Odors can evoke powerful memories, an experience enshrined in literature by Marcel Proust and his beloved madeleine, described in his novel “Remembrance of Things Past.” A new paper authored by investigators at Northwestern University Feinberg School of Medicine, and colleagues, is the first to identify a neural basis for how the brain enables odors to so powerfully elicit those memories. The paper shows unique connectivity between the hippocampus--the seat of memory in the brain--and olfactory areas in humans. This new research suggests a neurobiological basis for privileged access by olfaction to memory areas in the brain. The study compares connections between primary sensory areas--including visual, auditory, touch, and smell--and the hippocampus. It found olfaction has the strongest connectivity. It's like a superhighway from smell to the hippocampus. "During evolution, humans experienced a profound expansion of the neocortex that re-organized access to memory networks," said lead investigator Christina Zelano, PhD, Assistant Professor of Neurology at Northwestern University Feinberg School of Medicine. "Vision, hearing, and touch all re-routed in the brain as the neocortex expanded, connecting with the hippocampus through an intermediary--association cortex--rather than directly. Our data suggests olfaction did not undergo this re-routing, and instead retained direct access to the hippocampus." The new article, "Human Hippocampal Connectivity Is Stronger in Olfaction Than Other Sensory Systems" was published online on February 25, 2021 in Progress in Neurobiology (https://www.sciencedirect.com/science/article/pii/S0301008221000411). In COVID-19, smell loss has become epidemic, and understanding the way odors affect our brains--memories, cognition, and more--is more important than ever, Dr. Zelano noted.
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