سياحة داخل مخ بشري.. (مقال علمي كتبته قديما)

Quote: The nerve action potential has the form of a moving, azimuthally symmetric solitary wave (I) which can be modeled as two opposing current dipoles driven by a potential change of the order of 70 mV. The peak currents range from 5 to 10 µA If the nerve is immersed in a conducting medium, the maximum magnetic field of 10-10 T occurs at the nerve surface (radius r ≤ 0.3 mm), with the numbers epending upon the preparation used. As the distance from the nerve is increased, an increasing fraction of the external current returns within c, so that the field at 1 cm is a few picoteslas and decreases thereafter in proportion to the inverse cube of the distance . The weakness of the magnetic field, its rapid falloff with distance, and the required l-to 2-kHz bandwidth place the signal at the limit of detectability of magnetometers used for biomagnetic measurements