Neurodegenerative diseases are a group of disorders that primarily affect the neurons in the brain. These diseases are characterized by the progressive degeneration of nerve cells, leading to a range of symptoms including impaired cognition, movement disorders, and behavioral changes. Common neurodegenerative diseases include Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis (ALS). Research in this area focuses on understanding the underlying causes of these diseases, developing treatments to slow or halt disease progression, and improving quality of life for individuals affected by neurodegenerative diseases.