Neuromagnetic signals associated with number comparison task

The present study attempted to specify the brain regions involved in a number comparison task by magnetoencephalography (MEG) measurement. Five normal subjects were required to see a pair of random digits displayed for 1.0 s and to judge which digit was larger. Neuromagnetic measurements were carried out with a whole-scalp 204 planar superconducting quantum device magnetometer. We estimated the location of single equivalent current dipoles (ECDs) in the comparison task. The ECDs related to the number comparison task were estimated in the vicinity of the superior parietal lobule of the left hemisphere at the latency of 254.8 [+ or -] 18.9 ms. Index Terms--Equivalent current dipole, magnetoencephalography, mental calculation, number comparison.