Decoding neurobiological spike trains using recurrent neural networks: a case study with electrophysiological auditory cortex recordings

Recent advancements in multielectrode methods and spike-sorting algorithms enable the in vivo recording of the activities of many neurons at a high temporal resolution. These datasets offer new opportunities in the investigation of the biological neural code, including the direct testing of specific coding hypotheses, but they also reveal the limitations of present decoder algorithms. Classical methods rely on a manual feature extraction step, resulting in a feature vector, like the firing rates of an ensemble of neurons. In this paper, we present a recurrent neural-network-based decoder and evaluate its performance on experimental and artificial datasets. The experimental datasets were obtained by recording the auditory cortical responses of rats exposed to sound stimuli, while the artificial datasets represent preset encoding schemes. The task of the decoder was to classify the action potential timeseries according to the corresponding sound stimuli. It is illustrated that, depending on the coding scheme, the performance of the recurrent-network-based decoder can exceed the performance of the classical methods. We also show how randomized copies of the training datasets can be used to reveal the role of candidate spike-train features. We conclude that artificial neural network decoders can be a useful alternative to classical population vector-based techniques in studies of the biological neural code.

Ephaptic Coupling in Hybrid Neuronal Model

In recent decades, there has been growing interest in the impact of electric fields generated in the brain. Transmembrane ionic currents originate electric fields in the extracellular space and are capable of affecting nearby neurons, a phenomenon called ephaptic neuronal communication. In the present work, the Quadratic Integrate-and-Trigger model (QIF-E) underwent an adjustment/improvement to include the ephaptic coupling behavior between neurons and their results are compared to the empirical results. In this way, the analysis tools are employed according to the neuronal activity regime: (i) for the subthreshold regime, the circular statistic is used to describe the phase differences between the input stimulus signal and the modeled membrane response; (ii) in the suprathreshold regime, the Population Vector and the Spike Field Coherence are employed to estimate phase preferences and the coupling intensity between the input stimulus and the Action Potentials. The results observed are i) in the subthreshold regime the values of the phase differences change with distinct frequencies of an input stimulus; ii) in the supra-threshold regime the preferential phase of Action Potentials changes for different frequencies. In addition, we explore other parameters of the model, such as noise and membrane characteristic-time, in order to understand different types of neurons and extracellular environment related to ephaptic communication. Such results are consistent with results observed in empirical experiments based on ephaptic coupling behavior. In addition, the QIF-E model allows further studies on the physiological importance of ephaptic coupling in the brain, and its simplicity can open a door to simulating ephaptic coupling in neuron networks and evaluating the impact of ephaptic communication in such scenarios.

Hippocampal place cells use vector computations to navigate

One function of the Hippocampal Cognitive Map is to provide information about salient locations in familiar environments such as those containing reward or danger, and to support navigation towards or away from those locations. Although much is known about how the hippocampus encodes location in world-centred coordinates, how it supports flexible navigation is less well understood. We recorded from CA1 place cells while rats navigated to a goal or freely foraged on the honeycomb maze. The maze tests the animal's ability to navigate using indirect as well as direct paths to the goal and allows the directionality of place cells to be assessed at each choice point during traversal to the goal. Place fields showed strong directional polarization in the navigation task, and to a lesser extent during random foraging. This polarization was characterized by vector fields which converged to sinks distributed throughout the environment. The distribution of these convergence sinks was centred near the goal location, and the population vector field converged on the goal, providing a strong navigational signal. Changing the goal location led to the movement of ConSinks and vector fields towards the new goal and within-days, the ConSink distance to the goal decreased with continued training. The honeycomb maze allows the independent assessment of spatial representation and spatial action in place cell activity and shows how the latter depends on the former. The results suggest a vector-based model of how the hippocampus supports flexible navigation, allowing animals to select optimal paths to destinations from any location in the environment.

Analysis of Strategies for Preventing and Controlling the Chikungunya Virus

Alternatives to stop chikungunya outbreaks are oriented to vector control and developing a specific treatment and a preventive vaccine. Environmental control and mosquito bite prevention are undoubtedly essential to decrease the disease burden, but Aedes vectors continue to expand geographically and re-emerge. So, vaccination is proposed to respond to this etiology and recognized as a pressing need for affected countries. A mathematical host-vector model, including asymptomatic population, vector control, and vaccination (assuming the existence of a safe protective vaccine against the chikungunya virus), is suggested to analyze the effects of these efforts. Poisson distribution is applied to interpret the basic reproduction number. Then vaccination and vector control thresholds are established to prescribe the most effective protection measures against exposure to the chikungunya virus. In conclusion, it is advisable to continue with integrated control to reduce the economic impact of relevant public health responses and mitigate other infections since Aedes is a transmitter of other arboviruses such as dengue, Zika, and Mayaro. Furthermore, vaccinating all individuals in a community could be a costly and gradual process.

