Whereas other sensory systems are thought to have been re-routed during human evolution, [a new] study suggests that olfactory-hippocampal functional connectivity was preserved and not re-routed. “We show that [the] human primary olfactory cortex—including the anterior olfactory nucleus, olfactory tubercle, and piriform cortex—has stronger functional connectivity with hippocampal networks at rest, compared to other sensory systems,” the authors write in the paper’s abstract.
For this study, senior author Christina Zelano and colleagues in the Northwestern Human Neuroscience Lab used functional neuroimaging (fMRI) combined with intracranial electrophysiology (iEEG) to directly compare the functional connectivity of hippocampal networks across a wide range of human sensory systems (e.g., auditory, touch, visual, and smell).
Zelano and her lab members speculate that olfaction was not re-routed during mammalian evolution; therefore, we have especially robust functional connectivity between our olfactory system and memory hub. “It’s like a superhighway from smell to the hippocampus,” the authors note.
“Nearly everyone has been transported by a whiff of an odor to another time and place, an experience that sights or sounds rarely evoke. Yet, we haven’t known why. The study found the olfactory parts of the brain connect more strongly to the memory parts than other senses. This is a major piece of the puzzle, a striking finding in humans.”