‘Magnetized’ brains are slower: The cognitive effects of fMRI
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- ULP / HUS / INSERM, Physiology & Psychiatry
- ULP / HUS / LINC, Biophysics
- ULP / INSERM
- ULP / LINC
- ULP / LINC, Psychology
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- Document Type:
- Manuscript
- Date:
- Received 27 October 2008 11:02 UTC; Posted 29 October 2008
- Subjects:
- Neuroscience
- Abstract:
MRI is generally thought to have no impact on cognition. Although safety experiments have shown that MRI is not harmful, its finer effects have not been investigated. Because we repeatedly observed delayed response time during functional MRI (fMRI), we designed an experiment to confirm this effect and to identify its causal factor(s), including environment, noise, static magnetic field and/or gradient switch. Here we show that the participants had increased response times of +70 ms (up to +30%) in two different detection tasks, with most of this effect due to the 2 Tesla static magnetic field. The latter also specifically accounted for the longer time interval needed to detect two stimuli as occurring successively rather than simultaneously. These observations demonstrate that brain processes are slowed during fMRI, and that this slowing is caused by the static magnetic field. This may be the behavioral counterpart of the effects of static magnetic fields on neuronal excitability. Consequences on fMRI data should be taken into account especially considering the forthcoming very high field MRI. The ability of magnetic fields to modify brain activity suggest that they may be used for therapeutic purposes.
Discussion
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4 votes
- Comments:
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2 comments
I agree with Geoff that this is indeed a very intriguing finding. Have you examined the effects of scanner niavety at all ?
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- License:
- This document is licensed to the public under the Creative Commons Attribution 3.0 License
- How to cite this document:
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Foucher, Jack, Gounot, Daniel, Pham, Bich-Thuy, Marrer, Corinne, and Dufour, Andre. ‘Magnetized’ brains are slower: The cognitive effects of fMRI. Available from Nature Precedings <http://hdl.handle.net/10101/npre.2008.2443.1> (2008)
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Geoff Aguirre on 30 October 2008 17:05 UTC
This is an intriguing finding. Can the authors distinguish between the possibility of slowed cortical processing versus slowed transmission of action potentials from the pyramidal cells to alpha motor neurons and on to the muscle to execute a motor response? If the later was the case, one might expect a larger effect of fMRI to appear in responses made by foot movement as opposed to finger movement.