Scientists studying how sleep affects memory have found that the whiff of a familiar scent can help a slumbering brain better remember things that it learned the evening before: Research has shown that regions of the cortex, the thinking and planning part of the brain, communicate during deep sleep with a sliver of tissue deeper in the brain called the hippocampus, which records each day's memories of odors and memory responses.

The hippocampus encodes odors and memory responses by firing sequences back in the cortex, consolidating the memory.

Olfactory sensing pathways of odors and memory responses in the brain which lead more directly to the hippocampus than visual and auditory ones. That may be why smell can be linked so closely to memory.