Measurement of visual evoked magnetic fields associated with pattern recognition

The endogenous negativity of the early negative component of event-related potential or event-related magnetic field might reveal some aspects of cognitive processes or stimulus identification. The authors identified the activated area for an early negative component (NA), which seems to be associated with pattern recognition processes, by measuring the magnetic fields. The difference between the 50%/50% discriminative response and the 80%/20% discriminative response was also obtained. The visual evoked magnetic field was measured with a 204-channel whole-scalp superconducting quantum interference device gradiometer and estimated the equivalent current dipoles (ECD) to clarify the source localization of NA. Localization of a single ECD was applied for the main peak of the NA component in the magnetoencephalogram response. The ECD sources were localized in the frontal and temporal sections of the brain.