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A novel method for recording neuronal depolarization with recording at 125–825 Hz: implications for imaging fast neural activity in the brain with electrical impedance tomography

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Abstract

Electrical impedance tomography (EIT) is a recently developed medical imaging method which has the potential to produce images of fast neuronal depolarization in the brain. Previous modelling suggested that applied current needed to be below 100 Hz but the signal-to-noise ratio (SNR) recorded with scalp electrodes during evoked responses was too low to permit imaging. A novel method in which contemporaneous evoked potentials are subtracted is presented with current applied at 225 Hz to cerebral cortex during evoked activity; although the signal is smaller than at DC by about 10×, the principal noise from the EEG is reduced by about 1000×, resulting in an improved SNR. It was validated with recording of compound action potentials in crab walking leg nerve where peak changes of −0.2% at 125 and 175 Hz tallied with biophysical modelling. In recording from rat cerebral cortex during somatosensory evoked responses, peak impedance decreases of −0.07 ± 0.006% (mean ± SE) with a SNR of >50 could be recorded at 225 Hz. This method provides a reproducible and artefact free means for recording resistance changes during neuronal activity which could form the basis for imaging fast neural activity in the brain.

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Acknowledgments

The National Institutes of Health (NIH), US under Grant 5R01EB006597-03 from the National Institute of Biomedical Imaging and Bioengineering (NIBIB) and the National Eye Institute (NEI).

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Authors and Affiliations

  1. Department of Medical Physics, University College London, London, UK

    T. Oh, O. Gilad, A. Ghosh & D. S. Holder

  2. Bio-Medical Engineering Dept, Kyunghee University, Yongin, South Korea

    T. Oh

  3. Corotix Technologies Ltd., 29 Inbar St, 30900, Zichron Yaakov, Israel

    O. Gilad

  4. Department of Neurosurgery, King’s College Hospital, London, UK

    A. Ghosh

  5. Department of Microsystems Engineering, IMTEK University of Freiburg, Freiburg, Germany

    M. Schuettler

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  1. T. Oh
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  2. O. Gilad
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  3. A. Ghosh
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  4. M. Schuettler
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  5. D. S. Holder
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Correspondence to D. S. Holder.

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Oh, T., Gilad, O., Ghosh, A. et al. A novel method for recording neuronal depolarization with recording at 125–825 Hz: implications for imaging fast neural activity in the brain with electrical impedance tomography. Med Biol Eng Comput 49, 593–604 (2011). https://doi.org/10.1007/s11517-011-0761-z

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