scholarly journals Effects of generalized pooling on binocular disparity selectivity of neurons in the early visual cortex

2016 ◽  
Vol 371 (1697) ◽  
pp. 20150266 ◽  
Author(s):  
Daisuke Kato ◽  
Mika Baba ◽  
Kota S. Sasaki ◽  
Izumi Ohzawa
Keyword(s):  
Parameter Space ◽  
Three Dimensional ◽  
Stereoscopic Vision ◽  
Dimensional Parameter ◽  
Space Domain ◽  
Spatial Pooling ◽  
Proposed Model ◽  
Early Visual Cortex ◽  
Object Features ◽  
Theoretical Analyses

The key problem of stereoscopic vision is traditionally defined as accurately finding the positional shifts of corresponding object features between left and right images. Here, we demonstrate that the problem must be considered in a four-dimensional parameter space; with respect not only to shifts in space ( X , Y ), but also spatial frequency (SF) and orientation (OR). The proposed model sums outputs of binocular energy units linearly over the multi-dimensional V1 parameter space ( X , Y , SF, OR). Theoretical analyses and physiological experiments show that many binocular neurons achieve sharp binocular tuning properties by pooling the output of multiple neurons with relatively broad tuning. Pooling in the space domain sharpens disparity-selective responses in the SF domain so that the responses to combinations of unmatched left–right SFs are attenuated. Conversely, pooling in the SF domain sharpens disparity selectivity in the space domain, reducing the possibility of false matches. Analogous effects are observed for the OR domain in that the spatial pooling sharpens the binocular tuning in the OR domain. Such neurons become selective to relative OR disparity. Therefore, pooling allows the visual system to refine binocular information into a form more desirable for stereopsis. This article is part of the themed issue ‘Vision in our three-dimensional world’.

Encoding of Three-Dimensional Surface Slant in Cat Visual Areas 17 and 18

2006 ◽  
Vol 95 (5) ◽  
pp. 2768-2786 ◽  
Author(s):  
Takahisa M. Sanada ◽  
Izumi Ohzawa
Keyword(s):  
Alternative Hypothesis ◽  
Three Dimensional ◽  
Correlation Technique ◽  
Three Dimensional Objects ◽  
Spatial Pooling ◽  
Surface Slant ◽  
Visual Areas ◽  
Early Visual Cortex ◽  
Areas 17 And 18 ◽  
Electrophysiological Methods

How are surface orientations of three-dimensional objects and scenes represented in the visual system? We have examined an idea that these surface orientations are encoded by neurons with a variety of tilts in their binocular receptive field (RF) structure. To examine whether neurons in the early visual areas are capable of encoding surface orientations, we have recorded from single neurons extracellularly in areas 17 and 18 of the cat using standard electrophysiological methods. Binocular RF structures are obtained using a binocular version of the reverse correlation technique. About 30% of binocularly responsive neurons have RFs with statistically significant tilts from the frontoparallel plane. The degree of tilts is sufficient for representing the range of surface slants found in typical visual environments. For a subset of neurons having significant RF tilts, the degrees of tilt are correlated with the preferred spatial frequency difference between the two eyes, indicating that a modified disparity energy model can account for the selectivity, at least partially. However, not all cases could be explained by this model, suggesting that multiple mechanisms may be responsible. Therefore an alternative hypothesis is also examined, where the tilt is generated by pooling of multiple disparity detectors whose preferred disparities progressively shift over space. Although there is evidence for extensive spatial pooling, this hypothesis was not satisfactory either, in that the neurons with extensive pooling tended to prefer an untilted surface. Our results suggest that encoding of surface orientations may begin with the binocular neurons in the early visual cortex.

scholarly journals CLOSED CURVES OF GLOBAL BIFURCATIONS IN CHUA'S EQUATION: A MECHANISM FOR THEIR FORMATION

2003 ◽  
Vol 13 (03) ◽  
pp. 609-616 ◽  
Author(s):  
ANTONIO ALGABA ◽  
MANUEL MERINO ◽  
FERNANDO FERNÁNDEZ-SÁNCHEZ ◽  
ALEJANDRO J. RODRÍGUEZ-LUIS
Keyword(s):  
Parameter Space ◽  
Three Dimensional ◽  
Global Bifurcations ◽  
Dimensional Parameter ◽  
Closed Curves

