Neuronal current distribution imaging using magnetic resonance

A new functional magnetic resonance imaging (fMRI) technique to visualize t he distribution of neuronal currents in the human brain was developed Measu rements of the internal magnetic field deformation caused by an electric cu rrent dipole in a phantom were performed using a method based on the micros copic magnetic resonance imaging technique. The minimal value of the curren t dipole moment detected by the present method was determined to be 90 nAm. The technique was applied to obtain maps of human brain activity by using motor and sensory stimulus paradigms. Measurements were made with an EPI se quence at 1.5T. Intensity changes, resulting from causes other than neurona l currents, were eliminated by editing functional images obtained with fiel d gradients of different polarities. MRI mapping of the neuronal currents i n the brain during middle finger and thumb tapping was clearly obtained.