MRI scanners affect concentration and visuospatial awareness
August 31, 2012
Standard head movements made while exposed to static 7 Tesla magnetic fields produced by a heavy duty magnetic resonance imaging (MRI) scanner seem to temporarily lower concentration and visuospatial awareness, an experimental study published online in Occupational and Environmental Medicine shows.
The effects were particularly noticeable in tasks requiring high levels of working memory, which may have implications for surgeons and other healthcare staff working within the vicinity of an MRI scanner, the research indicates.
A question not addressed in the study: what do these findings suggest for the validity of fMRI neuroscience study results (at 7T and lower magnetic fields), especially for studies involving the specific effects found in this study? And will future fMRI studies have to control for subject awareness of this study and its possible implications on behavior and performance?
(MRI uses strong magnetic fields and radio waves to take very detailed pictures of the brain and spine. Three types of electromagnetic fields are required to create an image: static and switched gradient magnetic, and radio frequency. The static magnetic field is always present, even when no imaging is taking place.)
Thirty one volunteers made standard head movements within the static magnetic field of a higher field 7 Tesla MRI scanner at exposure levels of zero (sham), 0.5 (medium), and 1 (high)Tesla, in a random order, one week apart.
After each exposure level, the volunteers were set 12 timed cognitive tasks, designed to test the sorts of skills that a surgeon or other healthcare professional might need to deploy within the vicinity of an MRI scanner. These included visual tracking and movement, as well as more general functions, such as attention, concentration and working memory. The tests were neutral in that they didn’t test intelligence or depend on practice.
In all, 30 volunteers completed all three sessions. Compared with the sham test, the results showed that functions such as attention, concentration, and visuospatial awareness were significantly affected.
- For complex mental tasks, reaction and disengagement times were longer, varying from 5% to 21%, the higher the level of magnetic exposure. Complex tasks rely on working memory, suggesting that less of this is available to keep the same levels of attention and concentration going at higher levels of exposure, say the authors.
- While non-verbal memory did not seem to be affected, there was a fall in verbal memory, although this only reached borderline significance.
- At the highest level of exposure, volunteers also experienced some physical symptoms, including metallic taste in the mouth (12 people), dizziness (6), headache (5), and nausea (1).
The exact implications and mechanisms of these subtle acute effects in [practice] remain unclear,” write the authors, who also note that “it has been hypothesized that these effects probably arise due to induced electrical currents in the body that are generated during movement in the static magnetic field.
The introduction of increasingly more powerful MRI machines has boosted exposure levels to static electromagnetic fields for both patients and staff, the researchers say. “To date, mainly health and safety concerns for patients have been evaluated, but possible consequences are particularly important for professionals, cleaners, and MRI engineers, since they are repeatedly exposed to static magnetic fields.”