary pressure curves from nuclear magnetic resonance (NMR) data: a case study from the Cooper Basin, Australia

This study evaluates the accuracy of generating pseudo-capillary pressure curves from laboratory nuclear magnetic resonance (NMR) analysis and NMR wireline log data by comparing threshold pressures and curve characteristics to rock-derived mercury injection capillary pressure (MICP) analysis. Accurate production of pseudo-capillary pressure curves from NMR data could negate or reduce the need for expensive and rig-time-consuming core acquisition and subsequent MICP analysis. Successful application of this technique will allow production of pseudo-capillary pressure curves for large stratigraphic intervals at a significantly reduced cost and help to better constrain petroleum reserves and improve near field exploration prediction outcomes. The Tindilpie-11 well in the Cooper Basin, Australia, was used as a case study because of extensive existing conventional ore analysis and presence of an NMR wireline log covering the sampled intervals in the Permian-aged Patchawarra Formation. Six core samples underwent MICP and laboratory NMR analyses, with capillary pressure curves generated for each method. Six pseudo-capillary pressure curves were also generated from the NMR wireline log data at the coincident sample depths. The pseudo-capillary pressure curves generated from laboratory NMR data closely resemble the MICP results (mean threshold pressure error of 0.63 MPa absolute [91.4 psi]) and proved the applicability of this approach. The NMR wireline log data used is an average over a ∼1.6 m interval, which has likely led to discrepancies when compared with laboratory NMR pseudo-capillary pressure curves and MICP curves. Nonetheless, this study confirms the applicability of using laboratory NMR data to generate pseudo-capillary pressure curves that resemble MICP results. Continued development of NMR log technology and reduced logging speeds will improve the data resolution and ultimately provide high density NMR data that can be used to create pseudo-capillary pressure curves for large stratigraphic intervals at a significantly reduced cost. KEY POINTS Pseudo-capillary pressure curves derived from NMR data. Reservoir characterisation requiring minimal rock acquisition for ground truthing. Case study on the Patchawarra Formation (Cooper Basin, Australia) using SCAL data.

A new numerical approach for DNA representation using modified Gabor wavelet transform for the identification of protein coding regions

The fundamental step in genomic signal processing applications is to assign mathematical descriptor to nucleotides {A, T, G, C} of DNA molecule for discrete representation. The discrete representation should replicate biological information of gene when analyzed with digital signal processing tools. In this aspect, a novel binary representation of DNA sequence by combining structural and chemical information of original DNA sequence has been proposed for the identification of protein coding regions of eukaryotes. The identification model comprises two stages, mainly, numerical encoding in first stage, and analysis of biological behavior through digital signal processing algorithms in second stage. In the first stage, a new numerical encoding method based on Walsh codes of order-4 is proposed to obtain 1-D binary discrete sequence. In the second stage, the modified Gabor wavelet transform (MGWT) is employed on the discretized DNA sequence for spectrum analysis. The optimal gene numerical encoding and multiresolution approach of MGWT has readily identified the structures of coding regions of unknown gene sequences. The proposed model is validated by analyzing prediction efficiency in terms of statistical metrics such as sensitivity, specificity, accuracy on both sequence and data base level. Furthermore, the results are compared by plotting receiver operating curves (ROC) for all classification thresholds for the state-of-art encoding methods. Area under curve (AUC) value of 0.86 at sequence level and 0.84 at database level is achieved. Performance metrics indicate that the proposed encoding method exhibits relatively better performance than other numerical encoding methods.

A Shoulder Injury Criterion for the EuroSID-2re Applicable in a Large Loading Condition Spectrum of the Military Domain.

