A Digital Realization of Astrocyte and Neural Glial Interactions

Abstract

The implementation of biological neural networks is a key objective of the neuromorphic research field. Astrocytes are the largest cell population in the brain. With the discovery of calcium wave propagation through astrocyte networks, now it is more evident that neuronal networks alone may not explain functionality of the strongest natural computer, the brain. Models of cortical function must now account for astrocyte activities as well as their relationships with neurons in encoding and manipulation of sensory information. From an engineering viewpoint, astrocytes provide feedback to both presynaptic and postsynaptic neurons to regulate their signaling behaviors. This paper presents a modified neural glial interaction model that allows a convenient digital implementation. This model can reproduce relevant biological astrocyte behaviors, which provide appropriate feedback control in regulating neuronal activities in the central nervous system (CNS). Accordingly, we investigate the feasibility of a digital implementation for a single astrocyte constructed by connecting a two coupled FitzHugh Nagumo (FHN) neuron model to an implementation of the proposed astrocyte model using neuron-astrocyte interactions. Hardware synthesis, physical implementation on FPGA, and theoretical analysis confirm that the proposed neuron astrocyte model, with significantly low hardware cost, can mimic biological behavior such as the regulation of postsynaptic neuron activity and the synaptic transmission mechanisms.

Digital FPGA implementation of spontaneous astrocyte signalling

“…24,25 These papers use from different astrocyte models called tripartite synapse model. 7,12 As mentioned before, we used the spontaneous model of astrocyte that is a more complete and complex astrocyte model and is different from other astrocyte models. Since our model is complex than the models in Soleimani et al 7 and Hayati et al, 12 the resource usage of the FPGA in this proposed model is more than other papers.…”

“…To achieve an impact hardware of the neuronal models, a mathematical model of CNS behaviors is required. [12][13][14][15] These neuronal models are described by first-order differential equations in different levels of complexity because of their biological accuracy. [16][17][18][19][20] In this way, some neuronal models are presented.…”

“…In some cases, although these digital solutions are flexible, they use more energy and power than analog circuits to accomplish the same tasks. [12][13][14][15] • The third category is field-programmable gate array (FPGA) that is an integrated circuit designed to be configured by a customer or a designer after manufacturing. FPGAs contain an array of programmable logic blocks and a hierarchy of reconfigurable interconnects that allow the blocks to be wired together, like many logic gates that can be inter-wired in different configurations.…”

Pulse Width Modulation (PWM) Signals Based on Spiking Neuronal Networks

“…3 confirms that the proposed model mimics the main spiking patterns. In Table II, the Mean Absolute Error (MAE) [4] is calculated at the time step of 0.25 ms.…”

“…One of the well-known models is the Hodgkin Huxley (HH) model where the membranes surface ionic structure is taken into consideration [4] [9]. FitzHugh-Nagumo (FHN) is another simplified model of the HH model [8].…”