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.
Impedance changes during the compound nerve action potential: implications for impedance imaging of neuronal depolarisation in the brain
Detection of cerebral ischaemia in the anaesthetised rat by impedance measurement with scalp electrodes: implications for non-invasive imaging of stroke by electrical impedance tomography
Impedance changes during evoked nervous activity in human subjects: implications for the application of applied potential tomography (APT) to imaging neuronal discharge
Feasibility of developing a method of imaging neuronal activity in the human brain: a theoretical review
Design considerations and performance of a prototype system for imaging neuronal depolarization in the brain using 'direct current' electrical resistance tomography
The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz
Evaluation of inverse methods and head models for EEG source localization using a human skull phantom
Multi-frequency electrical impedance tomography (EIT) of the adult human head: initial findings in brain tumours, arteriovenous malformations and chronic stroke, development of an analysis method and calibration
Factors limiting the application of electrical impedance tomography for identification of regional conductivity changes using scalp electrodes during epileptic seizures in humans
Design of electrodes and current limits for low frequency electrical impedance tomography of the brain
Impedance changes recorded with scalp electrodes during visual evoked responses: implications for Electrical Impedance Tomography of fast neural activity
A method for recording resistance changes non-invasively during neuronal depolarization with a view to imaging brain activity with electrical impedance tomography.
A modelling study to inform specification and optimal electrode placement for imaging of neuronal depolarization during visual evoked responses by electrical and magnetic detection impedance tomography
A cable theory based biophysical model of resistance change in crab peripheral nerve and human cerebral cortex during neuronal depolarisation: implications for electrical impedance tomography of fast neural activity in the brain.
Characterisation and imaging of cortical impedance changes during interictal and ictal activity in the anaesthetised rat
Microwave technology for detecting traumatic intracranial bleedings: tests on phantom of subdural hematoma and numerical simulations
Characterising the frequency response of impedance changes during evoked physiological activity in the rat brain
Imaging fast neural traffic at fascicular level with electrical impedance tomography: proof of principle in rat sciatic nerve.
Frequency-dependent characterisation of impedance changes during epileptiform activity in a rat model of epilepsy
A method for reconstructing tomographic images of evoked neural activity with electrical impedance tomography using intracranial planar arrays
Investigation of potential artefactual changes in measurements of impedance changes during evoked activity: implications to electrical impedance tomography of brain function
Increasing signal amplitude in electrical impedance tomography of neural activity using a parallel resistor inductor capacitor (RLC) circuit
Empirical validation of statistical parametric mapping for group imaging of fast neural activity using electrical impedance tomography
Validation of finite element model of transcranial electrical stimulation using scalp potentials: implications for clinical dose
Imaging slow brain activity during neocortical and hippocampal epileptiform events with electrical impedance tomography.
Optimisation of bioimpedance measurements of neuronal activity with an ex vivo preparation of Cancer pagurus peripheral nerves.
Feasibility of imaging evoked activity throughout the rat brain using electrical impedance tomography
In vivo imaging of deep neural activity from the cortical surface during hippocampal epileptiform events in the rat brain using electrical impedance tomography.
Fascicle localisation within peripheral nerves through evoked activity recordings: A comparison between electrical impedance tomography and multi-electrode arrays.
Drive and measurement electrode patterns for electrode impedance tomography (EIT) imaging of neural activity in peripheral nerve.
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