The EuroSID-2re (ES-2re) is an Anthropometric Test Device (ATD) from the automotive domain designed for lateral impact. Since the 2000's, it has also been used by NATO armies to assess the risk of injury to armored vehicles occupants submitted to an Improvised Explosive Device (IED) attack. The resulting loading conditions from an explosion can vary a lot in term of impact velocity and duration. They range from high velocity impacts (~28 m/s), characterized by a short duration (~10 ms) corresponding to cases where the panel deforms under an explosion, to low velocity impacts (~4 m/s), ch aracterized by a long duration (~50 ms) similar to the automotive domain. The goal of the study is to develop a shoulder injury criterion for the EuroSID- 2re that is relevant over the whole loading conditions spectrum of the military domain. For that purpose, thirty-three laboratory ES-2re tests are conducted to replicate four PMHS shoulder impactor test series from the literature. Each test series corresponds to a different loading condition in term of impact velocity and duration: [28 m/s, 3 ms], [14 m/s, 9 ms], [7 m/s, 30 ms], [4 m/s, 50 ms]. The injury result (AIS 2015 scale) of each PMHS test is paired with the shoulder sensor force response signal of the corresponding ES-2re test, resulting in a sample of 75 paired-data. The proposed injury criterion resulting from the sample analysis is the straightened peak force Fs, which is an estimate of the peak of the external force applied to the shoulder. This criterion combines two metrics from the response signal of the shoulder force sensor Y-axis of the ES-2re ATD: the initial slope (S) and the peak (Fmax). The threshold value for a given injury risk depends on the duration of the impact: it is higher for the shorter duration. Thus, a third metric should be extracted from the ES-2re shoulder load cell: the duration of the force T. The present study proposes three force-duration threshold curves Fs=f(T) for low, medium, and high risks of shoulder AI2+ injury.

Critical thresholds in one-dimensional damped Euler–Poisson systems

This paper is concerned with the critical threshold phenomenon for one-dimensional damped, pressureless Euler–Poisson equations with electric force induced by a constant background, originally studied in [S. Engelberg and H. Liu and E. Tadmor, Indiana Univ. Math. J. 50 (2001) 109–157]. A simple transformation is used to linearize the characteristic system of equations, which allows us to study the geometrical structure of critical threshold curves for three damping cases: overdamped, underdamped and borderline damped through phase plane analysis. We also derive the explicit form of these critical curves. These sharp results state that if the initial data is within the threshold region, the solution will remain smooth for all time, otherwise it will have a finite time breakdown. Finally, we apply these general results to identify critical thresholds for a non-local system subjected to initial data on the whole line.

Structural Uncertainty in Onchocerciasis Transmission Models Influences the Estimation of Elimination Thresholds and Selection of Age Groups for Seromonitoring.

BackgroundThe World Health Organization recommends monitoring Onchocerca volvulus Ov16 serology in children aged <10 years for stopping mass ivermectin administration. Transmission models can help to identify the most informative age groups for serological monitoring and investigate the discriminatory power of serology-based elimination thresholds. Model predictions depend on assumed age-exposure patterns and transmission efficiency at low infection levels.MethodsThe individual-based transmission model, EPIONCHO-IBM, was used to assess (1) the most informative age groups for serological monitoring using receiver operating characteristic curves for different elimination thresholds under various age-dependent exposure assumptions, including those of ONCHOSIM (another widely used model), and (2) the influence of within-human density-dependent parasite establishment (included in EPIONCHO-IBM but not ONCHOSIM) on positive predictive values for different serological thresholds.ResultsWhen assuming EPIONCHO-IBM exposure patterns, children aged <10 years are the most informative for seromonitoring; when assuming ONCHOSIM exposure patterns, 5–14 year olds are the most informative (as published elsewhere). Omitting density-dependent parasite establishment results in more lenient seroprevalence thresholds, even for higher baseline infection prevalence and shorter treatment durations.ConclusionsSelecting appropriate seromonitoring age groups depends critically on age-dependent exposure patterns. The role of density dependence on elimination thresholds largely explains differing EPIONCHO-IBM and ONCHOSIM elimination predictions.

