Strategies used by two memories to share space in a small molluscan neural network

Distinct memories are often encoded into the same network space without destructive interference. In this study, we explored how this can be possible in Tritonia diomedea's dorsal/ventral escape swim network during two distinct forms of non-associative learning: sensitization and habituation. Sensitization and habituation altered non-identical parameters of the escape behavior, suggesting independent encoding sites. Activity imaging with voltage-sensitive dyes found that while both memories only alter neuronal participation in the dorsal phase, sensitization is phase-specific while habituation is phase-general when altering burst intensity. Intracellular recordings found that sensitization elevates intrinsic excitability in neurons from both phases, while habituation only reduces excitability in ventral phase neurons. Phase-specific mechanisms appear to be involved-ventral phase neurons through spike frequency adaptation, while dorsal phase neurons through resting membrane potential. These results show highly specific network storage sites for distinct non-associative memories, a potential strategy for maintaining different memories without destructive interference.