Associative regulation of Pavlovian fear conditioning: unconditional stimulus intensity, incentive shifts, and latent inhibition

J Exp Psychol Anim Behav Process. 1992 Oct;18(4):400-13. doi: 10.1037//0097-7403.18.4.400.


Conditional stimuli (CS) associated with painful unconditional stimuli (US) produce a naloxone-reversible analgesia. The analgesia serves as a negative-feedback regulation of fear conditioning that can account for the impact of US intensity and CS predictiveness on Pavlovian fear conditioning. In Experiment 1 training under naloxone produced learning curves that approached the same high asymptote despite US intensity. Shifting drug treatment during acquisition had effects that paralleled US intensity shifts. In Experiment 3 naloxone reversed Hall-Pearce (1979) negative transfer using a contextual CS, indicating that conditional analgesia acquired during the CS-weak-footshock phase retards acquisition in the CS-strong-footshock phase. Experiment 5 used a tone CS in both a latent-inhibition and a negative-transfer procedure. Only negative transfer was blocked by naloxone. Therefore, negative transfer but not latent inhibition is mediated by a reduction of US processing.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Arousal / drug effects
  • Association Learning / drug effects*
  • Conditioning, Classical / drug effects*
  • Dose-Response Relationship, Drug
  • Fear / drug effects*
  • Female
  • Mental Recall / drug effects
  • Motivation*
  • Motor Activity / drug effects
  • Naloxone / pharmacology*
  • Rats
  • Transfer, Psychology


  • Naloxone