Our ability to encode the events that occur in our world, store that information, and then retrieve it at a later time is essential for survival. Our memory serves the essential capacity to integrate past events into current adaptive behavior. Thus, understanding brain processes involved in memory formation is of critical importance from a basic scientific perspective, as it can provide mechanistic insights into a fundamental aspect of cognitive behavior. The overarching goal of this research project is to elucidate brain mechanisms of memory by using a powerful model system, the marine mollusk Aplysia, to forge direct links between neuronal plasticity expressed at the cellular and molecular levels, and specific phases of enduring memory for sensitization expressed behaviorally. To accomplish this goal, there are three Specific Aims: A BEHAVIORAL ANALYSIS will be aimed at identifying the "rules" that govern memory formation for a range of temporally discrete forms of memory for sensitization. Of special importance will be the unique roles of different patterns of training in the formation of mechanistically distinct forms of memory. A SYNAPTIC ANALYSIS will be aimed at establishing synaptic analogs of the different forms of memory revealed in the Behavioral Analysis, and determining the synaptic mechanisms that are recruited into play in forming these diverse memories. A MOLECULAR ANALYSIS will be aimed at identifying "molecular profiles" for different forms of memory by examining the molecular cascades (the genes, messages and proteins) that are involved in altering synaptic strength during memory formation. Relevance to public health: The importance of understanding brain mechanisms underlying memory can be especially appreciated in cases where memory is impaired, such as in Alzheimer's Disease, Post-Traumatic Stress Disorders, and in victims of accidents or strokes. Thus a major challenge in mental health is to achieve a basic understanding of the brain mechanisms that are engaged in normal memory formation, and how those mechanisms are impaired when memory is compromised by disease or injury. Such an understanding is essential for developing effective therapies for cognitive problems involving memory impairment.