Extinction Processes Research Articles

Infralimbic and prelimbic prefrontal cortex activation is necessary to the enhancement of aversive memory extinction promoted by reactivation

Memory extinction has been used in behavioral therapy to treat post-traumatic stress disorders. It was demonstrated that memory reactivation before extinction could facilitate this process. However, the mechanisms involved are still unclear. Here, we investigated the participation of two regions of the ventromedial prefrontal cortex (vmPFC), the infralimbic (IL) and prelimbic (PL), in the memory reactivation modulatory effect of fear extinction. We confirmed that the reactivation facilitates the fear extinction in an inhibitory aversive task; however, when the muscimol (a GABAergic agonist) is infused in IL or PL vmPFC after reactivation, extinction's facilitation was not observed. These findings support the idea that the reactivation can modulate the fear extinction process, facilitating it, and that this effect requires the activation of both IL and PL regions of vmPFC.

Mathematical Modelling on Extinction of Metallized Composite Solid Propellant Under a Sudden Drop in Pressure

AbstractThis paper presents a physico‐mathematical combustion model of the metallized composite solid propellant (MCSP), which takes into account the chemical reactions in the condensed and gas phases. The model describes convection and diffusion of the propellant components in the two‐phase flow over the fuel surface and combustion of the aluminium particles emitted from the fuel. The constructed model provides the opportunity to calculate the fuel combustion rate under the constant and variable pressure. The obtained calculation results of the MCSP combustion rate using the model are in good agreement with the known experimental data. The manuscript also provides data on the modelling of the MCSP extinction under the sudden pressure change. According to the conducted numerical simulations, the value of the pressure drop, leading to the fuel extinction, depends on the mass fraction of the aluminium powder in the fuel composition and its dispersion. With an increase in the mass fraction of the aluminium powder and/or a decrease in the size of the aluminium particles emitting from the fuel surface, the extinction process occurs at a greater value and under a higher rate of the pressure drop. The numerical simulation has also shown that the addition of the aluminium powder to the composition of the propellant increases the combustion stability under the sudden drop in pressure over the combustion surface.

The two extinctions of the Carolina ParakeetConuropsis carolinensis

SummaryDue to climate change and habitat conversion, estimates of the resulting levels of species extinction over the next century are alarming. Devising conservation solutions will require many different approaches, including examining the extinction processes of recently extinct species. Given that parrots are one of the most threatened groups of birds, information regarding parrot extinction is pressing. While most recent parrot extinctions have been island endemics, the Carolina ParakeetConuropsis carolinensishad an 18th-century range covering nearly half of the present-day United States, yet mostly disappeared by the end of the 19thcentury. Despite a great deal of speculation, the major cause of its extinction remains unknown. Establishing the date when a species went extinct is one of the first steps in determining what caused their extinction. While there have been estimates of their extinction date, these analyses used a limited dataset and did not include observational data. We used a recently published, extensive dataset of Carolina Parakeet specimens and observations combined with a Bayesian extinction estimating model to determine the most likely extinction dates. By considering each of the two subspecies independently, we found that they went extinct ˜30 years apart: the western subspeciesC. c. ludovicianusgoing extinct around 1914 and the eastern subspeciesC. c. carolinensiseither in the late 1930s or mid-1940s. Had we only considered all observations together, this pattern would have been obscured, possibly missing a major clue in solving the mystery of the parakeet’s extinction. Since the Carolina Parakeet was a wide-ranging species that went extinct during a period of rapid agricultural and industrial expansion, conditions that mirror those occurring in many parts of the world where parrot diversity is highest, any progress we make in unraveling the mystery of their disappearance may be vital to modern conservation efforts.

Low Estradiol May Not Impede Cognitive Restructuring in Women With Anxiety Disorders.

