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Scott Chamberlain - One of the best experts on this subject based on the ideXlab platform.
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how Context Dependent are species interactions
Ecology Letters, 2014Co-Authors: Scott Chamberlain, Judith L Bronstein, Jennifer A RudgersAbstract:The net effects of interspecific species interactions on individuals and populations vary in both sign (-, 0, +) and magnitude (strong to weak). Interaction outcomes are Context-Dependent when the sign and/or magnitude change as a function of the biotic or abiotic Context. While Context dependency appears to be common, its distribution in nature is poorly described. Here, we used meta-analysis to quantify variation in species interaction outcomes (competition, mutualism, or predation) for 247 published articles. Contrary to our expectations, variation in the magnitude of effect sizes did not differ among species interactions, and while mutualism was most likely to change sign across Contexts (and predation least likely), mutualism did not strongly differ from competition. Both the magnitude and sign of species interactions varied the most along spatial and abiotic gradients, and least as a function of the presence/absence of a third species. However, the degree of Context dependency across these Context types was not consistent among mutualism, competition and predation studies. Surprisingly, study location and ecosystem type varied in the degree of Context dependency, with laboratory studies showing the highest variation in outcomes. We urge that studying Context dependency per se, rather than focusing only on mean outcomes, can provide a general method for describing patterns of variation in nature.
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density mediated Context Dependent consumer resource interactions between ants and extrafloral nectar plants
Ecology, 2008Co-Authors: Scott Chamberlain, Nathaniel J HollandAbstract:Interspecific interactions are often mediated by the interplay between resource supply and consumer density. The supply of a resource and a consumer's density response to it may in turn yield Context-Dependent use of other resources. Such consumer-resource interactions occur not only for predator-prey and competitive interactions, but for mutualistic ones as well. For example, consumer-resource interactions between ants and extrafloral nectar (EFN) plants are often mutualistic, as EFN resources attract and reward ants which protect plants from herbivory. Yet, ants also commonly exploit floral resources, leading to antagonistic consumer-resource interactions by disrupting pollination and plant reproduction. EFN resources associated with mutualistic ant-plant interactions may also mediate antagonistic ant-flower interactions through the aggregative density response of ants on plants, which could either exacerbate ant-flower interactions or alternatively satiate and distract ants from floral resources. In this study, we examined how EFN resources mediate the density response of ants on senita cacti in the Sonoran Desert and their Context-Dependent use of floral resources. Removal of EFN resources reduced the aggregative density of ants on plants, both on hourly and daily time scales. Yet, the increased aggregative ant density on plants with EFN resources decreased rather than increased ant use of floral resources, including contacts with and time spent in flowers. Behavioral assays showed no confounding effect of floral deterrents on ant-flower interactions. Thus, ant use of floral resources depends on the supply of EFN resources, which mediates the potential for both mutualistic and antagonistic interactions by increasing the aggregative density of ants protecting plants, while concurrently distracting ants from floral resources. Nevertheless, only certain years and populations of study showed an increase in plant reproduction through herbivore protection or ant distraction from floral resources. Despite pronounced effects of EFN resources mediating the aggregative density of ants on plants and their Context-Dependent use of floral resources, consumer-resource interactions remained largely commensalistic.
