Robust Functional Magnetoencephalographic Brain Measures with 1.0 Millimeter Spatial Separation

Neuroelectric currents were extracted from free-running magnetoencephalographic (MEG) rest and task recordings from 617 normative subjects (ages: 18-87). State-dependent neuroelectric differential activation (DA) with spatial resolution comparable to that of local field potentials was detected in the majority of this cohort. Rest-high (rest greater than task) or task-high DA was found in the majority of individual subjects in more than 13,000 1 mm^3 voxels per subject. On average, 6% of the DA voxels bordered a second voxel whose DA was opposite, i.e., one was rest-high and the other was task-high. 516 subjects showed more than 100 such opposite voxel pairs 1 mm apart; 226 subjects showed more than 1000. The number of bordering voxel pairs with the same DA was consistently higher for almost all subjects and averaged 20%, ruling out the possibility that opposite bordering voxels occur simply by chance. For 65 brain regions, more than 10% of the cohort showed significantly more same than opposite pairs. These findings taken together support the conclusion that neuroelectric DA is consistently distinguishable at single 1 mm^3 brain voxels with 1-mm spatial separation. When restricted to voxels with near-zero rest or task counts, significantly more rest-high than task-high voxels were found in 35 regions for at least 10 percent of the subjects. This inequality was not found when all DA-voxels were included. This supports the conclusion that the DA found in many rest-high voxels with near-zero task counts is due in part to task-dependent inhibition.