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Sample records for arvo makke juhan

  1. BAO Plate Archive and Armenian Virtual Observatory (ArVO)

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M. 1; Astsatryan, H. V. 2; Magakian, T. Yu. 1; Sargsyan, L. A. 1; Gigoyan, K. S. 1; Erastova, L. K. 1; Gyulzadyan, M. V. 1; Sinamyan, P. K. 1; Paronyan, G. M. 1; Knyazyan, A. V. 2; Mikayelyan, G. A. 1; Farmanyan, S. V. 1; Hovhannisyan, L. R. 1; Nikoghosyan, E. H. 1; Abrahamyan, H. V. 1; Andreasyan, H. R. 1; Azatyan, N. M. 1; Khachatryan, K. G. 1; Kostandyan, G. R. 1; Vardanyan, A. V. 1

    2016-09-01

    A review on Byurakan Astrophysical Observatory (BAO) Plate Archive and Armenian Virtual Observatory (ArVO) projects is given. BAO Plate Archive consists of 37,500 photographic plates and films, obtained with 2.6m telescope, 1m and 0.5m Schmidt telescopes and other smaller ones during 1947-1991. The famous Markarian Survey (or the First Byurakan Survey, FBS) 2000 plates were digitized in 2002-2005 and the Digitized FBS (DFBS, www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on this low-dispersion spectroscopic material. Several other smaller digitization projects have been carried out as well, such as part of Second Byurakan Survey (SBS) plates, photographic chain plates in Coma, where the blazar ON 231 is located and 2.6m film spectra of FBS Blue Stellar Objects. However, most of the plates and films are not digitized. In 2015, we have started a project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage. Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) database will accommodate all new data. The project runs in collaboration with the Armenian Institute of Informatics and Automation Problems (IIAP) and will continue during 3 years in 2015-2017. The final result will be an Electronic Database and online Interactive Sky map to be used for further research projects. ArVO will provide all standards and tools for efficient usage of the scientific output and its integration in international databases.

  2. ARVO-CL: The OpenCL version of the ARVO package — An efficient tool for computing the accessible surface area and the excluded volume of proteins via analytical equations

    NASA Astrophysics Data System (ADS)

    Buša, Ján; Hayryan, Shura; Wu, Ming-Chya; Buša, Ján; Hu, Chin-Kun

    2012-11-01

    Introduction of Graphical Processing Units (GPUs) and computing using GPUs in recent years opened possibilities for simple parallelization of programs. In this update, we present the modernized version of program ARVO [J. Buša, J. Dzurina, E. Hayryan, S. Hayryan, C.-K. Hu, J. Plavka, I. Pokorný, J. Skivánek, M.-C. Wu, Comput. Phys. Comm. 165 (2005) 59]. The whole package has been rewritten in the C language and parallelized using OpenCL. Some new tricks have been added to the algorithm in order to save memory much needed for efficient usage of graphical cards. A new tool called ‘input_structure’ was added for conversion of pdb files into files suitable for work with the C and OpenCL version of ARVO.

  3. Report of the TFOS/ARVO Symposium on global treatments for dry eye disease: an unmet need.

    PubMed

    Sullivan, David A; Hammitt, Katherine M; Schaumberg, Debra A; Sullivan, Benjamin D; Begley, Carolyn G; Gjorstrup, Per; Garrigue, Jean-Sébastien; Nakamura, Masatsugu; Quentric, Yann; Barabino, Stefano; Dalton, Michelle; Novack, Gary D

    2012-04-01

    In September 2010, a Symposium in Florence, Italy, was held to address the unmet need for global treatments for dry eye disease (DED). It was sponsored by The Tear Film & Ocular Surface Society (TFOS; www.TearFilm.org) and co-sponsored by the Association for Research in Vision & Ophthalmology (www.arvo.org). The Symposium objectives were two-fold: first, to discuss accepted and emerging clinical endpoints of DED with regulatory experts from around the world; and second, to consider how to improve clinical trials of treatments for DED. The Symposium focused on the personal and collective burden of DED, as well as the developmental and regulatory challenges associated with generating new DED therapeutics. This article provides a synopsis of many of the presentations, discussions and recommendations of this Symposium. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Association for Research in Vision and Ophthalmology (ARVO)--2010 Annual Meeting. For Sight: The Future of Eye and Vision Research--part 2.

    PubMed

    Hookes, Livia

    2010-07-01

    The 2010 Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO), held in Fort Lauderdale, FL, USA, included topics covering new therapeutic developments in the field of eye and vision research. This conference report highlights selected presentations on the development of OT-440 (Othera Pharmaceuticals Inc) for the potential treatment of glaucoma, an extended-release implant of brimonidine (pSivida Corp) for ocular hypertension, AR-12286 (Aerie Pharmaceuticals Inc) for ocular hypertension or glaucoma, AC-8 (Calmune Corp/RiboVax Biotechnologies SA) for ocular diseases following HSV infection, and fidarestat (Sanwa Kagaku Kenkyusho Co Ltd) and the recombinant proteins NOV and NOVCter (INSERM/University Rene Descartes) for corneal neovascularization.

  5. ARVO: A Fortran package for computing the solvent accessible surface area and the excluded volume of overlapping spheres via analytic equations

    NASA Astrophysics Data System (ADS)

    Buša, Ján; Džurina, Jozef; Hayryan, Edik; Hayryan, Shura; Hu, Chin-Kun; Plavka, Ján; Pokorný, Imrich; Skřivánek, Jaroslav; Wu, Ming-Chya

    2005-01-01

    In calculating the solvation energy of proteins, the hydration effects, drug binding, molecular docking, etc., it is important to have an efficient and exact algorithms for computing the solvent accessible surface area and the excluded volume of macromolecules. Here we present a Fortran package based on the new exact analytical methods for computing volume and surface area of overlapping spheres. In the considered procedure the surface area and volume are expressed as surface integrals of the second kind over the closed region. Using the stereographic projection the surface integrals are transformed to a sum of double integrals which are reduced to the curve integrals. MPI Fortran version is described as well. The package is also useful for computing the percolation probability of continuum percolation models. Program summaryTitle of program: ARVO Catalogue identifier: ADUL Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUL Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Operating system under which the program has been tested: LINUX system and Windows system Programming language used: FORTRAN Computer: PC Pentium; SPP'2000; Number of bytes in distributed program, including test data, etc.: 322 633 Number of lines in distributed program, including test data, etc.: 5051 Distribution format: tar.gz Card punching code: ASCII Nature of physical problem: Molecular mechanics computations, continuum percolations. Method of solution: Numerical algorithm based on the analytical formulas, after using the stereographic transformation. Restriction on the complexity of the problem: The program does not account explicitly for cavities inside the molecule. Typical running time: Depends on the size of the molecule under consideration. Unusual features of the program: No

  6. Science with the Armenian Virtual Observatory (ArVO)

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Sargsyan, L. A.; Gigoyan, K. S.; Erastova, L. K.; Sinamyan, P. K.; Hovhannisyan, L. R.; Massaro, E.; Nesci, R.; Rossi, C.; Gaudenzi, S.; Sclavi, S.; Cirimele, G.; Weedman, D.; Houck, J.; Barry, D.; Sarkissian, A.; Thuillot, W.; Berthier, J.; Prugniel, P.; Kochiashvili, I.; Mikayelyan, G. A.

    The main goal of the Armenian Virtual Observatory is to develop efficient methods for science projects based on the digitized famous Markarian survey (Digitized First Byurakan Survey, DFBS) and other large astronomical databases, both Armenian and international. Two groups of projects are especially productive: search for new interesting objects of definite types by low-dispersion template spectra, and optical identifications of new gamma, X-ray, IR and radio sources. The first one is based on modeling of spectra for a number of types of objects: QSOs, Seyfert galaxies, white dwarfs, subdwarfs, cataclysmic variables, planetary nebulae, C stars, etc. Each kind of object appears in the DFBS with its typical SED and spectral lines (for objects having broad lines only). The search criteria define how many objects will be found for further study, and may restrict these numbers leaving with the best candidates. At present, a number of science projects of search for new objects have been started: search for blue stellar objects, search for extremely red objects, search for variable objects, etc. Optical identifications have been proven to be rather efficient for IR sources from IRAS PSC and FSC. Tests have been carried out for X-ray and radio sources as well.

