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The accurate measurement of fear memory in Pavlovian conditioning: Resolving the baseline issue.

ABSTRACT: Fear conditioning has become an indispensable behavioral task in an increasingly vast array of research disciplines. Yet one unresolved issue is how conditional fear to an explicit cue interacts with and is potentially confounded by fear prior to tone presentation, referred to as baseline fear. After tone-shock pairings, we experimentally manipulated baseline fear by presenting unpaired shocks in the testing chamber and then analyzed the accuracy of common methods for reporting tone fear. Our findings indicate that baseline fear and tone fear tend to interact, where freezing to the tone increases as baseline fear increases. However, the form of interaction is not linear across all conditions and none of the commonly used reporting methods were consistently able to eliminate the confounding effects of baseline fear. We propose a methodological solution in which baseline fear is reduced to very low levels by first extinguishing fear to the training context and then pre-exposing to the testing context.

SUBMITTER: Jacobs NS

PROVIDER: S-EPMC2905525 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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The accurate measurement of fear memory in Pavlovian conditioning: Resolving the baseline issue.

Jacobs Nathan S NS Cushman Jesse D JD Fanselow Michael S MS

Journal of neuroscience methods 20100513 2

Fear conditioning has become an indispensable behavioral task in an increasingly vast array of research disciplines. Yet one unresolved issue is how conditional fear to an explicit cue interacts with and is potentially confounded by fear prior to tone presentation, referred to as baseline fear. After tone-shock pairings, we experimentally manipulated baseline fear by presenting unpaired shocks in the testing chamber and then analyzed the accuracy of common methods for reporting tone fear. Our fi ...[more]

PMID: 20471421

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Project description:BackgroundAssociative conditioning is a ubiquitous form of learning throughout the animal kingdom and fear conditioning is one of the most widely researched models for studying its neurobiological basis. Fear conditioning is also considered a model system for understanding phobias and anxiety disorders. A fundamental issue in fear conditioning regards the existence and location of neurons in the brain that receive convergent information about the conditioned stimulus (CS) and unconditioned stimulus (US) during the acquisition of conditioned fear memory. Convergent activation of neurons is generally viewed as a key event for fear learning, yet there has been almost no direct evidence of this critical event in the mammalian brain.Methodology/principal findingsHere, we used Arc cellular compartmental analysis of temporal gene transcription by fluorescence in situ hybridization (catFISH) to identify neurons activated during single trial contextual fear conditioning in rats. To conform to temporal requirements of catFISH analysis we used a novel delayed contextual fear conditioning protocol which yields significant single- trial fear conditioning with temporal parameters amenable to catFISH analysis. Analysis yielded clear evidence that a population of BLA neurons receives convergent CS and US information at the time of the learning, that this only occurs when the CS-US arrangement is supportive of the learning, and that this process requires N-methyl-D-aspartate receptor activation. In contrast, CS-US convergence was not observed in dorsal hippocampus.Conclusions/significanceBased on the pattern of Arc activation seen in conditioning and control groups, we propose that a key requirement for CS-US convergence onto BLA neurons is the potentiation of US responding by prior exposure to a novel CS. Our results also support the view that contextual fear memories are encoded in the amygdala and that the role of dorsal hippocampus is to process and transmit contextual CS information.

Dataset Information

The accurate measurement of fear memory in Pavlovian conditioning: Resolving the baseline issue.

Publications

The accurate measurement of fear memory in Pavlovian conditioning: Resolving the baseline issue.

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