Contrary to the long held belief that human sense of smell is less sophisticated than that of other species, several studies performed by Dr. Greer and his collaborators indicate otherwise. In fact, their results show a significant level of organization and complexity with the human olfactory system. In the study, tissues from human olfactory bulbs were extracted and analyzed. In doing so, researchers were able to determine the presence and characteristics of several neurons/circuits. Results have prompted the notion that olfactory deficits associated with particular disorders may actually be caused by pathologies within the olfactory bulb. One finding, for example, indicated the presence of TH-like immunoreactive neurons in the olfactory bulb, which may have links to smell disorders in patients with Parkinson’s Disease.