  7. Science with the Armenian Virtual Observatory (ArVO)

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.

    2007-08-01

    The main goal of the Armenian Virtual Observatory is to develop efficient methods for science projects based on the digitized famous Markarian survey (Digitized First Byurakan Survey, DFBS) and other large astronomical databases, both Armenian and international. Two groups of projects are especially productive: search for new interesting objects of definite types by low-dispersion template spectra, and optical identifications of new gamma, X-ray, IR and radio sources. The first one is based on modeling of spectra for a number of types of objects: QSOs, Seyfert galaxies, white dwarfs, subdwarfs, cataclysmic variables, planetary nebulae, C stars, etc. Each kind of object appears in the DFBS with its typical SED and spectral lines (for objects having broad lines only), however affected also by its brightness, so that each template works for definite range of magnitudes. The search criteria define how many objects will be found for further study, and may restrict these numbers leaving with the best candidates. At present, three projects of search for new objects have been started: search for blue stellar objects (see Sinamyan et al.), search for extremely red objects (see Gigoyan et al.), and search for variable objects (see Hovhannisyan et al.). Optical identifications have been proven to be rather efficient for IR sources from IRAS PSC and FSC. Tests have been carried out for X-ray and radio sources as well.

  8. Armenian virtual observatory simple image access service

    NASA Astrophysics Data System (ADS)

    Knyazyan, A. V.; Astsatryan, H. V.; Mickaelian, A. M.

    2017-04-01

    The aim of the article is to introduce the data sharing service of the Armenian Virtual Observatory (ArVO) based on the Simple Image Access (SIA) Protocol of the International Virtual Observatory Alliance (IVOA).

  9. Ten Years of the Armenian Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Astsatryan, H. V.; Knyazyan, A. V.; Magakian, T. Yu.; Mikayelyan, G. A.; Erastova, L. K.; Hovhannisyan, L. R.; Sargsyan, L. A.; Sinamyan, P. K.

    2016-06-01

    Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) was created 10 years ago, in 2005, when after the accomplishment of the Digitized First Byurakan Survey (DFBS, www.aras.am/Dfbs/dfbs.html) we had enough resources to run a VO project and contribute in the International Virtual Observatory Alliance (IVOA, www.ivoa.net). ArVO is a project of Byurakan Astrophysical Observatory (BAO) aimed at construction of a modern system for data archiving, extraction, acquisition, reduction, use and publication. ArVO technical and research projects include Global Spectroscopic Database, which is being built based on DFBS. Quick optical identification of radio, IR or X-ray sources will be possible by plotting their positions in the DFBS or other spectroscopic plate and matching all available data. Accomplishment of new projects by combining data is so important that the International Council of Scientific Unions (ICSU) recently created World Data System (WDS, www.icsu-wds.org/) for unifying data coming from all science areas, and BAO has also joined it due to DFBS and ArVO projects.

  10. Post-communist lavender menace: lesbians in mainstream East European film.

    PubMed

    Moss, Kevin; Simić, Mima

    2011-01-01

    The article examines four films-Károly Makk's Egymásra nézve (Another Way, Hungary, 1982), Maja Weiss's Varuh meje (Guardian of the Frontier, Slovenia 2002), Dalibor Matanić's Fine mrtve djevojke (Fine Dead Girls, Croatia, 2002), and Dragan Marinković's Diši duboko (Take a Deep Breath, Serbia, 2004)-as post-communist or dissident national allegories. In all of these films by straight directors the lesbians represent a metaphorical threat to the hetero/sexist national order, but they are unfortunately little more than simulacra. They can be emotionally real (and fun for the straight male audience to ogle), but that ultimately works against them, because instead of representing real lesbian communities, they still have to affirm the stereotype of tragic lesbian destiny straight audiences find comforting.

  11. [Monitoring the flux of carbon dioxide gas with tunable diode laser absorption spectroscopy].

    PubMed

    Song, Xue-Mei; Liu, Jian-Guo; Zhang, Yu-Jun; Zeng, Zong-Yong; He, Ying; Cui, Yi-Ben; Chen, Yin; Tian, Yong-Zhi; Zhang, Liang

    2011-01-01

    The greenhouse effect exacerbated by the increase of Carbon-containing gases is the more important causes of the climate change, It is very meaningful to the large-scale flux of carbon dioxide detection for the estimate the contributions of the main greenhouse gases in the atmosphere of various errestrial eco-systems. Tunable diode laser absorption spectroscopy (TDLAS) is a highly sensitive, highly selective and fast time response trace gas detection technique. In the present paper, the authors used a DFB laser was used as the light source, and by employing wavelength modulation method, and measuring the second harmonic signal of one absorption line near 1.573 microm of carbon dioxide molecule, the authors built a system for online monitoring of carbon dioxide concentration within the optical path of more than 700 meters at different heights. Combined with Alonzo Mourning -Obukhov length and characteristic velocity detected by large aperture scintillometer, the flux of carbon dioxide gas within one day calculated by the formula is within--1.5-2.5, breaking through the phenomenon of only providing the flux of trace gases near the ground at present, makking the measurement of trace gas fluxes within a large area possible.

  12. Levels of the Novel Glycoprotein Lacritin in Human Tears After Laser Refractive Surgery

    DTIC Science & Technology

    2013-10-01

    antimicrobial activity in recombinant human lacritin. ARVO, Fort Lauderdale, FL, May 2009. Poster presentation. 7. Netto MV et al. Wound healing in the...13. SUPPLEMENTARY NOTES 14. ABSTRACT Lacritin is a naturally occurring tear protein with antimicrobial activity that is capable of stimulating...with the possibility of the development of recombinant lacritin as a novel therapeutic agent for wound healing. Up to 196 patients eligible to undergo

  13. Non-Invasive Cell-Based Therapy for Traumatic Optic Neuropathy

    DTIC Science & Technology

    2014-10-01

    Functional Changes in an Animal Model of Retinitis Pigmentosa . Vis Neurosci, 2013: 1-13. Bin Lu, Catherine W. Morgans, Sergey Girman, Jing Luo, Jiagang...human retinal progenitor cells for treatment of retinitis pigmentosa 2013, ARVO, A0106. Benjamin Bakondi; YuChun Tsai; Bin Lu; Sergey...degeneration. Pending NEI (R24) Wang (PI) Preclinical program for Treating Retinitis Pigmentosa by Neural Progenitor Cells   18

  14. Achievements of the Armenian Astronomy and the Present Activities of the Armenian Astronomical Society

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2014-10-01

    A report is given on the achievements of the Armenian astronomy during the last years and on the present activities of the Armenian Astronomical Society (ArAS). ArAS membership, ArAS electronic newsletters (ArASNews), ArAS webpage, international collaboration, Armenian Virtual Observatory (ArVO), membership in international organizations, grants, prizes, meetings, summer schools, astronomical Olympiads, other matters related to astronomical education, archaeoastronomy, astronomy outreach and ArAS further projects are discussed.

  15. Armenian Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2015-07-01

    Vast amount of information continuously accumulated in astronomy requires finding new solutions for its efficient storage, use and dissemination, as well as accomplishing new research projects. Virtual Observatories (VOs) have been created in a number of countries to set up a new environment for these tasks. Based on them, the International Virtual Observatory Alliance (IVOA) was created in 2002, which unifies 19 VO projects, including Armenian Virtual Observatory (ArVO) founded in 2005. ArVO is a project of Byurakan Astrophysical Observatory (BAO) aimed at construction of a modern system for data archiving, extraction, acquisition, reduction, use and publication. ArVO technical and research projects are presented, including the Global Spectroscopic Database, which is being built based on Digitized First Byurakan Survey (DFBS). Quick optical identification of radio, IR or X-ray sources will be possible by plotting their positions in the DFBS or other spectroscopic plate and matching all available data. Accomplishment of new projects by combining data is so important that the International Council of Scientific Unions (ICSU) recently created World Data System (WDS) for unifying data coming from all science areas, and BAO has also joined it.