Prior research suggests that estradiol may moderate fear extinction in animal models and humans. Based on these findings, estradiol may also moderate cognitive reappraisal, which is theorized to be an important mechanism of change in extinction-based therapy (exposure therapy). We compared cognitive restructuring (CR) skills acquisition and outcome between women with primary anxiety disorders who had high versus low estradiol using a standardized CR task that closely resembles clinical practice. As a proxy of CR outcome, we assessed subjective distress ratings before and after the task and psychophysiological arousal (heart rate and electrodermal activity) throughout the task. Contrary to predictions, results showed that CR skills acquisition and outcome did not differ between the high and low estradiol groups. Although both groups demonstrated reductions in negative affect and skin conductance responses during the CR task, suggesting that participants were able to acquire CR skills and use them effectively to regulate distress, the groups did not differ with respect to CR ability or outcome. The findings suggest that estradiol may not moderate cognitive reappraisal, and may have more of an effect on basic habituation and extinction processes instead.

Psychophysiological evidence for fear extinction learning via mental imagery.

Imagery-based extinction procedures have long been used in the treatments of fear-related conditions. The assumption is that imagery can substitute for the perceptual stimuli in the extinction process. Yet, experimental validations of this assumption have been limited in number and some have relied exclusively on measures of autonomic reactivity without consideration of conscious feelings of fear. The current investigation sought to assess whether imagery-based exposure could lead to extinction of conditioned fear to the corresponding perceptual stimulus. Conditioned fear responses were measured by both a physiological (i.e., skin conductance response [SCR]) and a subjective (i.e., self-reported fear) measure. Participants (N=56) first underwent perceptual differential fear conditioning, then imagery extinction, then perceptual extinction. SCR evidence was found for successful fear conditioning, generalization of fear from viewing to imagery, and most importantly, the absence of differential fear after imagery extinction upon re-exposure to the conditioned perceptual stimulus. Self-reported fear confirmed the acquisition and generalization of fear and provided evidence of a significant reduction in differential fear conditioning across extinction. Consistent with clinical evidence of the efficacy of imagery extinction and the existing limited experimental literature, this study offers support for fear extinction to perceptual stimuli via imagery exposure.

Homo Sapiens Sapiens Progressive Defaunation During The Great Acceleration: The Cli-Fi Apocalypse Hypothesis

Homo Sapiens Sapiens Progressive Defaunation During The Great Acceleration: The Cli-Fi Apocalypse Hypothesis

Spatio-temporal dynamics of conventional soliton and breathing soliton in an anomalous dispersion fiber laser

The evolutions of conventional soliton (CS) and breathing soliton (BS) dynamics in an anomalous dispersion Er-doped fiber laser are investigated experimentally and numerically. Based on the dispersive Fourier transform technique, the evolution processes of CS buildup and extinction are observed and discussed. It was found that a transitional unstable stage exists during the buildup and extinction process. In the same laser, BS state is also reached. Simulation results of CS and BS evolutionary dynamics are anastomotic with experimental results. The results may contribute to better understanding of the complex pulse dynamics in ultrafast fiber lasers.

Analysis of geographic centrality and genetic diversity in the declining grasshopper species Bryodemella tuberculata (Orthoptera: Oedipodinae)

Human-induced ecological and climatic changes have led to the decline and even local extinction of many formerly widely distributed temperate and cold-adapted species. Determining the exact causes of this decline remains difficult. Bryodemella tuberculata was a widely distributed orthopteran species before the mid-19th century. Since then, many European populations have suffered drastic declines and are now considered extinct or critically endangered. We used ecological niche modelling based on a large dataset of extant and extinct occurrence data to investigate whether poor climatic suitability in the periphery of its global range was a possible cause of the local extinction of the European populations of B. tuberculata. We also used population genetics based on the COI marker to estimate and compare the genetic diversity of extant populations. We found that Europe still provides highly suitable habitats close to the climatic optimum, contradicting the assumption of climate change as major driver of this decline. Instead, changes in land-cover and other anthropogenic modifications of the habitats at the local scale seem to be the major reasons for local extinctions. Genetic analysis suggests Central Asia as center of diversity with a stable population size, whereas the effective sizes of the remaining European populations are decreasing. We found European genetic lineages nested within Central Asian lineages, suggesting a Central Asian source distribution area. Our results suggest that the declining European populations represent relics of a formerly wider distribution, which was fragmented by changes in land-use. These relics are now threatened by limited connectivity and small effective population sizes. Specific conservation actions, such as the restoration of former or potential new habitats, and translocation of individuals from extant populations to these restored sites may help slow, stall, or even revert the extinction process.

