The purpose of this study is to collect 650 blood and 300 cerebrospinal fluid (CSF) samples from people with amyotrophic lateral sclerosis (ALS), pure lower or upper motor neuron diseases, as well as other neurodegenerative diseases and from people with no neurological disorder. Through comparison of these samples, the researchers hope to learn more about the underlying cause of ALS, as well as find unique biological markers, which could be used to diagnose ALS and monitor disease progression.