Pairs-trading under geometric Brownian motions: An optimal strategy with cutting losses

Pairs trading is about simultaneously trading a pair of stocks. A pairs trade is triggered when their prices diverge and consists of a short position of the strong stock and a long position of the weak one. Pairs trading bets on the reversal of their price strengths. In this paper, we study the optimal pairs-trading problem under general geometric Brownian motions and focus on trading with cutting losses. The objective is to trade the pairs over time to maximize an overall return with a fixed transaction cost. Our optimal policy is characterized by threshold curves obtained by solving the associated HJB equations. We provide sufficient conditions that guarantee the optimality of our trading rules. We also present numerical examples to illustrate.

Earthquake risk in reinforced concrete buildings during aftershock sequences based on period elongation and operational earthquake forecasting

Rapid post-earthquake damage assessment is critical to short-term earthquake crisis management. Reinforced concrete buildings may accumulate damage during an aftershock sequence, and short-term damage forecasts after the mainshock can aid in decision-making (in particular, on whether to allow immediate occupancy) before further damage actually occurs. This paper presents an operative damage forecasting and building tagging procedure for reinforced concrete buildings during synthetic aftershock sequences near Thessaloniki, Greece, for two hypothetical earthquake scenarios. The synthetic aftershock sequences are simulated, and the time-variant seismic vulnerability is modeled based on fragility curves for the damage state thresholds in terms of period elongation. Period elongation is chosen as a damage proxy because it is available for rapid damage assessment in buildings with permanent monitoring systems or for city-scale post-earthquake surveys. Time-variable damage state probabilities owing to aftershocks are estimated, and a building tagging scheme is proposed based on a traffic-light concept (red-orange-green) to assist in seismic crisis management during aftershock sequences.

Coding source localization through inter-spike delay: modelling a cluster of Pacinian Corpuscles using time-division multiplexing approach

The Pacinian Corpuscle (PC) is the most sensitive mechanoreceptor in the human body found in clusters of two or three. We extended our previous model of an isolated-PC to a cluster-PC focussing on relative spike delay and displacement threshold for understanding how the stimulus location is coded. In our model, two PCs with Gaussian overlapping receptive fields are arranged beneath the skin model. For a spatiotemporal stimulus (vibration), the model response is proposed to be a time-division multiplexing of responses from two PCs within the cluster. While the spike rate characteristics and pole-zero plot of cluster-PC model show similarities with the isolated-PC model, the frequency response shows ripples after 1 kHz as the distance (d) between the PCs increases. The stimulus location and d influence the relative spike delay and the displacement threshold, but not the spike rate. The novel contributions from our model include prediction of (i) relative spike delay for various d, stimulus frequency (f), and ψ, (ii) spike rate characteristics for varying f, and (iii) displacement threshold curve as a function of frequency for various d. Although the physiological validation of the novel predictions is impractical, we have validated the relative spike delay and the displacement threshold curves with experimental data in the literature.

On the fatigue crack growth behaviour of selective laser melting fabricated Inconel 625: Effects of build orientation and stress ratio

AbstractThe building of Inconel 625 material was carried out using the selective laser melting method, and its fatigue crack growth property at ambient temperature was experimentally investigated. Compact‐tension specimens with different building orientations were utilized to determine the stress intensity factor threshold and fatigue crack growth rate curves at different stress ratios (R). The results indicated that the fatigue crack growth properties in the near threshold stress intensity factor and Paris regions were greatly affected by the loading factor, as well as the orientation of the alloy. The mechanism of fatigue crack growth at different stages was observed and discussed using scanning electron microscopy. Finally, based on the framework of the linear elastic fracture, a new and applicable effective driving force factor range was introduced to replace the traditional stress intensity factor range (ΔK) with good accuracy for all of the fatigue crack growth test data, considering both the stress ratio and orientation.

Analytical treatment for cyclic three-state dynamics on static networks.

