Hemiaulus hauckii and the heterocyst-forming cyanobacterium Richelia intracellularis makes an important contribution to new production in the world’s oceans, but its study is limited by short-term survival in the laboratory. In this symbiosis, R. intracellularis fixes atmospheric dinitrogen in the heterocyst and provides H. hauckii with fixed nitrogen. Here, we conducted an electron microscopy study of H. hauckii and found that the filaments of the R. intracellularis symbiont, typically composed of one terminal heterocyst and three or four vegetative cells, are located in the diatom’s cytoplasm not enclosed by a host membrane. A second prokaryotic cell was also detected in the cytoplasm of H. hauckii, but observations were infrequent. The heterocysts of R. intracellularis differ from those of free-living heterocyst-forming cyanobacteria in that the specific components of the heterocyst envelope seem to be located in the periplasmic space instead of outside the outer membrane. This specialized arrangement of the heterocyst envelope and a possible association of the cyanobacterium with oxygen-respiring mitochondria may be important for protection of the nitrogen-fixing enzyme, nitrogenase, from photosynthetically produced oxygen. The cell envelope of the vegetative cells of R. intracellularis contained numerous membrane vesicles that resemble the outer-inner membrane vesicles of Gram-negative bacteria. These vesicles can export cytoplasmic material from the bacterial cell and, therefore, may represent a vehicle for transfer of fixed nitrogen from R. intracellularis to the diatom’s cytoplasm. The specific morphological features of R. intracellularis described here, together with its known streamlined genome, likely represent specific adaptations of this cyanobacterium to an intracellular lifestyle.The symbiosis between the diatom  Hemiaulus hauckii (2 fixation (primary productivity) supported by N2 fixation (diazotrophy)  are a morphologically and ecologically diverse group of algae that have a cell wall, known as a “frustule,” that incorporates silica as a main component . The fru hauckii . As in o hauckii . Diatoms hauckii , making otrophy) . Some of partner .2-fixing enzyme, nitrogenase, is sensitive to oxygen, these organisms usually separate nitrogen fixation from photosynthesis in either time or space , bear outside of the outer membrane an extra envelope that is composed of an inner laminated glycolipid layer (Hgl) and an outer homogeneous polysaccharide layer (Hep)  are concentrated close to the heterocyst poles, where they form a “honeycomb”-like structure  . The Hgler (Hep) . Interesbacteria . In the tructure . Terminatructure . Heterocst neck” . Cyanophst neck” .H. hauckii with an emphasis on its endosymbiont, R. intracellularis. We show that R. intracellularis resides directly in the cytoplasm of the diatom. Additionally, a second prokaryotic organism, which was less frequently observed, appeared also integrated in the H. hauckii cytoplasm. The cell envelope of R. intracellularis contains numerous membrane vesicles and shows a close association to the diatom host’s mitochondria. We also found that heterocyst morphology is different in R. intracellularis than in free-living heterocyst-forming cyanobacteria.In this work, we present an electron microscopic study of Hemiaulus hauckii cells grown from samples collected with net tows in the channel at Port Aransas, Texas, Gulf of Mexico in Fall 2012. Late exponential phase, dense cultures were prepared using an artificial seawater medium as described in L-Lys for subsequent processing.This study was performed with symbiotic 1, from which 70-nm sections were picked up on Formvar-coated grids and imaged with a Tecnai T12 TEM, operated at 80 kV.For electron microscopy, cells were initially fixed overnight at room temperature, in a mixture of EM-grade aldehyde fixatives: 4% glutaraldehyde and 2% formaldehyde in 0.1 M cacodylate buffer at pH 7.4 with 35 mg/mL Instant Ocean. After rinses in buffer with decreasing salinity, the cells were fixed in reduced osmium . Before additional processing, the cell preparations were dehydrated in an ethanol series, in which 2% uranyl acetate was incorporated in the 70% ethanol step. From this point there were two paths: (i) cells for scanning electron microscopy (SEM) were dehydrated with critical point drying (CPD) and then coated with 15 nm of platinum-palladium and imaged with a Zeiss Supra 40VP SEM; (ii) cells for transmission electron microscopy (TEM) were embedded in Epon Hard 812 (Electron Microscopy Sciences)H. hauckii. The average and standard deviation of the three measurements is reported. Additionally, the numbers of chloroplasts per H. hauckii were also enumerated when cross sectioning allowed full visualization.Measurements of cell characters were made in ImageJ . BrieflyR. intracellularis strain HH01 (available at https://img.jgi.doe.gov/cgi-bin/m/main.cgi) was performed by BLASTp analysis  showed chains of diatom cells (R. intracellularis (A sample of om cells . In thesom cells  of the fom cells . The disom cells . The lonllularis . The frullularis . Diatomsllularis .H. hauckii were prepared for transmission electron microscopy (TEM). Longitudinal . In total, 34 R. intracellularis filaments were measured for cell dimensions of the heterocyst and vegetative cells. Considering the dimensions summarized in R. intracellularis filaments visualized by fluorescence microscopy  were clearly observed in some images  or an established third partner in the symbiosis. Interestingly, visualization by epifluorescence microscopy has shown the presence of a possible second non-filamentous cyanobacterial endosymbiont in H. hauckii collected from the same location as the cells presented here  of molecular exchange between the two partners. The cyanobacterium fixes CO2 and N2  from the cyanobacterium to its host. Interestingly, membrane vesicles have been observed in the proximity of the periplasmic symbiont of the diatom Rhizosolenia clevei (Anabaena cells to the growth medium (Azolla (R. intracellularis HH01 is about 3.24 Mbp, much smaller than the genome size of most free-living heterocyst-forming cyanobacteria, which is about 7–9 Mbp (The location of 2 and N2 , and it ied here , has ideied here . Richelinitrogen , and themporters , suggestmaterial . We hypoa clevei  and a cya clevei . Membranh medium . Outer-ih medium , and mem (Azolla . The siz 7–9 Mbp . If some 7–9 Mbp , the mem2 fixation is very sensitive to oxygen, and in R. intracellularis the N2 fixation machinery is likely exposed not only to ambient oxygen but also to oxygen produced photosynthetically by both its vegetative cells and host diatom. Here we have observed the presence of numerous mitochondria nearby the cyanobacteria in the diatom’s cytoplasm. Although this might reflect the presence of a high number of mitochondria in the diatom, mitochondria frequently appeared to be tightly associated to the outer membrane of the cyanobacterium, revealing a possible specific relation. It is possible that the mitochondria contribute to decreasing the level of intracellular oxygen in the vicinity of the cyanobacterium. Whether the endosymbiont could additionally interact with the host mitochondria as has been shown for some endosymbiotic algae (Midichloria mitochondrii (Nic algae  and for chondrii , or altechondrii , is unknR. intracellularis lack the extra envelope deposited outside of the outer membrane that is characteristic of the heterocysts of free-living heterocyst-forming cyanobacteria (R. intracellularis appear to contain specific envelope components in the periplasm, between the cytoplasmic and outer membranes, making a heterocyst periplasm that is different from that of the vegetative cells. Because the genome of R. intracellularis HH01 contains most of the genes that are necessary in Anabaena for production of the Hep and Hgl layers (R. intracellularis Hep and Hgl layers. However, the hep and hgl gene complement of R. intracellularis HH01 is not identical to that of Anabaena (Hemiaulus-associated Richelia (R. intracellularis are indeed the Hep and Hgl layers of this cyanobacterium, the genetic basis for deposition of these layers in the periplasmic space is still unknown. The role of the Hep layer protecting the Hgl layer from dispersion in the diluted external medium in free-living organisms might be unsuitable for the intracellular location in which R. intracellularis thrives. Thus, the possible specific arrangement in the periplasmic space of the heterocyst Hep and Hgl layers may represent an adaptation to the intracellular lifestyle of R. intracellularis, impacting the protection of nitrogenase from oxygen.The heterocysts of bacteria . Insteadl layers , 2, it iAnabaena , 2, and Richelia . If the R. intracellularis to the cytoplasm of H. hauckii have been observed only in vegetative cells, raising the question of why are they missing from heterocysts. Intercellular molecular exchange in filamentous cyanobacteria takes place through proteinaceous septal junctions (R. intracellularis can make the vegetative cells a platform for the transfer of fixed nitrogen to the diatom. This indirect route of transfer of the nitrogen fixed in the heterocyst to the cytoplasm of the diatom may be needed because the specialized cell envelope of the heterocyst may impede the formation and export of membrane vesicles.The membrane vesicles that may be involved in molecular transfer from unctions . Althougunctions . InterceH. hauckii-R. intracellularis symbiosis the cyanobacterium is not enclosed by a host membrane and resides directly in the cytoplasm of the diatom. Lack of extra membranes around the cyanobacterium indicates that this is not an organelle resulting from serial endosymbiosis. However, after 50–100 million years since it was established (In summary, in the ablished , the endablished  and adapablished  and the ablished . As showThe original contributions presented in the study are included in the article/TV designed the research. TV and DR performed the research. EF, MN-M, and RF analyzed the data. EF wrote the manuscript. TV, DR, MN-M, and RF provided the manuscript revisions. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. 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Equation learning aims to infer differential equation models from data. While a number of studies have shown that differential equation models can be successfully identified when the data are sufficiently detailed and corrupted with relatively small amounts of noise, the relationship between observation noise and uncertainty in the learned differential equation models remains unexplored. We demonstrate that for noisy datasets there exists great variation in both the structure of the learned differential equation models and their parameter values. We explore how to exploit multiple datasets to quantify uncertainty in the learned models, and at the same time draw mechanistic conclusions about the target differential equations. We showcase our results using simulation data from a relatively straightforward agent-based model (ABM) which has a well-characterized partial differential equation description that provides highly accurate predictions of averaged ABM behaviours in relevant regions of parameter space. Our approach combines equation learning methods with Bayesian inference approaches so that a quantification of uncertainty can be given by the posterior parameter distribution of the learned model. Understanding the mechanistic basis for the observed macroscale behaviour, in order to gain fundamental insights into biological phenomena, is one of the key challenges in biology.Mathematical models are well placed to help provide such insights, providing a rigorous framework where hypotheses can be generated, tested and refined. While interactions between individual agents can be naturally described by agent-based models (ABMs) that prescribe precise rules for the interactions between agents –4, prediTraditional approaches to mathematical modelling use experimentally derived mechanistic hypotheses to derive differential equation models in which the various terms of a given model are designed to describe the hypothesized mechanisms for that scenario. Calibration of the model to data then involves finding the parameters that minimize the discrepancy between the model output and data. The ensuing, iterative process of testing and refining the model against further experimental data allows the original hypotheses