Extinction Processes Research Articles

MIDDLE-LATE PERMIAN AND EARLY TRIASSIC FORAMINIFERAL ASSEMBLAGES IN THE WESTERN SALT RANGE, PAKISTAN

A newly obtained foraminiferal assemblage from the Guadalupian−Lopingian, and Induan of the Western Salt Range (Pakistan) comprises 47 species (including 7 species of fusulinoideans) of 24 genera and 71 species (including 9 species of fusulinoideans) of 41 genera, in Nammal and Zaluch sections, respectively. Our results show that only 4 species went extinct during the Guadalupian−Lopingian mass extinction (GLME), suggesting the GLME was minor for smaller foraminifers in the Salt Range. Most species went extinct during the Permian-Triassic mass extinction (PTME), except the two survivor genera, Nodosinelloides and Planiinvoluta. During the end-Permian mass extinction, majorities of the species became extinct in lower part of Chhidru Formation, beacuse they are not tolerant to the terigenious-clastic input in the upper part of Chhidru Formation. The extinction process of foraminifers in the Nammal and Zaluch sections has been documented for the first time. Five foraminiferal assemblages are established in the shallow marine shelf deposits of Western Salt Range, i.e., Wordian Geinitzina araxensis assemblage in tide-influenced subaqueous delta to middle shelf environment, Capitanian Baisalina pulchra assemblage and Wuchiapingian Codonofusiella schubertellinoides assemblage in inner-outer shelf carbonate deposits, Changhsingian Colaniella pseudolepida assemblage and Induan Nodosinelloides-Planiinvoluta assemblage in mixed siliciclastic–carbonate shelf setting. The Baisalina pulchra and Codonofusiella schubertellinoides assemblages have wide geographic distribution and have been found in Transcaucasus, China, Turkey, Crimea and Oman. The other three assemblages (i.e., Geinitzina araxensis, Colaniella pseudolepida, and Nodosinelloides-Planiinvoluta assemblages) found in this study are likely local/regional assemblages. The foraminifers were observed with the standard microscopic system Leica-DM500. A total of 681 specimens of foraminifers are reported in the Zaluch Group and Mianwali Formation of Nammal and Zaluch sections. Five hundred ninety-nine smaller foraminifers specimens were recovered. Among the smaller foraminifera, Nodosinelloides, Pachyphloia, Geinitzina, Colaniella, Hemigordius, Tuberitina, and Langella are the most dominant genera. Larger foraminifera genera include Nankinella, Codonofusiella, Reichelina, Necdetina and Pisolina, represented by 82 specimens. A total of 3 classes (e.g., Nodosariata, Fusulinata, and Tubothalamea) and seven orders (i.e., Miliolida, Spirillinida, Lagenida, Parathuramminida, Endothyrida, Fusulinida, and Earlandiida) are identified in the current study. Among them, Lagenida becomes the most dominant by diversity and abundance. Shannon diversity and other indices rise progressively from Wordian to Changhsingian in the shallow marine sediments before dropping to zero in the Early Triassic mixed siliciclastic–carbonate shelf deposits.

The influence of FAAH genetic variation on physiological, cognitive, and neural signatures of fear acquisition and extinction learning in women with PTSD

BackgroundPosttraumatic Stress Disorder (PTSD) is commonly treated with exposure-based cognitive therapies that are based on the principles of fear acquisition and extinction learning. Elevations in one of the major endocannabinoids (anandamide) either via inhibition of the primary degrading enzyme (fatty acid amide hydrolase; FAAH) or via a genetic variation in the FAAH gene (C385A; rs324420) has resulted in accelerated extinction learning and enhanced extinction recall among healthy adults. These results suggest that targeting FAAH may be a promising therapeutic approach for PTSD. However, these effects have not yet been comprehensively examined in a PTSD population. MethodsThe current study examined whether genetic variation in the FAAH gene (CC [n = 49] vs AA/AC [n = 36] allele carriers) influences physiological (skin conductance), cognitive (threat expectancy), and neural (network and voxel-wise activation) indices of fear acquisition and extinction learning among a sample of adult women with PTSD (N = 85). ResultsThe physiological, cognitive, and neural signatures of fear acquisition and extinction learning varied as a function of whether or not individuals possess the FAAH C385A polymorphism. For instance, we report divergent responding between CC and AA/AC allele carriers to CS + vs CS- in limbic and striatum networks and overall greater activation throughout the task among AA/AC allele carriers in several regions [e.g., inferior frontal, middle frontal, parietal] that are highly consistent with a frontoparietal network involved in higher-order executive functions. ConclusionsThese results suggest that genetic variation within the FAAH gene influences physiological, cognitive, and neural signatures of fear learning in women with PTSD. In order to advance our understanding of the efficacy of FAAH inhibition as a treatment for PTSD, future clinical trials in this area should assess genetic variation in the FAAH gene in order to fully depict and differentiate the acute effects of a drug manipulation (FAAH inhibition) from more chronic (genetic) influences on fear extinction processes.