A framework for understanding how biodiversity patterns unfold across multiple spatial scales in urban ecosystems

AbstractWhether cities are more or less diverse than surrounding environments, and the extent to which non‐native species in cities impact regional species pools, remain two fundamental yet unanswered questions in urban ecology. Here we offer a unifying framework for understanding the mechanisms that generate biodiversity patterns across taxonomic groups and spatial scales in urban systems. One commonality between existing frameworks is the collective recognition that species co‐occurrence locally is not simply a function of natural colonization and extinction processes. Instead, it is largely a consequence of human actions that are governed by a myriad of social processes occurring across groups, institutions, and stakeholders. Rather than challenging these frameworks, we expand upon them to explicitly consider how human and non‐human mechanisms interact to control urban biodiversity and influence species composition over space and time. We present a comprehensive theory of the processes that drive biodiversity within cities, between cities and surrounding non‐urbanized areas and across cities, using the general perspective of metacommunity ecology. Armed with this approach, we embrace the fact that humans substantially influence β‐diversity by creating a variety of different habitats in urban areas, and by influencing dispersal processes and rates, and suggest ways how these influences can be accommodated to existing metacommunity paradigms. Since patterns in urban biodiversity have been extensively described at the local or regional scale, we argue that the basic premises of the theory can be validated by studying the β‐diversity across spatial scales within and across urban areas. By explicitly integrating the myriad of processes that drive native and non‐native urban species co‐occurrence, the proposed theory not only helps reconcile contrasting views on whether urban ecosystems are biodiversity hotspots or biodiversity sinks, but also provides a mechanistic understanding to better predict when and why alternative biodiversity patterns might emerge.

Kinetic effects of methyl radicals on PRF lean ignition: a comparative study of skeletal mechanisms

Despite considerable achievements of combustion kinetics, the chemical kinetic impacts of trace promoting species on practical fuel combustion has been hitherto handled seperately either as ignition or extinction-related effects, overlooking the impact of the extinction process on re-ignition kinetics. We herein demonstrate the applicability of oscillatory stirred reactor configuration to quantify the combined impacts of the methyl radical on ignition/extinction of primary reference fuels (PRF) in stoichiometric and ultra-lean conditions, thereby complementing steady-state configurations for kinetic mechanism validation. A new convenient reactivity metric is proposed based on the matching of temperature Fourier spectrum of additivated fuels with corresponding PRF. Using a new skeletal mechanism obtained from calibration on a variety of ignition experiments, we characterize ignition regimes by CEMA analysis and highlight the key reactions of the C1-C3 reaction subsets that should be included in minimal skeletal mechanisms used in reactive CFD modeling to properly describe re-ignition phenomena over a variety of new combustion applications involving methyl radical injection.

Phylogeny and historical biogeography of the pantropical genus Parkia (Leguminosae, Caesalpinioideae, mimosoid clade)

