Olfaction and Neurodegenerative Disease

The olfactory sensory network is a unique brain system. Among human sensory systems, only olfaction has a direct connection to the brain and no thalamic relay. In terms of tissue and cellular repair, the olfactory system is unusual, along with the hippocampal dentate gyrus, as an example of central nervous tissue in which neurogenesis persists. Additionally, olfaction has been shown to have an essential role in behavior and memory. Extensive investigations have confirmed an association between neurodegenerative disease and olfactory impairment. Olfactory dysfunction is a common and early feature of neurodegenerative diseases including Alzheimer’s disease (AD) and Lewy body diseases (LBD), including Dementia with Lewy bodies (DLB), Parkinson’s disease (PD), and Parkinson’s disease dementia (PDD) [13]. Additionally, other neurodegenerative diseases such as frontotemporal dementias (FTD), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), multiple system atrophy (MSA), amyotrophic lateral sclerosis (ALS), and Huntington’s disease (HD) also show varying degrees of olfactory dysfunction [1,4-6]. NEURODEGENERATIVE DISEASES AND OLFACTORY DYSFUNCTION