to be refined, and so new insights gained.Equation learning (EQL) methods take a different approach to model building, aiming to infer the dynamical systems model that best describes given time-series data by leveraging statistical and machine learning tools to learn the appropriate terms of a differential equation model directly from the data. In particular, the PDE-FIND algorithm ,12 takesEQL methods have rapidly gained popularity, mainly owing to increases in computational power, and a number of other techniques to establish models from data now exist. For example, biologically informed neural networks , an exteet al. [The fact that EQL can discover previously undetected mechanisms, discriminate between competing models or estimate biological quantities of interest that are difficult to measure experimentally makes EQL attractive to scientists working with real-world data. However, practitioners wishing to develop models that they can use in real-world settings require, in addition, a thorough quantification of uncertainty ,16–19. Tet al.  have recet al. [et al. [Recently, some authors ,22 have et al.  investigIn this work, we demonstrate that noise can significantly impact both the structure and the values of the parameters of learned differential equation models, rendering uncertainty quantification a crucial component of the EQL process. As such, our overarching aim is to develop and showcase a method for uncertainty quantification in the context of EQL, where we harness the immense computational efficiencies of PDE-FIND in learning point estimates of governing equations, together with the power of computational Bayesian inference in evaluating the level uncertainty in the learned equation. Our motivation is thus: on the one hand, PDE-FIND provides a computationally cheap method to obtain a point estimate for the governing equation from a single time series. However, when the data are noisy, the individual predictions are unreliable. This is seen on the left-hand side of https://github.com/simonmape/UQ-for-pdefind.In this work, we demonstrate the potential of this approach using synthetic data generated from a widely used ABM that describes the behaviour of a motile and proliferative cell population and can be coarse-grained to a mean-field PDE that accurately describes ABM dynamics in certain regions of parameter space. In §2, we describe the ABM and discuss in detail its relation with a governing PDE, as well as the PDE-FIND algorithm. In §3, we demonstrate both that the PDE models learnt using PDE-FIND are intrinsically variable when the data are noisy and that PDE-FIND can learn unphysical models. We provide an explanation for this in terms of the objective function of the PDE-FIND algorithm. In §4, we propose a method to combine methods for Bayesian inference with PDE-FIND in order to learn the structure of the governing PDE model, construct a prior parameter distribution for the PDE model and infer the posterior parameter distribution of the learned PDE model. We conclude in §5 with a discussion of our results, and avenues for future research. Code for all algorithms can be found at . 2We begin by describing the ABM and briefly outlining how to derive the corresponding coarse-grained PDE model, and then we provide details of the PDE-FIND algorithm. (a)ABMs allow practitioners to investigate the collective behaviour of a population of individuals based on a description of the behaviour of individuals within that population. Here, in order to take into account the interactions between individuals of the population, we follow the volume-exclusion model presented in ,23–26 foWe assume that agents occupy sites on a square lattice of spacing At each time step, Let  (i)To make progress in deriving a coarse-grained PDE equivalent, we first note that the choice of a pseudo-one-dimensional initial condition means that we can consider deriving a one-dimensional PDE for ximation –29.We then identify eader to .Identification of the ABM with a coarse-grained macroscale PDE model motivates us to investigate the performance of EQL methods trained on data generated by the ABM, since the PDE accurately describes the time evolution of the expected value of the density profile and so we can evaluate the performance of EQL methods against equation . Note thve to pm ,27,30. (ii)As test cases for learning the governing equations from data, we explore three different parameter regimes in the model, which each correspond to a biologically relevant setting: in case I, we consider agents moving without bias and without proliferation , so that we have a ‘ground truth’ PDE against which to benchmark the EQL methodology. Second, at early times the density profiles are very similar for the three different cases, but at later times differences due to the effects of bias and proliferation are clearly discernible. This observation implies that the EQL methodology will require data on sufficiently long time scales to be able to accurately learn the correct PDE model. (b)et al. [In the following, assume that we have time-series data for an unknown function equation . We foll . For more details and motivation of the method, we refer to [The default implementation of PDE-FIND as proposed by Rudy et al.  supplemeequation  is foundequation  may contrefer to , and for (i)We first generate ABM data for cases I, II and III. For each, we generate two datasets with different noise levels, denoting them PDE-FIND  and use We select a library of candidate terms that includes all polynomial terms up to order 2 and up to the second derivative. . 3In this section, we showcase three different, but related, directions in the uncertainty quantification of the learned differential equations. In §3a, we demonstrate the intrinsic variability of the learned coefficients in the presence of observation noise. We evaluate how uncertainty changes as the noise level is varied and suggest that even when using state-of-the-art denoising approaches a need for uncertainty quantification remains. Although increasing the signal-to-noise ratio helps, regardless of the method there is still variability that needs to be quantified. In particular, this is important in biological applications where observations are often very noisy and practitioners rarely have access to very large amounts of data. In §3b, we investigate the impact of varying the regularization hyperparameter in PDE-FIND with a view to asking whether this can be optimized to reduce uncertainty. We find that, while this is possible, parameter estimates are still uncertain and this uncertainty needs to be quantified. Finally, in §3c, we demonstrate that a key issue with PDE-FIND is that it aims to fit the time derivative of the solution and does not take into account the fit of the observed density to the data, leading to unphysical predictions. We demonstrate how to mitigate these issues in §4 through the use of Bayesian methods where we can evaluate uncertainty in a framework that optimizes the fit of the model density profile to the data.identification ratio. Assume that for each sample, In order to quantify the variability in results from the application of PDE-FIND, we introduce a statistic which we term the equation  is inclu (a)11These settings were used in the context of estimating the diffusion parameter in a random walk model in the electronic supplementary material of .We first demonstrate that a naive application of PDE-FIND on noisy synthetic data yields variable and unreliable parameter estimates. For this application, we do not carry out hyperparameter tuning, but simply use widely adopted parameter settings to learn the coefficients. For each of the two datasets associated with each of case I, case II and case III, where dataset n ratios  to quant (i)c). In some cases, PDE-FIND identifies just one of the two terms, and in others it identifies a combination of the two. This result highlights that potentially the wrong PDE can be learnt from noisy data, partly because of the fact that different PDEs can give rise to similar predictions. Since all of the ABM data samples have the same corresponding coarse-grained PDE, this highlights the inability of PDE-FIND to confidently learn the governing PDE from noisy data.For case I, recall that the true PDE model contains only the term  dataset . In addirrelated c. In som (ii)For case II, where motility is biased, For the low-noise dataset  (iii)For case III, which includes proliferation, iability ,35. For  (iv)To investigate the impact of noise on PDE-FIND, we carried out two further studies in which the noise in the data is reduced. First, we investigated whether choosing a more coarse spatial grid improves the PDE-FIND predictions. Choosing a more coarse spatial discretization results in a smoother density profile; however, greater errors are incurred in the approximation of the spatial derivatives and fewer data points are available. For this experiment, we subsampled the data along the et al. [Second, we investigated other means to reduce observation noise. In applications of PDE-FIND to real-life data, practitioners will typically not be able to control for the amount of observation noise in the way that is done in the numerical experiments of this work, hence methods to smooth data may be useful in allowing identification of the PDE model. In electronic supplementary material, §S3, we explore two practically appealing methods, convolution with a Gaussian kernel and an implementation of principal component analysis for EQL by Li et al. . Our res (b)et al. [Recall that, in algorithm 1, a free parameter, equation . It is w 22For functions  However, when the data are noisy, a number of different linear combinations of the spatial derivatives can result in an We now provide an explanation for the poor performance of PDE-FIND on the ABM data. The PDE-FIND algorithm solves a sparse regression problem to fit linear combinations of spatial derivatives to the time derivative. When data contain little to no noise, the temporal and spatial derivatives can be accurately estimated, and so the relationship between spatial and temporal derivatives can be inferred from observed data. In this context, comparing model predictions by their performance with respect to the ruth PDE . In eleca), as well as the difference between the density predicted by the PDE model and that of the averaged ABM data (b). We estimate the sum of the In summary, what this striking difference in predictive capabilities of the learned PDEs reveals is that coefficients that optimize equation  do not nequation . The two Ci(t)⟩  a, as welABM data b. We estIn summary, in this section we have shown that the density profile loss landscape is much more informative about the underlying PDE model than the derivative loss landscape. We exploit this observation in the following section, where we propose a method which we term ‘Bayes-PDE-FIND’ both to tackle the issues relating to the uncertainty in the predictions of PDE-FIND for noisy data and to quantify the uncertainty in PDE-FIND predictions.. 