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density mediated Context Dependent consumer resource interactions between ants and extrafloral nectar plants
Ecology, 2008Co-Authors: Scott Chamberlain, Nathaniel J HollandAbstract:Interspecific interactions are often mediated by the interplay between resource supply and consumer density. The supply of a resource and a consumer's density response to it may in turn yield Context-Dependent use of other resources. Such consumer-resource interactions occur not only for predator-prey and competitive interactions, but for mutualistic ones as well. For example, consumer-resource interactions between ants and extrafloral nectar (EFN) plants are often mutualistic, as EFN resources attract and reward ants which protect plants from herbivory. Yet, ants also commonly exploit floral resources, leading to antagonistic consumer-resource interactions by disrupting pollination and plant reproduction. EFN resources associated with mutualistic ant-plant interactions may also mediate antagonistic ant-flower interactions through the aggregative density response of ants on plants, which could either exacerbate ant-flower interactions or alternatively satiate and distract ants from floral resources. In this study, we examined how EFN resources mediate the density response of ants on senita cacti in the Sonoran Desert and their Context-Dependent use of floral resources. Removal of EFN resources reduced the aggregative density of ants on plants, both on hourly and daily time scales. Yet, the increased aggregative ant density on plants with EFN resources decreased rather than increased ant use of floral resources, including contacts with and time spent in flowers. Behavioral assays showed no confounding effect of floral deterrents on ant-flower interactions. Thus, ant use of floral resources depends on the supply of EFN resources, which mediates the potential for both mutualistic and antagonistic interactions by increasing the aggregative density of ants protecting plants, while concurrently distracting ants from floral resources. Nevertheless, only certain years and populations of study showed an increase in plant reproduction through herbivore protection or ant distraction from floral resources. Despite pronounced effects of EFN resources mediating the aggregative density of ants on plants and their Context-Dependent use of floral resources, consumer-resource interactions remained largely commensalistic.
Nathaniel J Holland - One of the best experts on this subject based on the ideXlab platform.
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density mediated Context Dependent consumer resource interactions between ants and extrafloral nectar plants
Ecology, 2008Co-Authors: Scott Chamberlain, Nathaniel J HollandAbstract:Interspecific interactions are often mediated by the interplay between resource supply and consumer density. The supply of a resource and a consumer's density response to it may in turn yield Context-Dependent use of other resources. Such consumer-resource interactions occur not only for predator-prey and competitive interactions, but for mutualistic ones as well. For example, consumer-resource interactions between ants and extrafloral nectar (EFN) plants are often mutualistic, as EFN resources attract and reward ants which protect plants from herbivory. Yet, ants also commonly exploit floral resources, leading to antagonistic consumer-resource interactions by disrupting pollination and plant reproduction. EFN resources associated with mutualistic ant-plant interactions may also mediate antagonistic ant-flower interactions through the aggregative density response of ants on plants, which could either exacerbate ant-flower interactions or alternatively satiate and distract ants from floral resources. In this study, we examined how EFN resources mediate the density response of ants on senita cacti in the Sonoran Desert and their Context-Dependent use of floral resources. Removal of EFN resources reduced the aggregative density of ants on plants, both on hourly and daily time scales. Yet, the increased aggregative ant density on plants with EFN resources decreased rather than increased ant use of floral resources, including contacts with and time spent in flowers. Behavioral assays showed no confounding effect of floral deterrents on ant-flower interactions. Thus, ant use of floral resources depends on the supply of EFN resources, which mediates the potential for both mutualistic and antagonistic interactions by increasing the aggregative density of ants protecting plants, while concurrently distracting ants from floral resources. Nevertheless, only certain years and populations of study showed an increase in plant reproduction through herbivore protection or ant distraction from floral resources. Despite pronounced effects of EFN resources mediating the aggregative density of ants on plants and their Context-Dependent use of floral resources, consumer-resource interactions remained largely commensalistic.
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density mediated Context Dependent consumer resource interactions between ants and extrafloral nectar plants
Ecology, 2008Co-Authors: Scott Chamberlain, Nathaniel J HollandAbstract:Interspecific interactions are often mediated by the interplay between resource supply and consumer density. The supply of a resource and a consumer's density response to it may in turn yield Context-Dependent use of other resources. Such consumer-resource interactions occur not only for predator-prey and competitive interactions, but for mutualistic ones as well. For example, consumer-resource interactions between ants and extrafloral nectar (EFN) plants are often mutualistic, as EFN resources attract and reward ants which protect plants from herbivory. Yet, ants also commonly exploit floral resources, leading to antagonistic consumer-resource interactions by disrupting pollination and plant reproduction. EFN resources associated with mutualistic ant-plant interactions may also mediate antagonistic ant-flower interactions through the aggregative density response of ants on plants, which could either exacerbate ant-flower interactions or alternatively satiate and distract ants from floral resources. In this study, we examined how EFN resources mediate the density response of ants on senita cacti in the Sonoran Desert and their Context-Dependent use of floral resources. Removal of EFN resources reduced the aggregative density of ants on plants, both on hourly and daily time scales. Yet, the increased aggregative ant density on plants with EFN resources decreased rather than increased ant use of floral resources, including contacts with and time spent in flowers. Behavioral assays showed no confounding effect of floral deterrents on ant-flower interactions. Thus, ant use of floral resources depends on the supply of EFN resources, which mediates the potential for both mutualistic and antagonistic interactions by increasing the aggregative density of ants protecting plants, while concurrently distracting ants from floral resources. Nevertheless, only certain years and populations of study showed an increase in plant reproduction through herbivore protection or ant distraction from floral resources. Despite pronounced effects of EFN resources mediating the aggregative density of ants on plants and their Context-Dependent use of floral resources, consumer-resource interactions remained largely commensalistic.
