625 research outputs found
Neuronal behaviors: A control perspective
The purpose of this tutorial is to introduce and analyze models of neurons from a control perspective and to show how recently developed analytical tools help to address important biological questions. A first objective is to review the basic modeling principles of neurophysiology in which neurons are modeled as equivalent nonlinear electrical circuits that capture their excitable properties. The specific architecture of the models is key to the tractability of their analysis: in spite of their high-dimensional and nonlinear nature, the model properties can be understood in terms of few canonical positive and negative feedback motifs localized in distinct timescales. We use this insight to shed light on a key problem in experimental neurophysiology, the challenge of understanding the sensitivity of neuronal behaviors to underlying parameters in empirically-derived models. Finally, we show how sensitivity analysis of neuronal excitability relates to robustness and regulation of neuronal behaviors.This paper presents research results of the Belgian Network DYSCO (Dynamical Systems, Control, and Optimization), funded by the Interuniversity Attraction Poles Programme, initiated by the Belgian State, Science Policy Office. G.D. is a Marie-Curie COFUND postdoctoral fellow at the University of Liege. Co-funded by the European Union. J.D. is supported by the F.R.S.-FNRS (Belgian Fund for Scientific Research. The scientific responsibility rests with its authors.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/CDC.2015.740249
Spike Avalanches Exhibit Universal Dynamics across the Sleep-Wake Cycle
Scale-invariant neuronal avalanches have been observed in cell cultures and
slices as well as anesthetized and awake brains, suggesting that the brain
operates near criticality, i.e. within a narrow margin between avalanche
propagation and extinction. In theory, criticality provides many desirable
features for the behaving brain, optimizing computational capabilities,
information transmission, sensitivity to sensory stimuli and size of memory
repertoires. However, a thorough characterization of neuronal avalanches in
freely-behaving (FB) animals is still missing, thus raising doubts about their
relevance for brain function. To address this issue, we employed chronically
implanted multielectrode arrays (MEA) to record avalanches of spikes from the
cerebral cortex (V1 and S1) and hippocampus (HP) of 14 rats, as they
spontaneously traversed the wake-sleep cycle, explored novel objects or were
subjected to anesthesia (AN). We then modeled spike avalanches to evaluate the
impact of sparse MEA sampling on their statistics. We found that the size
distribution of spike avalanches are well fit by lognormal distributions in FB
animals, and by truncated power laws in the AN group. The FB data are also
characterized by multiple key features compatible with criticality in the
temporal domain, such as 1/f spectra and long-term correlations as measured by
detrended fluctuation analysis. These signatures are very stable across waking,
slow-wave sleep and rapid-eye-movement sleep, but collapse during anesthesia.
Likewise, waiting time distributions obey a single scaling function during all
natural behavioral states, but not during anesthesia. Results are equivalent
for neuronal ensembles recorded from V1, S1 and HP. Altogether, the data
provide a comprehensive link between behavior and brain criticality, revealing
a unique scale-invariant regime of spike avalanches across all major behaviors.Comment: 14 pages, 9 figures, supporting material included (published in Plos
One
Cellular automata and artificial brain dynamics
[EN] Brain dynamics, neuron activity, information transfer in brains, etc., are a vast field where
a large number of questions remain unsolved. Nowadays, computer simulation is playing a key role
in the study of such an immense variety of problems. In this work, we explored the possibility of
studying brain dynamics using cellular automata, more precisely the famous Game of Life (GoL).
