scholarly journals Emergence of Lie Symmetries in Functional Architectures Learned by CNNs

2021 ◽  
Vol 15 ◽  
Author(s):  
Federico Bertoni ◽  
Noemi Montobbio ◽  
Alessandro Sarti ◽  
Giovanna Citti
Keyword(s):  
Short Range ◽  
Brain Plasticity ◽  
Natural Images ◽  
Lateral Connectivity ◽  
Geometric Properties ◽  
Qualitative And Quantitative ◽  
Symmetric Pattern ◽  
Visual Systems ◽  
Horizontal Connections ◽  
External Stimuli

In this paper we study the spontaneous development of symmetries in the early layers of a Convolutional Neural Network (CNN) during learning on natural images. Our architecture is built in such a way to mimic some properties of the early stages of biological visual systems. In particular, it contains a pre-filtering step ℓ0 defined in analogy with the Lateral Geniculate Nucleus (LGN). Moreover, the first convolutional layer is equipped with lateral connections defined as a propagation driven by a learned connectivity kernel, in analogy with the horizontal connectivity of the primary visual cortex (V1). We first show that the ℓ0 filter evolves during the training to reach a radially symmetric pattern well approximated by a Laplacian of Gaussian (LoG), which is a well-known model of the receptive profiles of LGN cells. In line with previous works on CNNs, the learned convolutional filters in the first layer can be approximated by Gabor functions, in agreement with well-established models for the receptive profiles of V1 simple cells. Here, we focus on the geometric properties of the learned lateral connectivity kernel of this layer, showing the emergence of orientation selectivity w.r.t. the tuning of the learned filters. We also examine the short-range connectivity and association fields induced by this connectivity kernel, and show qualitative and quantitative comparisons with known group-based models of V1 horizontal connections. These geometric properties arise spontaneously during the training of the CNN architecture, analogously to the emergence of symmetries in visual systems thanks to brain plasticity driven by external stimuli.

Grid Cells Lose Coherence in Realistic Environments

2021 ◽  
Author(s):  
Yifan Luo ◽  
Matteo Toso ◽  
Bailu Si ◽  
Federico Stella ◽  
Alessandro Treves
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Grid Cell ◽  
Place Cells ◽  
Grid Cells ◽  
Lateral Connectivity ◽  
Cell Pattern ◽  
In The Wild ◽  
Freely Moving ◽  
Adaptation Model

Spatial cognition in naturalistic environments, for freely moving animals, may pose quite different constraints from that studied in artificial laboratory settings. Hippocampal place cells indeed look quite different, but almost nothing is known about entorhinal cortex grid cells, in the wild. Simulating our self-organizing adaptation model of grid cell pattern formation, we consider a virtual rat randomly exploring a virtual burrow, with feedforward connectivity from place to grid units and recurrent connectivity between grid units. The virtual burrow was based on those observed by John B. Calhoun, including several chambers and tunnels. Our results indicate that lateral connectivity between grid units may enhance their “gridness” within a limited strength range, but the overall effect of the irregular geometry is to disable long-range and obstruct short-range order. What appears as a smooth continuous attractor in a flat box, kept rigid by recurrent connections, turns into an incoherent motley of unit clusters, flexible or outright unstable.

Peridynamic Modeling of Concrete Structures

2014 ◽  
Vol 638-640 ◽  
pp. 1725-1729 ◽  
Author(s):  
Dan Huang ◽  
Guang Da Lu ◽  
Meng Wei Wang
Keyword(s):  
Finite Element Analysis ◽  
Short Range ◽  
Progressive Failure ◽  
Equations Of Motion ◽  
Concrete Structures ◽  
Element Analysis ◽  
Qualitative And Quantitative ◽  
Peridynamic Model ◽  
Short Range Repulsion ◽  
Material Points

An improved nonlocal peridynamic model was proposed to analyze the progressive failure and crack propagation in concrete structures. Integration-typed equations of motion rather than partial differential equations are utilized so that the cracks will propagate naturally as a consequence of simulation. The anisotropy of concrete and the short-range repulsion between material points were incorporated into the pericynamic constitutive model for concrete, and the damage of material was defined locally at the level of pairwise bond. Its validity was established through qualitative and quantitative comparisons against finite element analysis and experimental observations.

