Anecdotally, many of us have had experiences where a certain smell—perhaps chlorine, fresh baked cookies, or the salty beach air—floods our brain with memories of a distinct event or location that we associate clearly with certain emotions.
So why is this? The majority of us clearly rely more on a sense of sight than our sense of smell day to day, so what is it about our sense of smell that works to better trigger our memory and our emotions? The link may simply be due to the architectural layout of our brain.
Your olfactory bulb runs from your nose to the base of your brain and has direct connections to your amygdala (the area of the brain responsible for processing emotion) and to your hippocampus (an area linked to memory and cognition). Neuroscientists have suggested that this close physical connection between the regions of the brain linked to memory, emotion, and our sense of smell may explain why our brain learns to associate smells with certain emotional memories.
So many of these odor-driven memories may further be childhood memories because those years are when we experience most smells for the first time. There is not yet research to suggest that we can tap into the link between scents and memory to help us cram for tests or remember where we put our car keys as adults.
Source: Why do some scents trigger powerful memories? | Genetic Literacy Project