Whenever a dynamical process unfolds on static networks, the dynamical state of any focal individual will be exclusively influenced by directly connected neighbors, rather than by those unconnected ones, hence the arising of the dynamical correlation problem, where mean-field-based methods fail to capture the scenario. The dynamic correlation coupling problem has always been an important and difficult problem in the theoretical field of physics. The explicit analytical expressions and the decoupling methods often play a key role in the development of corresponding field. In this paper, we study the cyclic three-state dynamics on static networks, which include a wide class of dynamical processes, for example, the cyclic Lotka-Volterra model, the directed migration model, the susceptible-infected-recovered-susceptible epidemic model, and the predator-prey with empty sites model. We derive the explicit analytical solutions of the propagating size and the threshold curve surface for the four different dynamics. We compare the results on static networks with those on annealed networks and made an interesting discovery: for the symmetrical dynamical model (the cyclic Lotka-Volterra model and the directed migration model, where the three states are of rotational symmetry), the macroscopic behaviors of the dynamical processes on static networks are the same as those on annealed networks; while the outcomes of the dynamical processes on static networks are different with, and more complicated than, those on annealed networks for asymmetric dynamical model (the susceptible-infected-recovered-susceptible epidemic model and the predator-prey with empty sites model). We also compare the results forecasted by our theoretical method with those by Monte Carlo simulations and find good agreement between the results obtained by the two methods.

Evaluation of novel multiplex qPCR assays for diagnosis of pathogens associated with the bovine respiratory disease complex

Bovine respiratory disease complex is the most common disease requiring the use of antimicrobials in industrial calf production worldwide. Pathogenic bacteria (Mannheimia haemolytica (Mh), Pasteurella multocida (Pm), Histophilus somni (Hs), and Mycoplasma bovis) and a range of viruses (bovine respiratory syncytial virus, bovine coronavirus, bovine parainfluenza virus type 3, bovine viral diarrhea virus and bovine herpesvirus type 1) are associated with this complex. As most of these pathogens can be present in healthy and diseased calves, simple detection of their presence in diseased calves carries low predictive value. In other multi-agent diseases of livestock, quantification of pathogens has added substantially to the predictive value of microbiological diagnosis. The aim of this study was to evaluate the ability of two recently developed quantitative PCR (qPCR) kits (Pneumo4B and Pneumo4V) to detect and quantify these bacterial and viral pathogens, respectively.Test efficiencies of the qPCR assays, based on nucleic acid dilution series of target bacteria and viruses, were 93–106% and 91–104%, respectively, with assay detection limits of 10–50 copies of nucleic acids. All 44 strains of target bacteria were correctly identified, with no false positive reactions in 135strains of non-target bacterial species. Based on standard curves of log10 CFU versus cycle threshold (Ct) values, quantification was possible over a 5-log range of bacteria. In 92 tracheal aspirate samples, the kappa values for agreement between Pneumo4B and bacterial culture were 0.64-0.84 for Mh, Pm and Hs. In an additional 84 tracheal aspirates, agreement between Pneumo4B or Pneumo 4V and certified diagnostic qPCR assays was moderate (0.57) for M. bovis and high (0.71–0.90) for viral pathogens. Thus Pneumo4 kits specifically detected and quantified the relevant pathogens.

Advanced Signal Sensing Method With Adaptive Threshold Curve Based on Time Frequency Domain Reflectometry Compensating the Signal Attenuation

Adaptive fault detection method, which is compensating the wave attenuation along the propagation, is proposed in this article. Long cable system installed in the factory need to develop precise fault detection method considering propagation dispersion. Using the derived time delay between the incident and reflected wave which is generated from the fault, fault can be localized. The time-frequency cross correlation (TFCC) is a signal scanning process based on the similarity of the energy spectrum for detecting the reflected signal mixed with the noise. The threshold value in TFCC is a reference constant value for judging whether or not a fault is present. Due to the attenuation and dispersion of signal along the propagation, a new threshold value function considering attenuation and dispersion is needed. We propose the adaptive threshold curve for compensating the signal attenuation. We design the equivalent circuit of target cable ( $\text{7}\,\text{m}$ length) and optimal reference signal based on the comparative analysis between the results of computer simulation and actual experiments of $\text{7}\,\text{m}$ length cable. Based on the designed equivalent circuit of target cable( $\text{7}\,\text{m}$ length), a long cable system is modeled by simulation and the performance of the proposed method is proved through the simulation under the various noise level environments.