scholarly journals Learning to be on time: temporal coordination of neural dynamics by activity-dependent myelination

2021 ◽  
Author(s):  
Afroditi Talidou ◽  
Paul Frankland ◽  
Donald Mabbott ◽  
Jeremie Lefebvre
Keyword(s):  
Conduction Velocity ◽  
Neural Activity ◽  
Structural Changes ◽  
Brain Plasticity ◽  
Learning Rule ◽  
Axonal Conduction ◽  
Neural Communication ◽  
External Stimuli ◽  
Neural Signaling ◽  
Activity Dependent

Activity-dependent myelination is the mechanism by which myelin changes as a function of neural activity, and plays a fundamental role in brain plasticity. Mediated by structural changes in glia, activity-dependent myelination regulates axonal conduction velocity. It remains unclear how neural activity impacts myelination to orchestrate the timing of neural signaling. We developed a model of spiking neurons enhanced with neuron-glia feedback. Inspired by experimental data and use-dependent synaptic plasticity, we introduced a learning rule, called the Activity-Dependent Myelination (ADM) rule, by which conduction velocity scales with firing rates. We found that the ADM rule implements a homeostatic control mechanism that promotes and preserves synchronization. ADM-mediated plasticity was found to optimize synchrony by compensating for variability in axonal lengths by scaling conduction velocity in an axon-specific way. This property was maintained even when the network structure is altered. We further explored how external stimuli interact with the ADM rule to trigger bidirectional and reversible changes in conduction delays. These results highlight the role played by activity-dependent myelination in synchronous neural communication and brain plasticity.

scholarly journals Some contributions from Neurosciences to Education: do enriched environments increase the learning capacity of our brain?

2021 ◽  
Vol 3 (2) ◽  
pp. 25-39
Author(s):  
Luís Calafate ◽  
◽  
Sara Calafate ◽  
Keyword(s):  
Brain Plasticity ◽  
Current Debate ◽  
Genetic Inheritance ◽  
Functional Changes ◽  
Learning Capacity ◽  
Enriched Environments ◽  
The One ◽  
External Stimuli ◽  
The Brain

The reflection and discussion on the role of genetic specification and experience in the acquisition of a function and in the development of an individual reflects a fascinating and very current debate among those working in the area of behavior and development. Concerning the development of human behavior and the influence of biological heritage and the envitonment, conflicting and sometimes exclusive positions were established. On the one hand, adherents of genetic inheritance exclude the possibility of the influence of the environment. On the other hand, supporters of the environment exclude genetic inheritance. There is also an eclectic position, reconciling both extremes. Furthermore, within the scope of the trends themselves, differentiating nuances emerge. It is therefore, a very controversial subject to which we dedicate this work from a Neuroscience perspective. We will approach brain neuroplasticity as the ability of the nervous system to change and adapt, in response to internal and external stimuli, including structural and / or functional changes throughout life. Brain plasticity is one of the pillars of learning and memory processes. In short, the role of Neurosciences in the field of Educational Sciences is taking shape and the concept of neuroplasticity is a sine qua non condition for trying to establish a connection between education, behavior and the brain.

The Characterisation of Stereotyped Behaviour in Stalled Sows By Informational Redundancy

Behaviour ◽  
1983 ◽  
Vol 87 (3-4) ◽  
pp. 157-182 ◽  
Author(s):  
A. Stolba ◽  
D.G.M. Wood-Gush ◽  
N. Baker
Keyword(s):  
Operational Definition ◽  
Abnormal Behaviour ◽  
Qualitative And Quantitative ◽  
Focal Animal ◽  
Variable Activity ◽  
Lactating Sows ◽  
External Stimuli ◽  
Sow Stalls ◽  
Firm Evidence ◽  
Lactating Sow

