Page 113 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 3 – Internet of Bio-Nano Things for health applications

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 3

INFORMATION THEORETIC MODELING OF P ARANODAL REGIONS IN MYELINATED AXONS

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Caglar Koca , Ozgur Ergul , Meltem Civas , Ozgur B. Akan 1,3
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Internet of Everthing (IoE) Group, Department of Engineering, University of Cambridge, UK , Gazi University, Faculty of
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Engineering, Department of Electrical and Electronics Engineering, Ankara, Turkey, Next‑generation and Wireless
Communications Laboratory (NWCL), Department of Electrical and Electronics Engineering,
Koç University, Istanbul, Turkey
NOTE: Corresponding author: Caglar Koca, ck542@cam.ac.uk

Abstract – As a natural form of nanoscale communication, neuro‑spike communication inspires the deployment of nanoma‑
chines inside the human body for healthcare. To this end, the identi ication of failure mechanisms in normal and diseased
connections of nervous nano‑networks is crucial. Thus, in this paper, we investigate the information transmission through
a single myelinated axon segment. We introduce a realistic multi‑compartmental model for a single myelinated segment
by incorporating the axon’s paranodal regions to the model. Next, we characterize the myelinated segment communication
channel in terms of attenuation over the range of frequencies. Based on this, we derive the rate per channel use and upper
bound on the information capacity. The performance evaluations reveal that our approach provides dramatic correction re‑
garding frequency response. We believe that this result could have a signi icant effect on the characterization of demyelinated
axons from the information and communication technology (ICT) perspective.

Keywords – ICT‑based treatment, intra‑body nano‑networks, Internet of Bio‑Nano Things, demyelination, neuro‑spike
communication

1. INTRODUCTION Regarding axonal transmission, communication and com‑
putational models of axons exist in the literature. Com‑
Advances in nanotechnology have opened the way for the munication models mostly assume the axon as an ideal
deployment of nanomachines collaborating within the In‑ all‑pass ilter [8]. In biologically detailed communication
ternet of Bio‑Nano Things (IoBNT) framework inside the models, the axon is modeled as a low‑pass ilter, and mod‑
human body as a new means of information and com‑ ied second‑order Butterworth ilters [9, 10]. In more
munication technology (ICT)‑based treatment technique complex models, axonal propagation is represented with
[1, 2]. IoBNT offers both the abstraction necessary for a several state transitions in the case of hippocampal pyra‑
deeper look into the evolution of intra‑body communica‑ midal neurons [11]. Moreover, an inite transmission
tions [3] and the foundation for analyzing and interacting line model is also available [12]. The limitations of com‑
with living organisms. For example, as a large scale intra‑ munication models include that they cannot fully capture
body nano‑network, the human nervous system bears an the behavior of axons, which arises from the axon’s phys‑
enormous potential to inspire architectures for such sys‑ iology. The computational models, on the other hand,
tems with novel applications in diverse areas, including are accepted as biologically accurate. Thus, computa‑
smart healthcare [4]. tional models can be used to construct the realistic chan‑
nel model of axons, enabling accurate analyses. In this re‑
Shannon’s information theory is usually applied to ex‑ spect, multi‑compartment models successfully describe
isting intra‑body nano‑networks to analyze intra‑body the axonal transmission by dividing an axonal cable into
communication mechanisms, one of which is neuro‑spike compartments, where each compartment has the same
communication achieved via molecules [5]. Neuro‑spike membrane properties [13]. However, this approach ne‑
communication consists of consecutive stages, namely, glects some parts of the axon, e.g., paranodal regions of
spike generation, axonal and synaptic transmission. Un‑ myelinated axons, where the membrane properties are
derstanding of communication failures within any of not uniform.
these stages due to nervous system diseases such as
spinal cord injury and Multiple Sclerosis (MS) is crucial In many vertebrates, an insulating substance called
to the designs of assistive or replacement nanomachines myelin sheath surrounds axons. The myelin sheath is the
[6]. Accordingly, an accurate communication theoret‑ extension of the plasma membrane of glial cells wrap‑
ical analysis of intra‑body communication channels re‑ ping the axon, possibly in a multilayered structure. Myelin
quires realistic channel modeling of healthy and diseased sheaths are formed in periodic segments. The short por‑
connections, which is promising in understanding dis‑ tions of the axon left uncovered by myelin are called the
ease mechanisms in biological systems communicating nodes of Ranvier. Axonal transmission is achieved by
via molecules [7].

© International Telecommunication Union, 2021 101