MEG and Pico Tesla- TMS in Greece

Time varying electric currents, in wires or brain cells, all produce time-varying magnetic fields. Even though transmembrane, intracellular and extracellular neuronal currents each produce surrounding magnetic flux, the neuromagnetic field recordable outside of the head is a selective reflection of intracellular currents flowing in the apical dendrites of pyramidal cells oriented parallel to the skull surface. This is because of the biophysical properties of neuronal currents and the volume conduction properties of the head. The key to successful isolation of neuromagnetic signals is to use sensors that take advantage of how the strength of a magnetic field changes as a function of the distance from its source. Such magnetic fields emitted from the brain are very weak (of the order of pT=10 ¹²T), so very sophisticated devices must be utilized in order to detect and record these fields. Such sophisticated device is the biomagnetometer SQUID (Superconductive Quantum Interference Device) which has the ability to detect magnetic fields of the order of 10 ¹ T (=1fT).