AbstractThis investigation on stereotypies of domestic sows has two aims: 1) to investigate the behavioural profiles shown in the different parities and stages of the reproductive cycle, and 2) to characterise stereotypies by descriptive qualitative and quantitative parameters. As the commonly used functional characteristics of stereotypies were felt to be largely hypothetical at this stage, preventing a deeper understanding of this abnormal behaviour, two purely descriptive approaches were adopted: the first one separated such behaviour from other activities by intuitively essential features, that were condensed into an operational definition. Observations were made on the intensively kept sows of the Edinburgh School of Agriculture pig unit kept in the dry sow house and the lactating sow stalls. From scanning surveys and continuous focal animal samples, behavioural profiles were obtained for the sows of different ages and physiological states. Parity 1 was characterised by frequent and long lasting drowsy stances which probably were a "cut-off" reaction to the unfamiliar Dry-Sow-House environment. In parity 2 and 3 the sows showed increased investigative and manipulative behaviour, but also rapidly emerging stereotyped activities. These increased in kind, frequency and duration over the parities, but were confined to the pregnant animals in the dry sow stalls and virtually absent from the lactating sows which could interact with their piglets. The second approach was to measure the general repetitivity in the behavioural sequences by quantifying their informational content with the redundancy measure C. Both appraoches largely agreed when the intuitively defined stereotyped or non-stereotyped sections of behaviour were assessed for redundancy, the former being significantly more redundant in spite of overlapping C-values. The redundancy of all behaviour, summing variable, positional and stereotyped activities, gradually rose with parity through all cycle stages. In part this was due to the increasing proportion of the intuitively stereotyped sequences, and in part to the increasing redundancy of the remaining variable activity. The redundancy in the stereotyped sequences however remained fairly constant once they were established, and were in all parities well above the levels of variable behaviour. In order to appropriately compare stereotyped and variable activity, redundancies were not only calculated relative to the entire range of elements observed in the stalled dry sows, but also relative to the restricted range of the active elements of all or of each individual sow. All ANOVAs showed significant increases of redundancy over parities, but no effects of pregnancy or interaction to parity. In the discussion the two approaches are compared; from the process of acquiring the sterotypies we then derived the hypothesis, that a likely function could be to reach homeostasis in arousal by warding-off external stimuli and self-generating known sensory input. So far there is nevertheless firm evidence, that stereotypies are signs of major behavioural problems and of concurrently impaired welfare, especially at times of acquisition.

Expression of laminin and beta-1 integrin in embryonic, neonatal, and adult rat heart

1991 ◽  
Vol 49 ◽  
pp. 182-183
Author(s):  
R.L. Price ◽  
T.K. Borg ◽  
L. Terracio ◽  
M. Nakagawa
Keyword(s):  
Temporal Expression ◽  
Qualitative And Quantitative ◽  
Adult Rat ◽  
Cytoplasmic Face ◽  
Extracellular Matrix Components ◽  
Basement Membrane Component ◽  
Beta 1 Integrin ◽  
Quantitative Changes ◽  
Cytoskeletal Elements ◽  
External Face

Little is known about the temporal expression of extracellular matrix components (ECM) and its receptors during development of the heart. Recent reports have shown that ECM components undergo both qualitative and quantitative changes during development, and it is believed that ECM components are important in the regulation of cell migration and cell:cell and cell:ECM recognition and adhesion.Integrins are transmembrane glycoproteins which bind several ECM components on their external face and cytoskeletal elements on the cytoplasmic face. Laminin is a basement membrane component which has been recognized as an important site for cell adhesion. Both the integrins and laminin are expressed early in development and continue to be expressed in the adult heart. With their documented roles in cell recognition, and cell:cell and cell:ECM migration and adhesion these proteins appear to be important components in development of the heart, and their temporal expression may play a pivotal role in morphogenesis and myofibrillogenesis of the heart.

In situ microprobe quantitation of inorganic particle burden in paraffin sections of lung tissue

1988 ◽  
Vol 46 ◽  
pp. 990-991
Author(s):  
Jerrold L. Abraham
Keyword(s):  
Lung Tissue ◽  
Quantitative Information ◽  
Particulate Material ◽  
Paraffin Sections ◽  
Tissue Samples ◽  
Qualitative And Quantitative ◽  
The Past ◽  
Quantitative Analyses ◽  
Data Result