Colonization and extinction dynamics and their link to the distribution of European trees at the continental scale

AbstractAimThe population processes that drive tree species distribution are still widely debated. We test the hypotheses that metapopulation processes of colonization and extinction are linked to predictions of species distribution models.LocationEurope: Spain, France, Germany, Finland and Sweden.TaxonAngiosperms and Gymnosperms.MethodsFor 17 tree species analysed, we fitted species distribution models (SDM) relating environmental variables to presence–absence data across Europe. Then, using independent data from national forest inventories across Europe, we tested whether colonization and extinction probabilities are related to SDM occurrence probabilities. Finally, we assessed the probability of presence at metapopulation equilibrium depending on colonization and extinction probabilities.ResultsWe found that for most species at least one process (colonization/extinction) is related to SDM occurrence probability, but rarely both (only two species). Depending on the species, the link was either for colonization or for extinction, but relationships were generally weak. In addition, the metapopulation models tended to overestimate the occurrence probability at equilibrium.Main conclusionsOur study shows that metapopulation processes are only weakly related to SDM occurrence probability and call for caution in extrapolating SDM models to metapopulation dynamics.

A simulation-based method for selecting calibration areas for ecological niche models and species distribution models

Ecological niche models and species distribution models (ENM and SDM, respectively) are tools that have seen massive use and considerable improvement during the last twenty years. The choice of calibration areas for such models has strong effects on model outcomes and model interpretation, as well as on model transfer to distinct environmental settings. However, approaches to selecting these areas remain simple and/or unlinked to biological concepts. Such models should be calibrated within areas that the species of interest has explored throughout its recent history, the accessible area (M). In this paper, we provide a simulation approach for estimating a species’ M considering processes of dispersal, colonization, and extinction in constant current climate or glacial-interglacial climate change frameworks, implemented within a new R package we developed called grinnell. Using the avian genus Aphelocoma, we explored different parameterizations of our simulation, and compared them to current approaches for M selection, in terms of model performance and risk of extrapolation using the algorithm Maxent and mobility-oriented parity analyses. Model calibration exercises from all approaches resulted in at least one model meeting optimal performance criteria for each species; however, we noted high variability among taxa and M selection methods. More importantly, M hypotheses derived directly from simulations of key biological processes, rather than being based on simple proxies of those processes, and as such are better suited to erecting biologically appropriate contrasts in model calibration, and to characterizing the potential for model extrapolation more rigorously. Major factors in our simulations were environmental layer resolution, dispersal kernel characteristics, and the inclusion of a changing framework of climatic conditions. This contribution represents the first simulation-based method for selecting calibration areas for ENM and SDM, offering a quantitative approach to estimate the accessible area of a species while considering its dispersal ability, along with patterns of change in environmental suitability across space and time.

Schizotypal personality traits and the social learning of fear

Schizotypy can be defined as a combination of traits qualitatively similar to those found in schizophrenia, but milder in their expression, that can be found in clinical and non-clinical populations. In this research, we explore, to our knowledge, for the first time, whether schizotypal personality traits may affect the acquisition of conditioned fear by social means only. Apart from being an essential capacity to ensure learning in safe environments, social fear learning shares important characteristics with direct fear acquisition, which also makes it a great candidate for developing successful extinction procedures. Undergraduate students (n = 72) performed a task of social fear learning. In this task, participants watched a video of a person that simulated to receive electric shocks (unconditioned stimulus; US) paired with a coloured square (conditioned stimulus plus; CS+), while another coloured square was never paired (conditioned stimulus minus; CS−) with the shock. After that, they were presented with a similar sequence of coloured screens. Their Skin Conductance Responses (SCRs) were registered during the whole process. Once they finished, they completed the Schizotypal Personality Questionnaire (SPQ). Our results revealed that participants with a low score in the Cognitive-Perceptual factor of the SPQ exhibited higher SCRs when they saw the US than when they saw the CS− (all ps < 0.01) during the learning phase. Nevertheless, those with higher scores did not present any difference in their SCRs toward both stimuli (all ps > 0.05), a pattern that has been similarly found in schizophrenia. During the final trials of the test phase, participants with the highest scores in the Disorganized factor were the only ones that maintained a higher SCR towards the CS+ than towards the CS− (p = 0.006), which could be associated with an impairment in their extinction processes.

