Motion sickness, also known as kinetosis and travel sickness, is a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement. Depending on the cause, it can also be referred to as seasickness, car sickness, simulation sickness or airsickness. Sopite syndrome, in which a person feels fatigue or tiredness, is also associated with motion sickness. "Nausea" in Greek means seasickness (naus means ship).
==Types== Motion sickness can be divided into three categories: # Motion sickness caused by motion that is felt but not seen # Motion sickness caused by motion that is seen but not felt # Motion sickness caused when both systems detect motion but they do not correspond.
===Motion is felt but not seen=== In these cases, motion is sensed by the vestibular system and hence the motion is felt, but no motion or little motion is detected by the visual system.
A specific form of motion sickness, car sickness is quite common and often evidenced by the inability to read a map or book during travel. Car sickness results from the sensory conflict arising in the brain from differing sensory inputs. Varying theories exist as to cause. One suggests the eyes view motion while riding in the moving vehicle while other body sensors sense stillness, creating conflict between the eyes and inner ear. Another suggests the eyes mostly see the interior of the car which is motionless while the vestibular system of the inner ear senses motion as the vehicle goes around corners or over hills and even small bumps. Therefore, the effect is worse when looking down but may be lessened by looking outside of the vehicle.
In the early 20th century, Austro-Hungarian scientist Robert Barany observed the back and forth movement of the eyes of railroad passengers as they looked out the side windows at the scenery whipping by. He called it "railway nystagmus." Also called "optokinetic nystagmus." It causes nausea and vomiting. His findings were published in the journal Laeger, 83:1516, Nov.17, 1921.
Air sickness is a sensation which is induced by air travel. Studies have shown that exposure to rotational motions in a virtual environment can cause significant increases in nausea and other symptoms of motion sickness.
In a study conducted by the U.S. Army Research Institute for the Behavioral and Social Sciences in a report published May 1995 titled "Technical Report 1027 - Simulator Sickness in Virtual Environments", out of 742 pilot exposures from 11 military flight simulators, "approximately half of the pilots (334) reported post-effects of some kind: 250 (34%) reported that symptoms dissipated in less than one hour, 44 (6%) reported that symptoms lasted longer than four hours, and 28 (4%) reported that symptoms lasted longer than six hours. There were also four (1%) reported cases of spontaneously occurring flashbacks."
Space sickness was effectively unknown during the earliest spaceflights, as these were undertaken in very cramped conditions; it seems to be aggravated by being able to freely move around, and so is more common in larger spacecraft. Such a device functions by providing the wearer with digital reference lines in their field of vision that indicate the horizon’s position relative to the user’s head. This is accomplished by combining readings from accelerometers and gyroscopes mounted in the device (US Patent 5,966,680). This technology has been implemented in both standalone devices and Google Glass. In two NIH-backed studies, greater than 90% of patients experienced a reduction in the symptoms of motion sickness while using this technology.
While playing computer games, and mainly in first-person shooter games, some cases of simulation sickness can be resolved by changing the field of view in the game. Some games have a default setting which places a player's vision a small distance ahead of the actual object controlled, which will most likely trigger simulation sickness.
=== Medication === Over-the-counter and prescription medications are readily available, such as Dramamine/Gravol (dimenhydrinate), Bonine/Antivert (meclizine), promethazine, cyclizine, and Stugeron (cinnarizine).
* *[http://www.nlm.nih.gov/medlineplus/motionsickness.html Motion Sickness] from MedlinePlus *[http://www.motion-sickness.co.uk Visually induced motion sickness research] *[http://ed.ted.com/lessons/the-mystery-of-motion-sickness-rose-eveleth Motion Sickness Educational Video]
Category:Neurological disorders Category:Effects of external causes Category:Vomiting *