Emma R Wood - One of the best experts on this subject based on the ideXlab platform.
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exploring the role of Context Dependent hippocampal activity in spatial alternation behavior
Hippocampus, 2007Co-Authors: James A Ainge, Matthijs A A Van Der Meer, Rosamund F Langston, Emma R WoodAbstract:In a continuous T-maze spatial alternation task, CA1 place cells fire differentially on the stem of the maze as rats are performing left- and right-turn trials (Wood et al. (2000) Neuron 27:623-633). This Context-Dependent hippocampal activity provides a potential mechanism by which animals could solve the alternation task, as it provides a cue that could prime the appropriate goal choice. The aim of this study was to examine the relationship between Context-Dependent hippocampal activity and spatial alternation behavior. We report that rats with complete lesions of the hippocampus learn and perform the spatial alternation task as well as controls if there is no delay between trials, suggesting that the observed Context-Dependent hippocampal activity does not mediate alternation behavior in this task. However lesioned rats are significantly impaired when delays of 2 or 10 s are interposed. Recording experiments reveal that Context-Dependent hippocampal activity occurs in both the delay and no-delay versions of the task, but that in the delay version it occurs during the delay period, and not on the stem of the maze. These data are consistent with a role for Context-Dependent hippocampal activity in delayed spatial alternation, but suggest that, according to specific task demands and memory load, the activity may be generated by different mechanisms and/or in different brain structures.
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exploring the role of Context Dependent hippocampal activity in spatial alternation behavior
Hippocampus, 2007Co-Authors: James A Ainge, Matthijs A A Van Der Meer, Rosamund F Langston, Emma R WoodAbstract:In a continuous T-maze spatial alternation task, CA1 place cells fire differentially on the stem of the maze as rats are per- forming left- and right-turn trials (Wood et al. (2000) Neuron 27:623- 633). This Context-Dependent hippocampal activity provides a potential mechanism by which animals could solve the alternation task, as it pro- vides a cue that could prime the appropriate goal choice. The aim of this study was to examine the relationship between Context-Dependent hippocampal activity and spatial alternation behavior. We report that rats with complete lesions of the hippocampus learn and perform the spatial alternation task as well as controls if there is no delay between trials, suggesting that the observed Context-Dependent hippocampal ac- tivity does not mediate alternation behavior in this task. However lesioned rats are significantly impaired when delays of 2 or 10 s are interposed. Recording experiments reveal that Context-Dependent hippo- campal activity occurs in both the delay and no-delay versions of the task, but that in the delay version it occurs during the delay period, and not on the stem of the maze. These data are consistent with a role for Context-Dependent hippocampal activity in delayed spatial alternation, but suggest that, according to specific task demands and memory load, the activity may be generated by different mechanisms and/or in differ- ent brain structures. V C 2007 Wiley-Liss, Inc.
Alex Acero - One of the best experts on this subject based on the ideXlab platform.
