scholarly journals Peripheral Contour Grouping and Saccade Targeting: The Role of Mirror Symmetry

Symmetry ◽  
2014 ◽  
Vol 6 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Michaël Sassi ◽  
Maarten Demeyer ◽  
Johan Wagemans
Keyword(s):  
Mirror Symmetry ◽  
Contour Grouping

scholarly journals Pure spin photocurrent in non-centrosymmetric crystals: bulk spin photovoltaic effect

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Haowei Xu ◽  
Hua Wang ◽  
Jian Zhou ◽  
Ju Li
Keyword(s):  
Mirror Symmetry ◽  
Photovoltaic Effect ◽  
Transition Metal Dichalcogenides ◽  
Spin Current ◽  
Pure Spin ◽  
Light Illumination ◽  
Metal Dichalcogenides ◽  
Critical Components ◽  
Topological Crystalline Insulator

AbstractSpin current generators are critical components for spintronics-based information processing. In this work, we theoretically and computationally investigate the bulk spin photovoltaic (BSPV) effect for creating DC spin current under light illumination. The only requirement for BSPV is inversion symmetry breaking, thus it applies to a broad range of materials and can be readily integrated with existing semiconductor technologies. The BSPV effect is a cousin of the bulk photovoltaic (BPV) effect, whereby a DC charge current is generated under light. Thanks to the different selection rules on spin and charge currents, a pure spin current can be realized if the system possesses mirror symmetry or inversion-mirror symmetry. The mechanism of BSPV and the role of the electronic relaxation time $$\tau$$ τ are also elucidated. We apply our theory to several distinct materials, including monolayer transition metal dichalcogenides, anti-ferromagnetic bilayer MnBi2Te4, and the surface of topological crystalline insulator cubic SnTe.

The causal role of the lateral occipital complex in visual mirror symmetry detection and grouping: An fMRI-guided TMS study

Cortex ◽  
2014 ◽  
Vol 51 ◽  
pp. 46-55 ◽  
Author(s):  
Silvia Bona ◽  
Andrew Herbert ◽  
Carlo Toneatto ◽  
Juha Silvanto ◽  
Zaira Cattaneo
Keyword(s):  
Mirror Symmetry ◽  
Causal Role ◽  
Symmetry Detection ◽  
Lateral Occipital Complex

scholarly journals A Neural Model of Figure–Ground Organization

2007 ◽  
Vol 97 (6) ◽  
pp. 4310-4326 ◽  
Author(s):  
Edward Craft ◽  
Hartmut Schütze ◽  
Ernst Niebur ◽  
Rüdiger von der Heydt
Keyword(s):  
Neural Circuits ◽  
Neural Model ◽  
Self Organization ◽  
Lateral Interactions ◽  
Early Visual Cortex ◽  
Experimental Findings ◽  
Psychophysical Studies ◽  
Contour Grouping ◽  
Ground Organization

Psychophysical studies suggest that figure–ground organization is a largely autonomous process that guides—and thus precedes—allocation of attention and object recognition. The discovery of border-ownership representation in single neurons of early visual cortex has confirmed this view. Recent theoretical studies have demonstrated that border-ownership assignment can be modeled as a process of self-organization by lateral interactions within V2 cortex. However, the mechanism proposed relies on propagation of signals through horizontal fibers, which would result in increasing delays of the border-ownership signal with increasing size of the visual stimulus, in contradiction with experimental findings. It also remains unclear how the resulting border-ownership representation would interact with attention mechanisms to guide further processing. Here we present a model of border-ownership coding based on dedicated neural circuits for contour grouping that produce border-ownership assignment and also provide handles for mechanisms of selective attention. The results are consistent with neurophysiological and psychophysical findings. The model makes predictions about the hypothetical grouping circuits and the role of feedback between cortical areas.

scholarly journals Mid-level Priming by Completion vs. Mosaic Solutions

i-Perception ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 204166951882034 ◽  
Author(s):  
Antonio Peta ◽  
Carlo Fantoni ◽  
Walter Gerbino
Keyword(s):  
Image Segmentation ◽  
Mirror Symmetry ◽  
Matching Task ◽  
Structural Factors ◽  
Prime Duration ◽  
Fixation Cross ◽  
Prime Sequence ◽  
Matching Performance ◽  
Contour Curvature

We report two experiments on the role of mid-level processes in image segmentation and completion. In the primed matching task of Experiment 1, a cue→prime sequence was presented before the imperative stimulus consisting of target shapes with positive versus negative contour curvature polarity and one versus two axes of mirror symmetry. Priming shapes were included in two composite occlusion displays with the same T-junction information and different geometric features supporting a distinct balance between completion and mosaic solutions. A cue, either congruent or incongruent with targets, preceded the presentation of the composite priming display. Matching performance was affected by primes in the expected direction, while cue congruency participated only in a marginally significant three-way interaction, and prime duration had no effect. In Experiment 2, the cue→prime sequence was replaced by a fixation cross to control for the priming effect obtained in Experiment 1. The study confirmed that contour connectability and curvature polarity are effective structural factors capable of competing with symmetry in mid-level image segmentation and completion processes.

