Incubation of Fear

Charles L. Pickens1, Sam A. Golden2, Sunila G. Nair3

1 Department of Psychological Sciences, Kansas State University, Manhattan, Kansas, 2 Friedman Brain Institute and Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, 3 Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 6.27
DOI:  10.1002/0471142301.ns0627s64
Online Posting Date:  July, 2013
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While fear and anxiety can grow over time in anxiety disorders, most efforts to model this phenomenon with fear conditioning in rodents cause fear that remains stable or decreases across weeks or months. Here, we describe several methods to induce conditioned fear that grows over the course of 1 month and is sustained for at least 2 months using an extended fear conditioning approach. These methods include a very reliable standard method that causes multiple fear measures to increase over months, as well as alternative methods. Curr. Protoc. Neurosci. 64:6.27.1‐6.27.11. © 2013 by John Wiley & Sons, Inc.

Keywords: fear incubation; fear conditioning; delayed‐onset fear; PTSD; anxiety

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Table of Contents

  • Introduction
  • Basic Protocol 1: Concurrent Freezing/Conditioned Suppression Incubation with Short Cues
  • Alternate Protocol 1: Fear/Anxiety Incubation with Long Cues
  • Alternate Protocol 2: Fear Incubation Measured Without a Concurrent Operant Task
  • Commentary
  • Literature Cited
  • Figures
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Basic Protocol 1: Concurrent Freezing/Conditioned Suppression Incubation with Short Cues

  • Rats (e.g., Long‐Evans rats from Charles River Laboratory weighing 250 to 500 g; singly housed for the duration of the experiment)
  • Food chow
  • 45 mg food pellets (e.g., # F0021, 5.5% fat, 60% carbohydrate, 4.5% fiber; Bioserv)
  • A scale with gram sensitivity to weigh rats and food chow
  • Operant chambers (e.g., previous experiments have used Med Associates chambers with a retractable “active lever,” pellet dispenser to deliver 45‐mg pellets, Sonalert tone generator, red houselight, and shock generators programmed to deliver scrambled shocks)
  • A video camera for closed captioned viewing/recording of behavior (e.g., a system from Coulbourn Instruments mounted to the top of each chamber, extending 2 cm into the chamber with software to record behavior, has been used)
  • Software to control operant chambers installed on a desktop computer (e.g., Med Associates software‐ Med‐PC‐IV and Trans‐IV; sample Trans‐IV programs for all experimental phases for all three protocols are available by emailing the authors or at
  • A computer with software to view videos of rat behavior
  • A metronome (mechanical or a metronome program)

Alternate Protocol 1: Fear/Anxiety Incubation with Long Cues

  • The materials for this protocol are the same as those in the Basic Protocol, with two exceptions: (1) This procedure does not require the experimental chamber to contain an active lever (if an active lever is present, it should be retracted during all training sessions); and (2) 45‐mg food pellets are not required for this protocol
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Literature Cited

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Internet Resources
  Web site for the Pickens laboratory (Kansas State University) starting in August 2013. This site contains sample programs for all three protocols.
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