What is "hyperosmia"

n. Hypersensitivity of the sense of smell.

Hyperosmia is an increased olfactory acuity (heightened sense of smell), usually caused by a lower threshold for odor. This perceptual disorder arises when there is an abnormally increased signal at any point between the olfactory receptors and the olfactory cortex. The causes of hyperosmia may be genetic, environmental or the result of benzodiazepine withdrawal syndrome.

When odorants enter the nasal cavity, they bind to odorant receptors at the base of the olfactory epithelium. These receptors are bipolar neurons that connect to the glomerular layer of the olfactory bulb, traveling through the cribriform plate. At the glomerular layer, axons from the olfactory receptor neurons intermingle with dendrites from intrinsic olfactory bulb neurons: mitrial/tufted cells and dopaminergic periglomerular cells. From the olfactory bulb, mitral/tufted cells send axons via the lateral olfactory tract (the cranial nerve I) to the olfactory cortex, which includes the piriform cortex, entorhinal cortex, and parts of the amygdala. From the entorhinal cortex, axons extend to the medial dorsal nucleus of the thalamus, which then proceed to the orbitofrontal cortex.