  16. Armenia as a Regional Centre for Astronomy for Development activities

    NASA Astrophysics Data System (ADS)

    Mickaelian, A.

    2015-03-01

    The Byurakan Astrophysical Observatory (BAO, Armenia, http://www.bao.am) are among the candidate IAU Regional Nodes for Astronomy for Development activities. It is one of the main astronomical centers of the former Soviet Union and the Middle East region. At present there are 48 qualified researchers at BAO, including six Doctors of Science and 30 PhDs. Five important observational instruments are installed at BAO, the larger ones being 2.6m Cassegrain (ZTA-2.6) and 1m Schmidt (the one that provided the famous Markarian survey). BAO is regarded as a national scientific-educational center, where a number of activities are being organized, such as: international conferences (4 IAU symposia and 1 IAU colloquium, JENAM-2007, etc.), small workshops and discussions, international summer schools (1987, 2006, 2008 and 2010), and Olympiads. BAO collaborates with scientists from many countries. The Armenian Astronomical Society (ArAS, http://www.aras.am/) is an NGO founded in 2001; it has 93 members and it is rather active in the organization of educational, amateur, popular, promotional and other matters. The Armenian Virtual Observatory (ArVO, http://www.aras.am/Arvo/arvo.htm) is one of the 17 national VO projects forming the International Virtual Observatories Alliance (IVOA) and is the only VO project in the region serving also for educational purposes. A number of activities are planned, such as management, coordination and evaluation of the IAU programs in the area of development and education, establishment of the new IAU endowed lectureship program and organization of seminars and public lectures, coordination and initiation of fundraising activities for astronomy development, organization of regional scientific symposia, conferences and workshops, support to Galileo Teacher Training Program (GTTP), production/publication of educational and promotional materials, etc.

  17. Reflexive OKN is Biased Like Perception

    NASA Technical Reports Server (NTRS)

    Mulligan, Jeffrey B.; Beutter, B. R.; Stevenson, S. B.; Null, Cynthia H. (Technical Monitor)

    1995-01-01

    The classic "barber-pole illusion" demonstrates how the perceived motion of an ambiguous stimulus is influenced by the shape of the viewing aperture: the motion is preferentially seen in the direction of the long axis of the aperture. We have previously reported (ARVO 94) that we are able to continuously vary the strength of this effect by varying the aspect ratio of the window. In the present study we examined the motion of the eyes while subjects viewed such stimuli in an attempt to discover whether the eye movement control system performs the same computation underlying the perceptual judgments.

  18. Direction of Perceived Motion and Eye Movements Show Similar Biases for Asymmetrically Windowed Moving Plaids

    NASA Technical Reports Server (NTRS)

    Beutter, B. R.; Mulligan, J. B.; Stone, L. S.; Hargens, Alan R. (Technical Monitor)

    1995-01-01

    We have shown that moving a plaid in an asymmetric window biases the perceived direction of motion (Beutter, Mulligan & Stone, ARVO 1994). We now explore whether these biased motion signals might also drive the smooth eye-movement response by comparing the perceived and tracked directions. The human smooth oculomotor response to moving plaids appears to be driven by the perceived rather than the veridical direction of motion. This suggests that human motion perception and smooth eye movements share underlying neural motion-processing substrates as has already been shown to be true for monkeys.

  19. Gender Difference in Aerobic Capacity and the Contribution by Body Composition and Haemoglobin Concentration: A Study in Young Indian National Hockey Players

    PubMed Central

    Kailashiya, Jyotsna

    2016-01-01

    Introduction Although gender difference in aerobic capacity is known, the contributing factors have been researched seldom. Aim To investigate the gender gap and the contribution by percentage Body Fat (BF), Body Mass Index (BMI) and haemoglobin concentration Hb. Materials and Methods The study was conducted on 30 (17 males, 13 females) training status matched young hockey players. Healthy players who were playing upto national level competition were included. BW (Body Weight), BF, BMI, LBM (Lean Body Mass), rHR (restring Heart Rate), HRR (Heart Rate Recovery), Hb, a/rVO2max (absolute/relative), a/rPWC (Physical Work Capacity) and RMR (Resting Metabolic Rate) were measured and analysed. Results There was significant gender difference in the measured parameters. Difference in a/rVO2max remained significant even after controlling for BF, BMI and Hb. Multiple regression and correlation analysis revealed gender difference in VO2max/LBM was due to: BMI(31.91%)>BF(27.60%)>Hb(9.91%). BMI also significantly contributed 3.66% of VO2max/LBM variance, independent of that by gender. Difference in RMR was mainly related to LBM, BF and BMI. Conclusion The study provided an understanding for gender gap in aerobic capacity. Differences in BMI & BF were one of the main reasons. PMID:28050360

  20. Crowding by a single bar: probing pattern recognition mechanisms in the visual periphery.

    PubMed

    Põder, Endel

    2014-11-06

    Whereas visual crowding does not greatly affect the detection of the presence of simple visual features, it heavily inhibits combining them into recognizable objects. Still, crowding effects have rarely been directly related to general pattern recognition mechanisms. In this study, pattern recognition mechanisms in visual periphery were probed using a single crowding feature. Observers had to identify the orientation of a rotated T presented briefly in a peripheral location. Adjacent to the target, a single bar was presented. The bar was either horizontal or vertical and located in a random direction from the target. It appears that such a crowding bar has very strong and regular effects on the identification of the target orientation. The observer's responses are determined by approximate relative positions of basic visual features; exact image-based similarity to the target is not important. A version of the "standard model" of object recognition with second-order features explains the main regularities of the data. © 2014 ARVO.

  1. A computational visual saliency model based on statistics and machine learning.

    PubMed

    Lin, Ru-Je; Lin, Wei-Song

    2014-08-01

    Identifying the type of stimuli that attracts human visual attention has been an appealing topic for scientists for many years. In particular, marking the salient regions in images is useful for both psychologists and many computer vision applications. In this paper, we propose a computational approach for producing saliency maps using statistics and machine learning methods. Based on four assumptions, three properties (Feature-Prior, Position-Prior, and Feature-Distribution) can be derived and combined by a simple intersection operation to obtain a saliency map. These properties are implemented by a similarity computation, support vector regression (SVR) technique, statistical analysis of training samples, and information theory using low-level features. This technique is able to learn the preferences of human visual behavior while simultaneously considering feature uniqueness. Experimental results show that our approach performs better in predicting human visual attention regions than 12 other models in two test databases. © 2014 ARVO.

  2. Adaptive optics imaging of the retina.

    PubMed

    Battu, Rajani; Dabir, Supriya; Khanna, Anjani; Kumar, Anupama Kiran; Roy, Abhijit Sinha

    2014-01-01

    Adaptive optics is a relatively new tool that is available to ophthalmologists for study of cellular level details. In addition to the axial resolution provided by the spectral-domain optical coherence tomography, adaptive optics provides an excellent lateral resolution, enabling visualization of the photoreceptors, blood vessels and details of the optic nerve head. We attempt a mini review of the current role of adaptive optics in retinal imaging. PubMed search was performed with key words Adaptive optics OR Retina OR Retinal imaging. Conference abstracts were searched from the Association for Research in Vision and Ophthalmology (ARVO) and American Academy of Ophthalmology (AAO) meetings. In total, 261 relevant publications and 389 conference abstracts were identified.

