The overall long-term objective of this research program is to understand the involvement of the primary auditory cortex (A1) in auditory associative memory (AAM) and to identify mechanisms of AAM. In contrast to traditional views that A1 is strictly an acoustic analyzer, contemporary research has established that learning modifies the processing, representation and storage of acoustic information in highly-specific ways, to emphasize behaviorally important sounds. The specific aims of the experiments are to determine (1) the factors that govern the type, degree and retention of specific cortical plasticity, including learning strategy, amount of training and type of acoustic stimulus, (2) the nature of the development of plasticity during training and its long term-retention and (3) the attributes of auditory associative memory that is induced by sound paired with activation of the cholinergic nucleus basalis (NB). Rats will be trained in a variety of acoustically-based tasks involving detailed recording of neuronal discharges in A1 either during various stages of learning or comprehensive mapping of A1 after the completion of learning tasks. To test the hypothesis that activation of the cholinergic system is involved in the induction of normal auditory memory, we will determine if NB- induced memory also is capable of long-term retention, discrimination, and transfer to new situations. The findings will elucidate cortical mnemonic function and provide a foundation for therapeutic treatments including experience-dependent recovery of higher auditory function following insult, and learning to perceive speech following cochlear implant treatments. These findings will significantly increase our understanding of a fundamental aspect of auditory cortical function, that of experience-based neural plasticity. Therefore, they will be highly relevant both to the central issue of how features of sound interact with experience to produce auditory comprehension, and for therapeutic treatments of auditory system impairment and learning to understand speech via prosthetic means such as cochlear implants.