
Anthony Fung, Alex Tran, Diwei Xiong
Advisors: Sheik Sadique, Frederic Broccard, Gert Cauwenburghs, Bruce Wheeler
University of California, San Diego, Department of Bioengineering


Fig.1Spike travels down an axon, and is converted via low-pass filter to a current pulse that charges a capacitor much like a postsynaptic potential in a real neuron.8
Background
With an explosion of interest and research in recent decades, the field of Neuroscience would benefit from a ubiquitous standard in network modeling to investigate neural properties at large scales. The most physiologically representative model to date is the pulse-coded spiking neural network described above in Figure 1. Despite the biological realism, building these networks can be difficult for neurophysiologists and researchers without prior network engineering or computer science and engineering experience. The result is poorly documented and sparsely commented simulation attempts that lack a foundation for future hardware implementation. This directly impacts the reproducibility of research, both by the reviewers, as well as the publishers themselves.
The spiking neural network described here is a Leaky Integrate and Fire (LIF) model, which affords the direct manipulation of certain intrinsic neural parameters to easily study the effects of neurological degenerative diseases such as Alzheimer’s disease (AD). The Schaffer Collateral is represented by the edge connecting the CornuAmmonis(CA) regions CA3 and CA1 . Investigation of AD related dendritic spine shrinkage involves the analysis of patch clamp data showing the Excitatory Post-Synaptic Current of AMPA receptors on these spines. At subthreshold input, these receptors are responsible for the building of charge on the capacitor shown in figure 1 until the neuron reaches the threshold. Degradation of the dendritic spines on which these AMPA receptors are located is analogous to modulating the resistor that draws or directs current towards the capacitor in parallel. Modifying this neuron parameter, we can see how a signal were to propagate through a network of these hippocampal neurons.


Objectives
Create a Neural Network Simulator that:
1.Models a pulse-coded network
2.Incorporates input from interviewees
3.Is easy to use and intuitive to learn
4.Produces a variety of data representations
5.Allows for dynamic network visualization
6.Offers a variety of connectivity settings
7.Affords ubiquity as a standard by using opensource software packages
Measures of success were delivered through the verification and reproduction of published research, as well as application to current research
Design goal and constraints
Critical Functionalities
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The ultimate design has been conceptualized to have, inherent in itself, certain characteristics such
as minimal cost, high feasibility, and ease of access. These can be achieved through careful selection
of our materials and software package. The design will have components that are powerful, cheap,
and ubiquitous such that anyone wanting to create this design can do so. This design will utilize
open-source software packages specifically designed for neural network modeling, and individual
laptops to achieve the low costs required by the design considerations. The goal is to make the
design so feasible as to encourage a standard in neural network modeling. The design must also
successfully propagate an input signal or function without significant loss through several layers of
neurons. Signal preservation can be accomplished by imposing a small amount of noise on the
signal, the enhancement of input stimulus level in the first layer, as well as the conductance change
across the layers. Furthermore, the design should be able to accomplish complex tasks and present
meaningful pathway/simulation data and the proper visualization showing network structures and
graphs.
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Other Functionalities
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Other functionalities include the ability to customize the network model generation depending on the
user’s specific research interests. Specific input stimulus and background noisy current level, the
order of filtered input signal, axon resistances, time of running, the conductance change over the
layer, and number of neurons or layers are some examples of functions that should be specified by
the user to better represent their research subject.
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Constraints
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Design constraints come in the form of access to expert guidance. Many of the topics required for
this design are niche and require extensive review of the literature, such as the implementation and
instruction of the python package. In addition, program functionality is constrained by the functions
provided by the BRIAN toolbox, tkinter package, and python language. More specifically, since some
parameters of our model is hard coded, It is hard for GUI to include some function that can modify
the hard coded part. These functions are also constrained by the CPU and GPU performance of
users’ computer. Even if the end-user might need something specific, if there isn’t a class for it, or if
the computer doesn’t have the capacity to execute it, it cannot be done within the scope of this
design.
Diwei Xiong is the editor of this page