scholarly journals Detecting distortions of peripherally-presented letter stimuli under crowded conditions

2016 ◽  
Author(s):  
Thomas S. A. Wallis ◽  
Saskia Tobias ◽  
Matthias Bethge ◽  
Felix A. Wichmann
Keyword(s):  
Target Letter ◽  
Polar Coordinates ◽  
Retinal Eccentricity ◽  
Visual Features ◽  
Cartesian Space ◽  
Geometric Distortions ◽  
Radial Frequency ◽  
Distortion Type ◽  
Visual Crowding

AbstractWhen visual features in the periphery are close together they become difficult to recognise: something is present but it is unclear what. This is called “crowding”. Here we investigated sensitivity to features in highly familiar shapes (letters) by applying spatial distortions. In Experiment 1, observers detected which of four peripherally-presented (8 deg of retinal eccentricity) target letters was distorted (spatial 4AFC). The letters were presented either isolated or surrounded by four undistorted flanking letters, and distorted with one of two types of distortion at a range of distortion frequencies and amplitudes. The bandpass noise distortion (“BPN”) technique causes spatial distortions in cartesian space, whereas radial frequency distortion (“RF”) causes shifts in polar coordinates. Detecting distortions in target letters was more difficult in the presence of flanking letters, consistent with the effect of crowding. The BPN distortion type showed evidence of tuning, with sensitivity to distortions peaking at approximately 6.5 c/deg for un-flanked letters. The presence of flanking letters causes this peak to rise to approximately 8.5 c/deg. In contrast to the tuning observed for BPN distortions, RF distortion sensitivity increased as the radial frequency of distortion increased. In a series of follow-up experiments we found that sensitivity to distortions is reduced when flanking letters were also distorted, that this held when observers were required to report which target letter was undistorted, and that this held when flanker distortions were always detectable. The perception of geometric distortions in letter stimuli is impaired by visual crowding.

scholarly journals Dissociable effects of visual crowding on the perception of color and motion

2020 ◽  
Vol 117 (14) ◽  
pp. 8196-8202 ◽  
Author(s):  
John A. Greenwood ◽  
Michael J. Parsons
Keyword(s):  
Deleterious Effect ◽  
Peripheral Vision ◽  
The Other ◽  
Correct Recognition ◽  
Visual Features ◽  
Double Dissociation ◽  
Multiple Processes ◽  
Specific Manner ◽  
Visual Crowding ◽  
Selective Mechanism

Our ability to recognize objects in peripheral vision is fundamentally limited by crowding, the deleterious effect of clutter that disrupts the recognition of features ranging from orientation and color to motion and depth. Previous research is equivocal on whether this reflects a singular process that disrupts all features simultaneously or multiple processes that affect each independently. We examined crowding for motion and color, two features that allow a strong test of feature independence. “Cowhide” stimuli were presented 15° in peripheral vision, either in isolation or surrounded by flankers to give crowding. Observers reported either the target direction (clockwise/counterclockwise from upward) or its hue (blue/purple). We first established that both features show systematic crowded errors (biased predominantly toward the flanker identities) and selectivity for target–flanker similarity (with reduced crowding for dissimilar target/flanker elements). The multiplicity of crowding was then tested with observers identifying both features. Here, a singular object-selective mechanism predicts that when crowding is weak for one feature and strong for the other that crowding should be all-or-none for both. In contrast, when crowding was weak for color and strong for motion, errors were reduced for color but remained for motion, and vice versa with weak motion and strong color crowding. This double dissociation reveals that crowding disrupts certain combinations of visual features in a feature-specific manner, ruling out a singular object-selective mechanism. Thus, the ability to recognize one aspect of a cluttered scene, like color, offers no guarantees for the correct recognition of other aspects, like motion.

Spatial Attention Enhances Crowded Stimulus Encoding across Modeled Receptive Fields by Increasing Redundancy of Feature Representations

2021 ◽  
pp. 1-29
Author(s):  
Justin D. Theiss ◽  
Joel D. Bowen ◽  
Michael A. Silver
Keyword(s):  
Spatial Attention ◽  
Spatial Resolution ◽  
Receptive Fields ◽  
Visual Features ◽  
Target Classification ◽  
Dynamic Changes ◽  
Feature Representations ◽  
Feature Interactions ◽  
Spatial Locations ◽  
Visual Crowding

