Systems and methods detect electrical activity in the human brain in the form of the generated magnetic fields and map the magnetic field strength to the surface of the cerebral cortex. By mapping the measured magnetic fields to the sulcal-defined gyrus of the cerebral cortex rather than to its three-dimensional volume, the data complexity and the resulting image are dramatically reduced. The device allows an inventory of brain function, including, but not limited to, vision, sound, sensory, and cognition, with the sensors placed over the corresponding region or regions of interest of the brain.