Spin-lock T1ρ-weighted images of a subject are acquired and processed to produce an image that is indicative of bioelectromagnetic activity in the subject. A spin-lock RF field B1ρ is produced such that the Larmor frequency in the rotating frame corresponds to the expected frequency of the bioelectromagnetic activity. As a result, the magnetic field fluctuations generated by the bioelectromagnetic currents shorten the T1ρ of the surrounding tissue, creating a contrast mechanism that is seen as a reduced MR signal in the T1ρ-weighted image that is produced.