Abstract Any visual system, biological or artificial, must make a trade-off between the number of units used to represent the visual environment and the spatial resolution of the sampling array. Humans and some other animals are able to allocate attention to spatial locations to reconfigure the sampling array of receptive fields (RFs), thereby enhancing the spatial resolution of representations without changing the overall number of sampling units. Here, we examine how representations of visual features in a fully convolutional neural network interact and interfere with each other in an eccentricity-dependent RF pooling array and how these interactions are influenced by dynamic changes in spatial resolution across the array. We study these feature interactions within the framework of visual crowding, a well-characterized perceptual phenomenon in which target objects in the visual periphery that are easily identified in isolation are much more difficult to identify when flanked by similar nearby objects. By separately simulating effects of spatial attention on RF size and on the density of the pooling array, we demonstrate that the increase in RF density due to attention is more beneficial than changes in RF size for enhancing target classification for crowded stimuli. Furthermore, by varying target and flanker spacing, as well as the spatial extent of attention, we find that feature redundancy across RFs has more influence on target classification than the fidelity of the feature representations themselves. Based on these findings, we propose a candidate mechanism by which spatial attention relieves visual crowding through enhanced feature redundancy that is mostly due to increased RF density.

scholarly journals Investigating Visual Crowding of Objects in Complex Real-World Scenes

i-Perception ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 204166952199415
Author(s):  
Ryan V. Ringer ◽  
Allison M. Coy ◽  
Adam M. Larson ◽  
Lester C. Loschky
Keyword(s):  
Object Recognition ◽  
Real World ◽  
Target Location ◽  
Peripheral Vision ◽  
Retinal Eccentricity ◽  
Choice Response ◽  
Natural Scenes ◽  
Found Object ◽  
Visual Crowding ◽  
Effect Experiment

Visual crowding, the impairment of object recognition in peripheral vision due to flanking objects, has generally been studied using simple stimuli on blank backgrounds. While crowding is widely assumed to occur in natural scenes, it has not been shown rigorously yet. Given that scene contexts can facilitate object recognition, crowding effects may be dampened in real-world scenes. Therefore, this study investigated crowding using objects in computer-generated real-world scenes. In two experiments, target objects were presented with four flanker objects placed uniformly around the target. Previous research indicates that crowding occurs when the distance between the target and flanker is approximately less than half the retinal eccentricity of the target. In each image, the spacing between the target and flanker objects was varied considerably above or below the standard (0.5) threshold to either suppress or facilitate the crowding effect. Experiment 1 cued the target location and then briefly flashed the scene image before participants could move their eyes. Participants then selected the target object’s category from a 15-alternative forced choice response set (including all objects shown in the scene). Experiment 2 used eye tracking to ensure participants were centrally fixating at the beginning of each trial and showed the image for the duration of the participant’s fixation. Both experiments found object recognition accuracy decreased with smaller spacing between targets and flanker objects. Thus, this study rigorously shows crowding of objects in semantically consistent real-world scenes.

scholarly journals Dissociable effects of visual crowding on the perception of colour and motion

2019 ◽  
Author(s):  
John A. Greenwood ◽  
Michael J. Parsons
Keyword(s):  
Peripheral Vision ◽  
Population Coding ◽  
Visual Features ◽  
Double Dissociation ◽  
Multiple Processes ◽  
Underlying Mechanisms ◽  
High Level ◽  
Object Features ◽  
Visual Crowding ◽  
Selective Mechanism

AbstractOur ability to recognise objects in peripheral vision is fundamentally limited by crowding, the deleterious effect of clutter that disrupts the recognition of features ranging from orientation and colour to motion and depth. Prior research is equivocal on whether this reflects a singular process that disrupts all features simultaneously or multiple processes that affect each independently. We examined crowding for motion and colour, two features that allow a strong test of feature independence. ‘Cowhide’ stimuli were presented 15 degrees in peripheral vision, either in isolation or surrounded by flankers to give crowding. Observers reported either the target direction (clockwise/counterclockwise from upwards) or its hue (blue/purple). We first established that both features show systematic crowded errors (predominantly biased towards the flanker identities) and selectivity for target-flanker similarity (with reduced crowding for dissimilar target/flanker elements). The multiplicity of crowding was then tested with observers identifying both features: a singular object-selective mechanism predicts that when crowding is weak for one feature and strong for the other that crowding should be all-or-none for both. In contrast, when crowding was weak for colour and strong for motion, errors were reduced for colour but remained for motion, and vice versa with weak motion and strong colour crowding. This double dissociation reveals that crowding disrupts certain combinations of visual features in a feature-specific manner, ruling out a singular object-selective mechanism. The ability to recognise one aspect of a cluttered scene, like colour, thus offers no guarantees for the correct recognition of other aspects, like motion.Significance statementOur peripheral vision is primarily limited by crowding, the disruption to object recognition that arises in clutter. Crowding is widely assumed to be a singular process, affecting all of the features (orientation, motion, colour, etc.) within an object simultaneously. In contrast, we observe a double dissociation whereby observers make errors regarding the colour of a crowded object whilst correctly judging its direction, and vice versa. This dissociation can be reproduced by a population-coding model where the direction and hue of target/flanker elements are pooled independently. The selective disruption of some object features independently of others rules out a singular crowding mechanism, posing problems for high-level crowding theories, and suggesting that the underlying mechanisms may be distributed throughout the visual system.

scholarly journals Influencia del juego interior de la selección española de baloncesto en el rendimiento: análisis de coordenadas polares.

