Motivation and memory

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It is a fundamental principle of psychological theory that behaviour is guided by memories - memories of things that happened and how we felt about them, memories of where we find the things we need, memories of what relates to what, and memories of how we do things like ride a bicycle or drive car. Not all memories are helpful to us, memories of traumatic events or memories of euphoric drug effects are thought to maintain pathological states such as panic disorder or drug abuse. Contemporary theories of memory hold that memories are stored in biochemical and structural changes in the connections between the cells that participate in the perception of the remembered events. These changes were thought to be relatively permanent but more recently it has been suggested that when memories are re-activated the structural basis becomes temporarily plastic and memories can be altered or disrupted by treatments that interfere with the biochemical mechanisms of memory storage. It is not known whether this applies to all types of memory, or whether the disruption is permanent or not. We have evidence in rats that the memories of drug effects that are thought drive morphine addiction can be disrupted by memory-blocking drugs applied around the time a non-dependent animal expresses his motivation for the drug. However this effect seems to be temporary and is overcome by a new experience of the drug. Also when the animal is dependent the memories appear to be resistant to disruption. The aim of this project is to explore whether changing the dose, using more than one blocking drug or changing the timing of application of the memory blocking drug will improve the amnesia and make it permanent. At the same time we will probe whether the memory is truly lost or just suppressed. We will also examine anatomical markers for the biochemical changes that indicate memory in the brain to see if we can track the loss of the memory induced by memory blocking drugs.