4In this section, we propose an approach that harnesses the likelihood-free method of approximate Bayesian computation to quantify the uncertainty in estimates provided by PDE-FIND. In brief, our method involves the application of PDE-FIND to multiple datasets in order to define a prior distribution for the coefficients of the PDE library terms,  (a)The goal of Bayesian parameter estimation is to update prior beliefs about model parameters equation , which tApproximate Bayesian computation is a popular likelihood-free tool to estimate the posterior parameter distribution ,37. It aDespite the apparent simplicity of the ABC method, unless an informative prior is used to constrain the space of possible parameters and informative summary statistics can be found, the application of ABC methods to models with high-dimensional parameter space and output space is generally computationally prohibitive. In particular, this high computational cost means that the direct application of ABC methods to estimate the coefficients equation  is essen (b)Assume that, for each sample, equation  is incluTo make progress in specifying a prior distribution for the library coefficients, Spike-and-slab models are powerful tools to perform variable selection in regression problems –41. The exploration subset) and the other subset to perform inference (inference subset). We first set We follow the hierarchical Bayesian group LASSO model with an independent spike-and-slab-type prior for each coefficient . We set  & Ghosh , μ=0. InThese considerations now imply that the prior for The key advantage in specifying this prior distribution is that we are now only required to perform Bayesian inference for a reduced model that has a much lower dimensional parameter space We now outline the Bayes-PDE-FIND approach. In essence, we apply the PDE-FIND algorithm to each sample quations  and The aim of this section is to showcase how the Bayes-PDE-FIND algorithm can be used to significantly improve the quality of the learned PDE model. Recall that the aim is to reduce the uncertainty surrounding which coefficients to include in the model, to reduce uncertainty in the estimated model parameters and to improve the posterior predictive capability of the model by finding a posterior parameter distribution that takes into account properties of the observed density profiles. For each of the noisy-data test cases, that is, datasets  package  for the Recall that for case I, where the ABM contains only unbiased motility, the only two coefficients regularly identified using PDE-FIND are d cu⋅uxx . This meand cuxx  and so fand cuxx  and so ftoleranceWe explore the results of using Bayes-PDE-FIND with a form of ABC which is known as ABC-rejection sampling. At each step, equation  is integWe set  (i)a) results in a posterior distribution with the true parameter value contained in the support of the posterior. Moreover, the sparsity enforced by the prior ensures that the correct PDE structure, with only b), although the true parameter value is contained in the support of the posterior distribution, the correct PDE structure is generally not established, with both In the case of unbiased motility only In the case of biased motility In the case of unbiased motility and proliferation informed spike-and-slab and sparse uniform), we also consider a spike-and-slab prior with mean naive spike-and-slab, as well as a uniform prior on all library coefficients , which we refer to as classic Bayesian. In each of the experiments, we perform ABC rejection to sample 300 parameters from the ABC posterior with the same thresholds as used in cases I–III and record the time taken to complete. Inference is done on a Lenovo desktop computer using six Intel(R) i5-8500T cores with clock speed 2.10 GHz. To highlight the performance of our method, we compare the computational cost and the accuracy of our method against alternative options. In addition to the spike-and-slab model and uniform priors used to generate the posterior distributions In summary, figures ve check . For eac. 5The aim of this work was to develop and showcase a framework to perform uncertainty quantification for EQL methods in the context of noisy spatio-temporal data. In essence, our approach harnesses EQL methodologies to generate an informed prior distribution, which is then used within a Bayesian framework to estimate both the model structure and posterior parameter distribution. The framework was developed in the context of the PDE-FIND EQL methodology and ABC rejection sampling, but it is sufficiently general that it could be extended and applied in the context of other EQL and Bayesian inference methodologies.The motivation for developing such a framework stems from the fact that EQL methodologies such as PDE-FIND typically make variable predictions, in terms of both model structure and parameters, in the presence of noise, which is common for datasets in the life and biomedical sciences. Incorporating uncertainty quantification through the use of Bayesian statistics approaches provides a means to quantify the uncertainty in both model structure and parameter values, and understand how such uncertainty propagates into model predictions.We showcased our methodology in the context of noisy spatio-temporal data generated using a canonical ABM that has seen widespread use in the modelling of motile and proliferative cell populations, and which has a corresponding PDE model that can make accurate predictions of averaged ABM output. We used datasets generated in three different parameter regimes (which incorporate different cellular behaviours) to show how to combine the advantages of the PDE-FIND algorithm  with those of ABC (ability to quantify uncertainty in parameter estimates and model predictions).in vitro, so that the experimental design can provide as much information as possible. Nonetheless, the standard choice of PDE-FIND library means that it is possible for the PDE-FIND algorithm to return PDE models in which the density does not satisfy a conservation equation of the formThere are a number of ways in which our approach can be further improved going forward. For example, we saw that our approach may return models that fail to capture important features of the ABM, as a result of either learning the structure of the model incorrectly or inaccurate estimation of model parameter values. In the context of case II, which models biased cell motility, these inaccuracies arise partly as a result of the data used and stem from the choice of initial condition and the time scale over which the data are collected. Ultimately, the extensibility and robustness of any data-driven method are limited by the information contained in the data. Where the initial PDE-FIND screen fails to identify what are believed to be relevant terms in the PDE, it is likely that the supplied data do not provide enough information to discriminate between different forms of the PDE. In such a scenario, different experimental designs, such as a different initial condition or longer simulation time, might distinguish some of the terms of the system under consideration. We highlight that the flexibility of ABMs allows one to explore different behaviours in the model under varying experimental conditions. By analysing the effect of these variations on the resulting predictions, one can obtain important insights into how much information is contained in the data about the governing laws. This may be helpful in informing experimental design Secondly, our approach could be improved through the use of more efficient ABC samplers, such as ABC sequential Monte Carlo samplers that target the posterior distribution by evolving the prior distribution through a series of intermediate distributions. This requires the development of proposal distributions that can maintain the sparsity of PDE coefficients, as encoded by the PDE-FIND informed prior, so that the learned PDEs retain a simple and interpretable structure.Click here for additional data file.


The objective is to assess the benefit of cochlear implants in health-related quality of life among postlingually deaf adults in China.  Seventy-one postlingually deaf adult cochlear implant users in one cochlear implant center in China participated in this study. The HUI3 questionnaire as a measurement evaluated their quality of life. A cross-sectional analysis was conducted.  Cochlear implant had made statistically significant improvements in quality of life among postlingually deaf adults. The HUI3 scores were significantly better in four attributes  after a cochlear implant. A positive correlation between change in hearing and improvement in emotion was significant. The change in pain and improvement in emotion also had a positive correlation. The duration of HA and CI use had no impact on the gain in HUI3 scores, and the baseline of hearing and emotion state had an influence on HUI3 gain.  This study found cochlear implant users had a greatly improved hearing, speech, emotion, and pain, which made statistically significant improvement in quality of life among postlingually deaf adults. There was a statistically significant association between the change of emotion state and improvement in hearing level. We also found a statistically significant correlation between the reduction of feeling in pain and improvement in emotion. The change of quality of life seemed to be influenced by the primary state of emotion and hearing. We believe the measurement HUI3 is suitable for these patients in China. In China, by 2014, deaf adults only occupy 15% of the total cochlear implants (CI), although the population of adult hearing loss is more than 10 times of the number of pediatric hearing loss. Since national programs like China Disabled Persons' Federation (CDPF) were initiated, more and more adults have restored their hearing by CI . TherefoA cross-sectional study was performed at the First Affiliated Hospital of Anhui Medical University, Anhui, China. This study was approved by the Health Research Ethics Committee. All subjects signed an informed consent prior to participating in this study.Seventy-one postlingually deaf adult patients with bilateral severe and (or) profound sensorineural hearing loss participated in this study; they were implanted at the Cochlear Implant Department of the First Affiliated Hospital of Anhui Medical University, Anhui, China, from January 2016 to December 2020. Baseline information was collected before activation of the cochlear implant processor. The demographic data contained gender, duration of wearing HA before implant, age at implant, duration of CI use, and the results of self-assessment at the last visit.Data were collected via a voluntary online questionnaire.The measurement used to assess the HRQOL of patients is HUI3. HUI3 is a self-completing questionnaire to evaluate health conditions from eight attributes, vision, hearing, speech, ambulation, dexterity, emotion, cognition, and pain; each dimension has five or six levels. Each level corresponds to a certain score which is used to be normalized to a utility from 0 to 1. 1 represents perfect health, and 0 represents the worst health. There are two ways to obtain the HUI3 scores single-attribute utility scores and multiattribute scores. Single-attribute utility scores were assessed when evaluated the changes of a single attribute. Multiattribute scores were used to compare integrated changes , 7.t-test was used to compare preoperative with postoperative scores. Multivariable linear regression was used to detect demographic variables associated with primary HUI3 multiattribute scores (preoperative HUI3 multiattribute scores) and gain in HUI3 multiattribute scores. Pearson's correlation tests were used to discover relationships among attributes that had statistically significant differences before and after CI.The SPSSAU20.0 software was used for statistical analysis. Paired sample HUI3 single-attribute scores and multiattribute scores were obtained from 71 participants. As shown in Pearson's correlation analysis shows the correlation between the change in the four attributes. There was a statistically significant positive correlation between change in hearing and change in emotion. Although the correlation between the change in hearing scores and change in pain scores was not significantly correlated, there was a statistically significant positive correlation for change in pain when compared to the change of emotion, as shown in The result showed no statistically significant difference for change in hearing scores in relation to the alteration of speech scores, and in this study  would not affect the quality of life, which is similar to Ramakers  and SousThe pain score of our patients was raised as well due to CI. Pearson correlation analysis showed the change of the pain scores had no relation with hearing improvement. If hearing improvement was not the direct cause of change in HUI3 pain scores, what was the reason for pain perception improvement after CI? The pain and emotion are converged on the anterior cingulate and insular cortices . It is tThe present study identified CI had effectively improved hearing, speech, emotion, and pain, which made statistically significant improvement in quality of life among postlingually deaf adults. There was a statistically significant association between the change of emotion state and improvement in hearing level. We also found a statistically significant correlation between the reduction of feeling in pain and improvement in emotion state. Sex and education level significantly influence the quality of life preoperative. Duration of HA use, age at implant, time of CI use, and bilateral or unilateral did not significantly impact the improvement in quality of life. The change of quality of life seemed to be influenced by the primary state of emotion and hearing. The HUI3 measure is suitable for this cohort of patients.