Parkia R.Br. (Leguminosae, Caesalpinioideae, mimosoid clade) is a pantropical genus with approximately 35 recognized species in three taxonomic sections (Parkia, Platyparkia and Sphaeroparkia), distributed widely in tropical forests and savannas in South and Central America, Africa-Madagascar and the Indo-Pacific region. In this study, phylogenetic analyses (Maximum Likelihood and Bayesian Inference), ancestral area and habitat estimations were performed using chloroplast (matK, trnL, psbA-trnH and rps16-trnQ) and nuclear (ITS/18S/26S) DNA sequences for the purpose of testing the monophyly of Parkia and inferring the geographic origin of the genus and times of divergence of the various lineages. This enabled investigation of factors that may have influenced its diversification in both hemispheres. Our results support the monophyly of the genus. A fossil-calibrated Bayesian analysis dated the Parkia crown node to the Miocene (at c. 18.85 Ma). Biogeographic analysis reconstructed an origin in the lowlands rainforests (terra firme) in Amazonia with subsequent radiation in the Neotropical region from the Miocene onwards, with dispersion events as far as Central America, and the Atlantic Forest and the cerrado of Brazil. A single dispersion from the Neotropics to the Paleotropics is hypothesised, with subsequent smaller radiations in Africa-Madagascar and the Indo-Pacific (crown ages 3.79 and 5.15 Ma respectively). Factors that may have influenced the radiation and speciation of Parkia include the elevation of the Andes (especially in the Miocene), and more recently the closing of the Panama gap in Neotropics, the climatic fluctuations of the Pleistocene influenced the diversification of species on both continents. The elevation of the Sunda Shelf in Indo-Pacific region during the last glacial maximum (LGM) appears to be the main driving force for speciation in that region. In Africa, the low number of species may be related to extinction processes.

Calcineurin Participation in Hebbian and Homeostatic Plasticity Associated With Extinction.

In nature, animals need to adapt to constant changes in their environment. Learning and memory are cognitive capabilities that allow this to happen. Extinction, the reduction of a certain behavior or learning previously established, refers to a very particular and interesting type of learning that has been the basis of a series of therapies to diminish non-adaptive behaviors. In recent years, the exploration of the cellular and molecular mechanisms underlying this type of learning has received increasing attention. Hebbian plasticity (the activity-dependent modification of the strength or efficacy of synaptic transmission), and homeostatic plasticity (the homeostatic regulation of plasticity) constitute processes intimately associated with memory formation and maintenance. Particularly, long-term depression (LTD) has been proposed as the underlying mechanism of extinction, while the protein phosphatase calcineurin (CaN) has been widely related to both the extinction process and LTD. In this review, we focus on the available evidence that sustains CaN modulation of LTD and its association with extinction. Beyond the classic view, we also examine the interconnection among extinction, Hebbian and homeostatic plasticity, as well as emergent evidence of the participation of kinases and long-term potentiation (LTP) on extinction learning, highlighting the importance of the balance between kinases and phosphatases in the expression of extinction. Finally, we also integrate data that shows the association between extinction and less-studied phenomena, such as synaptic silencing and engram formation that open new perspectives in the field.

Transient modelling and simulation of the forced arc extinguish period of the circuit breakers

Plasma transport during continuous extinction processes from high-current arcs to fully extinction is an important issue in the study of vacuum arcs. In this research a 3D hybrid plasma model has been developed to study the extinguish period of the DC vacuum arc. The model treats the electrons as a massless fluid and ions as macro particles. The ion-neutral collision processes including both charge exchange collisions and momentum exchange collisions are considered with Monte-Carlo method. By this approach, the vacuum arc model consists of plasma jets ejected from multiple cathode spots is established and the behaviours of ions under the collisions with neutral atoms are simulated. It is shown that a large number of low-speed ions are generated in the interelectrode region due to the chare exchange collisions between ions and neutrals. And as the arc current drops to zero, the proportion of low-speed ions to the total ions at each moment becomes higher and higher.

The effect of colonization dynamics in competition for space in metacommunities

One of the main factors that determines habitat suitability for sessile and territorial organisms is the presence or absence of another competing individual in that habitat. This type of competition arises in populations occupying patches in a metacommunity. Previous studies have looked at this process using a continuous-time modeling framework, where colonizations and extinctions occur simultaneously. However, different colonization processes may be performed by different species, which may affect the metacommunity dynamics. We address this issue by developing a discrete-time framework that describes these kinds of metacommunity interactions, and we consider different colonization dynamics. To understand potential dynamics, we consider specific functional forms that characterize the colonization and extinction processes of metapopulations competing for space as their limiting factor. We then provide a mathematical analysis of the models generated by this framework, and we compare these results to what is seen in nature and in previous models.

