Chapter 5 - Associative Learning and Unlearning

Abstract

This chapter explores various aspects of associative, operant, and instrumental conditioning. These types of learning can be promoted by either positive or negative reinforcement. In two instances—cued fear conditioning and eye-blink conditioning—researchers are able to explore the circuit and cellular basis of associative conditioning in the mammalian CNS. The various model systems and studies of associative conditioning allow several broad conclusions to be drawn. Both increases and decreases in synaptic strength can subserve memory. Increased synaptic strength does not necessarily imply learning, and decreased synaptic strength does not necessarily imply forgetting or extinction. Associative conditioning relies on the unmasking of a latent circuit. Moreover, the two relevant pathways, the CS pathway and the US pathway, must intersect somewhere in the nervous system in order for an association to be formed between the two stimuli. Associative conditioning can be mediated by both positive and negative reinforcers, and in the case of the reward system the psychological state of the animal may determine whether a given stimulus is perceived as a positive or negative stimulus. Despite their apparent simplicity, invertebrate animals exhibit an impressive array of capacities for associative learning. The adaptive power and survival value of associative conditioning are illustrated by its widespread presence in the animal kingdom.