Secure attachment priming protects against relapse of fear in Young adults

Previous studies have shown that activating the attachment system attenuates fear learning. This study aimed to explore whether attachment priming can also impact on fear extinction processes, which underpin the management of anxiety disorders. In this study, 81 participants underwent a standard fear conditioning and extinction protocol on day 1 and returned 24 h later for an extinction recall and reinstatement test. Half the participants were primed to imagine their closest attachment figure prior to undergoing extinction training, while the other half were instructed to imagine a positive situation. Fear-potentiated startle and subjective expectancies of shock were measured as the primary indicators of fear. Attachment priming led to less relapse during the reinstatement test at the physiological but not subjective levels. These findings have translational potential to imply that activating awareness of attachment figures might augment long-term safety memories acquired in existing treatments to reduce relapse of fear.

Different extinction debts among plants and arthropods after loss of grassland amount and connectivity

A decrease in habitat amount and connectivity causes immediate or delayed species extinctions in transformed landscapes due to reduced functional connections among populations and altered environmental conditions. We assessed the effects of present and historical grassland amount and connectivity as well as local habitat factors typical of the present landscape on the current species richness of grassland specialist and generalist plants and arthropods in grassland fragments. We surveyed herbaceous plants, ants, orthopterans, true bugs and rove beetles in 60 dry grassland fragments in Hungary. We recorded the area of the focal grassland, the slope and the cover of woody vegetation. By using habitat maps of the present and historical landscape, we calculated grassland amount and connectivity for four time periods covering 158 years (1858–2016). We found evidence for an unpaid extinction debt in specialist plants, suggesting that they have not come to equilibrium with the grassland amount and connectivity of the present landscape yet. This localised and typically long-lived group responded slowly to the landscape changes. Specialist arthropod taxa with short generation times responded much faster to habitat loss than plants and did not show an extinction debt. Generalist plants and animals adapted to a wide range of habitats were affected by the landscape-scale decline of grassland habitats. Despite decreased habitat connectivity, grassland fragments with dry environmental conditions and high environmental heterogeneity can sustain specialist plants in transformed landscapes. Unpaid extinction debt should be considered an early warning signal: Restoration of grassland connectivity is necessary to halt ongoing extinction processes.

Les faunes terrestres quaternaires des Îles du Japon

This paper explains a brief history of research on Quaternary terrestrial mammals in Japan and fossil occurrence of taxa at major localities of each time period at first. Based on these data, then, the changing history of Quaternary terrestrial mammals in Japan is reviewed, especially on such points as (1) importance of strait in western Japan as coming over route, (2) changing history of Plio-Pleistocene terrestrial mammals in Japan, (3) two faunas during the Late Pleistocene, (4) dates of extinctions of large mammals near the end of the Late Pleistocene. Formation process of Quaternary terrestrial mammal fauna in Japan must have been affected by condition of land connection with Asian continent at seaway west to Japan and changing history of climate and vegetation in East Asia, and it should be considered by different time period, e.g. before and after ca. 1.7 Ma. The time period after 1.7 Ma is one affected by glacial sea level fluctuations. Although a new fauna came over from the west to Japan when sea level was low, this time period is basically the age of insularization, and it is presumed that the fauna was becoming endemic during this time period. During the late Late Pleistocene, there were two faunas existed in Japan, e.g. one with Palaeoloxodon naumanni having come over from the west and another with Mammuthus primigenius having come over from the north. The former dwelled mainly in deciduous broad-leaved forest and mixed forest with conifers in temperate climate, while the latter dwelled in steppe and coniferous forest in subboreal climate. Both faunas changed their ranges to north and south repeatedly as climate changed, and the extinction of large mammals of the fauna with Palaeoloxodon naumanni occurred at the same time of the beginning of the LGM (ca. 25–16 ka). On the other hand, large mammals of the fauna with Mammuthus primigenius became extinct or moved to north as climate became warm quickly after the LGM. Thus, it is suggested that the extinction of large mammals at the late Late Pleistocene occurred by “two pulses.” The extinction process of large mammals in Japan seems likely that they went extinct finally near the end of the Pleistocene going through the reduction of habitat and fragmentation of populations caused by the repeated temperature change during the late Late Pleistocene, rather than a single drastic event.

