The discovery of a place in the brain that controls our perception of “up” and “down” may lead to a treatment for chronic dizziness.
The finding, described online in the journal Cerebral Cortex, reveals a potential strategy for treating the feelings of unsteadiness and “floating” that people experience when the brain fails to properly integrate input from the body’s senses.
“Our brain has this amazing way of knowing where we are in space, whether we are upright or tilted at an angle, even if it is completely dark and we can’t see anything around us,” says Amir Kheradmand, a neurology instructor at the Johns Hopkins University School of Medicine who conducted the research.
“This study suggests there’s a small area of neural tissue in the parietal cortex substantially involved in this ability,” he says, “giving us a place to start thinking about how we may be able to treat people with disorienting dizziness.”
Disabling dizziness can be a symptom of damage to the inner ear or other senses such as vision. In many cases, however, the problem appears to stem instead from a disruption of processes in the brain. Those processes translate gravity input from the inner ears and visual sensations from the eyes into what is known as upright perception.
Kheradmand says he and his team focused their attention on the right parietal cortex because studies in stroke victims with balance problems suggested that damage to that part of the brain was centrally involved in upright perception.
The team placed eight healthy people individually in a dark room and showed them lines illuminated on a screen. The researchers instructed the subjects to report the orientation of the lines by rotating a dial to the right, left, or straight up.
The subjects then received what is known as TMS, or trans-cranial magnetic stimulation, which painlessly and noninvasively delivers electromagnetic currents to precise locations in the brain to temporarily disrupt the function of the targeted area. TMS is considered safe and is approved to treat some patients with depression.
Each subject had an electromagnetic coil placed against the scalp in a 2-centimeter wide location across the right parietal lobe, behind the ear. After each 40-second session of TMS, the subjects were again asked to show researchers which way each illuminated line on the screen was oriented.
The researchers found that each subject’s sense of being upright was skewed in the same way after TMS in the same spot in the parietal cortex: the supramarginal gyrus.
Kheradmand says the study’s results raise the possibility that TMS could be used to treat chronic dizziness.
“If we can disrupt upright perception in healthy people using TMS, it might also be possible to use TMS to fix dysfunction in the same location in people with dizziness and spatial disorientation,” he says.
“It’s fascinating that we’ve gotten to the point that we can show that a subconscious perception can be altered using this simple, noninvasive technique,” he adds. “We’re excited that this could someday be a key to helping people who have dizziness and spatial disorientation to feel better.”
The National Institute on Deafness and Other Communication Disorders and the Leon Levy, Schwerin Family, and Landenberger foundations supported the research.
Source: Johns Hopkins University