Social Integrating Robots Suggest Mitigation Strategies for Ecosystem Decay.

We develop here a novel hypothesis that may generate a general research framework of how autonomous robots may act as a future contingency to counteract the ongoing ecological mass extinction process. We showcase several research projects that have undertaken first steps to generate the required prerequisites for such a technology-based conservation biology approach. Our main idea is to stabilise and support broken ecosystems by introducing artificial members, robots, that are able to blend into the ecosystem’s regulatory feedback loops and can modulate natural organisms’ local densities through participation in those feedback loops. These robots are able to inject information that can be gathered using technology and to help the system in processing available information with technology. In order to understand the key principles of how these robots are capable of modulating the behaviour of large populations of living organisms based on interacting with just a few individuals, we develop novel mathematical models that focus on important behavioural feedback loops. These loops produce relevant group-level effects, allowing for robotic modulation of collective decision making in social organisms. A general understanding of such systems through mathematical models is necessary for designing future organism-interacting robots in an informed and structured way, which maximises the desired output from a minimum of intervention. Such models also help to unveil the commonalities and specificities of the individual implementations and allow predicting the outcomes of microscopic behavioural mechanisms on the ultimate macroscopic-level effects. We found that very similar models of interaction can be successfully used in multiple very different organism groups and behaviour types (honeybee aggregation, fish shoaling, and plant growth). Here we also report experimental data from biohybrid systems of robots and living organisms. Our mathematical models serve as building blocks for a deep understanding of these biohybrid systems. Only if the effects of autonomous robots onto the environment can be sufficiently well predicted can such robotic systems leave the safe space of the lab and can be applied in the wild to be able to unfold their ecosystem-stabilising potential.

Biological and extrinsic correlates of extinction risk in Chinese lizards.

China is a country with one of the most species-rich reptile faunas in the world. However, nearly a quarter of Chinese lizard species assessed by the China Biodiversity Red List are threatened. Nevertheless, to date, no study has explicitly examined the pattern and processes of extinction and threat in Chinese lizards. In this study, we conducted the first comparative phylogenetic analysis of extinction risk in Chinese lizards. We addressed the following 3 questions: (1) What is the pattern of extinction and threat in Chinese lizards? (2) Which species traits and extrinsic factors are related to their extinction risk? (3) How can we protect Chinese lizards based on our results? We collected data on 10 species traits (body size [BS], clutch size, geographic range size, activity time, reproductive mode, habitat specialization [HS], habitat use, leg development, maximum elevation, and elevation range) and 7 extrinsic factors (mean annual precipitation (MAP), mean annual temperature, mean annual solar insolation, normalized difference vegetation index (NDVI), human footprint, human population density, and human exploitation). After phylogenetic correction, these variables were used separately and in combination to assess their associations with extinction risk. We found that Chinese lizards with a small geographic range, large BS, high HS, and living in high MAP areas were vulnerable to extinction. Conservation priority should thus be given to species with the above extinction-prone traits so as to effectively protect Chinese lizards. Preventing future habitat destruction should also be a primary focus of management efforts because species with small range size and high HS are particularly vulnerable to habitat loss.

Ignition characteristics of premixed cool flames on a heated wall

This work examined the cool flame ignition and stabilization on heated walls with different surface reactivities. A premixed mixture of dimethyl ether (DME) and O2 was impinged on a heated wall and the wall temperature was linearly ramped to determine the cool flame ignition temperature. Numerical analyses identify a hysteresis phenomenon in the cool flame ignition and extinction processes, which appears to be primarily governed by the low-temperature reaction kinetics. The formation of HCHO during the cool flame ignition process was monitored using the planar laser-induced fluorescence (PLIF) technique synchronized with instantaneous wall temperature measurements. The data indicated that the HCHO concentration near the wall surface abruptly increased at the ignition of the premixed cool flame. The predicted hysteresis behaviors for cool flame ignition and extinction with a nonlinear folded S-curve and a smoothly stretched S-curve were successfully observed experimentally for the first time ever for lean mixtures. Moreover, the results show that compared with the ignition limits on an inert SiO2 surface, noticeable increases and decreases of the cool flame ignition temperature were observed on Fe and Pt surfaces, respectively. These findings suggest that significant wall chemical effects occur during the cool flame ignition process, based on interactions between the gas phase and surface reactions.

