Neuronal current distribution imaging using magnetic resonance

A new functional magnetic resonance imaging (fMRI) technique to visualize the distribution of neuronal currents in the human brain was developed Measurements of the internal magnetic field deformation caused by an electric current dipole in a phantom were performed using a method based on the microscopic magnetic resonance imaging technique. The minimal value of the current 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 sequence at 1.5 T. Intensity changes, resulting from causes other than neuronal currents, were eliminated by editing functional images obtained with field gradients of different polarities. MRI mapping of the neuronal currents in the brain during middle finger and thumb tapping was clearly obtained.