Extinction of incident hydrogen/air detonation in fine water sprays

Two-dimensional numerical simulations with Eulerian–Lagrangian method are conducted to study propagation and extinction of stoichiometric hydrogen/air detonations in fine water sprays. Parameterized by water mass loading and droplet size, a detonation extinction map is predicted. Detonation extinction occurs with larger mass loading and/or smaller droplet size. General features of water droplets and local detonation frontal structures are well captured. Numerical soot foils are used to characterize the influence of mass loading and droplet size on the detonation wave. The results also show that the detonation cell size increases with increased mass loading or decreased droplet size. Analysis on unsteady detonation extinction process is performed with the evolutions of detonation frontal structure, spatial distribution of thermochemical variables, and interphase transfer rates (mass, energy, and momentum). Moreover, the chemical explosive mode analysis reveals that for stable detonation, thermal runaway dominates behind the Mach stem, while chemical propensities of autoignition and thermal runaway appear alternately behind the incident wave. When the induction zone length increases as the reaction front (RF) and shock front (SF) are decoupled, localized burned pockets surrounded by the autoignition chemical explosive mixture can be observed. In addition, the interactions between detonation wave and water droplets demonstrate that the energy and momentum transfer have more direct interaction with SF and RF than the mass transfer. The interphase transfer rates increase with the water mass loading. Under the same mass loading, the smaller the droplet size, the larger the interphase transfer rates. However, the size of fine water droplets has a limited influence on the interphase momentum exchange. Moreover, high energy and mass transfer rates are observed at the onset of detonation extinction, and they gradually decrease when the reaction and detonation fronts are decoupled.

A birth-death-migration model for life in astrophysical environments

ABSTRACT To assess the number of life-bearing worlds in astrophysical environments, it is necessary to take the intertwined processes of abiogenesis (birth), extinction (death), and transfer of life (migration) into account. We construct a mathematical model that incorporates this trio of mechanisms and accordingly derive the probability distribution function and other statistical properties (e.g. mean) for the number of worlds with biospheres. We show that a given astrophysical setting may become eventually saturated with life if the rate of successful transfers of organisms is higher than the extinction rate of biospheres. Based on the available data, we suggest that this criterion might be fulfilled for star-forming clusters (and perhaps the Galactic bulge under optimal circumstances), thereby indicating that such regions could constitute promising abodes for hosting and detecting life.

Oxytocin in dorsal hippocampus facilitates auditory fear memory extinction in rats

Fear extinction is impaired in some psychiatric disorders. Any treatment that facilitates the extinction of fear is a way to advance the treatment of related psychiatric disorders. Recent studies have highlighted the role of oxytocin (OT) in fear extinction, but the endogenous release of OT during fear extinction in the dorsal hippocampal (dHPC) is not clear. We investigated the release of OT during fear extinction and the role of the HPC - medial prefrontal cortex (mPFC) circuit and BDNF in the effects of exogenous OT on auditory fear conditioning in male rats. We found that the release of endogenous OT in the dHPC is significantly increased during the fear extinction process as measured by the microdialysis method. Increased freezing response in the OT-treated rats compared to saline-treated rats showed that exogenous OT in the dHPC enhanced the fear extinction. Injection of BDNF antagonist (ANA-12) into the infralimbic (IL) blocked the effect of exogenous OT on the dHPC. Following OT injection, BDNF levels increased in the dHPC, ventral HPC, and IL cortex; but decreased in the prelimbic cortex (PL). Finally, OT microinjected into the dHPC significantly increased neural activity of pyramidal neurons of the CA1-vHPC and IL but decreased the neural activity in the PL cortex. Our findings strongly support that the dHPC endogenous OT plays a crucial role in enhancing fear extinction. It seems that the activation of the HPC-mPFC pathway, and consequently, the release of BDNF in the IL cortex mediates the enhancing effects of OT on fear extinction.This article is part of the special Issue on ‘Stress, Addiction and Plasticity'.