Amphibious hearing in a diving bird, the great cormorant (Phalacrocorax carbo sinensis).

Diving birds can spend several minutes underwater during pursuit-dive foraging. To find and capture prey, such as fish and squid, they probably need several senses in addition to vision. Cormorants, very efficient predators of fish, have unexpectedly low visual acuity underwater. So, underwater hearing may be an important sense, as for other diving animals. We measured auditory thresholds and eardrum vibrations in air and underwater of the great cormorant (Phalacrocorax carbo sinensis). Wild-caught cormorant fledglings were anaesthetized, and their auditory brainstem response (ABR) and eardrum vibrations to clicks and tone bursts were measured, first in an anechoic box in air and then in a large water-filled tank, with their head and ears submerged 10 cm below the surface. Both the ABR waveshape and latency, as well as the ABR threshold, measured in units of sound pressure, were similar in air and water. The best average sound pressure sensitivity was found at 1 kHz, both in air (53 dB re. 20 µPa) and underwater (58 dB re. 20 µPa). When thresholds were compared in units of intensity, however, the sensitivity underwater was higher than in air. Eardrum vibration amplitude in both media reflected the ABR threshold curves. These results suggest that cormorants have in-air hearing abilities comparable to those of similar-sized diving birds, and that their underwater hearing sensitivity is at least as good as their aerial sensitivity. This, together with the morphology of the outer ear (collapsible meatus) and middle ear (thickened eardrum), suggests that cormorants may have anatomical and physiological adaptations for amphibious hearing.

EPOWT: A denoising technique of the electrocardiography signal transmission via 5G wireless communications

ABSTRACTThis article provides a thorough review of 5G wireless electrocardiography (ECG) communication for actual cardiac signal using both technical and clinical features for the purpose of recommending real‐time observation. Major issue regarding this frame work is the distortion and smoothness of ECG signal for the cardiologist advice also it needs correct diagnosis at the proper time. Extensive 5G wireless simulated scenarios are used to supervise the compressed ECG signal on reception. An efficient ECG transmission protocol is a modern and consistent ECG transmission protocol which is used to retransmit the noise signals. Thus, we are filtering the ECG signals to improve the quality which may directly affects the medical diagnosis. Because, time and frequency indicators can be obtained by the wavelet analysis but majority of the error functions cannot be flexible to various signals because of the static transition curve of threshold. Hence, we proposed a new emperor penguin optimization (EPO) together with wavelet thresholding (EPOWT) method. Here, the EPOWT is estimated through the means of real‐time ECG records. The outcomes of filtering process shows that the proposed EPOWT approach can achieve smooth threshold transition and soft thresholding bring the wavelet coefficient. EPOEPO algorithm is used to improve its flexibility to different signals. The EPOWT can generate an essential noise‐free signal by balancing the smoothness and signal distortion filtering for transmission. The proposed method can attains 2.9 seconds delay during simulation. Thus, the 5G wireless channel parameter's functioning zone is simple to acquire.

Auditory brainstem responses in the bat Carollia perspicillata: threshold calculation and relation to audiograms based on otoacoustic emission measurement.

