Neuroscience methods entailing in vivo measurements of brain activity have greatly contributed to our understanding of brain
function for the past decades, from the invasive early studies in animals using single-cell electrical recordings, to the
noninvasive techniques in humans of scalp-recorded electroencephalography (EEG) and magnetoencephalography (MEG), positron
emission tomography (PET), and, most recently, blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging
(fMRI). A central objective of these techniques is to measure neuronal activities with high spatial and temporal resolution.
Each of these methods, however, has substantial limitations in this regard. Single-cell recording is invasive and only typically
records cellular activity in a single location; EEG/MEG cannot generally provide accurate and unambiguous delineations of
neuronal activation spatially; and the most sophisticated BOLD-based fMRI methods are still fundamentally limited by their
dependence on the very slow hemodynamic responses upon which they are based. Even the latest neuroimaging methodology (e.g.,
multimodal EEG/fMRI) does not yet unambiguously provide accurate localization of neuronal activation spatially and temporally.
There is hence a need to further develop noninvasive imaging methods that can directly image neuroelectric activity and thus
truly achieve a high temporal resolution and spatial specificity in humans. Here, we discuss the theory, implementation, and
potential utility of an MRI technique termed Lorentz effect imaging (LEI) that can detect spatially incoherent yet temporally
synchronized, minute electrical activities in the neural amplitude range (microamperes) when they occur in a strong magnetic
field. Moreover, we demonstrate with our preliminary results in phantoms and in vivo, the feasibility of imaging such activities
with a temporal resolution on the order of milliseconds.
Key words BOLD - fMRI - neuroimaging - noninvasive - Lorentz effect