A framework for quantifying deviations from dynamic equilibrium theory

AbstractAimIn an age of increased anthropogenic changes, it is crucially important to understand how and why ecological communities change. Community assembly is governed by colonization and extinction processes, and the simplest model describing it is dynamic equilibrium (DE), which assumes that communities are shaped solely by stochastic colonization and extinction events. Deviations from this model can point to the role of species life histories, niches or human stressors acting on communities. Despite its potential to serve as a null model for community dynamics, there is currently no accepted methodology for identifying and measuring such deviations.InnovationHere we propose a new, easily applicable methodology for testing and quantifying deviations of empirically observed time series of community dynamics from the predictions and assumptions of the classical DE model, in which assemblages of independent species undergo stochastic colonization–extinction dynamics with constant rates. The methodology consists of a novel randomization‐based null model to generate synthetic time series (PARIS) and a set of statistics that quantify and test how different facets of community dynamics deviate from DE. These statistics are designed to test the assumptions of the theory, namely species independence and constancy of colonization and extinction rates, and the predictions of the theory regarding the magnitude of changes in species richness and composition.Main conclusionsTested against simulated data and a case study, the proposed methodology is shown to have good statistical properties: acceptable type I error rates, good statistical power and robustness against errors in the data. We discuss alternative methods and present guidelines for practical use of the methodology, hoping it will enhance the applicability of DE as a reference for studying changes in ecological communities.

Conditional Control of Instrumental Avoidance by Context Following Extinction.

Using rodents, three training arrangements (i.e., ABB vs. ABA, AAA vs. AAB and ABB vs. ABC) explored whether extinction influences the expression of avoidance in a manner controlled by context. Retention testing following extinction showed that more avoidance responding (i.e., renewal) was observed when extinguished cues were tested outside of the context where they had undergone extinction. In contrast, response rates were significantly lower when stimuli were tested within the context where extinction learning had occurred. These findings add to the emerging literature assessing the role of Pavlovian extinction processes in the development of instrumental avoidance responding by demonstrating conditional control over extinguished responding by context. This study was conducted using a within-subjects approach that minimized the potential for context-outcome associations to bias responding, and thus, reflects hierarchical control over behavior based on the specific associative status of each tested cue in each training context.

MDMA-Assisted Therapy as a Means to Alter Affective, Cognitive, Behavioral, and Neurological Systems Underlying Social Dysfunction in Social Anxiety Disorder.

Social anxiety disorder (SAD) is a prevalent and often debilitating psychiatric disorder that can assume a chronic course even when treated. Despite the identification of evidence-based pharmacological and behavioral treatments for SAD, much room for improved outcomes exists and 3,4-methylenedioxymethamphetamine (MDMA) has been proposed as a promising adjunctive treatment to psychological interventions for disorders characterized by social dysfunction. A small randomized, placebo-controlled trial of MDMA-assisted therapy (MDMA-AT) for social anxiety in autistic adults offered encouraging results, but more research is sorely needed to explore the potential for MDMA-AT in treating SAD. This review aims to stimulate future study by summarizing research on disruptions in neurological, perceptual, receptive, and expressive systems regulating social behavior in SAD and proposing how MDMA-AT may alter these systems across four domains. First, we review research highlighting the roles of social anhedonia and reduced social reward sensitivity in maintaining SAD, with specific attention to the reduction in positive affect in social situations, infrequent social approach behaviors, and related social skills deficits. We posit that MDMA-AT may enhance motivation to connect with others and alter perceptions of social reward for an extended period following administration, thereby potentiating extinction processes, and increasing the reinforcement value of social interactions. Second, we review evidence for the central role of heightened social evaluative threat perception in the development and maintenance of SAD and consider how MDMA-AT may enhance experiences of affiliation and safety when interacting with others. Third, we consider the influence of shame and the rigid application of shame regulation strategies as important intrapersonal processes maintaining SAD and propose the generation of self-transcendent emotions during MDMA sessions as a mechanism of shame reduction that may result in corrective emotional experiences and boost memory reconsolidation. Finally, we review research on the role of dysfunctional interpersonal behaviors in SAD that interfere with social functioning and, in particular, the development and maintenance of close and secure relationships. We discuss the hypothesized role of MDMA-AT in improving social skills to elicit positive interpersonal responses from others, creating a greater sense of belonging, acceptance, and social efficacy.