Chronic inflammatory demyelinating polyneuropathy (CIDP) is a potentially treatable condition with great variability in terms of clinical presentation, pathogenesis, auto-antibody profile, disease progression, and response to treatment. The recognition of several CIDP variants within the spectrum of CIDP, such as distal acquired symmetric neuropathy (DADS), multifocal acquired demyelinating sensory and motor neuropathy (MADSAM), focal CIDP forms, pure sensory and pure motor CIDP, and chronic immune sensory polyradiculopathy (CISP), emphasizes the need for accurate diagnosis and appropriate treatment.Over the last decade, the presence of several auto-antibodies against peripheral nerve targets has been reported in a minority of patients with CIDP. Some of them, such as neurofascin 155/186 or contactin 1 antibodies, have been associated with distinct clinical presentations and response to treatment. In cohorts of CIDP patients, the detection of different antibodies targeting nerve antigens and their clinical syndromes are currently under study. However, limited evidence is available in regards to optimal management, clinical course, and outcome of atypical CIDP. There are reports suggesting that not all CIDP sub-types respond equally well to first-line treatment, while novel immunomodulatory strategies have not been designed for CIDP variants.Stascheit et al. investigated calprotectin (CLP), a calcium-binding protein of the S100 family, which triggers signaling pathways involved in inflammatory processes as an index of CIDP activity. These authors performed a pilot cross-sectional case-control study of 63 patients with CIDP (46% CIDP variants) and showed that CLP and serum neurofilament light chain (sNfl) levels were significantly higher than those in 40 healthy controls. In the CIDP cohort, CLP was related to active inflammatory course assessed by CIDP disease activity scale (CDAS) and Medical Research Council (MRC)-sum score. On the other hand, sNfl levels were not correlated with CDAS but were associated with the severity of disease deficits assessed by MRC-sum score, inflammatory neuropathy cause and treatment disability score, grip strength, and walking distance. The clinical significance of these biomarkers should be further explored in larger studies allowing subgroup analysis.Currently, several potential biomarkers for quantitative evaluation of disease progression are under investigation in order to decide upon appropriate therapeutic approaches. Lukawska et al. retrospectively reviewed medical records of 37 children divided into age subgroups  with CIDP from a single center. The diagnosis was delayed by more than 1 year in 53.6% of children under the age of 13 years, implying difficulties in documentation of CIDP in this population. Noticeable findings were acute onset (<8 weeks) in 16.2% of patients, the symmetrical weakness of proximal and distal muscles in 53.8%, and the frequent cranial nerve involvement in children under 4 years of age. An unusually large percentage of 51.4% had an atypical presentation, i.e., a distal variant in 35.1%, pure motor variant in 13.5%, and pure sensory variant in 2.6% of the patients. Disease severity was milder compared to the adult population, with only 16.2% of children being unable to walk unaided at the disease nadir. Likewise, standard treatment approaches resulted in a favorable outcome in the majority of young patients, including complete remission in 51.4%, and minor residual deficits in 10.8%. Further studies are warranted in the pediatric population to facilitate timely diagnosis and inform optimal treatment approaches.Diagnosis of CIDP and CIDP variants in children is not an easy task, since these disorders are rarer than in adults and require differentiation from the hereditary demyelinating neuropathies that are by far more common in childhood. Menon et al. focused on the treatment approaches for atypical CIDP. This is a timely article since CIDP variants differ not just in their clinical, pathological, and electrophysiological characteristics, but also in their variable response to conventional immunosuppressive agents effective against typical CIDP, and high quality evidence is lacking regarding best management options. Based on existing data, DADS has the phenotype of a symmetric, demyelinating sensory, length-dependent polyneuropathy and is frequently associated with paraproteinemia and anti-myelin associated glycoprotein (MAG) antibodies. While the management of idiopathic DADS (DADS-I) is similar to classic CIDP, DADS with an M protein (DADS-M) response is suboptimal while it may show a more favorable response to rituximab. On the other hand, MADSAM manifests as a chronic progressive demyelinating mononeuropathy multiplex which can evolve into a confluent pattern indistinguishable from CIDP. Evidence favors treating MADSAM with conventional immunomodulatory therapy although the response tends to be less satisfactory than in CIDP. A subgroup of patients presenting with purely sensory symptoms are known as pure sensory CIDP or chronic inflammatory sensory polyradiculoneuropathy (CISP) with presumed underlying pre-ganglionic pathology. Both respond well to first-line immunomodulatory therapy, particularly to IVIG, but relapse without maintenance. The pure motor CIDP resembles multifocal motor neuropathy with conduction block (MMNCB). However, previous reports of worsening with steroids have not been reproduced in recent studies, and a good response to both intravenous immunoglobulin (IVIG) and steroids is likely. Some of the focal forms of CIDP would defy an accurate classification but nevertheless respond to first-line therapies. Similarly most of the patients with focal forms of CIDP respond well to IVIG. Overall, most types of atypical CIDP are amenable to treatment with first-line immunomodulatory therapy but the response may be suboptimal compared to CIDP. There is increasing evidence for agents such as rituximab, especially in DADS-M and in cases that are refractory to first-line therapies, although further studies are needed to support optimal treatment algorithms in each variant.The review by +) CIDP is unique because of the high frequency of subclinical demyelinating lesions in the central nervous system (CNS), owing to the expression of NF155 both in PNS and CNS paranodes. In NF155+ CIDP/CCPD hypertrophy of spinal nerve roots and cranial nerves, such as trigeminal and oculomotor nerves, and extremely high levels of cerebrospinal fluid (CSF) protein indicating nerve root inflammation are common. CXCL8/IL-8 and IL-13 levels are significantly higher in CSF, whereas IL-1β, IL-1ra, and IL-6 levels are lower in NF155+ CIDP than in NF155− CIDP. Canonical discriminant analysis revealed NF155+ and NF155− CIDP to be separable with IL-4, IL-10, and IL-13, the three most significant discriminators, all of which are required for IgG4 class-switching. Therefore, upregulation of both Th2 and Th1 cytokines and downregulation of macrophage-related cytokines are characteristic of NF155+ CIDP, which explains spinal root inflammation and the lack of macrophage infiltration in the sural nerves. At least in a Japanese cohort with NF155+ CIDP/CCPD, a higher prevalence of haplotypes HLA-DRB1*15:01-DQB1*06:02 was found compared with healthy controls, indicating a genetic predisposition with involvement of specific HLA class II molecules and relevant T cells in addition to IgG4 anti-NF155 antibodies in the mechanism underlying IgG4 NF155+ CIDP/CCPD. Further investigation of these immune and genetic aspects in other populations may shed more light on to the pathogenesis of this rare but challenging CIDP variant that responds well to rituximab treatment.Finally, the comprehensive review by Prof. Kira on combined central and peripheral demyelination (CCPD) associated with anti-neurofascin 155 (NF155) antibody provides a detailed description of diagnostic and treatment considerations for this very interesting CIDP variant. Overall, a small number of CIDP patients may harbor autoantibodies against molecules of the nodal region, such as nodal NF186, paranodal NF155, contactin 1 (CNTN1), or contactin-associated protein 1 (CASPR1). In most cases, the predominant IgG subclass is IgG4. These neuropathies present distinct features compared with antibody-negative CIDP, including poor response to IVIG. Neuropathology of the biopsied sural nerve shows detachment of Schwann cell paranodal loops from axons without macrophage infiltration or inflammation, partly attributable to IgG4 blocking protein-protein interaction without inducing inflammation. Anti-NF155 antibody-positive (NF155In summary, this collection of articles provides an important contribution to the better understanding of rare CIDP variants, including their clinical, electrophysiological, immunological, and genetic characteristics, and should be useful in increasing awareness and diagnostic accuracy for affected patients. Emerging novel biomarkers may further facilitate the distinction among these variants and support earlier differential diagnosis. Treatment considerations are increasingly studied and should be based on evidence, but the rarity of these disorders makes further collaborative study of optimal treatment approaches imperative, along with further research to develop more specific therapeutic protocols for each CIDP variant.All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Late-life depression is a comorbidity which may co-occur in older adults with hearing loss- each as prevalent and independent modifiable risk factors for dementia. We used data from 1,820 participants  from the Health Aging and Body Composition Study to test if the hearing loss-dementia/cognitive decline  relationship differed in hearing impaired participants who also had depressive symptoms. Depressive symptoms were defined as CES-D 10 ≥10) at one or more visits from years 1-5. Algorithmic incident dementia defined using medication use, hospitalizations and cognitive test scores. Audiometric hearing loss was measured at year 5 and categorized as normal/mild vs ≥moderate loss. In linear mixed models adjusted for demographic and clinical covariates, presence of both hearing loss and depressive symptoms (vs. having neither) was associated with faster rates of decline in 3MS  and DSST  over 10 years of follow-up. Both hearing loss and depressive symptoms (vs. neither) was associated with increased risk (hazard ratio (HR):2.91, 95%CI: 1.59, 5.33) of incident dementia in multivariable-adjusted Cox proportional hazards models. Comorbid conditions among hearing impaired older adults should be considered and may aid in dementia prevention and management strategies.


