Optimisation of bioimpedance measurements of neuronal activity with an ex vivo preparation of Cancer pagurus peripheral nerves

Smith, Trevor; Kelly, Max; Avery, James; Rouanet, Theo; Aristovich, Kirill; Chew, Daniel; Holder, David

doi:10.1016/j.jneumeth.2019.108322

Cited by 7 publications

(10 citation statements)

References 31 publications

(41 reference statements)

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“…For use in autonomic nerve studies, this poses a limitation, as the majority are slow conducting C fibers. Similar impedance changes occur in unmyelinated nerve and have been demonstrated in the walking leg nerve of the crab 46 . The frequency for recording these is different and probably optimal at 225 Hz 47 .…”

Section: Discussionsupporting

confidence: 75%

Imaging fascicular organization of rat sciatic nerves with fast neural electrical impedance tomography

et al. 2020

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Imaging compound action potentials (CAPs) in peripheral nerves could help avoid side effects in neuromodulation by selective stimulation of identified fascicles. Existing methods have low resolution, limited imaging depth, or are invasive. Fast neural electrical impedance tomography (EIT) allows fascicular CAP imaging with a resolution of <200 µm, <1 ms using a non-penetrating flexible nerve cuff electrode array. Here, we validate EIT imaging in rat sciatic nerve by comparison to micro-computed tomography (microCT) and histology with fluorescent dextran tracers. With EIT, there are reproducible localized changes in tissue impedance in response to stimulation of individual fascicles (tibial, peroneal and sural). The reconstructed EIT images correspond to microCT scans and histology, with significant separation between the fascicles (p < 0.01). The mean fascicle position is identified with an accuracy of 6% of nerve diameter. This suggests fast neural EIT can reliably image the functional fascicular anatomy of the nerves and so aid selective neuromodulation.

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Section: Discussionsupporting

confidence: 75%

Imaging fascicular organization of rat sciatic nerves with fast neural electrical impedance tomography

et al. 2020

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“…For use in autonomic nerve studies, this poses a limitation, as the majority are slow conducting C fibers. Similar impedance changes occur in unmyelinated nerve and have been demonstrated in the walking leg nerve of the crab 44 . The frequency for recording these is different and probably optimal at 225 Hz 45 .…”

Section: Discussionsupporting

confidence: 75%

Imaging fascicular organization of peripheral nerves with fast neural Electrical Impedance Tomography (EIT)

Ravagli

Mastitkaya

Thompson

et al. 2020

Preprint

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Imaging of the compound action potential (CAP) in fascicles in peripheral nerves could help avoid side effects in neuromodulation by selective stimulation of identified fascicles. Existing methods have low resolution, limited imaging depth, or are invasive. We propose fast neural electrical impedance tomography (EIT), which allows fascicular CAP imaging with a high resolution of ~200 µm, <1 ms. This uses a non-penetrating flexible cuff electrode array with 14 circumferential electrodes. This has been validated in rat sciatic nerve by comparison to micro-computed tomography (microCT) and histology with fluorescent dextran tracers (n=5). With EIT, there were reproducible localized changes in tissue impedance in response to stimulation of individual fascicles (tibial, peroneal and sural). The reconstructed EIT images corresponded to microCT scans and neural tracer histology, with significant separation between the fascicles (p<0.01), and no significant difference between techniques. The standard deviation from the mean fascicle position for EIT was 86 µm (6% of nerve diameter). This suggests fast neural EIT can reliably image the functional fascicular anatomy of the nerves and so aid selective neuromodulation.

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“…The feasibility of this objective can partly be justified by the fact that CAPs in nerves have more pronounced phasic nature than dZs which are mainly monophasic, as was measured experimentally in crabs [33], rats [12,19] and large animals [34] as well as confirmed in the current study (figure 6 in section 3). Therefore, the expectation is that CAPs will decrease in amplitude much faster than dZ so that dZ will be visible further from the stimulation point than CAPs are.…”

Section: Temporal Dispersionsupporting

confidence: 75%

Overcoming temporal dispersion for measurement of activity-related impedance changes in unmyelinated nerves

et al. 2022

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Objective: Fast neural Electrical Impedance Tomography (FnEIT) is an imaging technique that has been successful in visualising electrically evoked activity of myelinated fibres in peripheral nerves by measurement of the impedance changes (dZ) accompanying excitation. However, imaging of unmyelinated fibres is challenging due to temporal dispersion (TP) which occurs due to variability in conduction velocities of the fibres and leads to a decrease of the signal below the noise with distance from the stimulus. To overcome TP and allow EIT imaging in unmyelinated nerves, a new experimental and signal processing paradigm is required allowing dZ measurement further from the site of stimulation than compound neural activity is visible. The development of such a paradigm was the main objective of this study. Approach: A FEM-based statistical model of temporal dispersion in porcine subdiaphragmatic nerve was developed and experimentally validated ex-vivo. Two paradigms for nerve stimulation and processing of the resulting data – continuous stimulation and trains of stimuli, were implemented; the optimal paradigm for recording dispersed dZ in unmyelinated nerves was determined. Main results: While continuous stimulation and coherent spikes averaging led to higher signal-to-noise ratios (SNR) at close distances from the stimulus, stimulation by trains was more consistent across distances and allowed dZ measurement at up to 15 cm from the stimulus (SNR = 1.8±0.8) if averaged for 30 minutes. Significance: The study develops a method that for the first time allows measurement of dZ in unmyelinated nerves in simulation and experiment, at the distances where compound action potentials are fully dispersed.

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Optimisation of bioimpedance measurements of neuronal activity with an ex vivo preparation of Cancer pagurus peripheral nerves

Cited by 7 publications

References 31 publications

Imaging fascicular organization of rat sciatic nerves with fast neural electrical impedance tomography

Imaging fascicular organization of rat sciatic nerves with fast neural electrical impedance tomography

Imaging fascicular organization of peripheral nerves with fast neural Electrical Impedance Tomography (EIT)

Overcoming temporal dispersion for measurement of activity-related impedance changes in unmyelinated nerves

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