163,859 research outputs found
Synchronization in model networks of class I neurons
We study a modification of the Hoppensteadt-Izhikevich canonical model for networks of class I neurons, in which the 'pulse' emitted by a neuron is smooth rather than a delta-function. We prove two types of results about synchronization and desynchronization of such networks, the first type pertaining to 'pulse' functions which are symmetric, and the other type in the regime in which each neuron is connected to many other neurons
An Adaptive Locally Connected Neuron Model: Focusing Neuron
This paper presents a new artificial neuron model capable of learning its
receptive field in the topological domain of inputs. The model provides
adaptive and differentiable local connectivity (plasticity) applicable to any
domain. It requires no other tool than the backpropagation algorithm to learn
its parameters which control the receptive field locations and apertures. This
research explores whether this ability makes the neuron focus on informative
inputs and yields any advantage over fully connected neurons. The experiments
include tests of focusing neuron networks of one or two hidden layers on
synthetic and well-known image recognition data sets. The results demonstrated
that the focusing neurons can move their receptive fields towards more
informative inputs. In the simple two-hidden layer networks, the focusing
layers outperformed the dense layers in the classification of the 2D spatial
data sets. Moreover, the focusing networks performed better than the dense
networks even when 70 of the weights were pruned. The tests on
convolutional networks revealed that using focusing layers instead of dense
layers for the classification of convolutional features may work better in some
data sets.Comment: 45 pages, a national patent filed, submitted to Turkish Patent
Office, No: -2017/17601, Date: 09.11.201
Leader neurons in leaky integrate and fire neural network simulations
Several experimental studies show the existence of leader neurons in
population bursts of 2D living neural networks. A leader neuron is, basically,
a neuron which fires at the beginning of a burst (respectively network spike)
more often that we expect by looking at its whole mean neural activity. This
means that leader neurons have some burst triggering power beyond a simple
statistical effect. In this study, we characterize these leader neuron
properties. This naturally leads us to simulate neural 2D networks. To build
our simulations, we choose the leaky integrate and fire (lIF) neuron model. Our
lIF model has got stable leader neurons in the burst population that we
simulate. These leader neurons are excitatory neurons and have a low membrane
potential firing threshold. Except for these two first properties, the
conditions required for a neuron to be a leader neuron are difficult to
identify and seem to depend on several parameters involved in the simulations
themself. However, a detailed linear analysis shows a trend of the properties
required for a neuron to be a leader neuron. Our main finding is: A leader
neuron sends a signal to many excitatory neurons as well as to a few inhibitory
neurons and a leader neuron receives only a few signals from other excitatory
neurons. Our linear analysis exhibits five essential properties for leader
neurons with relative importance. This means that considering a given neural
network with a fixed mean number of connections per neuron, our analysis gives
us a way of predicting which neuron can be a good leader neuron and which
cannot. Our prediction formula gives us a good statistical prediction even if,
considering a single given neuron, the success rate does not reach hundred
percent.Comment: 25 pages, 13 figures, 2 table
Stochastic IMT (insulator-metal-transition) neurons: An interplay of thermal and threshold noise at bifurcation
Artificial neural networks can harness stochasticity in multiple ways to
enable a vast class of computationally powerful models. Electronic
implementation of such stochastic networks is currently limited to addition of
algorithmic noise to digital machines which is inherently inefficient; albeit
recent efforts to harness physical noise in devices for stochasticity have
shown promise. To succeed in fabricating electronic neuromorphic networks we
need experimental evidence of devices with measurable and controllable
stochasticity which is complemented with the development of reliable
statistical models of such observed stochasticity. Current research literature
has sparse evidence of the former and a complete lack of the latter. This
motivates the current article where we demonstrate a stochastic neuron using an
insulator-metal-transition (IMT) device, based on electrically induced
phase-transition, in series with a tunable resistance. We show that an IMT
neuron has dynamics similar to a piecewise linear FitzHugh-Nagumo (FHN) neuron
and incorporates all characteristics of a spiking neuron in the device
phenomena. We experimentally demonstrate spontaneous stochastic spiking along
with electrically controllable firing probabilities using Vanadium Dioxide
(VO) based IMT neurons which show a sigmoid-like transfer function. The
stochastic spiking is explained by two noise sources - thermal noise and
threshold fluctuations, which act as precursors of bifurcation. As such, the
IMT neuron is modeled as an Ornstein-Uhlenbeck (OU) process with a fluctuating
boundary resulting in transfer curves that closely match experiments. As one of
the first comprehensive studies of a stochastic neuron hardware and its
statistical properties, this article would enable efficient implementation of a
large class of neuro-mimetic networks and algorithms.Comment: Added sectioning, Figure 6, Table 1, and Section II.E Updated
abstract, discussion and corrected typo
Stochastic IMT (insulator-metal-transition) neurons: An interplay of thermal and threshold noise at bifurcation
Artificial neural networks can harness stochasticity in multiple ways to
enable a vast class of computationally powerful models. Electronic
implementation of such stochastic networks is currently limited to addition of
algorithmic noise to digital machines which is inherently inefficient; albeit
recent efforts to harness physical noise in devices for stochasticity have
shown promise. To succeed in fabricating electronic neuromorphic networks we
need experimental evidence of devices with measurable and controllable
stochasticity which is complemented with the development of reliable
statistical models of such observed stochasticity. Current research literature
has sparse evidence of the former and a complete lack of the latter. This
motivates the current article where we demonstrate a stochastic neuron using an
insulator-metal-transition (IMT) device, based on electrically induced
phase-transition, in series with a tunable resistance. We show that an IMT
neuron has dynamics similar to a piecewise linear FitzHugh-Nagumo (FHN) neuron
and incorporates all characteristics of a spiking neuron in the device
phenomena. We experimentally demonstrate spontaneous stochastic spiking along
with electrically controllable firing probabilities using Vanadium Dioxide
(VO) based IMT neurons which show a sigmoid-like transfer function. The
stochastic spiking is explained by two noise sources - thermal noise and
threshold fluctuations, which act as precursors of bifurcation. As such, the
IMT neuron is modeled as an Ornstein-Uhlenbeck (OU) process with a fluctuating
boundary resulting in transfer curves that closely match experiments. As one of
the first comprehensive studies of a stochastic neuron hardware and its
statistical properties, this article would enable efficient implementation of a
large class of neuro-mimetic networks and algorithms.Comment: Added sectioning, Figure 6, Table 1, and Section II.E Updated
abstract, discussion and corrected typo
Similarity networks for classification: a case study in the Horse Colic problem
This paper develops a two-layer neural network in which the neuron model computes a user-defined similarity function between inputs and weights. The neuron transfer function is formed by composition of an adapted logistic function with the mean of the partial input-weight similarities. The resulting neuron model is capable of dealing directly with variables of potentially different nature (continuous, fuzzy, ordinal, categorical). There is also provision for missing values. The network is trained using a two-stage procedure very similar to that used to train a radial basis function (RBF) neural network. The network is compared to two types of RBF networks in a non-trivial dataset: the Horse Colic problem, taken as a case study and analyzed in detail.Postprint (published version
Switched-Current Chaotic Neurons
The Letter presents two nonlinear CMOS current-mode circuits that implement neuron soma equations for chaotic neural networks. They have been fabricated in a double-metal, single-poly 1.6µm CMOS technology. The neuron soma circuits use a novel, highly accurate CMOS circuit strategy to realise piecewise-linear characteristics in the current-mode domain. Their prototypes obtain reduced area and low voltage power supply (down to 3V) with a clock frequency of 500 kHz
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