An apparatus and method for non-invasively sensing physiological changes in the brain is disclosed. The apparatus and method uses an electromagnetic field to measure localized impedance changes in brain matter and fluid. Various spatial and temporal techniques are used to localize impedance changes in...http://www.google.com/patents/US4690149?utm_source=gb-gplus-sharePatent US4690149 - Non-invasive electromagnetic technique for monitoring physiological changes in the brain