In this work, the presence of closed bifurcation curves of homoclinic and heteroclinic connections has been detected in Chua's equation. We have numerically found and qualitatively described the mechanism of the formation/destruction of such closed curves. We relate this phenomenon to a failure of transversality in a curve of T-points in a three-dimensional parameter space.

Imaginary Scators Bound Set Under the Iterated Quadratic Mapping in 1 + 2 Dimensional Parameter Space

2016 ◽  
Vol 26 (01) ◽  
pp. 1630002 ◽  
Author(s):  
M. Fernández-Guasti
Keyword(s):  
Parameter Space ◽  
Complex Structure ◽  
Three Dimensional ◽  
Periodic Points ◽  
Mandelbrot Set ◽  
Three Dimensions ◽  
Quadratic Mapping ◽  
Two Dimensional ◽  
Dimensional Parameter ◽  
Nilpotent Elements

The quadratic iteration is mapped within a nondistributive imaginary scator algebra in [Formula: see text] dimensions. The Mandelbrot set is identically reproduced at two perpendicular planes where only the scalar and one of the hypercomplex scator director components are present. However, the bound three-dimensional S set projections change dramatically even for very small departures from zero of the second hypercomplex plane. The S set exhibits a rich fractal-like boundary in three dimensions. Periodic points with period [Formula: see text], are shown to be necessarily surrounded by points that produce a divergent magnitude after [Formula: see text] iterations. The scator set comprises square nilpotent elements that ineluctably belong to the bound set. Points that are square nilpotent on the [Formula: see text]th iteration, have preperiod 1 and period [Formula: see text]. Two-dimensional plots are presented to show some of the main features of the set. A three-dimensional rendering reveals the highly complex structure of its boundary.

INTERACTIVE GRAPHICAL EXPLORATION OF MULTIDIMENSIONAL NONLINEAR DYNAMICAL SYSTEMS

1992 ◽  
Vol 02 (02) ◽  
pp. 251-261 ◽  
Author(s):  
JUDY CHALLINGER
Keyword(s):  
Dynamical System ◽  
Parameter Space ◽  
Nonlinear Dynamical Systems ◽  
Nonlinear Dynamical System ◽  
Three Dimensional ◽  
Initial Point ◽  
Unit Cube ◽  
Dimensional Parameter ◽  
Data Set ◽  
Nonlinear Dynamical

This paper discusses the application of an inherently three-dimensional graphical representation tool, isosurfaces, as a means to interactively explore and visualize the attractors of a nonlinear dynamical system with a fifteen-dimensional parameter space. A program has been written which allows the scientist to interactively select and visualize three-dimensional sub-spaces of the fifteen-dimensional parameter space. The dynamical system used to illustrate these concepts is a discrete-time, nonlinear, three-nation Richardson model with economic constraints. This dynamical system, which models the shifting alliances of nations in an arms race, maps an initial point in the unit cube to another point in the unit cube after multiple iterations of the model functions. Using an isosurface function on the resulting volumetric data set, surfaces indicating the changing alliances of nations are generated and rendered.

scholarly journals A unified framework for 21 cm tomography sample generation and parameter inference with progressively growing GANs

2020 ◽  
Vol 493 (4) ◽  
pp. 5913-5927 ◽  
Author(s):  
Florian List ◽  
Geraint F Lewis
Keyword(s):  
Brightness Temperature ◽  
Parameter Space ◽  
Three Dimensional ◽  
Training Data ◽  
X Rays ◽  
Unified Framework ◽  
Generative Adversarial Network ◽  
Dimensional Parameter ◽  
Adversarial Network ◽  
Approximate Bayesian

