Feasibility of imaging evoked activity throughout the rat brain using electrical impedance tomography
File(s)1-s2.0-S1053811918304270-main.pdf (2.23 MB)
Published version
Author(s)
Faulkner, M
Hannan, S
Aristovich, K
Avery, J
Holder, D
Type
Journal Article
Abstract
Electrical Impedance Tomography (EIT) is an emerging technique which has been used to image evoked activity during whisker displacement in the cortex of an anaesthetised rat with a spatiotemporal resolution of 200 μm and 2 ms. The aim of this work was to extend EIT to image not only from the cortex but also from deeper structures active in somatosensory processing, specifically the ventral posterolateral (VPL) nucleus of the thalamus. The direct response in the cortex and VPL following 2 Hz forepaw stimulation were quantified using a 57-channel epicortical electrode array and a 16-channel depth electrode. Impedance changes of −0.16 ± 0.08% at 12.9 ± 1.4 ms and −0.41 ± 0.14% at 8.8±1.9 ms were recorded from the cortex and VPL respectively. For imaging purposes, two 57-channel epicortical electrode arrays were used with one placed on each hemisphere of the rat brain. Despite using parameters optimised toward measuring thalamic activity and undertaking extensive averaging, reconstructed activity was constrained to the cortical somatosensory forepaw region and no significant activity at a depth greater than 1.6 mm below the surface of the cortex could be reconstructed. An evaluation of the depth sensitivity of EIT was investigated in simulations using estimates of the conductivity change and noise levels derived from experiments. These indicate that EIT imaging with epicortical electrodes is limited to activity occurring 2.5 mm below the surface of the cortex. This depth includes the hippocampus and so EIT has the potential to image activity, such as epilepsy, originating from this structure. To image deeper activity, however, alternative methods such as the additional implementation of depth electrodes will be required to gain the necessary depth resolution.
Date Issued
2018-09-01
Date Acceptance
2018-05-08
Citation
NeuroImage, 2018, 178, pp.1-10
ISSN
1053-8119
Publisher
Elsevier
Start Page
1
End Page
10
Journal / Book Title
NeuroImage
Volume
178
Copyright Statement
© 2018 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
License URL
Subjects
Science & Technology
Life Sciences & Biomedicine
Neurosciences
Neuroimaging
Radiology, Nuclear Medicine & Medical Imaging
Neurosciences & Neurology
Electrical impedance tomography
Evoked potentials
Cortex
VPL
Fast neural EIT
Rat
SPINAL-CORD-INJURY
SOMATOSENSORY THALAMUS
2-PHOTON MICROSCOPY
SOURCE ORIENTATION
NEURONAL-ACTIVITY
DEPTH ELECTRODES
LARGE-SCALE
POTENTIALS
EEG
CORTEX
Cortex
Electrical impedance tomography
Evoked potentials
Fast neural EIT
Rat
VPL
Animals
Electric Impedance
Electric Stimulation
Electrodes
Evoked Potentials, Somatosensory
Feasibility Studies
Female
Forelimb
Humans
Rats
Rats, Sprague-Dawley
Sensitivity and Specificity
Somatosensory Cortex
Tomography
Ventral Thalamic Nuclei
Ventral Thalamic Nuclei
Somatosensory Cortex
Forelimb
Animals
Humans
Rats
Rats, Sprague-Dawley
Tomography
Sensitivity and Specificity
Feasibility Studies
Electric Stimulation
Electrodes
Electric Impedance
Evoked Potentials, Somatosensory
Female
11 Medical and Health Sciences
17 Psychology and Cognitive Sciences
Neurology & Neurosurgery
Publication Status
Published
Date Publish Online
2018-05-10