The importance of tele-audiology has been heightened by the current COVID-19 pandemic. The present article reviews the current state of tele-audiology practice while presenting its limitations and opportunities. Specifically, this review addresses: (1) barriers to hearing healthcare, (2) tele-audiology services, and (3) tele-audiology key issues, challenges, and future directions. Accumulating evidence suggests that tele-audiology is a viable service delivery model, as remote hearing screening, diagnostic testing, intervention, and rehabilitation can each be completed reliably and effectively. The benefits of tele-audiology include improved access to care, increased follow-up rates, and reduced travel time and costs. Still, significant logistical and technical challenges remain from ensuring a secure and robust internet connection to controlling ambient noise and meeting all state and federal licensure and reimbursement regulations. Future research and development, especially advancements in artificial intelligence, will continue to increase tele-audiology acceptance, expand remote care, and ultimately improve patient satisfaction. Recentlramming) , 5. The In 2021, the World Health Organization (WHO) estimated that 1 in 5 or about 1.5 billion people have some degree of hearing loss. Of those, approximately one-third need hearing healthcare intervention, and 80% live in low- and middle-income nations. Despite the global prevalence of hearing loss, only a fraction of those who could benefit from hearing healthcare services actually receive care .Of hearing aid candidates, Grundfast and Liu  reportedFailure to receive appropriate intervention comes at an enormous price. The global economic impact of unaddressed hearing loss is $980 billion, annually . The impThus, it begs the question—what most contributes to the lack of care, and how can this be improved? While reasons vary from community-to-community and from individual-to-individual, common factors include cost of services –20, a shA review of the literature was completed between September 2020—November 2021. The search was primarily conducted by the first author (KD) with additional contribution from the second author (FGZ) using two electronic databases, PubMed and Google Scholar. Eligible peer-reviewed articles were searched for using combinations of keywords including telemedicine, tele-audiology, telehealth, audiology, hearing, hearing aid, cochlear implant, otoscopy, audiometry, DPOAE, ABR, smartphone, tablet. For inclusion, articles were required to address the following: (1) barriers to hearing healthcare, (2) tele-audiology services, and/or (3) tele-audiology key issues, challenges, and future directions. Articles were excluded if they were not peer-reviewed, if they were not written in English, and if they were not directly germane to the topics and purpose of this review. Based on our specified criteria, our literature review identified 70 total articles, including 19 articles on barriers to hearing healthcare, 45 articles on tele-audiology services  testing studies, 16 tele-audiology diagnostic studies, including 11 audiometry studies and 5 ABR studies, and 13 tele-audiology intervention and rehabilitation studies, including 4 on hearing aids and 9 on cochlear implants), and 6 articles on challenges and future directions.Hearing technology, including its associated components , can be financially burdensome to patients . It is rIn addition to being a financial hardship for patients, hearing healthcare providers can also be burdened by the high purchase price of testing/programming equipment , as well as routine equipment maintenance. In areas that lack repair and/or calibration services, necessary maintenance can be cost prohibitive as it may require sending equipment overseas . Thus, cThe number of clinical professionals and/or specialized services is disproportionately low in developing countries. Compared with one audiologist per ~25,000 individuals in the United States , the proThe shortage of providers and/or specialized services also exists in many rural and remote communities in developed countries. Powell et al.  cited a r = 0.5) with the delay in both hearing aid and cochlear implant intervention.Inconvenience, time, and cost associated with travel to an on-site clinic can be a significant barrier to care, especially for those in developing countries or rural areas of developed countries. Bush et al.  reportedWhile travel distance is often shorter for patients in non-rural areas, unique travel challenges also exist for patients in urban communities. For example, patients in urban communities cite overall health issues, mobility challenges, and/or difficulty accessing transportation as barriers to care—all of which can contribute to a lack of or a reduction in traditional, in-person healthcare visits .Patients or families of patients with hearing loss routinely report a lack of communication or information as a barrier to care, especially regarding available services and financial support. In rural Kentucky, primary care physicians were found to have limited resources and knowledge about hearing loss , which cMinority groups face additional barriers to care, and importantly, disparities may be present even when minorities have reasonable access to care, have advanced levels of education, and are of high socioeconomic status , 40. WitThe efficacy of home-based otoscopy is of particular interest, as tele-otoscopy holds significant potential in reducing expenditure and costs associated with travel to a clinic. About 80% of children have at least one episode of acute otitis media (AOM) prior to age 3. In fact, otitis media is the most frequent cause of healthcare visits in the pediatric population. Because AOM diagnosis is heavily dependent upon visualization of the tympanic membrane via otoscopy, home-based otoscopy devices can allow parents/caregivers to complete otoscopy and then transmit videos to a physician for remote diagnosis and treatment recommendations. While the viability of smartphone otoscope use by healthcare professionals has previously been demonstrated e.g., , 42], it, it42)],Shah et al.  evaluatewith instruction, parents are capable of obtaining adequate video of the tympanic membrane. Importantly, physicians were able to detect or exclude presence of AOM in the majority of smartphone otoscopy videos obtained by trained parents. Further, parents reported that at-home use of smartphone otoscopy was both feasible and easy to perform.Using the same CellScope iPhone device, Erkkola-Anttinen et al.  examinedbetter than conventional methods.Recently, artificial intelligence algorithms have been developed to improve the sensitivity and specificity of home-based otoscopy, making it a reliable and useful alternative to the current standard care model. Chan et al.  utilizedn = 32). On average, the two test methods produced no significant differences, except for a discrepancy in results for 5 of the 32 children. In such cases, the discrepancies were simply due to the lack of a response at one of the three test frequencies .Lancaster et al.  comparedMore recently, investigators have examined the reliability of tablet-based, computer-based, and smartphone-based audiometry, but results have been mixed. Khoza-Shangase and Kassner  comparedn = 394 with normal hearing, n = 97 with known hearing loss), as well as adults with normal hearing (n = 50). The screening program tested speech-in-quiet, speech-in-noise, and tones-in-noise. The goal of the study was to investigate whether the program was engaging and held the children's attention, whether it detected hearing loss, and whether it could differentiate between conductive and sensorineural hearing loss types. The authors concluded that sensitivity and specificity was sufficiently high, particularly when all three tests were averaged; however, hearing loss type was only identified correctly in two-thirds of cases. Thus, this program is an appropriate hearing screening tool for children in the 5–14 year old age range, particularly when accompanied by follow-up testing to more accurately determine hearing loss type.Similarly, Dillon et al.  examinedSmartphone-based audiometry applications have also been examined for hearing screening use in recent years. In a study of 6,288 children, Wu et al.  examinedSeveral studies have examined whether remote synchronous  DPOAE testing could be completed reliably. Krumm et al.  comparedn = 411) in the United States. Compared to traditional, in-person testing, the reliability was 100% for remote pure-tone and DPOAE screenings, and around 84% for tympanometry. Monica et al. (n = 31) in India using teachers as facilitators and found results similar to traditional, in-person testing. Ameyaw et al. (n = 50) in Ghana. Screenings were completed in-person and remotely by an audiologist via the internet with real-time audio, video, and text messaging between the facilitator and audiologist. Again, no differences were found between the two screening methods. Although these studies provided support for the effectiveness of remote DPOAE screening, they also noted technical challenges, such as high ambient noise levels and slow internet speed in rural areas. Further, they highlighted the need for additional research in difficult-to-test populations .Ciccia et al.  likewisea et al.  conductew et al.  examinedGivens and Elangovan  comparedWhile many researchers offer support for the reliable use of tele-audiometry in children , 66, othMore recently, smartphone-based automated audiometric testing has been examined, as it presents an affordable, cost-effective testing mechanism. van Tonder et al.  comparedn = 21) completed air conduction pure-tone audiometry. Similar threshold estimates were obtained using both methods (mean absolute difference: 3.24 ± 5.15 dB). Thus, online machine learning can be utilized with similar reliability and accuracy with the important benefit of a shorter test duration. Additional advantages include its flexibility for expansion to bone conduction, speech perception, and masking. Crowson et al.  in California and examined parent/caregiver satisfaction, as well as the impact these remote services had on improving what had been a high loss to follow-up rate. The procedure included a case history, video otoscopy, tympanometry, acoustic reflexes, DPOAEs, and diagnostic ABR testing. An audiologist conducted the testing remotely via an on-site facilitator who positioned the otoscope and tympanometry probe, and also prepped the skin and placed the electrodes for ABR testing. Thirteen of the 22 children tested were diagnosed with hearing loss. All parents/caregivers rated the importance of remote audiology services as a 7 on a 7-point Likert scale (7 = “extremely important”). Importantly, all infants completed the diagnostic testing with zero loss to follow-up, representing a marked improvement compared to a 22% loss to follow-up rate in the region prior to the study. Thus, a remote option can significantly reduce loss to follow-up rates in infants who fail their newborn hearing screenings and experience barriers to traditional, in-person diagnostic test services. Ramkumar et al. (n = 102) in British Columbia. Remote testing with an on-site trained facilitator determined that 50 of the 102 children had hearing loss, with efficiency and accuracy being comparable to traditional, in-person testing. Most importantly, remote testing resulted in a significant reduction in travel costs . There are clear benefits to offering a remote option, though the current lack of standardized procedures and insufficient information technology support across test centers needs to be addressed prior to widespread usage.Dharmar et al.  conducter et al.  likewiser et al.  examinedFerrari and Bernardez-Braga  comparedNovak et al.  examinedPross et al.  examinedin