  3. Adaptive optics imaging of the retina

    PubMed Central

    Battu, Rajani; Dabir, Supriya; Khanna, Anjani; Kumar, Anupama Kiran; Roy, Abhijit Sinha

    2014-01-01

    Adaptive optics is a relatively new tool that is available to ophthalmologists for study of cellular level details. In addition to the axial resolution provided by the spectral-domain optical coherence tomography, adaptive optics provides an excellent lateral resolution, enabling visualization of the photoreceptors, blood vessels and details of the optic nerve head. We attempt a mini review of the current role of adaptive optics in retinal imaging. PubMed search was performed with key words Adaptive optics OR Retina OR Retinal imaging. Conference abstracts were searched from the Association for Research in Vision and Ophthalmology (ARVO) and American Academy of Ophthalmology (AAO) meetings. In total, 261 relevant publications and 389 conference abstracts were identified. PMID:24492503

  4. Spatial statistics and attentional dynamics in scene viewing.

    PubMed

    Engbert, Ralf; Trukenbrod, Hans A; Barthelmé, Simon; Wichmann, Felix A

    2015-01-14

    In humans and in foveated animals visual acuity is highly concentrated at the center of gaze, so that choosing where to look next is an important example of online, rapid decision-making. Computational neuroscientists have developed biologically-inspired models of visual attention, termed saliency maps, which successfully predict where people fixate on average. Using point process theory for spatial statistics, we show that scanpaths contain, however, important statistical structure, such as spatial clustering on top of distributions of gaze positions. Here, we develop a dynamical model of saccadic selection that accurately predicts the distribution of gaze positions as well as spatial clustering along individual scanpaths. Our model relies on activation dynamics via spatially-limited (foveated) access to saliency information, and, second, a leaky memory process controlling the re-inspection of target regions. This theoretical framework models a form of context-dependent decision-making, linking neural dynamics of attention to behavioral gaze data. © 2015 ARVO.

  5. Reinforcing saccadic amplitude variability in a visual search task.

    PubMed

    Paeye, Céline; Madelain, Laurent

    2014-11-20

    Human observers often adopt rigid scanning strategies in visual search tasks, even though this may lead to suboptimal performance. Here we ask whether specific levels of saccadic amplitude variability may be induced in a visual search task using reinforcement learning. We designed a new gaze-contingent visual foraging task in which finding a target among distractors was made contingent upon specific saccadic amplitudes. When saccades of rare amplitudes led to displaying the target, the U values (measuring uncertainty) increased by 54.89% on average. They decreased by 41.21% when reinforcing frequent amplitudes. In a noncontingent control group no consistent change in variability occurred. A second experiment revealed that this learning transferred to conventional visual search trials. These results provide experimental support for the importance of reinforcement learning for saccadic amplitude variability in visual search. © 2014 ARVO.

  6. Volume perception: Disparity extraction and depth representation in complex three-dimensional environments.

    PubMed

    Harris, Julie M

    2014-10-13

    Our sensitivity to binocular disparity is exquisite under the best conditions, typically in uncluttered scenes with few small objects. Yet binocular vision can deliver a very strong impression of depth for complex, cluttered scenes with lots of objects and overlaps. How good is disparity processing under these conditions? Here we explored a novel task: depth volume perception, to study how a global representation of depth is obtained using binocular disparity information. We found that the human visual system is sensitive to depth volume but that the volume perceived is dependent on the local and global arrangement of scene content. We also show how a model of early disparity extraction and combination can account for some of the biases found. Our work shows that the visual system is not able to correctly represent and interpret disparity for all locations in a complex three-dimensional scene. © 2014 ARVO.

  7. Understanding eye movements in face recognition using hidden Markov models.

    PubMed

    Chuk, Tim; Chan, Antoni B; Hsiao, Janet H

    2014-09-16

    We use a hidden Markov model (HMM) based approach to analyze eye movement data in face recognition. HMMs are statistical models that are specialized in handling time-series data. We conducted a face recognition task with Asian participants, and model each participant's eye movement pattern with an HMM, which summarized the participant's scan paths in face recognition with both regions of interest and the transition probabilities among them. By clustering these HMMs, we showed that participants' eye movements could be categorized into holistic or analytic patterns, demonstrating significant individual differences even within the same culture. Participants with the analytic pattern had longer response times, but did not differ significantly in recognition accuracy from those with the holistic pattern. We also found that correct and wrong recognitions were associated with distinctive eye movement patterns; the difference between the two patterns lies in the transitions rather than locations of the fixations alone. © 2014 ARVO.

  8. Eye Movement Latencies to Direction Change for Different Classes of Motion

    NASA Technical Reports Server (NTRS)

    Mulligan, Jeffrey B.; Null, Cynthia H. (Technical Monitor)

    1997-01-01

    In the analysis of visual motion, local features such as orientation are analyzed early in the cortical processing stream (V1), while integration across orientation and space is thought to occur in higher cortical areas such as MT, MST, etc. If all areas provide inputs to eye movement control centers, we would expect that local properties would drive eye movements with relatively short latencies, while global properties would require longer latencies. When such latencies are observed, they can provide information about when (and where?) various stimulus properties are analyzed. To this end, a stimulus was employed in which local and global properties determining perceived direction-of-motion could be manipulated independently: an elliptical Gabor patch with a drifting carrier, with variable orientation of the carrier grating and the contrast window. We have previously demonstrated that the directional percepts evoked by this stimulus vary between the "grating direction" (the normal to the grating's orientation) and the "window direction" (ARVO 91, 94), and that similar effects can be observed in reflexive eye movements (ARVO 95). Subjects viewed such a stimulus while attempting to maintain steady fixation on the center of the pattern, and the small reflexive eye movements ("stare OKN") were recorded. In the middle of the trial, the orientation of either the grating or the window was rotated smoothly by 30 degrees. Responses to the shift of both grating orientation and window orientation are seen in the average OKN slow phase velocity. Grating rotations produce a rapid OKN rotation to the grating direction (100 ms latency, 300 ms time constant), followed by a slower rebound to the steady state perceived direction midway between the grating and window directions. Window rotations, on the other hand, evoke a slower response (200 ms latency, 500 ms time constant). The results demonstrate multiple cortical inputs to eye movement control: a taste early input driven by

  9. Using ClinicalTrials.gov to Supplement Information in Ophthalmology Conference Abstracts about Trial Outcomes: A Comparison Study

    PubMed Central

    Scherer, Roberta W.; Huynh, Lynn; Ervin, Ann-Margret; Dickersin, Kay

    2015-01-01

    Background Including results from unpublished randomized controlled trials (RCTs) in a systematic review may ameliorate the effect of publication bias in systematic review results. Unpublished RCTs are sometimes described in abstracts presented at conferences, included in trials registers, or both. Trial results may not be available in a trials register and abstracts describing RCT results often lack study design information. Complementary information from a trials register record may be sufficient to allow reliable inclusion of an unpublished RCT only available as an abstract in a systematic review. Methods We identified 496 abstracts describing RCTs presented at the 2007 to 2009 Association for Research in Vision and Ophthalmology (ARVO) meetings; 154 RCTs were registered in ClinicalTrials.gov. Two persons extracted verbatim primary and non-primary outcomes reported in the abstract and ClinicalTrials.gov record. We compared each abstract outcome with all ClinicalTrials.gov outcomes and coded matches as complete, partial, or no match. Results We identified 800 outcomes in 152 abstracts (95 primary [51 abstracts] and 705 [141 abstracts] non-primary outcomes). No outcomes were reported in 2 abstracts. Of 95 primary outcomes, 17 (18%) agreed completely, 53 (56%) partially, and 25 (26%) had no match with a ClinicalTrials.gov primary or non-primary outcome. Among 705 non-primary outcomes, 56 (8%) agreed completely, 205 (29%) agreed partially, and 444 (63%) had no match with a ClinicalTrials.gov primary or non-primary outcome. Among the 258 outcomes partially agreeing, we found additional information on the time when the outcome was measured more often in ClinicalTrials.gov than in the abstract (141/258 (55%) versus 55/258 (21%)). We found no association between the presence of non-matching “new” outcomes and year of registration, time to registry update, industry sponsorship, or multi-center status. Conclusion Conference abstracts may be a valuable source of