2021 ◽  
Vol 21 (3) ◽  
pp. 179-191
Author(s):  
Juan Pablo Morillo-Baro ◽  
Belén Troyano-Gallegos ◽  
Alberto Alejandre Estable ◽  
Juan Antonio Vázquez-Diz ◽  
Rafael E. Reigal Garrido ◽  
...  
Keyword(s):  
Team Performance ◽  
Team Sports ◽  
Polar Coordinates ◽  
Quality Analysis ◽  
Observational Tool ◽  
Observational Design ◽  
Basketball Team ◽  
Data Quality Analysis ◽  
Do So

En los últimos años se ha incrementado el interés por conocer las acciones más efectivas durante la competición ya que este hecho se ha mostrado esencial para mejorar el rendimiento de los jugadores en el deporte de élite; particularmente en los deportes colectivos el análisis táctico ha crecido de forma exponencial. El objetivo de este estudio fue detectar las relaciones que se establecen entre las conductas de finalización de los jugadores interiores de un equipo de baloncesto y su repercusión en el rendimiento del equipo. Para ello, y utilizando un diseño nomotético, de seguimiento y multidimensional, se realizó un análisis de coordenadas polares con las observaciones del juego de la Selección Española de Baloncesto Senior Masculina durante su participación en el Campeonato de Europa de 2015. La herramienta de observación creada ha superado el análisis de calidad del dato exigible en Metodología Observacional y está compuesta por 5 criterios y 29 categorías exhaustivas y mutuamente excluyentes. Se registraron un total de 316 acciones ofensivas, que pusieron de manifiesto la influencia de los jugadores que ocupan las posiciones interiores en el ataque estático. Los resultados muestran una alta efectividad cuando los ataques son acabados por ellos y la alta producción ofensiva de estos jugadores en acciones individuales, siendo capaces de conseguir canastas o provocar faltas a sus defensores. El análisis de coordenadas polares se ha mostrado como una técnica útil para el análisis táctico de las conductas que suceden en el deporte de competición. In recent years, there has been an increased interest in knowing the most effective actions during competition, as this fact has proven essential to improve the performance of players in elite sport; particularly in team sports, tactical analysis has grown exponentially. The objective of this study was to detect the relationships that were obtained between the finishing behaviors of the inside players of a basketball team and it is impact on team performance. To do so, and using nomothetic, follow-up and multidimensional observational design, polar coordinates analysis was performed from the observations of the game of the Spanish men basketball team during European Championships in 2015. The observational tool, formed by 5 criteria and 29 exhaustive and mutually exclusive categories, was created and passed the data quality analysis required in Observational Methodology. A total of 316 offensive actions were registered and revealed the influence of the inside players in the static attack. The results showed a high effectiveness when the attacks are finished by inside players, and the high offensive production of these players in individual actions, being able to get baskets or cause fouls to their defenders. Polar coordinates analysis has been shown as a useful technique to tactical analysis of the behaviors that occur in competitive sport. Nos últimos anos tem havido um interesse crescente em conhecer as acções mais eficazes durante a competição, uma vez que este facto se revelou essencial para melhorar o desempenho dos jogadores no desporto de elite; particularmente nos desportos colectivos, a análise táctica tem crescido exponencialmente. O objectivo deste estudo era detectar as relações estabelecidas entre os comportamentos finais dos jogadores internos de uma equipa de basquetebol e o seu impacto no desempenho da equipa. Para o fazer, e utilizando um design nomotético, de seguimento e multidimensional, foi realizada uma análise de coordenadas polares com as observações do jogo da Selecção Espanhola de Basquetebol Masculino Sénior durante a sua participação no Campeonato Europeu de 2015. O instrumento de observação criado passou a análise da qualidade dos dados exigida na Metodologia de Observação e é composto por 5 critérios e 29 categorias exaustivas e mutuamente excludentes. Foi registado um total de 316 acções ofensivas, que mostraram a influência de jogadores que ocupavam posições internas no ataque estático. Os resultados mostram uma elevada eficácia quando os ataques são finalizados por eles e a elevada produção ofensiva destes jogadores em acções individuais, podendo obter cestos ou causar faltas aos seus defensores. A análise das coordenadas polares demonstrou ser uma técnica útil para a análise táctica dos comportamentos que ocorrem no desporto de competição.

Therapy and prevention for mental health: What if mental diseases are mostly not brain disorders?

