Magnetic camera based on optical magnetometer for neuroscience research

Abstract During Phase Iwe will test the feasibility of developing a magnetographic camera technology as a new tool in neuroscience to facilitate the detailed analysis of electrical currents in diverse neuronal circuitsInstead of photographic imagesthe camera will produce single shot images of the magnetic fields from in vivo samples of interestsuch as a patch of the grey matter in the cerebral cortex or the dorsal hippocampusThe camera will be based on the room temperature microfabricated optically pumped magnetometerOPMtechnology that we have been developing during the past decadeOur stand alone singleOPMs have noise levels comparable to the magnetometers based on superconducting technologybut we have not yet used OPMs to develop a multipixel cameraWe believe they can be used to build a camera with more than one megapixelsproviding high spatial and temporal resolutionIn Aimwe will build a bench top proof of concept camera system operating in a magnetically shielded roomThe OPM transduces each magnetic image into an optical image that is detected by the CMOS detector atfps or greaterOur preliminary results have noise levels of andltfTHz for ampixel size and andltfTHz for ampixelIn Phase Iwe will improve the noise level of the detector by a factor ofand will improve our detector design to reduce the currentmm gap between the sample and detectorOur target Phase II goal is to reduce this gap tomIn Aimwe will evaluate the possibility of using the camera in combination with an array of electrodes to analyze neuronal currents in a novel wayIn neurophysiological studiesthe emphasis has been placed almost exclusively on analyzing the neuronal interactions along the radial direction in the cortexperpendicular to the cortical surfaceThe physiology of the horizontal connections parallel to the cortical surface has been much less emphasizedA high densityD array of intracortical electrodes can in principle be used to determine both types of currents from the potential measurementsHoweverthis is quite complex with large uncertaintyThe horizontal and radial circuitries can be decomposed and separately analyzed by using the camera with an electrode array since the camera will preferentially see the B fields produced by the horizontal circuitwhile the electrode array will see bothTogetherthese two types of circuitry can be analyzed to provide a better understanding of the cortical circuitWe will determine how well the Phase I camera can determine the horizontal circuitry in a simulation study and in an in vitro intact isolated lissencephalic cerebellum of a turtle with the well known parallel fiber system in the superficial molecular layer running parallel to the cortical surfaceIn Phase IIwe plan to develop a completely self contained portable multi pixel camera with a magnetic shield inside the camera casing so that it can be used anywhere without an extra shieldingIts usefulness will be evaluated for studying cortical and hippocampal physiology in in vivo ratsSince the camera uses the MEMS technologyit can be eventually mass produced economically for wide use in neuroscience Narrative We will develop a novel type of magnetographic camera as a new tool in neurosciencecapable of providing single shot images of electrical currents in neuronal circuits in vitro and in vivo with a millisecond time resolutionIn Phase Iwe will test the feasibility of developing such a camera and evaluate its potential applications in neuroscienceBy the end of Phase IIwe plan to produce a camera that can image neuronal current distributions with a large array of pixelsi exhaving a spatial resolution as high asmatfpsbetter thanms resolutionand with a noise level of andltfTHz depending on pixel size