  10. ClinicalTrials.gov registration can supplement information in abstracts for systematic reviews: a comparison study.

    PubMed

    Scherer, Roberta W; Huynh, Lynn; Ervin, Ann-Margret; Taylor, Jakeisha; Dickersin, Kay

    2013-06-18

    The inclusion of randomized controlled trials (RCTs) reported in conference abstracts in systematic reviews is controversial, partly because study design information and risk of bias is often not fully reported in the abstract. The Association for Research in Vision and Ophthalmology (ARVO) requires trial registration of abstracts submitted for their annual conference as of 2007. Our goal was to assess the feasibility of obtaining study design information critical to systematic reviews, but not typically included in conference abstracts, from the trial registration record. We reviewed all conference abstracts presented at the ARVO meetings from 2007 through 2009, and identified 496 RCTs; 154 had a single matching registration record in ClinicalTrials.gov. Two individuals independently extracted information from the abstract and the ClinicalTrials.gov record, including study design, sample size, inclusion criteria, masking, interventions, outcomes, funder, and investigator name and contact information. Discrepancies were resolved by consensus. We assessed the frequencies of reporting variables appearing in the abstract and the trial register and assessed agreement of information reported in both sources. We found a substantial amount of study design information in the ClinicalTrials.gov record that was unavailable in the corresponding conference abstract, including eligibility criteria associated with gender (83%; 128/154); masking or blinding of study participants (53%, 82/154), persons administering treatment (30%, 46/154), and persons measuring the outcomes (40%, 61/154)); and number of study centers (58%; 90/154). Only 34% (52/154) of abstracts explicitly described a primary outcome, but a primary outcome was included in the "Primary Outcome" field in the ClinicalTrials.gov record for 82% (126/154) of studies. One or more study interventions were reported in each abstract, but agreed exactly with those reported in ClinicalTrials.gov only slightly more than half

  11. Using ClinicalTrials.gov to supplement information in ophthalmology conference abstracts about trial outcomes: a comparison study.

    PubMed

    Scherer, Roberta W; Huynh, Lynn; Ervin, Ann-Margret; Dickersin, Kay

    2015-01-01

    Including results from unpublished randomized controlled trials (RCTs) in a systematic review may ameliorate the effect of publication bias in systematic review results. Unpublished RCTs are sometimes described in abstracts presented at conferences, included in trials registers, or both. Trial results may not be available in a trials register and abstracts describing RCT results often lack study design information. Complementary information from a trials register record may be sufficient to allow reliable inclusion of an unpublished RCT only available as an abstract in a systematic review. We identified 496 abstracts describing RCTs presented at the 2007 to 2009 Association for Research in Vision and Ophthalmology (ARVO) meetings; 154 RCTs were registered in ClinicalTrials.gov. Two persons extracted verbatim primary and non-primary outcomes reported in the abstract and ClinicalTrials.gov record. We compared each abstract outcome with all ClinicalTrials.gov outcomes and coded matches as complete, partial, or no match. We identified 800 outcomes in 152 abstracts (95 primary [51 abstracts] and 705 [141 abstracts] non-primary outcomes). No outcomes were reported in 2 abstracts. Of 95 primary outcomes, 17 (18%) agreed completely, 53 (56%) partially, and 25 (26%) had no match with a ClinicalTrials.gov primary or non-primary outcome. Among 705 non-primary outcomes, 56 (8%) agreed completely, 205 (29%) agreed partially, and 444 (63%) had no match with a ClinicalTrials.gov primary or non-primary outcome. Among the 258 outcomes partially agreeing, we found additional information on the time when the outcome was measured more often in ClinicalTrials.gov than in the abstract (141/258 (55%) versus 55/258 (21%)). We found no association between the presence of non-matching "new" outcomes and year of registration, time to registry update, industry sponsorship, or multi-center status. Conference abstracts may be a valuable source of information about results for outcomes of

  12. ClinicalTrials.gov registration can supplement information in abstracts for systematic reviews: a comparison study

    PubMed Central

    2013-01-01

    Background The inclusion of randomized controlled trials (RCTs) reported in conference abstracts in systematic reviews is controversial, partly because study design information and risk of bias is often not fully reported in the abstract. The Association for Research in Vision and Ophthalmology (ARVO) requires trial registration of abstracts submitted for their annual conference as of 2007. Our goal was to assess the feasibility of obtaining study design information critical to systematic reviews, but not typically included in conference abstracts, from the trial registration record. Methods We reviewed all conference abstracts presented at the ARVO meetings from 2007 through 2009, and identified 496 RCTs; 154 had a single matching registration record in ClinicalTrials.gov. Two individuals independently extracted information from the abstract and the ClinicalTrials.gov record, including study design, sample size, inclusion criteria, masking, interventions, outcomes, funder, and investigator name and contact information. Discrepancies were resolved by consensus. We assessed the frequencies of reporting variables appearing in the abstract and the trial register and assessed agreement of information reported in both sources. Results We found a substantial amount of study design information in the ClinicalTrials.gov record that was unavailable in the corresponding conference abstract, including eligibility criteria associated with gender (83%; 128/154); masking or blinding of study participants (53%, 82/154), persons administering treatment (30%, 46/154), and persons measuring the outcomes (40%, 61/154)); and number of study centers (58%; 90/154). Only 34% (52/154) of abstracts explicitly described a primary outcome, but a primary outcome was included in the “Primary Outcome” field in the ClinicalTrials.gov record for 82% (126/154) of studies. One or more study interventions were reported in each abstract, but agreed exactly with those reported in Clinical

  13. A computational theory of da Vinci stereopsis.

    PubMed

    Tsirlin, Inna; Wilcox, Laurie M; Allison, Robert S

    2014-06-09

    In binocular vision, occlusion of one object by another gives rise to monocular occlusions—regions visible only in one eye. Although binocular disparities cannot be computed for these regions, monocular occlusions can be precisely localized in depth and can induce the perception of illusory occluding surfaces. The phenomenon of depth perception from monocular occlusions, known as da Vinci stereopsis, is intriguing, but its mechanisms are not well understood. We first propose a theory of the mechanisms underlying da Vinci stereopsis that is based on the psychophysical and computational literature on monocular occlusions. It postulates, among other principles, that monocular areas are detected explicitly, and depth from occlusions is calculated based on constraints imposed by occlusion geometry. Next, we describe a biologically inspired computational model based on this theory that successfully reconstructs depth in a large range of stimuli and produces results similar to those described in the psychophysical literature. These results demonstrate that the proposed neural architecture could underpin da Vinci stereopsis and other stereoscopic percepts. © 2014 ARVO.

  14. Simulated disparity and peripheral blur interact during binocular fusion.

    PubMed

    Maiello, Guido; Chessa, Manuela; Solari, Fabio; Bex, Peter J

    2014-07-17

    We have developed a low-cost, practical gaze-contingent display in which natural images are presented to the observer with dioptric blur and stereoscopic disparity that are dependent on the three-dimensional structure of natural scenes. Our system simulates a distribution of retinal blur and depth similar to that experienced in real-world viewing conditions by emmetropic observers. We implemented the system using light-field photographs taken with a plenoptic camera which supports digital refocusing anywhere in the images. We coupled this capability with an eye-tracking system and stereoscopic rendering. With this display, we examine how the time course of binocular fusion depends on depth cues from blur and stereoscopic disparity in naturalistic images. Our results show that disparity and peripheral blur interact to modify eye-movement behavior and facilitate binocular fusion, and the greatest benefit was gained by observers who struggled most to achieve fusion. Even though plenoptic images do not replicate an individual’s aberrations, the results demonstrate that a naturalistic distribution of depth-dependent blur may improve 3-D virtual reality, and that interruptions of this pattern (e.g., with intraocular lenses) which flatten the distribution of retinal blur may adversely affect binocular fusion. © 2014 ARVO.