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Context-Dependent pre-trained deep neural networks for large-vocabulary speech recognition
IEEE Transactions on Audio Speech and Language Processing, 2012Co-Authors: George Edward Dahl, Dong Yu, Alejandro Acero, Li Deng, Alex AceroAbstract:We propose a novel Context-Dependent (CD) model for large-vocabulary speech recognition (LVSR) that leverages recent advances in using deep belief networks for phone recognition.We describe a pre-trained deep neural network hidden Markov model (DNN-HMM) hybrid architecture that trains the DNN to produce a distribution over senones (tied triphone states) as its output. The deep belief network pre-training algorithm is a robust and often helpful way to initialize deep neural networks generatively that can aid in optimization and reduce generalization error. We il- lustrate the key components of our model, describe the procedure for applying CD-DNN-HMMs to LVSR, and analyze the effects of various modeling choices on performance. Experiments on a chal- lenging business search dataset demonstrate thatCD-DNN-HMMs can significantly outperform the conventional Context-Dependent Gaussian mixture model (GMM)-HMMs, with an absolute sen- tence accuracy improvement of 5.8% and 9.2% (or relative error reduction of 16.0% and 23.2%) over theCD-GMM-HMMstrained using the minimum phone error rate (MPE) and maximum-likeli- hood (ML) criteria, respectively.
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large vocabulary continuous speech recognition with Context Dependent dbn hmms
International Conference on Acoustics Speech and Signal Processing, 2011Co-Authors: George Edward Dahl, Li Deng, Alex AceroAbstract:The Context-inDependent deep belief network (DBN) hidden Markov model (HMM) hybrid architecture has recently achieved promising results for phone recognition. In this work, we propose a Context-Dependent DBN-HMM system that dramatically outperforms strong Gaussian mixture model (GMM)-HMM baselines on a challenging, large vocabulary, spontaneous speech recognition dataset from the Bing mobile voice search task. Our system achieves absolute sentence accuracy improvements of 5.8% and 9.2% over GMM-HMMs trained using the minimum phone error rate (MPE) and maximum likelihood (ML) criteria, respectively, which translate to relative error reductions of 16.0% and 23.2%.
Dong Yu - One of the best experts on this subject based on the ideXlab platform.
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Context-Dependent pre-trained deep neural networks for large-vocabulary speech recognition
IEEE Transactions on Audio Speech and Language Processing, 2012Co-Authors: George Edward Dahl, Dong Yu, Alejandro Acero, Li Deng, Alex AceroAbstract:We propose a novel Context-Dependent (CD) model for large-vocabulary speech recognition (LVSR) that leverages recent advances in using deep belief networks for phone recognition.We describe a pre-trained deep neural network hidden Markov model (DNN-HMM) hybrid architecture that trains the DNN to produce a distribution over senones (tied triphone states) as its output. The deep belief network pre-training algorithm is a robust and often helpful way to initialize deep neural networks generatively that can aid in optimization and reduce generalization error. We il- lustrate the key components of our model, describe the procedure for applying CD-DNN-HMMs to LVSR, and analyze the effects of various modeling choices on performance. Experiments on a chal- lenging business search dataset demonstrate thatCD-DNN-HMMs can significantly outperform the conventional Context-Dependent Gaussian mixture model (GMM)-HMMs, with an absolute sen- tence accuracy improvement of 5.8% and 9.2% (or relative error reduction of 16.0% and 23.2%) over theCD-GMM-HMMstrained using the minimum phone error rate (MPE) and maximum-likeli- hood (ML) criteria, respectively.
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Feature engineering in Context-Dependent Deep Neural Networks for conversational speech transcription
2011 IEEE Workshop on Automatic Speech Recognition and Understanding ASRU 2011 Proceedings, 2011Co-Authors: Frank Seide, Xie Chen, Gang Li, Dong YuAbstract:We investigate the potential of Context-Dependent Deep-Neural-Network HMMs, or CD-DNN-HMMs, from a feature-engineering perspective. Recently, we had shown that for speaker-inDependent transcription of phone calls (NIST RT03S Fisher data), CD-DNN-HMMs reduced the word error rate by as much as one third—from 27.4%, obtained by discriminatively trained Gaussian-mixture HMMs with HLDA features, to 18.5%—using 300+ hours of training data (Switchboard), 9000+ tied triphone states, and up to 9 hidden network layers.