situ hearing threshold measurements, followed by a prescriptive algorithm for hearing aid programming. However, the success of self-fitting depends not only on accurate threshold measurements [e.g., . Study participants completed a self-fitting session, including audiometry and spectral discrimination testing, 2 weeks after initial traditional, in-person activation. An artificial intelligence software system (FOX) was used for interpretation, analysis, and map recommendation. Specifically, it analyzes the test results and the patient's current map, then calculates predicted outcomes with alternative maps. The alternative map with the best predicted outcome is recommended to the patient. Importantly, this method does not completely preclude the role of an audiologist; a CI audiologist was still required to review the recommended map. Following programming of the new map, participants were then re-tested again after 2 months. A questionnaire was also completed. Four of the six participants were able to complete all tests without any additional assistance from the audiologist. Four were fitted with a new map without physical intervention. All six participants reported feeling comfortable with the autonomous process, but initial audiologist supervision may be required or preferred.Meeuws et al.  examinedspecific to the provision of remote care are necessary. Thus, prior to providing remote services, audiologists must be familiar with the unique licensure, reimbursement, and privacy/security regulations required for tele-audiology services.Recent literature has shown that tele-audiology can be completed accurately and reliably; however, additional measures and regulations and the location the patient is in when services are received. At present, American Speech-Language-Hearing Association (ASHA) is exploring licensing options that would facilitate multi-state service delivery . For example, while commercial payers and Medicaid have the discretion to provide coverage for tele-audiology services, Medicare does roviders . Thus, iTele-audiology services must adhere to state, federal, and international regulations with respect to patient privacy and security, particularly that which includes transmission and storage of patient data. Tele-audiology providers must abide by the same regulations applicable to traditional, in-person services. Current federal legislation includes (1) Health Insurance Portability and Accountability Act of 1996 (HIPAA), (2) Health Information Technology for Economic and Clinical Health Act of 2009 (HITECH), and 3) Family Educational Rights and Privacy Act of 1974 (FERPA) , modifications (if any) to clinical protocols and procedures, and any potential issues with patient confidentiality. In order to ensure patient confidentiality, the audiologist must be familiar with state and federal regulations regarding electronic storage of patient data, privacy protections , configuring software and hardware for use with firewalls, encryption, or VPN, and policies for breach notification .Taken together, the current body of literature suggests that tele-audiology provides a viable service delivery model. Remote hearing screenings, diagnostic testing, intervention, and rehabilitation can be completed safely and effectively, in both children and adults. Moreover, the accurate provision of tele-audiology care has been demonstrated both in developed and developing countries. Benefits of such services include but are not limited to improvement in loss to follow-up, reductions in travel time and costs, and improved access to services not otherwise available in one's physical location.Still, tele-audiology is not without its logistical challenges. Several modifications to the traditional testing paradigm may be needed in order to successfully implement remote testing. For example, the presence of ambient noise during testing can reduce the accuracy of results. While use of a soundproof or sound-treated test booth is ideal, this may not be feasible in all circumstances. To improve diagnostic accuracy in the absence of a sound-treated environment, headphones with real-time ambient noise monitoring are recommended, as well as detailed instructions for proper headphone use by the patient . Furtheraccess to digital services, the quality of the services must be sufficiently reliable  and the Computer Proficiency Questionnaire (CPQ-12). The MDPQ-16 consists of 8 domains  with 16 questions. The CPQ-12 consists of 6 domains  with 12 questions .Additional challenges include reluctance or even resistance from payers, as well as the increased regulation required, particularly with respect to licensure, reimbursement, and privacy and security. Specifically, remote care must be delivered in accordance with clinical guidelines, payer policies, and state and federal law. Further, audiologists must ensure that tele-audiology clinical care is equivalent in quality to care delivered in-person. While undoubtedly necessary, the additional levels of regulation and requirements may, at least in the short-term, serve as hurdles to the widespread implementation of tele-audiology care.Future advancements in technology, especially in artificial intelligence, may help facilitate the provision of remote care and may accelerate the adoption of tele-audiology services worldwide at affordable costs . To dateRecent research shows that tele-audiology services can increase patient accessibility and engagement, improve loss to follow-up rates, and reduce cost and travel time. Furthermore, remote services can be completed in a manner that is safe, valid, reliable, and satisfactory. Still, logistical challenges do remain. For example, careful attention must be given to controlling ambient noise (particularly when testing is completed in the absence of a sound-treated test booth), modifications to current testing procedures may be needed to tailor to the provision of remote care, and regulatory and reimbursement hurdles need to be overcome before tele-audiology may be implemented on a widescale. The current COVID-19 pandemic has caused mass disruption to the delivery of healthcare services and has consequently accelerated the pace of development and acceptance of tele-audiology. Future research, including advancements in artificial intelligence, will continue to improve not only the effectiveness and efficiency of tele-audiology services but also most importantly, patient acceptance and satisfaction.KD'O completed a review of the existing tele-audiology literature between September 2020–November 2021, wrote the initial draft of this manuscript, and reviewed and edited the final version. F-GZ provided input on topic coverage, wrote portions of the final manuscript, and reviewed and edited the final version. All authors contributed to the article and approved the submitted version.This study was supported in part by NIH NIDCD (3R01DC015587).F-GZ owns stock in Axonics, Dianavi, Nurotron, Syntiant, Velox, Voibook, and Xense. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


From their initial description in 2005 to this day, telocytes (TCs) have been described in the ovary, uterine tubes, uterus, vagina, mammary gland, and placenta. Their morphological features, immunophenotype, physiological functions, and roles in disease have been thoroughly documented in both animal models and human subjects. TCs, with their extremely long cytoplasmic processes called telopodes, play a pivotal role in the morphological and functional interconnection of all the components of the interstitial compartment, but also with constituents of the parenchyma. Although there is no specific immunohistochemical marker for their identification, the most cited are CD 117, CD 34, platelet-derived growth factor receptor (PDGFR), vimentin, and specific markers typical for the female reproductive system (FRS)—estrogen and progesterone receptors (ER and PR). This immunophenotype provides important clues to their physiological roles. Their main functions include the regulation of hormone-dependent processes, intercellular signaling, immune surveillance, microenvironmental maintenance, and the nursing of stem cells. In a situation where TCs are functionally or morphologically decimated, many disease entities may develop, including premature ovarian failure, endometriosis, ectopic pregnancy, infertility, preeclampsia, or even breast cancer. The common denominator of many of these conditions is that their etiopathogenesis is either partially known or completely obscure. Even though the exact role of TCs in these conditions is yet to be revealed, multiple lines of research indicate that their future clinical application may enrich diagnostic-therapeutic strategies of countless conditions. TCs are also heavily debated in terms of their possible use in regenerative medicine and tissue engineering. Some of the concepts related to TC research are strongly substantiated by experimental data, while others are highly speculative. Only future research endeavors will clearly distinguish dead-end lines of research from genuine contributions to the field. The female reproductive organs form a highly complex and intricately connected system with many peculiarities unlike any other when we consider other organ systems of the mammalian body. The most astonishing feature of the female reproductive system (FRS) is its capability to induce immune tolerance towards the hemiallogenic embryo. Although this characteristic has been evolutionarily conserved for tens of millions of years, we still do not fully understand it, despite the fact that over the last few decades, the knowledge of the morphology, physiology, and pathophysiology of the FRS has been growing exponentially ,2. The FThis paper aims to provide a comprehensive review of TCs in the organs of the FRS, focusing mainly on the past five years, with respect to their physiological roles, potential contribution to the pathogenesis of different FRS-related conditions, and the current understanding of TC roles in regenerative medicine concerning the FRS. In order to do so, we have searched the PubMed/MEDLINE, Scopus, and Web of Science databases to find relevant articles, mainly from the above-mentioned time span, specifically looking for original papers with experimental data on both human subjects and animal models.The history of TCs can be dated back to the works of Santiago Ramón y Cajal, published at the turn of the 19th and 20th century, who discovered a new cell population of “interstitial neurons” in the gut . A centuThe shortest and most pertinent definition is that TCs are cells with telopodes. Telopodes represent the most striking morphological feature of these cells—cytoplasmic projections of extraordinary proportions. Their length is surpassed only by that of nerve cell axons . The mosWithout overstating, it can be said that TCs have been described in almost every organ one can think of. Except of the FRS, TCs have been discovered in the intestine , lungs , skeletaOvarian TCs are among the least studied compared to other organs of the FRS. Liu et al. studied telocytes in mice ovarian stroma. Using a combination of different methods, including immunofluorescence, immunohistochemistry, flow cytometry, and electron microscopy, the authors identified cells with a small body, long dichotomously branching telopodes with a typical moniliform alternating pattern of podomers and podoms. From the functional perspective, the most probable is their participation in microenvironmental maintenance . MazzoniTubal TCs, on the other hand, are among the best studied in the FRS. They were first scrutinized shortly after the first description of ICLCs by the Romanian team in 2005. Popescu et al. used a wide spectrum of methods in order to thoroughly examine these cells, but most importantly, they extended the “gold standard” of ultrastructural