TWO PHOTON IN-VIVO IMAGING OF PRE-SEIZURE STATE

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Epilepsy, affecting about 1% of the population, comprises a group of disorders of the brain characterized by the periodic and unpredictable occurrence of seizures. The detection and localization of seizure foci is an integral part of the treatment for epilepsy. Brainwave patterns during seizures can be detected using recording electrodes, however current technology using these recording electrodes to localize seizure activity is limited. Surface electroencephalography (EEG) can detect seizure activity with electrodes placed on the skin, but cannot provide an exact location of the seizure focus. More exact localization is possible but only through the use of an array of EEG electrodes placed directly on the brain surface across a wide area, a highly invasive surgical procedure. We propose that an alternative to electrical recording can be developed through the use of optical imaging. Our major tool of investigation is an implantable fiberoptic 850nm laser emitter paired to a fiberoptic detector that sends photons to a silicon photodiode. Our experiments have shown seizure activity produces changes in the optical scattering of the brain cortex that can be detected just before and during seizures. These optical changes correlate with seizure activity as recorded with implanted electrodes. Demonstration of this phenomenon is not only interesting from the perspective of elucidating the mechanism for the optic changes, but also as the first step in the development of minimally invasive tools for seizure detection. In this collaboration, we hope to use in vivo 2 photon imaging through a cranial window to demonstrate morphological changes (swelling) in either astrocytes labeled with GFP or sulfarhodamine 101, or mitochondria or both before and during a seizure. This will involve image acquisition and post-hoc analysis from the 2 photon laser microscope at BLI.