  15. Optical angular constancy is maintained as a navigational control strategy when pursuing robots moving along complex pathways.

    PubMed

    Wang, Wei; McBeath, Michael K; Sugar, Thomas G

    2015-03-24

    The optical navigational control strategy used to intercept moving targets was explored using a real-world object that travels along complex, evasive pathways. Fielders ran across a gymnasium attempting to catch a moving robot that varied in speed and direction, while ongoing position was measured using an infrared motion-capture system. Fielder running paths were compared with the predictions of three lateral control models, each based on maintaining a particular optical angle relative to the robotic target: (a) constant alignment angle (CAA), (b) constant eccentricity angle (CEA), and (c) linear optical trajectory (LOT). Findings reveal that running pathways were most consistent with maintenance of LOT and least consistent with CEA. This supports that fielders use the same optical control strategy of maintaining angular constancy using a LOT when navigating toward targets moving along complex pathways as when intercepting simple ballistic trajectories. In those cases in which a target dramatically deviates from its optical path, fielders appear to simply reset LOT parameters using a new constant angle value. Maintenance of such optical angular constancy has now been shown to work well with ballistic, complex, and evasive moving targets, confirming the LOT strategy as a robust, general-purpose optical control mechanism for navigating to intercept catchable targets, both airborne and ground based. © 2015 ARVO.

  16. Individual differences in visual field shape modulate the effects of attention on the lower visual field advantage in crowding.

    PubMed

    Fortenbaugh, Francesca C; Silver, Michael A; Robertson, Lynn C

    2015-02-12

    It has previously been reported that visual crowding of a target by flankers is stronger in the upper visual field than in the lower, and this finding has been attributed to greater attentional resolution in the lower hemifield (He, Cavanagh, & Intriligator, 1996). Here we show that the upper/lower asymmetry in visual crowding can be explained by natural variations in the borders of each individual's visual field. Specifically, asymmetry in crowding along the vertical meridian can be almost entirely accounted for by replacing the conventional definition of visual field location, in units of degrees of visual angle, with a definition based on the ratio of the extents of an individual's upper and lower visual field. We also show that the upper/lower crowding asymmetry is eliminated when stimulus eccentricity is expressed in units of percentage of visual field extent but is present when the conventional measure of visual angle is used. We further demonstrate that the relationship between visual field extent and perceptual asymmetry is most evident when participants are able to focus their attention on the target location. These results reveal important influences of visual field boundaries on visual perception, even for visual field locations far from those boundaries. © 2015 ARVO.

  17. Time to wave good-bye to phase scrambling: creating controlled scrambled images using diffeomorphic transformations.

    PubMed

    Stojanoski, Bobby; Cusack, Rhodri

    2014-10-09

    To isolate the neural mechanisms associated with recognizing objects from those processing basic visual properties, control stimuli are required that contain the same perceptual properties as the objects but are unrecognizable. We demonstrate that conventional methods for generating control stimuli (phase scrambling, box scrambling, texture scrambling) yield poor controls because they dramatically distort the basic visual properties (e.g., spatial frequency, perceptual organization) to which even the earliest stages of visual processing are sensitive. We developed a new scrambling method, using a diffeomorphic transformation that preserves the basic perceptual properties of the image while removing meaning. We acquired perceptual ratings to determine the least amount of scrambling necessary to remove recognition. We hypothesized that our "diffeomorphic" images would produce neural activity at the earliest stages of the visual system that more closely matched activity in response to intact images relative to the other scrambling methods. To test this hypothesis, we used the HMAX computational model of object recognition and compared the simulated neural activity at the earliest stages of the visual system (layers S1, C1, and S2) between a set of 149 images scrambled using each distortion method to their intact version. We found that scrambled "diffeomorphed" images were indistinguishable to intact images in each layer of the model, but all of the other distortion methods yielded quite different patterns. Our results indicate that "diffeomorphed" images serve as more appropriate control stimuli in neuroimaging studies that aim to disentangle the representations of perceptual and semantic object properties. © 2014 ARVO.

  18. How the visual aspects can be crucial in reading acquisition? The intriguing case of crowding and developmental dyslexia.

    PubMed

    Gori, Simone; Facoetti, Andrea

    2015-01-14

    Developmental dyslexia (DD) is the most common neurodevelopmental disorder (about 10% of children across cultures) characterized by severe difficulties in learning to read. According to the dominant view, DD is considered a phonological processing impairment that might be linked to a cross-modal, letter-to-speech sound integration deficit. However, new theories-supported by consistent data-suggest that mild deficits in low-level visual and auditory processing can lead to DD. This evidence supports the probabilistic and multifactorial approach for DD. Among others, an interesting visual deficit that is often associated with DD is excessive visual crowding. Crowding is defined as difficulty in the ability to recognize objects when surrounded by similar items. Crowding, typically observed in peripheral vision, could be modulated by attentional processes. The direct consequence of stronger crowding on reading is the inability to recognize letters when they are surrounded by other letters. This problem directly translates to reading at a slower speed and being more prone to making errors while reading. Our aim is to review the literature supporting the important role of crowding in DD. Moreover, we are interested in proposing new possible studies in order to clarify whether the observed excessive crowding could be a cause rather than an effect of DD. Finally, we also suggest possible remediation and even prevention programs that could be based on reducing the crowding in children with or at risk for DD without involving any phonological or orthographic training. © 2015 ARVO.

  19. Can walking motions improve visually induced rotational self-motion illusions in virtual reality?

    PubMed

    Riecke, Bernhard E; Freiberg, Jacob B; Grechkin, Timofey Y

    2015-02-04

    Illusions of self-motion (vection) can provide compelling sensations of moving through virtual environments without the need for complex motion simulators or large tracked physical walking spaces. Here we explore the interaction between biomechanical cues (stepping along a rotating circular treadmill) and visual cues (viewing simulated self-rotation) for providing stationary users a compelling sensation of rotational self-motion (circular vection). When tested individually, biomechanical and visual cues were similarly effective in eliciting self-motion illusions. However, in combination they yielded significantly more intense self-motion illusions. These findings provide the first compelling evidence that walking motions can be used to significantly enhance visually induced rotational self-motion perception in virtual environments (and vice versa) without having to provide for physical self-motion or motion platforms. This is noteworthy, as linear treadmills have been found to actually impair visually induced translational self-motion perception (Ash, Palmisano, Apthorp, & Allison, 2013). Given the predominant focus on linear walking interfaces for virtual-reality locomotion, our findings suggest that investigating circular and curvilinear walking interfaces offers a promising direction for future research and development and can help to enhance self-motion illusions, presence and immersion in virtual-reality systems. © 2015 ARVO.

  20. Simulating newborn face perception.

    PubMed

    von Hofsten, Olov; von Hofsten, Claes; Sulutvedt, Unni; Laeng, Bruno; Brennen, Tim; Magnussen, Svein

    2014-11-18

    A frequently asked question concerns what a newborn infant can actually see. The contrast sensitivity function of newborn infants is well known, but its implications for the ability of newborns to perceive faces of adults remain unclear. We filtered gray scale animations of facial expressions in terms of both spatial frequency and contrast to correspond to the properties of newborn infants' acuity and showed them to adult participants. We reasoned that if adults were unable to identify the depicted facial expressions, then it would also seem unlikely that newborn infants could identify the same expressions. We found that for the simulated acuity the different expressions could be rather well identified at a distance of 30 cm, but when the distance was increased to 120 cm their discriminability was much degraded. This shows that although the perception of faces and facial expressions can function at the low visual resolution of the newborn infant, it is insufficient for distinguishing faces and facial expressions at moderate distances. © 2014 ARVO.