2019 ◽  
Vol 42 ◽  
Author(s):  
John P. A. Ioannidis
Keyword(s):  
Mental Health ◽  
Mental Disease ◽  
Brain Disorders ◽  
Social Stressors ◽  
Labor Education ◽  
Mental Diseases ◽  
Long Term Follow Up ◽  
Political Decisions

AbstractNeurobiology-based interventions for mental diseases and searches for useful biomarkers of treatment response have largely failed. Clinical trials should assess interventions related to environmental and social stressors, with long-term follow-up; social rather than biological endpoints; personalized outcomes; and suitable cluster, adaptive, and n-of-1 designs. Labor, education, financial, and other social/political decisions should be evaluated for their impacts on mental disease.

Brief summary of Kleť photographic search programme for minor planets

1999 ◽  
Vol 173 ◽  
pp. 189-192
Author(s):  
J. Tichá ◽  
M. Tichý ◽  
Z. Moravec
Keyword(s):  
Ccd Camera ◽  
Minor Planet ◽  
Minor Planets ◽  
Main Belt

AbstractA long-term photographic search programme for minor planets was begun at the Kleť Observatory at the end of seventies using a 0.63-m Maksutov telescope, but with insufficient respect for long-arc follow-up astrometry. More than two thousand provisional designations were given to new Kleť discoveries. Since 1993 targeted follow-up astrometry of Kleť candidates has been performed with a 0.57-m reflector equipped with a CCD camera, and reliable orbits for many previous Kleť discoveries have been determined. The photographic programme results in more than 350 numbered minor planets credited to Kleť, one of the world's most prolific discovery sites. Nearly 50 per cent of them were numbered as a consequence of CCD follow-up observations since 1994.This brief summary describes the results of this Kleť photographic minor planet survey between 1977 and 1996. The majority of the Kleť photographic discoveries are main belt asteroids, but two Amor type asteroids and one Trojan have been found.

Non-Polar Variation of Latitude

1972 ◽  
Vol 1 ◽  
pp. 93-101 ◽  
Author(s):  
S. Yumi
Keyword(s):  
Polar Motion ◽  
Polar Coordinates ◽  
Normal Variation ◽  
Latitude Variation ◽  
Local Trend

ABSTRACTAnalysing the residual latitude of the station, local trend in latitude variation other than by the polar motion was found.Residual latitude was calculated for each of 26 stations which gave the continuous records of observation during 6 years comprising — 1962 — 1967 as a difference between observed variation of latitude and – normal variation calculated by the polar coordinates Iderived from all the results of 26 stations.As far as the results during these six years are concerned, local trend at any station it seemed to be expressed in terms of 3λ.Assumed effect of local trend on the coordinates values of the instantaneous pole is also discussed.

Intranuclear Crystals in Regenerating Canine Kidneys

1973 ◽  
Vol 31 ◽  
pp. 412-413
Author(s):  
D.G. Osborne ◽  
L.J. McCormack ◽  
M.O. Magnusson ◽  
W.S. Kiser
Keyword(s):  
Epithelial Cell ◽  
Epithelial Cells ◽  
Tubular Epithelial Cell ◽  
Tubular Epithelial Cells ◽  
Cell Nuclei ◽  
Crystalline Structures ◽  
Small Crystals ◽  
Membrane Bound

During a project in which regenerative changes were studied in autotransplanted canine kidneys, intranuclear crystals were seen in a small number of tubular epithelial cells. These crystalline structures were seen in the control specimens and also in regenerating specimens; the main differences being in size and number of them. The control specimens showed a few tubular epithelial cell nuclei almost completely occupied by large crystals that were not membrane bound. Subsequent follow-up biopsies of the same kidneys contained similar intranuclear crystals but of a much smaller size. Some of these nuclei contained several small crystals. The small crystals occurred at one week following transplantation and were seen even four weeks following transplantation. As time passed, the small crystals appeared to fuse to form larger crystals.

Electron Microscopy of Human Gallstones

1971 ◽  
Vol 29 ◽  
pp. 296-297
Author(s):  
C. Wolpers ◽  
R. Blaschke
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bile Pigment ◽  
X Ray Diffraction ◽  
Triclinic Crystal System ◽  
X Ray ◽  
Follow Up Study ◽  
Infra Red ◽  
Main Components

Scanning microscopy was used to study the surface of human gallstones and the surface of fractures. The specimens were obtained by operation, washed with water, dried at room temperature and shadowcasted with carbon and aluminum. Most of the specimens belong to patients from a series of X-ray follow-up study, examined during the last twenty years. So it was possible to evaluate approximately the age of these gallstones and to get information on the intensity of growing and solving.Cholesterol, a group of bile pigment substances and different salts of calcium, are the main components of human gallstones. By X-ray diffraction technique, infra-red spectroscopy and by chemical analysis it was demonstrated that all three components can be found in any gallstone. In the presence of water cholesterol crystallizes in pane-like plates of the triclinic crystal system.

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