Superconducting quantuminterference devices are magnetic sensors utilizingthe Josephson effect (or tunnelling) formagnetic field recordings. For non-invasive magnetoencephalographic applications, low temperatureSQUIDs, cooled with liquid helium, are arrayed across the skull at about a distance of 15mm from the scalp, providing MEG with an advantage compared to EEG (see figure below). The devices allow therecording of faint magnetic fields in individual neural source currents in the human brain in the range of femto Tesla.
