Integrating past experiences

Abstract

New results help address a longstanding debate regarding which learning strategies allow animals to anticipate negative events based on past associations between sensory stimuli.

Keywords: chaining; fear; integration; mediated learning; memory; neuroscience; rat; sensory stimuli.

Figure 1.. Proposed mechanisms of learning during brief or extended preconditioning training.

Wong et al. used a preconditioning task to study how rats learn. In stage 1 (top), rats were exposed to a neutral stimulus pairing of sound followed by a light. In stage 2 (middle), the light was followed with an electric shock, which represents a negative outcome. In stage 3 (bottom), rats were presented with the neutral sound signal from stage 1. The rats associated this neutral stimulus with the electric shock and acted fearfully, even though the sound stimulus had not previously been presented with the electric shock. The stimuli were counterbalanced across all experiments, so that half of the rats in each group received the training in the order shown in this figure and half were trained with light-sound pairings in stage 1, sound-shock pairings in stage 2 and a light test in stage 3. Varying how many times the rats are presented with the neutral stimulus pairings in Stage 1 dictates the method they use to integrate associations between the neutral stimuli and the subsequent unpleasant electric shock. After brief training (left) rats use a mediated learning mechanism during stage 2 to associate the sound with the electric shock. With extended training (right), rather than carrying out mediated learning during stage 2, associations are made during the test phase (stage 3), using the chaining technique. This supports the theory that the sound elicits a prediction of the light and subsequent shock through reactivation of the memories stored during stage 1 and stage 2, respectively.