criteria for their identification, originally derived from the ultrastructural study of ICCs. They established the “platinum standard” that incorporated all typical features of the “characteristic cytoplasmic processes”, not yet known as telopodes, including their length, thickness, branching pattern, and organization. The authors also proposed several hypothetical physiological functions based on their morphological specifics–intercellular signaling, paracrine regulation of their surroundings, pacemaking, and mediation of neurotransmission. Interestingly, the authors also considered the possibility that they can act as further-differentiating progenitor cells or cells capable of phenotypic switch . In a laUterine TCs display several characteristics similar to those found in the uterine tube. They also express ER and PR, implying that TCs serve as hormone sensors and thus regulate hormone-dependent changes associated with the endometrial cycle, pregnancy-related changes, and motility ,37. SalaThe knowledge of TCs in the vagina is very limited. The only experimental paper studying TCs via immunohistochemical methods was authored by Shafik et al. back in 2005, who concluded that they regulate smooth muscle activity by slow wave initiation .Classifying the placenta as a part of the FRS can be problematic, because it is a temporary or transient organ developing during pregnancy, and on top of that, it is jointly formed by both the maternal and embryonic contribution. Nevertheless, we will describe placental TCs as a part of the FRS. Placental TCs can be discussed from two perspectives. First is their role in early changes that result from the trophoblast-endometrium interplay during embryo implantation, while the second focuses on TCs role in the mature placenta. In the early stages, the endometrium undergoes decidual changes, while at the same time, the immune response has to be adequately regulated in order to mitigate the recognition of the hemiallogenic embryo as non-self by the immune system. The participation of TCs in these processes can be deduced from the results of the already mentioned Jiang et al. study examining TC influence on immune cells . FocusinIn a like manner, TCs in the mammary gland are often discussed separately, since the mammary gland belongs, from the embryological perspective, to skin derivatives. In spite of that, we will discuss the mammary gland TCs within the scope of FRS, considering the fact that it is closely connected to reproduction. The electron microscopic identification of TCs in the mammary gland stroma was carried out by Gherghiceanu et al., who hypothesized that TCs are crucial in three-dimensional (3-D) organization and functional integration of stromal components of the mammary gland . Petre eBesides electron microscopic features, immunophenotypic traits are the most cited TC characteristics by which they can be distinguished. Unfortunately, as of today, no research endeavors have been successful in determining a unique and specific marker that would unambiguously differentiate TC from other populations of interstitial cells. Nevertheless, there are several immunohistochemical markers that can be considered reliable in TC identification. The most suitable approach is the combination of markers as a part of double immunohistochemistry, immunocytochemistry, immunofluorescence. These can also be used in tandem with other methods of TC detection. However, it is extremely important to note that there are organ-to-organ differences in the expression of these markers, which makes the straightforward detection of TCs even more challenging than the fact that there is no TC-specific marker.The handful of studies that we have at our disposal showed that ovarian TCs express CD 34, platelet-derived growth factor receptor (PDGFR) α/β, vimentin , MMP-2 aRegarding the immunophenotype of TCs in the uterine tube, Cretoiu published a comprehensive review on different aspects of tubal TCs, including the most typical markers detectable via immunohistochemistry or immunofluorescence. A marker that displayed the strongest positivity was CD 117, followed by CD 34. The former was located mostly on the cell body, while the latter was found predominantly on telopodes. S-100 positivity was also demonstrated with variations found in different histological layers of the uterine tube. The expression of other markers, namely NK-1, nestin, and vimentin, was either weak or inconsistent. Finally, yet importantly, tubal TCs expressed ER and PR, but also atypical markers caveolin-1 and caveolin-2 .Similar to those in the uterine tubes, uterine TCs are also thoroughly studied from various angles, including the expression of immunohistochemical markers. There is a substantial overlap with other organs of the FRS, especially the uterine tube, but as always, previous experimental works found several organ-specific markers. The immunophenotypic details of the uterine TCs were elucidated only one year after their initial discovery, indicating that uterine TCs are among the best documented overall, not only in the FRS. They express CD 117, CD 34, vimentin , ER, andCD 117 positive TCs in the vagina were described by Shafik et al., though they referred to these cells ambiguously as either pacemaking ICCs or ICLCs . In 2007, Suciu et al. used a multimodal approach to studying placental TCs, including immunofluorescence and cell cultivation. The authors described TCs (ICLCs) positive for CD 117, vimentin, α- smooth muscle actin (SMA), and caveolin-1 . SeveralA 2013 study by Mou et al. revealed that mammary gland TCs express typical markers, such as CD 117, vimentin, and CD 34 . A more Liu et al. established an animal model of cyclophosphamide-induced premature ovarian failure to study the potential role of ovarian TCs in its pathogenesis. The authors provided ultrastructural and immunohistochemical evidence of TC absence in the experimental group, suggesting that ovarian TCs might be important for the maintenance of the ovarian interstitial compartment. After TC loss and ensuing microenvironmental deregulation, premature ovarian failure may develop . Like inThere is a great abundance of publications dealing with the potential roles of tubal TCs in various pathological conditions. Based on their ultrastructural, functional, and immunophenotypic traits, tubal TCs have been considered in the pathogenesis of such conditions as tubal endometriosis, tubal infertility, ciliary dyskinesia, or even ectopic pregnancy. Aleksandrovych et al. conducted research on tubal specimens from human subjects diagnosed with uterine leiomyomas (fibroids). This recent study brought several surprising findings that may provide the necessary momentum to push the research of tubal TCs further. TCs were found to be positive for ER, PR, and SK3, secreted VEGF, and interacted with protein gene product 9.5 (PGP 9.5), iNOS, and choline acetyltransferase (ChAT)-positive nerve fibers. Taken together, the authors concluded that tubal TCs are involved in muscle contractility, angiogenesis, and overall maintenance of the local microenvironment. Such a broad spectrum of functional involvement indicates that when tubal TCs are damaged, various pathological changes may emerge. The most significant is tubal-factor infertility. A completely unique and previously unrecognized finding was that the number of tubal TCs in patients with uterine fibroids increased, possibly as a compensatory mechanism. Unfortunately, a more detailed explanation of this phenomenon was not provided . An entiOne of the most thoroughly researched conditions associated with a disturbance of uterine TCs is the development of uterine leiomyomas (fibroids). Leiomyomas are non-malignant smooth muscle neoplasms, that are, despite their non-invasiveness, related to clinically relevant morbidity and fertility problems . The rolTo the best of our knowledge, there are no experimental data indicating the involvement of TCs in any vaginal pathology.The knowledge on placental TCs partially overlaps with that of uterine TCs, since the placenta is formed by the interplay of both maternal and embryonic tissues. The most researched pathological condition concerning placental TCs is preeclampsia. This serious pregnancy-associated pathology typically results from defective placentation, abnormal spiral artery remodeling, placental insufficiency, and endothelial dysfunction. All these interconnected pathological processes eventually lead to ischemic-hypoxic damage. If left untreated, it can lead to life-threatening complications . PlacentOne of the most serious pathologies of the mammary gland is undoubtedly breast cancer. This malignant tumor is the most common type of cancer occurring in women worldwide . Mou et It can be summarized that the relationship between quantitative and/or qualitative alteration of TCs in the etiopathogenesis of a diverse spectrum of pathological conditions has been a staple motif in almost the whole bulk of publications on TCs published to this day. Some research teams, e.g., Yonghong et al., went so far as to associate TCs with such speculative concepts, like meridians in traditional Chinese medicine . RegardlAll the sections above are summarized in Regenerative medicine of the female reproductive organs is a highly relevant and up-to-date area of research. There are many diagnoses, as well as physiological processes in which the understanding of the mechanisms of tissue regeneration and repair is of paramount importance. Two examples for all are the intricate changes that occur during the menstrual cycle and pregnancy. Over the span of the reproductive period of a woman, uterine endometrium is subjected to around 400 (depending on parity) menstrual cycles that are characterized by a sophisticated coordination of cell proliferation, differentiation, angiogenesis, and subsequent disintegration, and sloughing off. Even more astonishing changes occur in pregnancy, when the weight of the uterus increases tenfold by the processes of hypertrophy and hyperplasia . DiscussSoon after the morphological and functional characterization of TCs, it has become evident that their role in tissue regeneration and repair will be a common denominator in most organs. Concerning uterine TCs, Campeanu et al. experimentally demonstrated that TCs from pregnant and non-pregnant uteri react differently to low-level-laser stimulation (LLLS). Upon LLLS, TCs from pregnant uteri reacted more intensely in terms of dynamic changes in the length, branching, and overall plasticity of telopodes. These results provided conclusive evidence that telopodes are sensitive to physical stimulation, which may open new possibilities in TC-associated regeneration . Apart fA lot has been discovered about TCs in the female reproductive organs over the 16 years that have passed since their initial description. From their peculiar morphology and function, to their roles in various diseases, to their potential in tissue regeneration, TCs contributed largely to many fields of biomedical sciences, including gynecology, obstetrics, and gynecological oncology. There are still many under-researched areas where TCs can provide additional insights into normal and pathological structure and function. The great potential of TCs lies in their ability to broaden the understanding of many diseases, which are now defined as idiopathic (without known cause), and bring novelties to diagnostic-therapeutic management of a wide array of pathological conditions. Finally, yet importantly, their contribution to regenerative medicine and tissue engineering is up-and-coming. Some of the concepts related to TC research are strongly substantiated by experimental data, while others are highly speculative. Only future research endeavors will clearly distinguish dead-end lines of research from genuine contributions to the field .