  1. Visual sensitivity is a stronger determinant of illusory processes than auditory cue parameters in the sound-induced flash illusion.

    PubMed

    Kumpik, Daniel P; Roberts, Helen E; King, Andrew J; Bizley, Jennifer K

    2014-06-24

    The sound-induced flash illusion (SIFI) is a multisensory perceptual phenomenon in which the number of brief visual stimuli perceived by an observer is influenced by the number of concurrently presented sounds. While the strength of this illusion has been shown to be modulated by the temporal congruence of the stimuli from each modality, there is conflicting evidence regarding its dependence upon their spatial congruence. We addressed this question by examining SIFIs under conditions in which the spatial reliability of the visual stimuli was degraded and different sound localization cues were presented using either free-field or closed-field stimulation. The likelihood of reporting a SIFI varied with the spatial cue composition of the auditory stimulus and was highest when binaural cues were presented over headphones. SIFIs were more common for small flashes than for large flashes, and for small flashes at peripheral locations, subjects experienced a greater number of illusory fusion events than fission events. However, the SIFI was not dependent on the spatial proximity of the audiovisual stimuli, but was instead determined primarily by differences in subjects' underlying sensitivity across the visual field to the number of flashes presented. Our findings indicate that the influence of auditory stimulation on visual numerosity judgments can occur independently of the spatial relationship between the stimuli. © 2014 ARVO.

  2. BAO Plate Archive Project: Digitization, Electronic Database and Research Programmes

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Abrahamyan, H. V.; Andreasyan, H. R.; Azatyan, N. M.; Farmanyan, S. V.; Gigoyan, K. S.; Gyulzadyan, M. V.; Khachatryan, K. G.; Knyazyan, A. V.; Kostandyan, G. R.; Mikayelyan, G. A.; Nikoghosyan, E. H.; Paronyan, G. M.; Vardanyan, A. V.

    2016-06-01

    The most important part of the astronomical observational heritage are astronomical plate archives created on the basis of numerous observations at many observatories. Byurakan Astrophysical Observatory (BAO) plate archive consists of 37,000 photographic plates and films, obtained at 2.6m telescope, 1m and 0.5m Schmidt type and other smaller telescopes during 1947-1991. In 2002-2005, the famous Markarian Survey (also called First Byurakan Survey, FBS) 1874 plates were digitized and the Digitized FBS (DFBS) was created. New science projects have been conducted based on these low-dispersion spectroscopic material. A large project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage was started in 2015. A Science Program Board is created to evaluate the observing material, to investigate new possibilities and to propose new projects based on the combined usage of these observations together with other world databases. The Executing Team consists of 11 astronomers and 2 computer scientists and will use 2 EPSON Perfection V750 Pro scanners for the digitization, as well as Armenian Virtual Observatory (ArVO) database will be used to accommodate all new data. The project will run during 3 years in 2015-2017 and the final result will be an electronic database and online interactive sky map to be used for further research projects, mainly including high proper motion stars, variable objects and Solar System bodies.

  3. An experimental method for the assessment of color simulation tools.

    PubMed

    Lillo, Julio; Alvaro, Leticia; Moreira, Humberto

    2014-07-22

    The Simulcheck method for evaluating the accuracy of color simulation tools in relation to dichromats is described and used to test three color simulation tools: Variantor, Coblis, and Vischeck. A total of 10 dichromats (five protanopes, five deuteranopes) and 10 normal trichromats participated in the current study. Simulcheck includes two psychophysical tasks: the Pseudoachromatic Stimuli Identification task and the Minimum Achromatic Contrast task. The Pseudoachromatic Stimuli Identification task allows determination of the two chromatic angles (h(uv) values) that generate a minimum response in the yellow–blue opponent mechanism and, consequently, pseudoachromatic stimuli (greens or reds). The Minimum Achromatic Contrast task requires the selection of the gray background that produces minimum contrast (near zero change in the achromatic mechanism) for each pseudoachromatic stimulus selected in the previous task (L(R) values). Results showed important differences in the colorimetric transformations performed by the three evaluated simulation tools and their accuracy levels. Vischeck simulation accurately implemented the algorithm of Brettel, Viénot, and Mollon (1997). Only Vischeck appeared accurate (similarity in huv and L(R) values between real and simulated dichromats) and, consequently, could render reliable color selections. It is concluded that Simulcheck is a consistent method because it provided an equivalent pattern of results for huv and L(R) values irrespective of the stimulus set used to evaluate a simulation tool. Simulcheck was also considered valid because real dichromats provided expected huv and LR values when performing the two psychophysical tasks included in this method. © 2014 ARVO.

  4. The effect of contrast on monocular versus binocular reading performance.

    PubMed

    Johansson, Jan; Pansell, Tony; Ygge, Jan; Seimyr, Gustaf Öqvist

    2014-05-14

    The binocular advantage in reading performance is typically small. On the other hand research shows binocular reading to be remarkably robust to degraded stimulus properties. We hypothesized that this robustness may stem from an increasing binocular contribution. The main objective was to compare monocular and binocular performance at different stimulus contrasts and assess the level of binocular superiority. A secondary objective was to assess any asymmetry in performance related to ocular dominance. In a balanced repeated measures experiment 18 subjects read texts at three levels of contrast monocularly and binocularly while their eye movements were recorded. The binocular advantage increased with reduced contrast producing a 7% slower monocular reading at 40% contrast, 9% slower at 20% contrast, and 21% slower at 10% contrast. A statistically significant interaction effect was found in fixation duration displaying a more adverse effect in the monocular condition at lowest contrast. No significant effects of ocular dominance were observed. The outcome suggests that binocularity contributes increasingly to reading performance as stimulus contrast decreases. The strongest difference between monocular and binocular performance was due to fixation duration. The findings may pose a clinical point that it may be necessary to consider tests at different contrast levels when estimating reading performance. © 2014 ARVO.

  5. Relative contributions of task-relevant and task-irrelevant dimensions in priming of pop-out.

    PubMed

    Michal, Audrey L; Lleras, Alejandro; Beck, Diane M

    2014-10-13

    Intertrial effects such as priming of pop-out (PoP) often occur for task-irrelevant dimensions as well as task-relevant dimensions, though to a weaker extent. Here we test the hypothesis that increased priming for task-relevant dimensions is due to greater passive build-up of priming for the task-relevant dimension rather than to an active filtering of task-irrelevant dimensions; if this is the case, then we should observe a positive correlation between the magnitude of task-relevant and task-irrelevant priming. We tested this hypothesis using a pop-out search task in which the task-relevant dimension was orientation and the task-irrelevant dimension was color. We found a strong, positive association between task-relevant and task-irrelevant priming across a large group of participants (N = 100); additionally, we observed increased priming over consecutive repetitions for the task-relevant dimension, whereas task-irrelevant priming was constant across multiple repetitions. As further evidence against an active filtering account, task-irrelevant priming showed no systematic relationship with visual short-term memory capacity, which has been shown to correlate with filtering ability. Together, our results suggest that task-irrelevant dimensions are co-selected rather than filtered out during target search. Further, increased task-relevant priming may reflect an enhanced representation of the task-relevant dimension that is reinforced over consecutive repetitions. © 2014 ARVO.

