Search results for "Extinction"
showing 10 items of 458 documents
Influence of warming temperatures on coregonine embryogenesis within and among species
2021
The greatest response of lakes to climate change has been the increase in water temperatures on a global scale. The responses of many lake fishes to warming water temperatures are projected to be inadequate to counter the speed and magnitude of climate change, leaving some species vulnerable to decline and extinction. We experimentally evaluated the responses of embryos from a group of cold, stenothermic fishes (Salmonidae Coregoninae) - within conspecifics across lake systems, between congeners within the same lake system, and among congeners across lake systems - to a thermal gradient using an incubation method that enabled global comparisons. Study groups included cisco (Coregonus artedi…
Scientific Reports
2019
Anthropogenic climate change ranks among the major global-scale threats to modern biodiversity. Extinction risks are known to increase via the interactions between rapid climatic alterations and environmentally-sensitive species traits that fail to adapt to those changes. Accumulating evidence reveals the influence of ecophysiological, ecological and phenological factors as drivers underlying demographic collapses that lead to population extinctions. However, the extent to which life-history traits influence population responses to climate change remains largely unexplored. The emerging 'cul-de-sac hypothesis' predicts that reptilian viviparity ('live-bearing' reproduction), a 'key innovati…
Early cave art and ancient DNA record the origin of European bison
2016
The two living species of bison (European and American) are among the few terrestrial megafauna to have survived the late Pleistocene extinctions. Despite the extensive bovid fossil record in Eurasia, the evolutionary history of the European bison (or wisent, Bison bonasus) before the Holocene (<11.7 thousand years ago (kya)) remains a mystery. We use complete ancient mitochondrial genomes and genome-wide nuclear DNA surveys to reveal that the wisent is the product of hybridization between the extinct steppe bison (Bison priscus) and ancestors of modern cattle (aurochs, Bos primigenius) before 120 kya, and contains up to 10% aurochs genomic ancestry. Although undetected within the fossil re…
Dopamine neurons drive fear extinction learning by signaling the omission of expected aversive outcomes
2018
Extinction of fear responses is critical for adaptive behavior and deficits in this form of safety learning are hallmark of anxiety disorders. However, the neuronal mechanisms that initiate extinction learning are largely unknown. Here we show, using single-unit electrophysiology and cell-type specific fiber photometry, that dopamine neurons in the ventral tegmental area (VTA) are activated by the omission of the aversive unconditioned stimulus (US) during fear extinction. This dopamine signal occurred specifically during the beginning of extinction when the US omission is unexpected, and correlated strongly with extinction learning. Furthermore, temporally-specific optogenetic inhibition o…
Early Cognitive Training Rescues Remote Spatial Memory but Reduces Cognitive Flexibility in Alzheimer’s Disease Mice
2020
Background: Spatial memory dysfunction has been demonstrated in mouse models of Alzheimer’s disease (AD) which is consistent with the clinical finding that the early signature of AD includes difficulties in the formation and/or storage of a memory. A stored memory—a long term memory—can be modulated via process called as memory retrieval that can either lead toward memory reconsolidation or even memory extinction. Objective: We aim to shed light on the fate of the spatial memory during memory reactivation and memory extinction using a water maze task. Methods: In Set-up I, we trained 3-month-old mice (wild-type mice and mice with cerebral β-amyloidosis) and assessed the fate of remote memor…
Modelos animales de adicción a las drogas
2017
El desarrollo de modelos animales de refuerzo y adicción a las drogas es imprescindible para el avance en el conocimiento de las bases biológicas de este trastorno y la identificación de nuevas dianas terapéuticas. En función del componente del refuerzo que deseemos estudiar podemos servirnos de un tipo de modelos animales u otros. Podemos utilizar modelos de refuerzo basados en el efecto hedónico primario que produce el consumo de la sustancia adictiva, como los modelos de autoadministración (AA) y autoestimulación eléctrica intracraneal (AEIC), o modelos basados en el componente relacionado con el aprendizaje asociativo y la capacidad cognitiva de realizar predicciones sobre la obtención …
Hippocampal theta phase-contingent memory retrieval in delay and trace eyeblink conditioning
2017
Hippocampal theta oscillations (3-12Hz) play a prominent role in learning. It has been suggested that encoding and retrieval of memories are supported by different phases of the theta cycle. Our previous study on trace eyeblink conditioning in rabbits suggests that the timing of the conditioned stimulus (CS) in relation to theta phase affects encoding but not retrieval of the memory trace. Here, we directly tested the effects of hippocampal theta phase on memory retrieval in two experiments conducted on adult female New Zealand White rabbits. In Experiment 1, animals were trained in trace eyeblink conditioning followed by extinction, and memory retrieval was tested by presenting the CS at t…
Beyond the classic extinction network: a wider, comparative view
2020
Abstract Extinction learning modifies the dynamics of brain circuits such that a previously learned conditioned response is no longer generated. The majority of extinction studies use fear conditioning in rodents and identified the prefrontal cortex, the hippocampus, and the amygdala as core regions of the extinction circuit. We sought to find answers to two questions: First, do we find a similar functional brain circuit in birds, which underwent a 300-million-year separate evolution from mammals? Second, do we have to incorporate the cerebellum as a key component of the central extinction circuit? We indeed show that the avian extinction pathways are not identical but highly similar to tho…
Optical activation of TrkB neurotrophin receptor in mouse ventral hippocampus promotes plasticity and facilitates fear extinction
2021
AbstractSuccessful extinction of traumatic memories depends on neuronal plasticity in the fear extinction network. However, the mechanisms involved in the extinction process remain poorly understood. Here, we investigated the fear extinction network by using a new optogenetic technique that allows temporal and spatial control of neuronal plasticity in vivo. We optimized an optically inducible TrkB (CKII-optoTrkB), the receptor of the brain-derived neurotrophic factor, which can be activated upon blue light exposure to increase plasticity specifically in pyramidal neurons. The activation of CKII-optoTrkB facilitated the induction of LTP in Schaffer collateral-CA1 synapses after brief theta-b…
Loss of habitats, naturalness and species diversity in Eurasian forest landscapes
2010
Abstract Man has exploited land and forests in Western and Central Europe longer and more intensively than in Northern Europe and further east in Eurasia. We estimated forest naturalness and modelled expected biodiversity loss in seven different landscapes (2500 km2 each) in the Netherlands, Sweden, Finland, Poland, St. Petersburg (Western European Russia), Perm (Eastern European Russia), and Irkutsk (Central Siberia) across the distribution of Pinus sylvestris L. in Eurasia. Field inventories showed that the mean living tree volumes were relatively similar in the studied sites, but the volumes of dead wood differed greatly. In Irkutsk and Perm the volume of dead trees per ha was about 5–10…