Attention drifts to the side: the strong magnetic field in magnetic resonance tomography distorts the perception of space during the scan, according to a study. The temporary effect is similar to perceptual disorders that can occur after a stroke. This means: The method for examining the brain, which is also often used in research, influences its performance itself. This possibly falsifying effect should therefore now be taken into account in studies. The researchers say there may also be medical potential in the phenomenon.
Hidden structures and processes in tissues and organs become visible: The various forms of magnetic resonance imaging (MRT) are among the most important examination methods in medical diagnostics and research. The procedure is based on the principles of what is known as magnetic resonance and is therefore also referred to as magnetic resonance imaging. The reaction of certain substances in the body to external magnetic fields is used to depict organs and their functions in sectional images. Specifically, an MRT scanner sets certain atoms into resonance vibrations using very strong magnetic fields, which induces an electrical signal in a receiver circuit. That sounds like a potentially considerable burden on the person being examined, one might think. But the long experience with the process gives the all-clear: “Investigations in a magnetic field are harmless and do not harm your health,” says Axel Lindner from the University of Tübingen.
On the trail of effects “in the tube”
However, side effects are well known during MRI examinations: “Some people notice the effects of the magnetic field by feeling dizzy in the scanner,” says Lindner. In addition, it has already been established that eye tremors can occur during an MRI scanner examination in the dark. This effect is attributed to the interaction of the magnetic field with ion currents in the endolymph fluid in the organ of equilibrium. As part of their study, Lindner and his colleagues have now investigated the question of whether MRT scans also change the spatial perception of test subjects. This is already known from other types of stimulation of the organ of equilibrium. The scientists examined the reactions of 17 healthy volunteers in an MRI scanner compared to conditions without the influence of a magnetic field.
The experiments showed: During the MRT scans, the perception of all test subjects changed significantly: Their spatial attention drifted to the right side and the feeling for the orientation of their own body in space was disturbed, according to the test results. “The brain activity is definitely changed under the magnetic field,” sums up Lindner. Co-author Hans-Otto Karnath from the University of South Carolina in Columbia adds: “The observations strongly reminded us of perceptual disorders that can occur after a stroke: patients with so-called spatial neglect neglect stimuli on one side of the room. For example, they only read the right half of a newspaper or run against the left side of the door frame because they overlook it there, ”explains the neurologist.
Significance for research and medicine
As the scientists emphasize, the results could now have far-reaching significance, especially in brain research. Certain forms of MRI are often used in this area to watch the brain think, as it were – this is how the nervous system perceives and processes stimuli. “Against this background, the new finding that the magnetic field has an influence on perception is an important result,” says Lindner. The researchers say that the effect should therefore definitely be taken into account in future neuroscientific studies.
But not only that: According to them, there could be medical potential in the observed effect of the magnetic field: It could possibly be used to treat stroke patients suffering from the phenomenon of neglect. That is why Lindner and his colleagues want to stay on the ball: In further experiments, they want to investigate whether longer and multiple MRI sessions cause long-term effects in perception and to what extent they can alleviate the symptoms of patients.
Source: University of Tübingen, specialist article: Elife, doi: 10.7554 / eLife.71076