The Role of Temperature in Transmission of Zoonotic Arboviruses

We reviewed the literature on the role of temperature in transmission of zoonotic arboviruses. Vector competence is affected by both direct and indirect effects of temperature, and generally increases with increasing temperature, but results may vary by vector species, population, and viral strain. Temperature additionally has a significant influence on life history traits of vectors at both immature and adult life stages, and for important behaviors such as blood-feeding and mating. Similar to vector competence, temperature effects on life history traits can vary by species and population. Vector, host, and viral distributions are all affected by temperature, and are generally expected to change with increased temperatures predicted under climate change. Arboviruses are generally expected to shift poleward and to higher elevations under climate change, yet significant variability on fine geographic scales is likely. Temperature effects are generally unimodal, with increases in abundance up to an optimum, and then decreases at high temperatures. Improved vector distribution information could facilitate future distribution modeling. A wide variety of approaches have been used to model viral distributions, although most research has focused on the West Nile virus. Direct temperature effects are frequently observed, as are indirect effects, such as through droughts, where temperature interacts with rainfall. Thermal biology approaches hold much promise for syntheses across viruses, vectors, and hosts, yet future studies must consider the specificity of interactions and the dynamic nature of evolving biological systems.

Pola Kepadatan Populasi Vektor Penyakit DBD Di Permukiman Penduduk Bantaran Sungai Martapura Kecamatan Martapura Timur Tahun 2017

Martapura river water is one of the source of water used for daily use by residents who live along the banks of the river Martapura. Almost every house along the river Martapura does not have adequate clean water facilities and is highly dependent on river water. The objective of the study was to know the pattern of population density of dengue fever vector in residential area of ​​river Martapura. This type of analytic research, using a cross sectional design. The population of all Aedes sp mosquitoes and all residents in the residential area of ​​river Martapura. The sample is partially Aedes sp mosquitoes and residents in the residential area of ​​the river Martapura river, the village Antasan Senor, Antasan Senor Ilir, and the village of Mekar). Purposive Sampling Sampling Technique. Methods of gathering observations, interviews and identification. Analytical data processing and analysis with one way ANOVA test. The results showed that the population density vector category "High" DF = 4.7 and ABJ 71.7%. The result of statistical test of population vector density pattern there is no significant difference (p-value> 0,05). The environmental condition of the settlement is quite clean, breading place of the existence of larvae is not found, the number of TPA varies in the form of plastic, rubber, cement, iron / aluminum. Type / material of positive landfill larvae made of plastic material. Suggestion of research, for related institution to socialize and mobilize community in PSN activity of 3M + movement routinely, larva survey once a week, train Jumantik officer, public health education activity and integrated vector eradication (physical, chemical or biological) and community PHBS found the family / community experiencing symptoms of dengue disease immediately report / bring to the nearest health officer / facility.

