Alexey Tonyushkin1, Andrew M. Kiruluta1,2
1Physics, Harvard University, Cambridge, Massachussetts, United States; 2Radiology, MGH, Boston, Massachussetts, United States
Current approaches aimed at understanding brain function can be broadly divided into those that rely on hemodynamic responses as indicators of neural activity (fMRI, Optical and PET) and methods that measure neural activity directly (MEG and EEG). These approaches all suffer from poor temporal resolution (fMRI), poor spatial localization (MEG and EEG), or indirectly measuring neuron activity (fMRI, Optical and PET). It has been suggested that the proton spin population will be altered by neural activity fields resulting in a measurable effect on the MR signal that can be imaged by MRI methods. Unfortunately, this effect has been determined to be too small to be detectable. We present the physical basis and experimental evidence for an alternative approach based on a resonant interaction between the magnetic fields such as those arising from neuron activity, with a spin population that is undergoing Rabi oscillations at a frequency commensurate with the neuron currents. It is well established that neural firing during an activation has a spectrum associated with it.