The model has some important features (i.e., pseudo-criticality, 1/f noise, universal computing),
which represent good reasons for its use in brain dynamics modelling. We have also considered that
the model maintains sufficient flexibility. For instance, the timestep is arbitrary, as are the spatial
dimensions. As first steps in our study, we used the GoL to simulate the evolution of several
neurons (i.e., a statistically significant set, typically a million neurons) and their interactions with
the surrounding ones, as well as signal transfer in some simple scenarios. The way that signals
(or life) propagate across the grid was described, along with a discussion on how this model could be
compared with brain dynamics. Further work and variations of the model were also examined.This work was partially supported by the European Union's Seventh Framework Programme (FP7-REGPOT-2012-2013-1) under grant agreement no 316165. This work was done with the support of the Czech Science Foundation, project 17-17921S.Fraile, A.; Panagiotakis, E.; Christakis, N.; Acedo Rodríguez, L. (2018). Cellular automata and artificial brain dynamics. Mathematical and Computational Applications (Online). 23(4):1-23. https://doi.org/10.3390/mca23040075S123234TURING, A. M. (1950). I.—COMPUTING MACHINERY AND INTELLIGENCE. Mind, LIX(236), 433-460. doi:10.1093/mind/lix.236.433Sarkar, P. (2000). A brief history of cellular automata. ACM Computing Surveys, 32(1), 80-107. doi:10.1145/349194.349202Ermentrout, G. B., & Edelstein-Keshet, L. (1993). Cellular Automata Approaches to Biological Modeling. 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Active dendrites enhance neuronal dynamic range
Since the first experimental evidences of active conductances in dendrites,
most neurons have been shown to exhibit dendritic excitability through the
expression of a variety of voltage-gated ion channels. However, despite
experimental and theoretical efforts undertaken in the last decades, the role
of this excitability for some kind of dendritic computation has remained
elusive. Here we show that, owing to very general properties of excitable
media, the average output of a model of active dendritic trees is a highly
non-linear function of their afferent rate, attaining extremely large dynamic
ranges (above 50 dB). Moreover, the model yields double-sigmoid response
functions as experimentally observed in retinal ganglion cells. We claim that
enhancement of dynamic range is the primary functional role of active dendritic
conductances. We predict that neurons with larger dendritic trees should have
larger dynamic range and that blocking of active conductances should lead to a
decrease of dynamic range.Comment: 20 pages, 6 figure
Pattern Recognition
A wealth of advanced pattern recognition algorithms are emerging from the interdiscipline between technologies of effective visual features and the human-brain cognition process. Effective visual features are made possible through the rapid developments in appropriate sensor equipments, novel filter designs, and viable information processing architectures. While the understanding of human-brain cognition process broadens the way in which the computer can perform pattern recognition tasks. The present book is intended to collect representative researches around the globe focusing on low-level vision, filter design, features and image descriptors, data mining and analysis, and biologically inspired algorithms. The 27 chapters coved in this book disclose recent advances and new ideas in promoting the techniques, technology and applications of pattern recognition
Memristor Platforms for Pattern Recognition Memristor Theory, Systems and Applications
In the last decade a large scientific community has focused on the study of the
memristor. The memristor is thought to be by many the best alternative to CMOS
technology, which is gradually showing its flaws. Transistor technology has developed
fast both under a research and an industrial point of view, reducing the
size of its elements to the nano-scale. It has been possible to generate more and
more complex machinery and to communicate with that same machinery thanks
to the development of programming languages based on combinations of boolean
operands. Alas as shown by Moore’s law, the steep curve of implementation and
of development of CMOS is gradually reaching a plateau. It is clear the need of
studying new elements that can combine the efficiency of transistors and at the same
time increase the complexity of the operations.
Memristors can be described as non-linear resistors capable of maintaining
memory of the resistance state that they reached. From their first theoretical treatment
by Professor Leon O. Chua in 1971, different research groups have devoted their
expertise in studying the both the fabrication and the implementation of this new
promising technology. In the following thesis a complete study on memristors
and memristive elements is presented. The road map that characterizes this study
departs from a deep understanding of the physics that govern memristors, focusing
on the HP model by Dr. Stanley Williams. Other devices such as phase change
memories (PCMs) and memristive biosensors made with Si nano-wires have been
studied, developing emulators and equivalent circuitry, in order to describe their
complex dynamics. This part sets the first milestone of a pathway that passes trough
more complex implementations such as neuromorphic systems and neural networks
based on memristors proving their computing efficiency. Finally it will be presented
a memristror-based technology, covered by patent, demonstrating its efficacy for
clinical applications. The presented system has been designed for detecting and
assessing automatically chronic wounds, a syndrome that affects roughly 2% of
the world population, through a Cellular Automaton which analyzes and processes
digital images of ulcers. Thanks to its precision in measuring the lesions the proposed
solution promises not only to increase healing rates, but also to prevent the worsening
of the wounds that usually lead to amputation and death
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