Fig. 2

A nasal clip modifying the key nasal region that may intensify the nasal airflow vortex towards the olfactory region. a, b Variation of anterior nasal airflow vortex in some but not all healthy controls (a), which is linked to a nasal vestibule narrowing—“notch” (b). c, d A narrower vestibule region (high “notch”) likely intensifies the airflow vortex toward the olfactory region, leading to better olfactory sensitivity to l-carvone. (e, f). A nasal clip pinches the nose to create an artificial notch (e) that, along with “nasal plug upwards,” both significantly improve olfactory sensitivity (f) for subjects with moderate baseline PEA detection thresholds (8–16.5) but not for those highly sensitive (> 16.5), and not in the control condition—nasal plug, “downward”