system was at the root of the problem. A 

 lack of circulation of blood to the brain 

 was once blamed for motion sickness. 

 And in the late 1800s, researchers began 

 to suspect the inner ear played a role in 

 causing the malady. 



Today, scientists say a neurosensory 

 mismatch in the brain causes motion 

 sickness, says Dr. Kenneth Koch, a 

 gastroenterologist who has studied the 

 syndrome at the Hershey Medical 



sensory mismatches begin the process of 

 motion sickness. 



To study motion sickness in the 

 laboratory, Koch places subjects inside a 

 large rotating vertical drum that creates 

 the illusion of motion. A study subject 

 sits on a stool inside the drum, which has 

 black-and-white vertical stripes painted 

 inside. 



The drum rotates clockwise around 

 the individual about 10 times per minute. 



Center in Pennsylvania. 



It involves three systems — the 

 eyes, the inner ear and sensory receptors 

 called proprioceptors. When these sys- 

 tems are in sync, all is well. 



But put a person in the cabin of a 

 rocking boat and the cues become mis- 

 matched. The inner ear detects the boat 

 rocking, and the proprioceptors in the 

 soles of the feet sense it too. But since the 

 cabin moves with the passenger, the eyes 

 don't see the motion. 



Similarly, a child in the backseat of 

 a car sees motion as objects flash by the 

 window, and his or her inner ear senses 

 it. But because the child's body moves 

 with the car, the proprioceptors in the 

 body don't feel the movement. These 



Within seconds, the individual is visually 

 fooled into believing that he or she is 

 moving and not the drum. But the inner 

 ear and proprioceptors are signaling the 

 brain that the body is still. According to 

 Koch, this sensory conflict provokes 

 motion sickness in approximately 60 

 percent of the healthy people tested. 



The Symptoms 



Causes of motion sickness aside, 

 Koch is also interested in what happens 

 between initial dizziness and the need to 

 heave. 



To determine an individual's re- 

 sponse during his experiments, Koch 

 measures the electrical rhythms in the 

 stomach and the hormones that affect the 



nervous system. He also asks the subject to 

 record his or her feelings. 



Soon after the drum begins to spin, 

 Koch's instruments can determine who will 

 be sick and who will not before the first 

 waves of nausea roll over the study subjects. 



One sign of the trouble to come occurs 

 when electrical rhythms in the stomach 

 muscles change, a condition called gastric 

 dysrhythmia. Normally, three impulses of 

 electricity pass from the top of the stomach 



SOME DOCTORS BELIEVED 

 THAT MOTION DISTURBED 

 THE NORMAL FUNCTIONING 

 OF THE STOMACH. 

 OTHERS THOUGHT THE 

 NERVOUS SYSTEM WAS AT 

 THE ROOT OF THE PROBLEM. 

 A LACK OF CIRCULATION 

 OF BLOOD TO THE BRAIN 

 WAS ONCE BLAMED FOR 



MOTION SICKNESS. 

 AND IN THE LATE 1800s, 

 RESEARCHERS BEGAN TO 

 SUSPECT THE INNER EAR 

 PLAYED A ROLE IN CAUSING 

 THE MALADY. 



down to the small intestine each minute. 

 But in people experiencing motion sick- 

 ness, the rhythms "go bonkers," increasing 

 to as many as nine cycles per minute, Koch 

 says. 



Interestingly, pregnant women who 

 experience nausea during their first trimes- 

 ter also show increased electrical rhythms 

 in the stomach when tested. 



In addition to gastric dysrhythmia, the 

 body's nervous system increases its secre- 

 tions of stress hormones epinephrine and 

 norepinephrine. And soon after, levels of 

 another hormone, vasopressin, skyrocket in 

 the blood. Vasopressin is associated with 

 nausea and vomiting in other instances and 

 other animals. 



As all of these factors act on the body, 



14 JANUARY/FEBRUARY 1994 



