Electrophysiological damage to neuronal membrane alters ephaptic entrainment

Abstract

The brain is commonly understood as a complex network system with a particular organization and topology that can result in specific electrophysiological patterns. Among all the dynamic elements resulting from the circuits of the brain’s network, ephapticity is a cellular communication mechanism that has received little attention. To understand the network’s properties of ephaptic entrainment, we start investigating the ephaptic effect on a single neuron. In this study, we used numerical simulations to examine the relationship between alterations in ephaptic neuronal entrainment and impaired electrophysiological properties of the neuronal membrane, which can occur via spike field coherence (SFC). This change in frequency band amplitude is observed in some neurodegenerative diseases, such as Parkinson’s or Alzheimer’s. To further investigate these phenomena, we proposed a damaged model based on the impairment of both the resistance of the ion channels and the capacitance of the lipid membrane. Therefore, we simulated ephaptic entrainment with the hybrid neural model quadratic integrate-and-fire ephaptic (QIF-E), which mimics an ephaptic entrainment generated by an LFP (simulate a neuronal group). Our results indicate a link between peak entrainment (ephapticity) preference and a shift in frequency band when damage occurs mainly in ion channels. Finally, we discuss possible relationships between ephaptic entrainment and neurodegenerative diseases associated with aging factors.

Thermal effects and ephaptic entrainment in Hodgkin-Huxley model

“…In this work, the influence of thermal variations on the ephaptic communication process is examined. Initially, we validated the Hodgkin and Huxley continuous model with ephaptic entrainment, establishing agreement with an empirical study 35 and hybrid model simulation 11,36 . After validation, we introduce the thermal factor, ∆T 10 , expanding the phenomenology of the Hodgkin and Huxley model to include thermal changes.…”

“…The development of ephaptic models represents a significant advance in recognizing the role of the ephaptic field in various brain functions, elevating ephaptic communication from its status as a secondary product to a central role 11,36 . Furthermore, considering the inclusion of temperature, the HH-E model could be extended.…”

“…To estimate the ephaptic influence on neuronal potential, a spherical electrode is considered in the extracellular environment. The potential induced by the injected current, by the extracellular electrode, follows the proposal of Holt and Koch 42 which was also employed in further studies 10,11,36 . The expression for the electrical potential in the extracellular environment is given by: V ext epha = ρ 4πr I ext (t), where ρ is the resistivity of the extracellular medium, and r is the distance between the source and the measurement point (neuron).…”

“…Moreover, using the association of resistors in parallel for the model circuit, the maximum equivalent conductance can be defined as G eq = g Na + g K + g L . Following the approach of other works on ephaptic drag 10,11,36 , the used ephaptic term is sinusoidal, I ext (t) = Asin(2π f t). Therefore, the equation for the membrane potential is given by:…”