? EIT is a new medical imaging method. Tomographic images of the electrical properties of a subject are produced with a box of electronics about the size of a DVD player, and EGG type electrodes placed around the head, chest or abdomen. Small, insensible, electrical signals are applied to the electrodes and sophisticated mathematical methods translate these into images with a PC in real time. It is portable, inexpensive, safe, and rapid. Unlike EEG source modelling, the images are unique; reconstruction is almost identical to that of optical tomography. Over the past two decades, the applicant has pioneered the use of EIT for imaging brain function. Most work has been into EIT to image the larger changes in impedance which occur related to changes in blood flow and cell swelling over seconds, as in stroke or epileptic seizures. EIT also has the unique potential to image the small impedance changes which occur in the brain as ion channels open during neuronal depolarization. There are strong grounds for believing that this is possible : Biophysical modelling indicates such activity changes resistance by 1% locally in the brain; the model has been validated in crab nerve recording, such changes are imageable in saline filled tanks, and detailed modelling of volume conducted fields indicates signals just large enough for reliable detection on the scalp. So far, human studies recording voltage or magnetic fields with Magnetoencephalography have shown marginal changes but have not been optimised. The purpose of this application is to validate the physiological basis of this method by recording these fast impedance changes in animals with implanted electrodes, during evoked normal activity. The method will be refined and then assessed for imaging accuracy in humans with indwelling electrodes already implanted for epilepsy surgery. If successful, this will set the foundation for the ultimate goal of future recordings non-invasively in humans. If successful, this would produce a revolutionary new non-invasive method for imaging the fast electrical activity over milliseconds which is the true basis of brain activity, with an inexpensive portable imaging device. It would enable a much deeper understanding of how the brain works, as it would enable mathematical analysis of the fast electrical activity in pathways in the brain. This would lead to radical improvements in understanding and treatment of disorders like schizophrenia, depression and epilepsy. ? ? ?
