Attention drifts to the side: The strong magnetic field in an MRI tomography distorts the perception of space during examination, according to a study. The temporary effect is similar to the cognitive disturbances that can occur after a stroke. This means that performing a brain scan, which is also often used in research, affects its performance itself. So this potential fake effect should now be taken into account in studies. The researchers say there may also be medical potential in this phenomenon.
Structures and processes hidden in tissues and organs become visible: various forms of magnetic resonance imaging (MRT) are among the most important examination methods in medical diagnosis and research. The procedure is based on the principles of what is called magnetic resonance and thus is also referred to as magnetic resonance tomography. The interaction of certain substances in the body with external magnetic fields is used to visualize organs and their functions on CT images. Specifically, an MRI scanner maps certain atoms into resonance vibrations using very strong magnetic fields, causing an electrical signal to be present in the receiving circuit. One might think that this sounds like a potentially huge burden on the person being examined. But the long experience in this process gives all the clarity: “Magnetic field investigations are harmless and do not harm your health,” says Axel Lindner of the University of Tübingen.
On Trace Effects “in the tube”
However, side effects are well known during MRI scans: “Some people notice magnetic field effects by feeling dizzy in the scanner,” Lindner says. It’s also already been proven that eye tremors can occur during an MRI scanner exam in the dark. This effect is attributed to the interaction of the magnetic field with ionic currents in the endolymph fluid in the equilibrium organ. As part of their study, Lindner and colleagues have now investigated the question of whether MRI scans also change the spatial perception of test subjects. This is already known from other types of stimulation of the equilibrium apparatus. The scientists examined the reactions of 17 healthy volunteers in an MRI scanner compared to conditions without the influence of the magnetic field.
The experiments showed that during MRI scans, the perception of all test subjects changed dramatically: their spatial attention drifted to the right side and the feeling of their bodies being orientated in space was disturbed, according to the test results. “Brain activity definitely changes under the magnetic field,” Lindner summarizes. Co-author Hans Otto Karnath of the University of South Carolina in Columbia adds: “The observations strongly reminded us of the perceptual disturbances that can occur after a stroke: patients with so-called spatial neglect stimuli on one side of the room. For example, they only read the right hemisphere. from the newspaper or they run against the left side of the door frame because they overlook it there,” the neurologist explains.
Importance of research and medicine
As the scientists stress, the findings could now have far-reaching significance, especially in brain research. Certain forms of MRI of this area are often used 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 effect on cognition is an important finding,” Lindner says. The researchers say the effect should definitely be taken into account in future neuroscience studies.
But not only that: according to them, the observed effect of the magnetic field can have medical potential: it can be used to treat stroke patients suffering from the phenomenon of neglect. That’s why Lindner and his colleagues want to stay on the ball: In other experiments, they want to investigate whether long, multiple MRI sessions cause long-term effects on cognition and to what extent they can relieve patients’ symptoms.
Source: University of Tübingen, specialized article: eLife, doi: 10.7554/eLife.71076
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