The effect of US signalling and the US–CS interval on backward conditioning in mice

David J Sanderson,Steven F Cuell,David M Bannerman

doi:10.1016/j.lmot.2014.08.002

Abstract

The effect of US signalling and the US–CS interval in backward conditioning was assessed in mice. For one group of mice the presentation of food was signalled by a tone and for another group, food was unsignalled. For half of the mice, within each group, the presentation of food preceded a visual cue by 10s. For the other half, food was presented at the start of the visual cue (0-s US–CS interval), resulting in simultaneous pairings of these events. A summation test and a subsequent retardation test were used to assess the inhibitory effects of backward conditioning in comparison to training with a non-reinforced visual cue that controlled for the possible effects of latent inhibition and conditioned inhibition caused as a consequence of differential conditioning. In the summation test unsignalled presentations of the US resulted in inhibition when the US–CS interval was 10s, but not 0s. Signalled presentations of the US resulted in inhibition, independent of the US–CS interval. In the retardation test, independent of US signalling, a US–CS interval of 10s failed to result in inhibition, but an interval of 0s resulted in greater conditioned responding to the backward CS than the control CS. A generalisation decrement account of the effect of signalling the US with a 0-s US–CS interval, which resulted in reduced responding in the summation test and faster acquisition in the retardation test, is discussed.

Highlights

The aim of the study was to test whether unconditioned stimulus (US) signalling and US–conditioned stimulus (CS) interval manipulations in backward conditioning have the same qualitative effect on learning, using summation and retardation tests of conditioned inhibition
A potential problem in examining the effects of backward conditioning is the change in the conditions during training and at the test of learning, leading to generalisation decrement
In the retardation test, these groups failed to show inhibition with conditioning progressing at a similar rate for the backward and control CSs

Summary

Introduction

US signalling can switch a backward CS from being an excitatory predictor of the US to being an inhibitor of the outcome (Dolan et al, 1985), suggesting that US signalling changes the nature of the association that is acquired Another factor that affects inhibitory backward conditioning is the interval between the US and the CS It was predicted that if US signalling and the US–CS interval both alter processing of the US such that B forms an inhibitory association, both manipulations should affect performance on the summation and retardation tests in a qualitatively similar manner.

Objectives

Methods

Results

Conclusion