Memory and sensory perception go hand in hand. If you think of something that had happened to you in the past, you’ll likely recall the sensory experience, i.e. sights, sounds and smells. Though we are primarily visual-based beings, the sense that is most connected to memory is the sense of smell.
Apparently, the olfactory system detects an odour in your nose, then sends the signal to your olfactory bulbs which then sends it to the rest of the brain, but first the limbic system and in particular the amygdala—the part of the brain involved most in emotion.
A study done showed that the amygdala lighted up more when a nostalgic smell was presented to a participant than when they presented the object as a visual. I.e. the smell made the participants more nostalgic that the sight.
Let me give you a clearer example. I don’t like soup. Especially not chicken soup. Every time I smell it, I feel sick. I can’t remember whether I was given this soup when I was sick or if I just made that connection after watching too much television. Regardless, I can make this connection even before realising what it is I’m smelling. I.e. I smell something and start to feel sick. What is that? I might ask. Chicken soup.
There will be certain smells that you will associate with certain things, be it Old Spice with your father or ginger bread cookies with your grandma’s kitchen. And nothing will succeed more in bringing back the memories and feelings than smelling that thing again.