One way to minimize excitation acquired by the conditioned stimulus (CS) is to introduce intertrial presentations of the unconditioned stimulus (US). However, even in the presence of frequent intertrial USs, Experiments 1a and 1b found that rats anticipated the customary arrival time of a food pellet US when it occurred before (embedded)-versus coincident with (delay)-the termination of a white noise CS. Delay conditioning emerged in Experiment 2 in the absence of intertrial USs; hence, the detrimental effects of intertrial USs depended on the CS-US relationship, delay versus embedded, and not the duration of CS-US interval. Experiments 3a, 3b, and 4 found that random USs located in the early portion of the intertrial interval increased the control acquired by contextual stimuli at the expense of temporal stimuli occasioned near CS termination. Our results suggest that delay relationships leave the CS especially vulnerable to the deleterious effects of intertrial USs.
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http://dx.doi.org/10.1037/a0016922 | DOI Listing |
Neuroscience
September 2020
Department of Biological Sciences, Konkuk University, Seoul, 05029, South Korea. Electronic address:
Neurons in the lateral habenula (LHb) are activated by reward omission and inhibited by reward delivery-reward processing functions opposite those of midbrain dopaminergic neurons. To further explore this, we examined the role of the LHb in associating a conditioned stimulus (CS) with the absence of an unconditioned stimulus (US) in an appetitive Pavlovian-conditioning paradigm. Rats underwent training in which a CS (light) was either paired (100% CS-US contingency) or unpaired (0% CS-US contiguity and negative contingency) with an US (food).
View Article and Find Full Text PDFScand J Pain
October 2020
Research Group Health Psychology, KU Leuven, Leuven, Belgium.
Objectives Contemporary fear-avoidance models of chronic pain posit that fear of pain, and overgeneralization of fear to non-threatening stimuli is a potential pathway to chronic pain. While increasing experimental evidence supports this hypothesis, a comprehensive investigation requires testing in multiple modalities due to the diversity of symptomatology among individuals with chronic pain. In the present study we used an established tactile fear conditioning paradigm as an experimental model of allodynia and spontaneous pain fluctuations, to investigate whether stimulus generalization occurs resulting in fear of touch spreading to new locations.
View Article and Find Full Text PDFLearn Behav
March 2017
University of Warwick, Coventry, UK.
Three experiments assessed how appetitive conditioning in rats changes over the duration of a trace conditioned stimulus (CS) when unsignaled unconditioned stimuli (USs) are introduced into the intertrial interval. In Experiment 1, a target US occurred at a fixed time either shortly before (embedded), shortly after (trace), or at the same time (delay) as the offset of a 120-s CS. During the CS, responding was most suppressed by intertrial USs in the trace group, less so in the delay group, and least in the embedded group.
View Article and Find Full Text PDFJ Exp Psychol Anim Behav Process
April 2010
Department of Psychology, University of Winnipeg, Winnipeg, Manitoba, Canada, R3B 2E9.
J Exp Psychol Anim Behav Process
January 2008
Psychology Department, University of Winnipeg, Manitoba, Canada.
Rats (rattus norvegicus) anticipated the arrival of a food pellet unconditioned stimulus (US) even when the conditioned stimulus (CS) signaled no overall change or a substantial decrease in the overall rate of US occurrence. Pellet USs were scheduled probabilistically in the intertrial interval at either an equivalent rate (Experiment 1) or a four times higher rate (Experiments 2 and 3) than in the CS, which included one fixed-time target US. Conditioning has been said to involve learning "whether" (contingency) the CS signals a change in the US, and if so, "when" (contiguity) the US is scheduled to arrive.
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