Abstract
It is unknown how salmon can imprint and retrieve information on their natal stream over a long period due to the lack of brain molecular markers for evaluating olfactory memory formation and retrieval. Memory in the brains of vertebrates is explained by the plasticity of the nervous system and the synaptic plasticity that promotes the ability of the chemical synapses to undergo changes in synaptic strength for long-term potentiation via the N-methyl-D-aspartate receptor, which has been identified a good molecular marker in the brain of salmon. This chapter describes the plasticity of the nervous system and synaptic plasticity, the involvement of the N-methyl-D-aspartate receptor in olfactory memory formation and retrieval in Pacific salmon, and functional magnetic resonance imaging of olfactory memory in lacustrine sockeye salmon.