PENYEBARAN VIRUS DENGUE SECARA TRANSOVARIAL PADA VEKTOR DEMAM BERDARAH DENGUE NYAMUK Aedes aegypti

TRANSOVARIAL TRANSMISSION OF DENV IN AEDES AEGYPTI Background: Transovarial transmission of dengue virus in Aedes aegypti mosquitoes is a vertical transmission of dengue virus infection in female Ae. aegypti mosquitoes to the offspring. The phenomenon of transovarial dengue virus transmission in Dengue Hemorrhagic Fever (DHF) vectors has been proven by laboratory and nature, which indicates the transovarial transmission of dengue virus has an important role in maintaining the dengue epidemic. DHF vector control especially Ae. aegypti mosquitoes is an effective method of stopping transmission and expansion of dengue cases.Purpose: This scientific article aims to understand the spread of dengue virus transovarially in dengue mosquito vectors, and its relation to the prediction of outbreak dengue cases as information on DHF vector surveillance so that it can make the appropriate control program.Methods: Collecting several scientific articles to obtain information on the studies that have been done and summarizing the results of the study.Results: Several result of study are proving that transovarial transmission of dengue virus in Aedes spp. mosquitoes can predict dengue outbreaks case by monitoring the stadium immature Aedes sp., but it need further comprehension statistically about occurrence of dengue outbreaks and the increasing of dengue virus infections in immature stadium of mosquitoes.Discussion: Transovarial transmission rates from Ae. aegypti mosquito sample obtained from nature may be lower than in the laboratory, because laboratory condition can be controlled in accordande with the development of viruses in mosquito bodies. The dengue virus is proven to be able to spread between stages from eggs, larvae, pupae to imago and Ae. aegypti mosquitoes can act as reservoirs for dengue virus until the 7th progeni.Conclusion: Dispersion dengue virus through transovarial in Ae. aegypti mosquito playing important role in viruses maintained in nature during absence of viremic vertebrata host or when the climate condition are not favorable for that viruses. Continuous monitoring of Ae. aegypti mosquitoes population vector related the early detection of virus circulation may contribute to the prediction models for dengue outbreaks, so that DHF control can be more effective.Pendahuluan: Penularan virus dengue secara transovarial pada nyamuk Aedes aegypti adalah transmisi secara vertikal dari nyamuk Ae. aegypti betina yang infektif virus dengue kepada keturunannya. Fenomena penularan transovarial virus dengue pada vektor Demam Berdarah Dengue (DBD) telah banyak dibuktikan skala laboratorium dan secara natural di alam, yang mengindikasikan penularan transovarial virus dengue memiliki peranan penting dalam mempertahankan epidemik DBD. Pengendalian vektor DBD khususnya nyamuk Ae. aegypti merupakan salah satu metode efektif dalam menghentikan penularan dan perluasan kasus DBD.Tujuan: Studi ini untuk memahami penyebaran virus dengue secara transovarial pada vektor nyamuk DBD, serta kaitannya terhadap prediksi kasus luar biasa (KLB) DBD sebagai informasi surveilans vektor DBD sehingga dapat membuat program pengendalian yang tepat.Metode: Dengan mengumpulkan beberapa artikel ilmiah untuk mendapatkan informasi studi yang telah dilakukan sebelumnya dan membuat ringkasan dari hasil studi tersebut.Hasil: Beberapa studi membuktikan penelitian transovarial virus dengue pada nyamuk Aedes spp. dapat memprediksi kasus KLB DBD dengan cara memonitoring stadium immature Aedes sp., namun perlu dilakukan studi statistik lebih lanjut untuk membuktikan hubungan terjadinya KLB DBD dan meningkatnya infeksi virus dengue pada stadium immature nyamuk.Pembahasan: Angka infeksi penularan transovarial virus dengue dari sampel nyamuk Ae. aegypti yang didapatkan langsung dari alam lebih rendah dari skala laboratorium, dikarenakan kondisi laboratorium dapat dikendalikan sesuai dengan perkembangan virus ditubuh nyamuk. Virus dengue terbukti dapat menyebar antar stadium dari telur, larva, pupa, sampai imago dan nyamuk Ae. aegypti dapat menjadi reservoir virus dengue sampai progeni ke 7.Kesimpulan: Penyebaran virus dengue secara transovarial pada nyamuk Ae. aegypti berperan penting dalam mempertahankan keberadaan virus di alam khususnya dimana tidak ada hospes vertebrata yang viremik atau ketika keadaan (kondisi iklim) yang tidak menguntungkan virus tersebut di alam. Pemantauan berkelanjutan pada vektor demam berdarah nyamuk Ae. aegypti terkait deteksi dini sirkulasi virus dengue dapat berkontribusi pada pengembangan model prediksi KLB DBD, sehingga pengendalian DBD dapat lebih efektif.

A Perceptual-Like Population-Coding Mechanism of Approximate Numerical Averaging

Humans possess a remarkable ability to rapidly form coarse estimations of numerical averages. This ability is important for making decisions that are based on streams of numerical or value-based information, as well as for preference formation. Nonetheless, the mechanism underlying rapid approximate numerical averaging remains unknown, and several competing mechanism may account for it. Here, we tested the hypothesis that approximate numerical averaging relies on perceptual-like processes, instantiated by population coding. Participants were presented with rapid sequences of numerical values (four items per second) and were asked to convey the sequence average. We manipulated the sequences' length, variance, and mean magnitude and found that similar to perceptual averaging, the precision of the estimations improves with the length and deteriorates with (higher) variance or (higher) magnitude. To account for the results, we developed a biologically plausible population-coding model and showed that it is mathematically equivalent to a population vector. Using both quantitative and qualitative model comparison methods, we compared the population-coding model to several competing models, such as a step-by-step running average (based on leaky integration) and a midrange model. We found that the data support the population-coding model. We conclude that humans' ability to rapidly form estimations of numerical averages has many properties of the perceptual (intuitive) system rather than the arithmetic, linguistic-based (analytic) system and that population coding is likely to be its underlying mechanism.