Motion sickness occurs when the body senses inconsistencies within the signals it is receiving from various systems. The conflict will occur in the nervous system, usually when one system senses or sees motion but another system is fixed. This is why motion sickness can happen while reading a book in a car – the vestibular system, located in the inner ear, senses that the body is in motion, while the eyes that are reading the book tell the brain that the book isn’t moving. However, people who are experiencing motion sickness when not in motion may have a problem in their inner ear that is causing confusion with the signals in the nervous system. This may be the result of an undiagnosed ear infection, or it could be a sign of fluid buildup in the ear. People with Parkinson’s disease can also experience motion sickness while not in motion as a side effect of the illness.