Exploring the Sensitivity Limits of Neuronal Current Imaging With MRI and MEG in the Human Brain.
Spin-lock fMRI's detection threshold was higher than actual neuronal magnetic fields, missing activity
Exploring the Sensitivity Limits of Neuronal Current Imaging With MRI and MEG in the Human Brain.
Conventional BOLD-fMRI relies on hemodynamic responses that are temporally and spatially indirect markers of neural activity.
This study evaluated whether spin-lock contrast can effectively detect and localize human neuronal activation, benchmarked against complementary functional modalities, magnetoencephalography (magnetoencephalography) and 3T BOLD-fMRI, to assess the sensitivity of MR-based neuronal current imaging.
Developing alternative contrasts, sensitive to neuroelectrical phenomena, is a critical challenge in brain imaging.
Thirteen healthy young volunteers underwent spin-lock-based imaging during 8 Hz visual stimulation, along with BOLD and magnetoencephalography acquisitions.
Magnetoencephalography revealed robust stimulus-locked responses in the occipital cortex, with estimated local magnetic field amplitudes of ~0.07 nT.
Under the present experimental conditions, the tested spin-lock fMRI implementations did not achieve sufficient sensitivity for reliable in vivo detection of neuronal magnetic fields at 3T.
These findings establish quantitative constraints on direct neuronal current imaging with MRI and provide a benchmark for future methodological developments aimed at bridging electrophysiology and functional MRI.