An objective method to evaluate auditory brainstem-evoked responses (ABR) based on the root-mean-square (rms) amplitude of the measured signal and bootstrapping procedures was used to determine threshold curves (see Lv et al. in Med Eng Phys 29:191-198, 2007; Linnenschmidt and Wiegrebe in Hear Res 373:85-95, 2019). The rms values and their significance for threshold determination depended strongly on the filtering of the signal. Using the minimum threshold values obtained at three different low-frequency filter corner frequencies (30, 100, 300Hz), ABR threshold curves were calculated. The course of the ABR thresholds was comparable to that of published DPOAE (distortion-product otoacoustic emission) thresholds based on a - 10dB SPL threshold criterion for the 2f1-f2 emission (Schlenther et al. in J Assoc Res Otolaryngol 15:695-705, 2014, frequency range 10-90kHz). For frequencies between 20 and 80kHz, which is the most sensitive part of the bat's audiogram, median thresholds ranged between 10 and 28dB SPL, and the DPOAE thresholds ranged between 10 and 23dB SPL. At frequencies below 20kHz (5-20kHz) and above 80kHz (80-120kHz), ABR thresholds increased by 20dB/octave and 45dB/octave, respectively. We conclude that the combination of objective threshold determination and multiple filtering of the signal gives reliable ABR thresholds comparable to cochlear threshold curves.

Effect of chronic nicotine consumption on motor cortical excitability: A transcranial magnetic stimulation study

Transcranial magnetic stimulation (TMS) allows exploration of the mode of action of neuroactive substances in the human brain, and allows evaluation of neuronal networks, which might be involved in the action of nicotine. The aim of the present study was to explore motor cortex excitability in chronic smokers and non-smokers using TMS. The study included 50 healthy subjects, of whom 25 were chronic smokers and 25 were age- and sex-matched non-smokers. Number of cigarettes per day and duration of smoking in years were documented. Serum level of cotinine was measured. Resting and active motor threshold (RMT, AMT) and input-output curves (I/O) were performed to assess corticospinal excitability. The duration of the contralateral silent period (cSP) at different ranges of stimulation intensities and ipsilateral silent period (iSP) were used as measures of inhibition. There were no significant differences either in RMT or AMT between groups. I/O curve showed a significant intensity×group interaction (P=0.008). This was attributable to significantly higher amplitudes of MEP among smokers than non-smokers especially at 130, 140 and 150% of RMT (P=0.0001 and P=0.03 and 0.02 respectively). The mean duration of the cSP at different intensities and iSP duration were similar in both groups. Nicotine level and smoking index were correlated respectively with rMT and iSP (P=0.03 and 0.01). The present results confirm previous findings by Grundey et al. (2013) that chronic nicotine consumption is characterized by hyperexcitability of corticospinal output. We speculate that it is a secondary adaptation to long-term nicotine use with high inter-individual variance.

Modeling stochastic resonance in humans: The influence of lapse rate.

Adding noise to sensory signals generally decreases human performance. However, noise can improve performance too, through a process called stochastic resonance (SR). This paradoxical effect may be exploited in psychophysical experiments to provide insights into how the sensory system processes noise. Here, I develop an extension on signal detection theory to model stochastic resonance. I show that the inclusion of lapse rate allows for the occurrence of stochastic resonance in terms of the performance metric d', when the criterion is set suboptimally. High levels of lapse rate, however, cause stochastic resonance to disappear. It is also shown that noise generated in the brain (i.e., internal noise) may obscure any effect of stochastic resonance in experimental settings. I further relate the model to a standard equivalent noise model, the linear amplifier model, and show that lapse rate scales the threshold versus noise (TvN) curve, similar to the efficiency parameter in equivalent noise (EN) models. Therefore, lapse rate provides a psychophysical explanation for reduced efficiency in EN paradigms. Furthermore, I note that ignoring lapse rate may lead to an overestimation of internal noise in EN paradigms. Overall, describing stochastic resonance in terms of signal detection theory, with the inclusion of lapse rate, may provide valuable new insights into how human performance depends on internal and external noise. It may have applications in improving human performance in situations where the criterion is set suboptimally, and it may provide additional insight into internal noise hypotheses related to autism spectrum disorder.