Findings revealed that olfaction has the strongest connectivity – a superhighway from smell to the hippocampus.
Christina Zelano, lead investigator, explained that evolution resulted in a profound expansion of the neocortex in humans that re-organized access to memory networks. Vision, hearing, and touch all re-routed in the brain connecting with the hippocampus through an intermediary (the association cortex) rather than directly.
She adds that results suggest olfaction did not undergo this re-routing and instead retained direct access to the hippocampus.
Zelano points out that smell loss has become epidemic due to COVID-19, and understanding the way odors affect our brains–memories, cognition, and more is more important than ever.
“There is an urgent need to better understand the olfactory system to better understand the reason for COVID-related smell loss, diagnose the severity of the loss, and to develop treatments,” said first author Guangyu Zhou. “Our study is an example of the basic research science that our understanding of smell, smell loss, and future treatments is built on.”
The authors highlight that loss of smell adversely affects the quality of life, being highly correlated with depression and poor quality of life. While most people who lose their smell to COVID regain it, the time frame varies widely, and some have had what appears to be a permanent loss, they add.
The researchers believe that their study’s findings are a major piece of the puzzle why odors elicit powerful memories and that their results will help future research solve the mystery.