Neurobehavioral Analysis to Assess Olfactory and Motor Dysfunction in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative condition, primarily affecting dopaminergic neurons. It is defined by motor impairments, such as bradykinesia, stiffness, resting tremor, and postural instability. The striatum, a structure essential for motor control, is impaired in function due to the significant loss of dopaminergic neurons in the substantia nigra and the development of Lewy bodies in the surviving nigral dopaminergic neurons. Olfactory impairment is one of the earliest indications of neurodegenerative disorders like PD that appear years before motor symptoms and cognitive decline development. Olfactory dysfunction is the most common nonmotor PD sign in at least 90% of cases, frequently occurring 5-10 years before motor disturbances. Surprisingly, even though olfactory impairment is intimately linked to PD and is thought to be a potential biomarker, little is known about the brain process underlying this failure. Exposure to environmental toxins has been linked to olfactory dysfunction, leading to nigral neurodegeneration and loss of motor functions. Behavioral neuroscience plays a significant role in identifying and characterizing these olfactory and motor symptoms. In preclinical research, novel treatment approaches are being evaluated in rodent models by behavioral phenotyping to ensure their efficacy. This chapter describes neurobehavioral analysis to assess olfactory and motor dysfunction in rodent models of Parkinson's disease.