Epileptic Activity Propagation by Electric Field Coupling
Abstract number :
2.346
Submission category :
14. Neuropathology of Epilepsy
Year :
2021
Submission ID :
1825848
Source :
www.aesnet.org
Presentation date :
12/5/2021 12:00:00 PM
Published date :
Nov 22, 2021, 06:50 AM
Authors :
Muthumeenakshi Subramanian, BE - Case Western Reserve University; Chia-Chu Chiang, PhD - Biomedical Engineering - Case Western Reserve University; Nicholas Couturier, PhD - Biomedical Engineering - Case Western Reserve University; Dominique Durand, PhD - EL Lindseth Professor of Biomedical Engineering, Biomedical Engineering, Case Western Reserve University
Rationale: Various types of neural activity such as slow-wave sleep and epileptiform can propagate without using synaptic connections at speeds of ~0.1 m/s in vitro. Non-synaptic neural activity propagation has been explained by electric field coupling in the hippocampus and cortex. However, the characteristics of neural activity that enables this type of propagation through volume conductor in vivo have not been studied. Thus, we tested the hypothesis that epileptic signals propagating in vivo across a transection in the hippocampus have distinct characteristics.
Methods: We induced epileptiform activity in 4 rats under anesthesia by injecting 4-aminopyridine in the temporal region of the hippocampus, four recording electrodes were inserted along the longitudinal axis of the hippocampus. A transection was made between the electrodes to study the propagation of the neural activity.
Results: We found that 54% of interictal spikes propagated through the cut. The distinguishing features between the propagating and non-propagating spikes were their amplitude and duration. Spikes with a high amplitude and short duration had a high probability to cross the transection. The activity was observed to propagate at a mean speed of 0.087 ± 0.05 m/s in the characteristic range of propagation using electric field coupling through the transection. Additionally, epileptic seizures and theta waves also propagated non-synaptically across the transection. We placed a dielectric layer within the transection and blocked the propagation further confirming electric field volume conduction mechanism. The speed of propagation was not affected by the transection.
Conclusions: This study characterized different parameters such as amplitude, duration, and most importantly, speed that contribute to propagation by ephaptic coupling. The endogenous electric field effect is responsible for the non-synaptic propagation of 4-AP induced neural activity at speeds of ~0.1 m/s in the hippocampus from in vivo experiments.
Funding: Please list any funding that was received in support of this abstract.: Financial support for this work was provided by NIH grant 1 R01 NS114120 01.
Neuropathology of Epilepsy