Memory is influenced by four factors: novelty, repetition, association, and emotional resonance. Novelty and attentional systems draw us to new experiences, while repetition helps us remember things we encounter frequently. Association helps us remember things that are connected to other things we already know, and emotional resonance helps us remember the happiest and saddest moments of our lives. The hippocampus is the key structure for long-term memory. Additionally, research has shown that certain genes and neurons can be manipulated to extend memory, and that lithium can switch off forgetfulness mechanisms.