Effects of low-field magnetic stimulation on brain glucose metabolism

Nora D. Volkow, Dardo Tomasi, Gene Jack Wang, Joanna S. Fowler, Frank Telang, Ruiliang Wang, Dave Alexoff, Jean Logan, Christopher Wong, Kith Pradhan, Elisabeth C. Caparelli, Yeming Ma, Millard Jayne

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

Echo planar imaging (EPI), the gold standard technique for functional MRI (fMRI), is based on fast magnetic field gradient switching. These time-varying magnetic fields induce electric (E) fields in the brain that could influence neuronal activity; but this has not been tested. Here we assessed the effects of EPI on brain glucose metabolism (marker of brain function) using PET and 18F 2-fluoro-2-deoxy-D-glucose (18FDG). Fifteen healthy subjects were in a 4 T magnet during the 18FDG uptake period twice: with (ON) and without (OFF) EPI gradients pulses along the z-axis (Gz: 23 mT/m; 250 μs rise-time; 920 Hz). The E-field from these EPI pulses is non-homogeneous, increasing linearly from the gradient's isocenter (radial and z directions), which allowed us to assess the correlation between local strength of the E-field and the regional metabolic differences between ON and OFF sessions. Metabolic images were normalized to metabolic activity in the plane positioned at the gradient's isocenter where E=0 for both ON and OFF conditions. Statistical parametric analyses used to identify regions that differed between ON versus OFF (p<0.05, corrected) showed that the relative metabolism was lower in areas at the poles of the brain (inferior occipital and frontal and superior parietal cortices) for ON than for OFF, which was also documented with individual region of interest analysis. Moreover the magnitude of the metabolic decrements was significantly correlated with the estimated strength of E (r=0.68, p<0.0001); the stronger the E-field the larger the decreases. However, we did not detect differences between ON versus OFF conditions on mood ratings nor on absolute whole brain metabolism. This data provides preliminary evidence that EPI sequences may affect neuronal activity and merits further investigation.

Original languageEnglish
Pages (from-to)623-628
Number of pages6
JournalNeuroImage
Volume51
Issue number2
DOIs
StatePublished - Jun 2010
Externally publishedYes

Keywords

  • Brain glucose metabolism
  • Brain imaging
  • Echo planar
  • FMRI

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