ABSTRACT Creating a data base of 21 cm brightness temperature signals from the Epoch of Reionization (EoR) for an array of reionization histories is a complex and computationally expensive task, given the range of astrophysical processes involved and the possibly high-dimensional parameter space that is to be probed. We utilize a specific type of neural network, a progressively growing generative adversarial network (PGGAN), to produce realistic tomography images of the 21 cm brightness temperature during the EoR, covering a continuous three-dimensional parameter space that models varying X-ray emissivity, Lyman band emissivity, and ratio between hard and soft X-rays. The GPU-trained network generates new samples at a resolution of ∼3 arcmin in a second (on a laptop CPU), and the resulting global 21 cm signal, power spectrum, and pixel distribution function agree well with those of the training data, taken from the 21SSD catalogue (Semelin et al.). Finally, we showcase how a trained PGGAN can be leveraged for the converse task of inferring parameters from 21 cm tomography samples via Approximate Bayesian Computation.

scholarly journals M-current induced Bogdanov–Takens bifurcation and switching of neuron excitability class

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Isam Al-Darabsah ◽  
Sue Ann Campbell
Keyword(s):  
Parameter Space ◽  
Neuron Model ◽  
Neuronal Excitability ◽  
Three Dimensional ◽  
Leak Current ◽  
Applied Current ◽  
Maximal Conductance ◽  
Dimensional Parameter ◽  
M Current ◽  
Numerical Bifurcation

AbstractIn this work, we consider a general conductance-based neuron model with the inclusion of the acetycholine sensitive, M-current. We study bifurcations in the parameter space consisting of the applied current $I_{app}$ I a p p , the maximal conductance of the M-current $g_{M}$ g M and the conductance of the leak current $g_{L}$ g L . We give precise conditions for the model that ensure the existence of a Bogdanov–Takens (BT) point and show that such a point can occur by varying $I_{app}$ I a p p and $g_{M}$ g M . We discuss the case when the BT point becomes a Bogdanov–Takens–cusp (BTC) point and show that such a point can occur in the three-dimensional parameter space. The results of the bifurcation analysis are applied to different neuronal models and are verified and supplemented by numerical bifurcation diagrams generated using the package . We conclude that there is a transition in the neuronal excitability type organised by the BT point and the neuron switches from Class-I to Class-II as conductance of the M-current increases.

scholarly journals Extraction of Potential Energy from Geostrophic Fronts by Inertial–Symmetric Instabilities

2018 ◽  
Vol 48 (5) ◽  
pp. 1033-1051 ◽  
Author(s):  
Nicolas Grisouard
Keyword(s):  
Potential Energy ◽  
Parameter Space ◽  
Richardson Number ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Dimensional Parameter ◽  
Flow Cells ◽  
Hydrostatic Balance ◽  
Symmetric Instability

AbstractSubmesoscale oceanic density fronts are structures in geostrophic and hydrostatic balance, which are prone to inertial and/or symmetric instabilities. We argue in this article that drainage of potential energy from the geostrophic flow is a significant source of their growth. We illustrate our point with two-dimensional Boussinesq numerical simulations of oceanic density fronts on the f plane. A set of two-dimensional initial conditions covers the submesoscale portion of a three-dimensional parameter space consisting of the Richardson and Rossby numbers and a measure of stratification or latitude. Because we let the lateral density gradient decay with depth, the parameter space map is nontrivial, excluding low-Rossby, low-Richardson combinations. Dissipation and the presence of boundaries select a growing mode of inertial–symmetric instability consisting of flow cells that disturb isopycnal contours. Systematically, these isopycnal displacements correspond to a drainage of potential energy from the geostrophic fronts to the ageostrophic perturbations. In the majority of our experiments, this energy drainage is at least as important as the drainage of kinetic energy from the front. Various constraints, some physical, some numerical, make the energetics in our experiments more related to inertial rather than symmetric instabilities. Our results depend very weakly on the Richardson number and more on the Rossby number and relative stratification.

Sign in / Sign up

Export Citation Format

Share Document