scholarly journals Mirror Symmetry of Life

2021 ◽  
Author(s):  
Beata Zagórska-Marek
Keyword(s):  
Mirror Symmetry ◽  
Expression Patterns ◽  
Vertical Axis ◽  
Posterior Pole ◽  
Gene Expression Patterns ◽  
Earth Gravity Field ◽  
Earth Gravity ◽  
Recent Developments ◽  
Living Organisms

Functioning in the Earth gravity field imposes on living organisms a necessity to read directions. The characteristic feature of their bodies, regardless unicellular or multicellular, is axial symmetry. The development of body plan orchestrated by spatiotemporal changes in gene expression patterns is based on formation of the vertical and radial axes. Especially for immobile plants, anchored to the substrate, vertical axis is primary and most important. But also in animals the primary is the axis, which defines the anterior and posterior pole of the embryo. There are many little known chiral processes and structures that are left- or right oriented with respect to this axis. Recent developments indicate the role of intrinsic cell chirality that determines the direction of developmental chiral processes in living organisms. The still enigmatic events in cambia of trees and handedness of phyllotaxis as well as plant living crystals are in focus of the chapter.

scholarly journals Young children pause on phrase boundaries in self-paced music listening: The role of harmonic cues

2017 ◽  
Author(s):  
Haley Elisabeth Kragness ◽  
Laurel Trainor
Keyword(s):  
Young Children ◽  
Dwell Time ◽  
Music Listening ◽  
Production Task ◽  
Phrase Boundary ◽  
Melodic Contour ◽  
Child Friendly ◽  
Musical Understanding ◽  
Contour Grouping

Proper segmentation of auditory streams is essential for understanding music. Many cues, including meter, melodic contour, and harmony, influence adults’ perception of musical phrase boundaries. To date, no studies have examined young children’s musical grouping in a production task. We used a musical self-pacing method to investigate (1) whether dwell times index young children’s musical phrase grouping and, if so, (2) whether children dwell longer on phrase boundaries defined by harmonic cues specifically. In Experiment 1, we asked 3-year-old children to self-pace through chord progressions from Bach chorales (sequences in which metrical, harmonic, and melodic contour grouping cues aligned) by pressing a computer key to present each chord in the sequence. Participants dwelled longer on chords in the eighth position, which corresponded to phrase endings. In Experiment 2, we tested 3-, 4-, and 7-year-old children’s sensitivity to harmonic cues to phrase grouping when metrical regularity cues and melodic contour cues were misaligned with the harmonic phrase boundaries. In this case, 7- and 4-year-olds but not 3-year-olds dwelled longer on harmonic phrase boundaries, suggesting that the influence of harmonic cues on phrase boundary perception develops substantially between 3 and 4 years of age in Western children. Overall, we show that the musical dwell time method is child-friendly and can be used to investigate various aspects of young children’s musical understanding, including phrase grouping and harmonic knowledge.

scholarly journals The role of vertical mirror symmetry in visualshape detection

2009 ◽  
Vol 9 (12) ◽  
pp. 11-11 ◽  
Author(s):  
B. Machilsen ◽  
M. Pauwels ◽  
J. Wagemans
Keyword(s):  
Mirror Symmetry

ISOBAR COMPONENTS AND MIRROR SYMMETRY BREAKING IN NUCLEI

1999 ◽  
Vol 08 (01) ◽  
pp. 11-16
Author(s):  
T. BAKER ◽  
B. LASIUK ◽  
C. RANGACHARYULU
Keyword(s):  
Simple Model ◽  
Symmetry Breaking ◽  
Mirror Symmetry ◽  
Degrees Of Freedom ◽  
Percent Level ◽  
Model Description ◽  
Symmetry Properties ◽  
Beta Decays ◽  
Gamow Teller

The possible role of isobar degrees of freedom in nuclear structure accounting for departures from the symmetry properties of mirror nuclei is investigated. Specifically for [Formula: see text] conjugate pairs, we evaluate the corresponding mirror Gamow-Teller beta decays. In a simple model description, admixtures of isobar components at the few percent level can accommodate the experimentally observed asymmetries in mirror pairs of masses A=13 and 17.

scholarly journals The role of color and attention-to-color in mirror-symmetry perception

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Elena Gheorghiu ◽  
Frederick A. A. Kingdom ◽  
Aaron Remkes ◽  
Hyung-Chul O. Li ◽  
Stéphane Rainville
Keyword(s):  
Mirror Symmetry ◽  
Symmetry Perception
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