Smell Test

Olfactory bulb (Yale School of Medicine image)

One symptom of Parkinson's Disease is the loss of the sense of smell, and Yale researchers may have discovered the connection.

Using buried food tests, the researchers found that the mice with later stage symptoms of Parkinson’s disease exhibited olfactory impairment. They found that those mice with olfactory deficits exhibited severe pathology in projection neurons of the olfactory pathway.

They also found these mice showed reduced neurogenesis in the olfactory bulb. In contrast, studies have shown that healthy aging brains continue to form new neurons in the olfactory bulb throughout life.

The Parkinson's finding on the degradation of olfactory cells may also provide a clue about why some COVID patients experience "brain fog" and the loss of their sense of smell.