Inorganic particulate material of diverse types is present in the ambient and occupational environment, and exposure to such materials is a well recognized cause of some lung disease. To investigate the interaction of inhaled inorganic particulates with the lung it is necessary to obtain quantitative information on the particulate burden of lung tissue in a wide variety of situations. The vast majority of diagnostic and experimental tissue samples (biopsies and autopsies) are fixed with formaldehyde solutions, dehydrated with organic solvents and embedded in paraffin wax. Over the past 16 years, I have attempted to obtain maximal analytical use of such tissue with minimal preparative steps. Unique diagnostic and research data result from both qualitative and quantitative analyses of sections. Most of the data has been related to inhaled inorganic particulates in lungs, but the basic methods are applicable to any tissues. The preparations are primarily designed for SEM use, but they are stable for storage and transport to other laboratories and several other instruments (e.g., for SIMS techniques).

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

Ordering in Ni4Mo by TEM and APFIM

1987 ◽  
Vol 45 ◽  
pp. 214-215
Author(s):  
E.A. Kenik ◽  
T.A. Zagula ◽  
M.K. Miller ◽  
J. Bentley
Keyword(s):  
Electron Irradiation ◽  
Low Temperatures ◽  
Short Range ◽  
Atom Probe ◽  
Range Order ◽  
Considerable Time ◽  
Probe Field ◽  
Disordered Phase ◽  
Transmission Electron ◽  
Diffraction Patterns

The state of long-range order (LRO) and short-range order (SRO) in Ni4Mo has been a topic of interest for a considerable time (see Brooks et al.). The SRO is often referred to as 1½0 order from the apparent position of the diffuse maxima in diffraction patterns, which differs from the positions of the LRO (D1a) structure. Various studies have shown that a fully disordered state cannot be retained by quenching, as the atomic arrangements responsible for the 1½0 maxima are present at temperatures above the critical ordering temperature for LRO. Over 20 studies have attempted to identify the atomic arrangements associated with this state of order. A variety of models have been proposed, but no consensus has been reached. It has also been shown that 1 MeV electron irradiation at low temperatures (∼100 K) can produce the disordered phase in Ni4Mo. Transmission electron microscopy (TEM), atom probe field ion microscopy (APFIM), and electron irradiation disordering have been applied in the current study to further the understanding of the ordering processes in Ni4Mo.

Qualitative and quantitative assessment of nailfold capillaries by capillaroscopy in healthy volunteers

VASA ◽  
2012 ◽  
Vol 41 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Hoerth ◽  
Kundi ◽  
Katzenschlager ◽  
Hirschl
Keyword(s):  
Scoring System ◽  
Morphological Changes ◽  
Connective Tissue Diseases ◽  
Capillary Density ◽  
Diagnostic Value ◽  
Healthy Individuals ◽  
Extreme Position ◽  
Qualitative And Quantitative ◽  
Diffuse Loss ◽  
Density Results

Background: Nailfold capillaroscopy (NVC) is a diagnostic tool particularly useful in the differential diagnosis of rheumatic and connective tissue diseases. Although successfully applied since many years, little is known about prevalence and distribution of NVC changes in healthy individuals. Probands and methods: NVC was performed in 120 individuals (57 men and 63 women; age 18 to 70 years) randomly selected according to predefined age and sex strata. Diseases associated with NVC changes were excluded. The nailfolds of eight fingers were assessed according to standardized procedures. A scoring system was developed based on the distribution of the number of morphologically deviating capillaries, microhaemorrhages, and capillary density. Results: Only 18 individuals (15 %) had no deviation in morphology, haemorrhages, or capillary density on any finger. Overall 67 % had morphological changes, 48 % had microhaemorrhages, and 40 % of volunteers below 40 years of age and 18 % above age 40 had less than 8 capillaries/mm. Among morphological changes tortous (43 %), ramified (47 %), and bushy capillaries (27 %) were the most frequently altered capillary types. A semiquantitative scoring system was developed in such a way that a score above 1 indicates an extreme position (above the 90th percentile) in the distribution of scores among healthy individuals. Conclusions: Altered capillaries occur frequently among healthy individuals and should be interpreted as normal unless a suspicious increase in their frequency is determined by reference to the scoring system. Megacapillaries and diffuse loss of capillaries were not found and seem to be of specific diagnostic value.

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