Drought responsiveness in two Mexican conifer species forming young stands at high elevations

Aim of study: To determine the response of high-altitudinal forests to seasonal drought.Area of study: Monte Tláloc, Estado de México and Rancho Joyas del Durazno, Municipality of Río Verde, San Luis Potosí, México.Materials and methods: In this study, we evaluate the response to drought and hydroclimate in two young Mexican conifers sampled at high elevation, correlating records of tree-ring growth and the Normalized Difference Vegetation Index (NDVI).Main results: The results show that Pinus teocote and Abies religiosa are vulnerable to the precipitation regime and warm conditions of winter-spring. The physiological response mechanisms seem to be differentiated between the species, according to the effects of drought stress. The NDVI demonstrated the different temporal responses of the species according to their inherent physiological mechanisms in response to hydroclimatic limitations. This differentiation can be attributed to the spatial variation present in the particular physical and geographic conditions of each area. The dry and warm seasonal climates reveal P. teocote and A. religiosa to be species that are vulnerable to drought conditions. However, further evaluation of the resistance and resilience of these species is necessary, as well as disentanglement of the effects of associated mechanisms that can influence the predicted processes of extinction or migration.Research highlights: Pinus teocote and Abies religiosa are vulnerable to the seasonal drought conditions. These results are of particular importance given the climatic scenarios predicted for elevated ecotones. Tree-ring widths and NDVI improved the response of radial growth to the climate, enhancing our understanding of forest growth dynamics. The response to climatic variability depends on the particular species.Keywords: High elevation; tree-ring; ENSO; NDVI; climate-growth relationship. Abbreviations used: Normalized Difference Vegetation Index (NDVI); Tree-Ring Width (TRw); precipitation (PP); maximum temperature (Tmax); minimum temperature (Tmin); El Niño-Southern Oscillation (ENSO); Climatic Research Unit Time-series data version 4.04 data (CRU TS v. 4.04); Standardized Precipitation-Evapotranspiration Index (SPEI); Climatic Research Unit Time-series data version 4.03 data (CRU TS v. 4.03); first-order autocorrelation (AC); mean sensitivity (MS); mean correlation between trees (Rbt); expressed population signal (EPS); Ring Width Index (RWI).

Biodiversity dynamics in the Anthropocene: how human activities change equilibria of species richness

We are living in a time of rapid environmental changes caused by anthropogenic pressures. Besides direct human exploitation of plant and animal populations and habitat transformation, biodiversity changes in the Anthropocene are affected by less trivial processes including rapid spreading of non‐native species, emergence of novel communities and modifications of ecosystem functioning due to changing nutrient cycles and climate changes. These processes are so complex that confident predictions and effective biodiversity conservation cannot be obtained without a suitable theory of biodiversity dynamics. We argue that such dynamics have particular attractors, i.e. stable equilibria, that are determined by environmental conditions. These stable equilibria set biodiversity limits, i.e. carrying capacities for biodiversity, from local to global scales. We point out the evidence of such limits at various spatiotemporal scales and show, using the new equilibrium theory of biodiversity dynamics (ETBD), how dynamics of diversity depend on non‐linear relationships between number of species, community abundance and population size‐dependent processes of species extinction and origination (speciation or colonization). We show that non‐linear effects of biodiversity on ecosystem functioning can lead to multiple biodiversity equilibria and tipping points. Various human activities, including species introductions, human appropriation of primary production and trophic downgrading, can change local, regional and global diversity equilibria by affecting processes that set equilibrium diversity levels. The existence of equilibrium and out‐of‐equilibrium states has important implications for conservation, restoration and reconciliation ecology. It highlights the need to more effectively and intentionally balance the historical focus on the preservation of natural habitats with management specifically directed towards the processes responsible for long‐term maintenance of biodiversity equilibria. The Anthropocene represents a unique situation in which people make decisions concerning the dynamics of the natural world, and we argue that ecological restoration requires wisely deciding which of the alternative equilibria are worth maintaining.

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.