Electrical stimulation fights motion sickness

By DUY PHAN

Motion sickness is the nauseated feeling some people may experience from riding a car, aircraft or boat. Although the condition is not life threatening, it can present major discomfort to a lot of people. There are medications available to mitigate motion sickness, albeit with side effects that can make people feel drowsy.

Published in a new issue of the journal Neurology, a study by Qadeer Arshad and colleagues at Imperial College London shows a novel method of treating motion sickness by delivering electrical currents to the brain without producing side effects commonly seen in medications.

In our everyday life the brain uses a mechanism called the vestibular system (located inside the ear) in order to maintain balance. Normally, we do not feel nauseated when we walk or run because the brain reconciles the feeling of being in motion with our visual perceptions such as changes in scenery.

During a car ride, however, our body “stays” in the seat while our eyes detect the surrounding world moving. This mismatch in what we see and our sense of being motionless causes the nauseated feelings commonly observed in motion sickness. In other words, the vestibular system is thought to be the biological cause of motion sickness.

Based on this hypothesis, Arshad and colleagues deduced that disrupting the vestibular system during a car or boat ride may be able to mitigate the symptoms of motion sickness. In order to test this hypothesis, the scientists turned to a brain stimulation technique called transcranial direct-current simulation (tDCS). Electrodes placed on a person’s head let tDCS deliver electrical currents to areas of interest.

In a previous study the research team determined that stimulation of an area at the back of the brain called the parietal cortex inhibited the vestibular system. They then wanted to address whether this suppression of the vestibular system could also reduce motion sickness.

In order to model motion sickness in an experimental setting, the researchers recruited human subjects to sit on a mechanical chair. The chair then tilts back and forth, causing subjects to experience symptoms similar to motion sickness, such as nausea. When tDCS was used to suppress the vestibular system, the subjects were less likely to experience motion sickness. They were also able to recover from the symptoms faster following tDCS. Astonishingly, none of the subjects reported any adverse effect from the stimulation therapy, suggesting that this method of treating motion sickness might be preferable over current medications.

How might tDCS play out in real life, such as during a boat ride? One advantage of this technique is that it is noninvasive, unlike other brain stimulation methods that require direct implantation of electrodes deep inside the brain. Electrode “pads” are instead placed over an individual’s scalp. The future of motion sickness treatment may be that a person could wear a hat containing the wirelessly controlled electrodes.