Advanced Behavioral Testing in Rodents: Assessment of Cognitive Function in Animals

Philip J. Bushnell1

1 National Health and Environmental Effects Research Laboratory, U.S. Environment Protection Agency, Research Triangle Park, North Carolina
Publication Name:  Current Protocols in Toxicology
Unit Number:  Unit 11.4
DOI:  10.1002/0471140856.tx1104s00
Online Posting Date:  May, 2001
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Abstract

In risk assessment of a neurotoxic chemical, it may be necessary to assess its effect on cognitive function, the information‐processing capacity of the animal. Such effects may be inferred from behavioral effects only after other explanations have been ruled out. Learning, memory, attention, and performance are elements of cognitive function that can be assessed in a variety of tests described in this unit: autoshaping the lever‐press response, repeated acquisition in the radial maze, delayed matching to position, two‐light visual discrimination, visual signal detection, and multiple fixed interval/fixed ratio operant schedule.

     
 
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Table of Contents

  • Strategic Planning
  • Basic Protocol 1: Assessment of Learning: Autoshaping the Lever‐Press Response
  • Basic Protocol 2: Assessment of Learning: Repeated Acquisition in the Radial Maze
  • Basic Protocol 3: Assessment of Working Memory: Delayed Matching to Position
  • Support Protocol 1: Assessment of Reference Memory: Two‐Light Visual Discrimination
  • Basic Protocol 4: Assessment of Sustained Attention: Visual Signal Detection
  • Basic Protocol 5: Multiple Fixed‐Interval/Fixed‐Ratio Operant Schedule
  • Commentary
  • Figures
  • Tables
     
 
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Materials

Basic Protocol 1: Assessment of Learning: Autoshaping the Lever‐Press Response

  Materials
  • Subject rats
  • Precision food pellets: 45 mg for male rats, 37 mg for females (BioServ or PJ Noyes)
  • Operant conditioning chamber (Fig. ; e.g., Coulbourn Instruments, MED Associates, CeNeS, or TSE Systems) including:
    • Incandescent house light (∼0.1 W)
    • Loudspeaker for white noise
    • Food cup that can be lighted from within
    • Signal light: LED or incandescent bulb behind a clear lens (if using an incandescent bulb, use a glass jewel dome in front of the bulb rather than plastic, as it cannot be gnawed down by the animal)
    • Retractable response lever
    • Pellet dispenser
    • Computer system and interface to control test environments and stimuli and to collect response data (see )

Basic Protocol 2: Assessment of Learning: Repeated Acquisition in the Radial Maze

  Materials
  • Subject rats
  • Reinforcers for manual system: any cereal‐ or sugar‐based foodstuff that can be delivered in small, reproducible quantities; pieces of breakfast cereal are frequently used (e.g., 1/4 of a Froot Loop)
  • Reinforcers for automated system: precision food pellets, 45 mg for male rats, 37 mg for females (BioServ or PJ Noyes)
  • Radial arm maze, manual or automated (unit 11.3; Coulbourn Instruments, MED Associates, or TSE Systems)
  • Stopwatch (for manual system)
  • Food pellet dispensers (one at end of each arm for automated system)

Basic Protocol 3: Assessment of Working Memory: Delayed Matching to Position

  Materials
  • Subject rats
  • Precision food pellets: 45 mg for male rats, 37 mg for females (BioServ or PJ Noyes)
  • Operant conditioning chamber (Fig. ; e.g., Coulbourn Instruments, MED Associates, or CeNeS, or TSE Systems) including:
    • Incandescent house light (∼0.1 W)
    • Loudspeaker for white noise
    • Food cup that can be lighted from within
    • Cue light: LED or incandescent bulb behind a clear lens (if using an incandescent bulb, use a glass jewel dome in front of the bulb rather than plastic, as it cannot be gnawed down by the animal)
    • Two retractable response levers
    • Pellet dispenser
    • Computer system and interface to control test environments and stimuli and to collect response data (see )

Support Protocol 1: Assessment of Reference Memory: Two‐Light Visual Discrimination

  • Tone generator (e.g., Sonalert)

