New Theories Regarding the Causes of Parkinson's Disease (1:27)

Environmental Factors as a Cause of Parkinson's (4:57)

Viruses or Toxins as Possible Causes of Parkinson's (2:03)

First Evidence of Environmental Causes (2:55)

New Clues About the Causes of Neuron Damage (2:44)

Researchers Continue to Look for Links (6:50)

Scientists Study the Transplanting of Brain Cells (3:49)

Scientists Study Using Stem Cells (4:50)

Scientist Study Using Retinal Cells (2:52)

Future Research (5:05)

Other Chemical Causes (1:43)

Caffeine and Nicotine May Protect Against Parkinson's (1:22)

Treating the Symptons of Parkinson's (1:00)

Continuing Stem Cell Research (3:17).