This fortuitous similarity of time scales ensures that stellate spikes get relegated to the least excitable phase of theta and the network encodes the external drive but ignores recurrent excitation. In contrast, in the absence of theta, rebound spikes compete with external inputs and disrupt the sequence that follows. Further, the same mechanism where theta modulates the gain of incoming inputs, can be used to select between competing inputs to create transient functionally connected networks. Our results concur with experimental data that show, subduing theta oscillations disrupts the spatial periodicity of grid cell receptive fields. In the bat MEC where grid cell receptive fields persist even in the absence of continuous theta oscillations, we argue that other low frequency fluctuations play the role of theta.Stability and precision of sequential activity in the entorhinal cortex (EC) is crucial for encoding spatially guided behavior and memory. These sequences are driven by constantly evolving sensory inputs and persist despite a noisy background. In a realistic computational model of a medial EC (MEC) microcircuit, we show that intrinsic neuronal properties and network mechanisms interact with theta oscillations to generate reliable outputs. In our model, sensory inputs activate interneurons near their most excitable phase during each theta cycle. As the inputs change, different interneurons are recruited and postsynaptic stellate cells are released from inhibition. This causes a sequence of rebound spikes. The rebound time scale of stellate cells, because of an  The theta rhythm is a prominent oscillation in the brain and known to play a role in different forms of learning and memory, for its association with movement and its disruption in some pathologies. Oscillations in general, and theta in particular, are thought to coordinate the activity of distributed brain regions. Our study provides a mechanistic understanding of the role of theta oscillations in the generation of stable sequences of activity and its transmission across brain regions. We model a specific microcircuit (stellate cells coupled via inhibitory interneurons) based on the known architecture of the medial entorhinal cortex (MEC). This circuit motif occurs across various brain regions. Thus, mechanisms of spatiotemporal patterning observed in the MEC are recapitulated in other circuits as well.The entorhinal cortex (EC) acts as a conduit between hippocampal and cortical circuits . SuperfiIn a biophysically realistic computational model of an MEC microcircuit, we show that a stable grid pattern can be generated by coupling the network to theta oscillations from the medial septum . Theta oh–channel varies systematically along the dorsoventral axis of the MEC .Stellate cells and interneurons were modeled as conductance based, single compartment spiking neuron models. In addition to sodium, potassium and leak channels, model stellate cells were also endowed with voltage dependent ion channels that were active at subthreshold membrane potentials. These ion channels enabled the neuron to produce sustained oscillations in response to a constant depolarization . The mod the MEC . In addi the MEC . A combiThe current balance equation for the equivalent circuit model of the membrane is given by the following:Stellate cell,Interneuron,Ionic currents were modeled as follows:where m was given by the following:mτ are functions of voltage.An equivalent representation isThe gating variables followed first order kinetics. For example, the gating variable, The functional form of each ionic current and the gating variables, maximal conductances and reversal potentials are provided in Stellate cells were randomly connected to inhibitory interneurons with an excitatory synapse. Interneurons sent inhibitory connections to stellate cells as well as to other interneurons. The inhibitory population was modeled as an all-to-all connected network. The synapse was modeled as a conductance with a gating variable modulated by the presynaptic voltage.The connectivity of the network motifs simulated here draws from several studies that have progressively established a detailed picture of the topology of the stellate cells and inhibitory interneuron networks . The reversal potential of the conductance was kept at –65 mV.A similar sequence of pulses was given to the two rings of interneurons in N = 8) that received input for all the theta frequencies that were simulated. The distribution of mean reliability across trials for each neuron is shown in To compare the reliability of the responses of the network for a given sequence of inputs across noisy trials, we used a measure of similarity between spike trains termed SPIKE distance . This mein silico, that uses odeint, a boost C++ library to solve ordinary differential equations. The differential equations were integrated using Eulers method with a time step of 0.01 ms. Simulations were run on Linux servers with Intel Xeon E5-2670 processors running Ubuntu 18.04. The codes and the documentation required to run the simulations and analyze the outputs are available in the following GitHub repository linked here ( https://github.com/arunneru/theta_gates_reliable_sequences_mEC). The repository contains a Jupyter notebook that documents and implements all the steps required to simulate the codes and generate figures.All the simulations were performed using a home-grown C++ library, h–current . We modeled interneurons using modified sodium and potassium currents that allowed them to spike at high frequency  driving the entire population of inhibitory interneurons. The pulse like input that was used to drive the neurons remained the same as in earlier simulations . Our modOur model network consisted of an equal number of stellate cells and inhibitory interneurons. This is in contrast to Layer II of the MEC where stellate cells are known to vastly outnumber interneurons. However, this does not pose a problem for our model, provided the distribution of inhibitory inputs to stellate cells is maintained. The stellate cells and inhibitory interneurons are organized in a ring network. Neighboring stellate cells received inputs from overlapping sets of inhibitory interneurons. Therefore, neighboring stellate cells also possess highly overlapping receptive fields. Adding more stellate cells in our model would result in denser overlap of receptive fields. This is evident in responses seen in the raster plot shown in How do theta oscillations affect the network such that it responds selectively to an external input and not to distractors, namely, competing excitatory spikes from stellate cells? The networks simulated in Stellate cells excite inhibitory interneurons . We modeh–current, τ, that varies along the dorsoventral axis of the MEC. Given the broad range of theta over which the network remains reliable, we anticipate that other values of τ would also give us a reliable response. However, dorsoventral gradients in τ can shift the regime where the network is reliable. Changes in theta frequency can signal changes in the animal’s behavior. For example, theta frequency is linearly related to the animal’s velocity (Theta oscillations span a range of frequencies from 6 to 12 Hz in rodents. Do changes in theta frequency compromise the reliability of the network responses? As theta frequency increased, the time between inhibitory bursts and rebound spikes remained nearly the same since this was determined by the time scale of the rebound kinetics of stellate cells. Therefore, the phase at which stellate cell spikes occurred started to shift systematically as the frequency increased A. As thevelocity  and can velocity C.When theta oscillations were present the network reliably followed external inputs that arrived at the receptive phase of theta. Here, we examine the response of the network when competing external inputs occur at different phases of the theta cycle. We simulated a network consisting of two groups of interneurons connected to the same pool of stellate cells. All the interneurons were coupled to each other. Each group of interneurons extended inhibitory connections to the stellate cells forming two separate ring networks A. The upIn the first of the cases tested B, one ofSeveral studies have shown that theta oscillation coherence plays an important role in interregional interactions. However, few studies have looked at how this can be implemented in different brain networks. We showed that the MEC interneurons are receptive to external inputs only within cyclic windows defined by theta oscillations. Further, theta oscillations corralled stellate cells to spike synchronously at a phase where inhibitory interneurons were hyperpolarized and less receptive to excitatory inputs. This prevented stellate spikes from depolarizing randomly connected postsynaptic inhibitory interneurons that could compete with external inputs to other neurons. This mechanism to generate reliable sequences can also be harnessed to ensure that the EC selectively gates inputs such that some inputs that arrive at specific phases are transmitted to postsynaptic targets while others are blocked. Note that the sequences considered here are distinct from theta sequences , where tInhibitory interneurons in Layer II of the MEC are broadly tuned to spatial location and, unlike grid cells, do not show periodic firing fields . SubsequOur model suggests that stable sequential activity is contingent on the presence of theta oscillations. In the absence of theta, multiple traversals over a given region of space failed to evoke a reliable response that is required to form grid-like receptive fields. However, recordings from Egyptian fruit bats show that grid-like receptive fields can be formed in the absence of continuous theta oscillations . This seBats show a large variability in the frequency of local field potential fluctuations unlike theta oscillations in rodents that vary over a smaller range. In our model network the input driven switch from one interneuron to another is rapid because of inhibitory competition between fast-spiking interneurons and occurs within a single theta cycle. Therefore, the network activity can respond to fluctuations in a cycle-by-cycle manner, relegating distractors to a hyperpolarized phase despite variations in instantaneous frequencies. Changes in instantaneous frequency that occur on a slower time scale than the switching time scale have little impact on perturbing the input driven dynamics of the network. Thus, the slow local field fluctuations seen in bats may be sufficient to evoke a reliable response in stellate cells.We showed that theta oscillations can gate the transmission of information between different brain regions. Mechanisms ranging from a cellular scale to that of populations of neurons can lead to coherent oscillations , 2010. OHowever, finer control over the input during each theta cycle is required to ensure that MEC networks selectively listen to or ignore incoming inputs. What are the mechanisms that ensure the right inputs arrive at the right phase of theta? Inhibitory interneurons that participate in generating and maintaining hippocampal theta rhythms broadcast rhythmic inhibition that targets inhibitory interneurons in other areas . These, Our simulations operated in a regime where the system responded to a sequential external drive and moved the locus of activity from one neuron to another. Stellate cells spiked and registered the temporal location of this transition. In the MEC network, GABAergic connections onto the principal neurons show spike timing dependent plasticity that enhances the weights of inhibitory connections for those synapses where the postsynaptic stellate cell spikes after the inhibitory interneuron . RepeateIn sum, our study highlights the central role of theta oscillations in generating reliable sequences and forming transient functionally connected networks. This is possible because of the fortuitous similarity between the time scales of theta oscillations and conductances of stellate cells together with the architecture of the MEC network.Note Added in Proof: The codes and the documentation required to run the simulations and analyze the outputs are also available as the 10.1523/ENEURO.0059-20.2021.ed1Extended Data 1Extended Data 1, ZIP file.Theta gates reliable sequences Download