Basic Protocol 4: Assessment of Sustained Attention: Visual Signal Detection

  Materials
  • Subject rats
  • Precision food pellets: 45 mg for male rats, 37 mg for females (BioServ or PJ Noyes)
  • Operant conditioning chamber (Fig. ; e.g., Coulbourn Instruments, MED Associates, or CeNeS, or TSE Systems) including:
    • Incandescent house light (∼0.1 W)
    • Loudspeaker for white noise
    • Food cup that can be lighted from within
    • Signal light: LED or incandescent bulb behind a clear lens (if using an incandescent bulb, use a glass jewel dome in front of the bulb rather than plastic, as it cannot be gnawed down by the animal)
    • Retractable levers
  • Pellet dispenser
  • Clear plastic tubing with inner diameter large enough to accommodate food pellets
  • Computer system and interface to control test environments and stimuli and to collect response data (see )

Basic Protocol 5: Multiple Fixed‐Interval/Fixed‐Ratio Operant Schedule

  Materials
  • Subject rats
  • Precision food pellets: 45 mg for male rats, 37 mg for females (BioServ or PJ Noyes)
  • Operant conditioning chamber (Fig. ; e.g., Coulbourn Instruments, MED Associates, or CeNeS, or TSE systems) including:
    • Incandescent house light (∼0.1 W)
    • Loudspeaker for white noise
    • Food cup
    • Cue light: LED or incandescent bulb behind a clear lens (if using an incandescent bulb, use a glass jewel dome in front of the bulb rather than plastic, as it cannot be gnawed down by the animal)
    • Response lever, fixed or retractable
    • Tone generator (e.g., Sonalert; optional)
  • Pellet dispenser
  • Computer system and interface to control test environments and stimuli and to collect response data (see )
  • Computer software for visualizing patterns of response in each component (MED Associates)
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Figures

Videos

Literature Cited

Literature Cited
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Key References
   Bushnell, 1998. See above.
  This review article describes a large number of approaches to the assessment of attention in experimental animals, primarily rodents. It also discusses general issues regarding the assessment of hypothetical cognitive processes, and the validation of procedures for conducting those assessments.
   Cohn and Paule, 1995/1996; Cohn et al., See above.
  This pair of reviews thoroughly covers the realm of repeated acquisition of response sequences, providing a history of the area and background information regarding the approach and implementation of repeated acquisition methods for assessing learning. The first paper reviews the behavioral phenomena and the second the influence of drugs and toxic chemicals on these behaviors.
   Heise and Milar, 1984. See above.
  This review chapter very nicely lays out the rationale and taxonomy of procedures for assessing learning and memory in animals. The section on memory is particularly useful for understanding and interpreting tests of working memory (e.g., DMTP).
   Iversen, I.H. and Lattal, K.A. (eds.) 1991. Experimental Analysis of Behavior, Parts 1 and 2. Elsevier/North‐Holland, Amsterdam.
  These two volumes discuss clearly and in detail behavioral methods for quantifying and analyzing the behavior of experimental animals. The contributions provide a wealth of information regarding basic techniques for handling and testing animals, and for quantifying patterns of behavior engendered by a wide variety of reinforcement schedules.
   Parasuraman, 1984. See above.
  This review chapter detailed current knowledge of sustained attention in humans. Much of the development of sustained attention methods in animals is based upon knowledge of human performance of these tasks and the variables that affect it.
   Robbins and Everitt, 1995. See above.
  This chapter very clearly summarizes current knowledge about the role of the ascending arousal systems in the CNS on attention in animals, as assessed primarily with the 5‐choice serial reaction‐time test. It is a good general reference for understanding the neurobiological substrates of readiness and directed attention.
   Schwartz and Gamzu, 1977. See above.
  This chapter reviews various phenomena of autoshaping, primarily in terms of the associative processes (operant and respondent) that support this unique form of conditioning. The chapter provides a readable presentation of many of the variables found to influence acquisition and maintenance of sign‐tracking behaviors, the kinds of behaviors that are supported by autoshaping contingencies, generalization to automaintenance schedules, and the theoretical analysis of the phenomenon.
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