Very High Resolution NeuroElectric Brain Imaging Realized by Referee Consensus Processing

Electrical current flow within populations of neurons is a fundamental constituent of brain function. The resulting fluctuating magnetic fields may be sampled noninvasively with an array of magnetic field detectors positioned outside a patient’s head.  This is magnetoencephalography (MEG).  Each source may be characterized by 5-6 parameters, the xyz location and the xyz direction.  The magnetic field measurements are nonlinear in the location parameters; hence the source location is identifiable only via search of the brain volume.  When there is one or a very few sources, this may be practical; solutions for the general problem are weak. Referee consensus is a new method which enables identification of one source at a time regardless of the number and location of others. This “independence” enables solution of the general problem and insures suitability to grid computing.  The computation scales linearly with the number of nonlinear parameters. MEG recordings were obtained from volunteers while they performed a cognitive task The recordings were processed on the Open Science Grid (≈150 CPU hours/sec of data).  On average 500-1500 sources were active throughout.  Statistical analyses demonstrated < 2 mm resolving power [1] and very strong findings (p < 0.02 400 ) when testing for task specific information in the extracted virtual recordings from each individual. 3D maps of differential activation, neuroelectric tomography, provide a very high resolution functional imaging modality which compares favorably with functional MR imaging. Referee consensus is applicable widely to measurement systems including microwave telescope  imaging, seismic tomography, and financial market linkage identification. Applicability requires: (1) The measurements are linear in at least one parameter of each “source.” (2) Each source is detectable at multiple sensors. (3) A sequence of measurements in time is available.   [1] Linear dimensions are represented in this standard form.  Volume dimensions are represented throughout in terms of the length of a side, e.g. 8mm 3 instead of ½ cc, ½ cm 3 or 512 mm 3 .