Evaluating extinction, renewal, and resurgence of operant behavior in humans with Amazon Mechanical Turk

Amazon Mechanical Turk (MTurk) is a crowdsourcing marketplace providing researchers with the opportunity to collect behavioral data from remote participants at a low cost. Recent research demonstrated reliable extinction effects, as well as renewal and resurgence of button pressing with MTurk participants. To further examine the generality of these findings, we replicated and extended these methods across six experiments arranging reinforcement and extinction of a target button press. In contrast to previous findings, we did not observe as reliable of decreases in button pressing during extinction (1) after training with VR or VI schedules of reinforcement, (2) in the presence or absence of context changes, or (3) with an added response cost for button pressing. However, we found that that a 1-point response cost for all button presses facilitated extinction to a greater extent than the absence of response cost. Nevertheless, we observed ABA renewal of button pressing when changing background contexts across phases and resurgence when extinguishing presses on an alternative button. Our findings suggest that MTurk could be a viable platform from which to ask and address questions about extinction and relapse processes, but further procedural refinements will be necessary to improve the replicability of control by experimental contingencies.

Elevated activity in the dorsal dentate gyrus reduces expression of fear memory after fear extinction training.

Background:Effectively reducing the expression of certain aversive memories (fear or trauma memories) with extinction training is generally viewed to be therapeutically important. A deeper understanding of the biological basis for a more effective extinction process is also of high scientific importance.Methods:Our study involved intraventricular injection or local injection into the dorsal dentate gyrus of anti-neuregulin 1 antibodies (anti-NRG1) before fear extinction training, followed by testing the expression of fear memory 24 hours afterward or 9 days later. We used local injection of chemogenetic or optogenetic viruses into the dorsal dentate gyrus to manipulate the activity of the dorsal dentate gyrus and test the expression of fear memory. We also examined the effect of deep brain stimulation in the dorsal dentate gyrus on the expression of fear memory.Results:Mice that received intraventricular injection with anti-NRG1 antibodies exhibited lower expression of fear memory and increased density of activated excitatory neurons in the dorsal dentate gyrus. Injection of anti-NRG1 antibodies directly into the dorsal dentate gyrus also led to lower expression of fear memory and more activated neurons in the dorsal dentate gyrus. Inhibiting the activity of dorsal dentate gyrus excitatory neurons using an inhibitory designer receptor exclusively activated by designer drugs (DREADD) eliminated the effects of the anti-NRG1 antibodies. Enhancing the activity of the dorsal dentate gyrus with an excitatory DREADD or optogenetic stimulation resulted in lower expression of fear memory in mice that did not receive infusion of anti-NRG1 antibodies. Deep brain stimulation in the dorsal dentate gyrus effectively suppressed expression of fear memory, both during and after fear extinction training.Limitations:The mechanism for the contribution of the dorsal dentate gyrus to the expression of fear memory needs further exploration.Conclusion:Activation of the dorsal dentate gyrus may play an important role in modulating the expression of fear memory; its potential use in fear memory extinction is worthy of further exploration.

Enhancing Trauma-Memories Reconsolidation With One-Time Ketamine Infusion

NMDA receptor antagonists were found to have a vital role in extinction and reconsolidation processes. During reconsolidation, memories are activated into a labile state and can be stored in an altered form. This idea might have clinical implications in the treatment of PTSD, with current psychotherapies’ success rate rounding 50%. Here we used a single subanesthetic intravenous infusion of ketamine (NMDA receptor antagonist; 0.5mg/kg over 40min) to enhance post-retrieval extinction of real traumatic memories.