  6. Spatial vision is superior in musicians when memory plays a role.

    PubMed

    Weiss, Atalia H; Biron, Tali; Lieder, Itay; Granot, Roni Y; Ahissar, Merav

    2014-08-21

    Musicians' perceptual advantage in the acoustic domain is well established. Recent studies show that musicians' verbal working memory is also superior. Additionally, some studies report that musicians' visuospatial skills are enhanced although others failed to find this enhancement. We now examined whether musicians' spatial vision is superior, and if so, whether this superiority reflects refined visual skills or a general superiority of working memory. We examined spatial frequency discrimination among musicians and nonmusician university students using two presentation conditions: simultaneous (spatial forced choice) and sequential (temporal forced choice). Musicians' performance was similar to that of nonmusicians in the simultaneous condition. However, their performance in the sequential condition was superior, suggesting an advantage only when stimuli need to be retained, i.e., working memory. Moreover, the two groups showed a different pattern of correlations: Musicians' visual thresholds were correlated, and neither was correlated with their verbal memory. By contrast, among nonmusicians, the visual thresholds were not correlated, but sequential thresholds were correlated with verbal memory scores, suggesting that a general working memory component limits their performance in this condition. We propose that musicians' superiority in spatial frequency discrimination reflects an advantage in a domain-general aspect of working memory rather than a general enhancement in spatial-visual skills. © 2014 ARVO.

  7. The sensory strength of voluntary visual imagery predicts visual working memory capacity.

    PubMed

    Keogh, Rebecca; Pearson, Joel

    2014-10-09

    How much we can actively hold in mind is severely limited and differs greatly from one person to the next. Why some individuals have greater capacities than others is largely unknown. Here, we investigated why such large variations in visual working memory (VWM) capacity might occur, by examining the relationship between visual working memory and visual mental imagery. To assess visual working memory capacity participants were required to remember the orientation of a number of Gabor patches and make subsequent judgments about relative changes in orientation. The sensory strength of voluntary imagery was measured using a previously documented binocular rivalry paradigm. Participants with greater imagery strength also had greater visual working memory capacity. However, they were no better on a verbal number working memory task. Introducing a uniform luminous background during the retention interval of the visual working memory task reduced memory capacity, but only for those with strong imagery. Likewise, for the good imagers increasing background luminance during imagery generation reduced its effect on subsequent binocular rivalry. Luminance increases did not affect any of the subgroups on the verbal number working memory task. Together, these results suggest that luminance was disrupting sensory mechanisms common to both visual working memory and imagery, and not a general working memory system. The disruptive selectivity of background luminance suggests that good imagers, unlike moderate or poor imagers, may use imagery as a mnemonic strategy to perform the visual working memory task. © 2014 ARVO.

  8. Basic-level categorization of intermediate complexity fragments reveals top-down effects of expertise in visual perception.

    PubMed

    Harel, Assaf; Ullman, Shimon; Harari, Danny; Bentin, Shlomo

    2011-07-28

    Visual expertise is usually defined as the superior ability to distinguish between exemplars of a homogeneous category. Here, we ask how real-world expertise manifests at basic-level categorization and assess the contribution of stimulus-driven and top-down knowledge-based factors to this manifestation. Car experts and novices categorized computer-selected image fragments of cars, airplanes, and faces. Within each category, the fragments varied in their mutual information (MI), an objective quantifiable measure of feature diagnosticity. Categorization of face and airplane fragments was similar within and between groups, showing better performance with increasing MI levels. Novices categorized car fragments more slowly than face and airplane fragments, while experts categorized car fragments as fast as face and airplane fragments. The experts' advantage with car fragments was similar across MI levels, with similar functions relating RT with MI level for both groups. Accuracy was equal between groups for cars as well as faces and airplanes, but experts' response criteria were biased toward cars. These findings suggest that expertise does not entail only specific perceptual strategies. Rather, at the basic level, expertise manifests as a general processing advantage arguably involving application of top-down mechanisms, such as knowledge and attention, which helps experts to distinguish between object categories. © ARVO

  9. The cost of misremembering: Inferring the loss function in visual working memory.

    PubMed

    Sims, Chris R

    2015-03-04

    Visual working memory (VWM) is a highly limited storage system. A basic consequence of this fact is that visual memories cannot perfectly encode or represent the veridical structure of the world. However, in natural tasks, some memory errors might be more costly than others. This raises the intriguing possibility that the nature of memory error reflects the costs of committing different kinds of errors. Many existing theories assume that visual memories are noise-corrupted versions of afferent perceptual signals. However, this additive noise assumption oversimplifies the problem. Implicit in the behavioral phenomena of visual working memory is the concept of a loss function: a mathematical entity that describes the relative cost to the organism of making different types of memory errors. An optimally efficient memory system is one that minimizes the expected loss according to a particular loss function, while subject to a constraint on memory capacity. This paper describes a novel theoretical framework for characterizing visual working memory in terms of its implicit loss function. Using inverse decision theory, the empirical loss function is estimated from the results of a standard delayed recall visual memory experiment. These results are compared to the predicted behavior of a visual working memory system that is optimally efficient for a previously identified natural task, gaze correction following saccadic error. Finally, the approach is compared to alternative models of visual working memory, and shown to offer a superior account of the empirical data across a range of experimental datasets. © 2015 ARVO.

  10. Changing viewer perspectives reveals constraints to implicit visual statistical learning.

    PubMed

    Jiang, Yuhong V; Swallow, Khena M

    2014-10-07

    Statistical learning-learning environmental regularities to guide behavior-likely plays an important role in natural human behavior. One potential use is in search for valuable items. Because visual statistical learning can be acquired quickly and without intention or awareness, it could optimize search and thereby conserve energy. For this to be true, however, visual statistical learning needs to be viewpoint invariant, facilitating search even when people walk around. To test whether implicit visual statistical learning of spatial information is viewpoint independent, we asked participants to perform a visual search task from variable locations around a monitor placed flat on a stand. Unbeknownst to participants, the target was more often in some locations than others. In contrast to previous research on stationary observers, visual statistical learning failed to produce a search advantage for targets in high-probable regions that were stable within the environment but variable relative to the viewer. This failure was observed even when conditions for spatial updating were optimized. However, learning was successful when the rich locations were referenced relative to the viewer. We conclude that changing viewer perspective disrupts implicit learning of the target's location probability. This form of learning shows limited integration with spatial updating or spatiotopic representations. © 2014 ARVO.

  11. Parameter recovery for the time-window-of-integration (TWIN) model of multisensory integration in focused attention.

    PubMed

    Kandil, Farid I; Diederich, Adele; Colonius, Hans

    2014-09-24

    In multisensory settings such as the focused attention paradigm (FAP), subjects are instructed to respond to stimuli of the target modality only, yet reaction times tend to be shorter if an unattended stimulus is presented within a certain spatiotemporal vicinity of the target. The time window of integration (TWIN) model predicts successfully these observed cross-modal reaction time effects. It proposes that all the initially unimodal information must arrive at a point of integration within a certain time window in order to be integrated and thus to initiate response enhancements like the observed reaction time reductions. Here we conducted a parameter recovery study of the TWIN model for focused attention tasks, with five parameters (the durations of the visual and auditory unimodal and the integrated second stage, the width of the time window, and the effect size). Results show that parameter estimates were highly accurate (unbiased, constant error less than 5 ms) and precise (variable error less than 8 ms) throughout, speaking to a high reliability and criterion validity of the process. Further analyses ensured that the estimation procedure is consistent and sufficiently robust against contamination (faulty integration). It can thus be used to estimate reliably the point of integration and the width of the time window. © 2014 ARVO.

  12. BAO Plate Archive digitization, creation of electronic database and its scientific usage

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.

    2015-08-01

    Astronomical plate archives created on the basis of numerous observations at many observatories are important part of the astronomical heritage. Byurakan Astrophysical Observatory (BAO) plate archive consists of 37,500 photographic plates and films, obtained at 2.6m telescope, 1m and 0.5m Schmidt telescopes and other smaller ones during 1947-1991. In 2002-2005, the famous Markarian Survey (First Byurakan Survey, FBS) 2000 plates were digitized and the Digitized FBS (DFBS, http://www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on these low-dispersion spectroscopic material. In 2015, we have started a project on the whole BAO Plate Archive digitization, creation of electronic database and its scientific usage. A Science Program Board is created to evaluate the observing material, to investigate new possibilities and to propose new projects based on the combined usage of these observations together with other world databases. The Executing Team consists of 9 astronomers and 3 computer scientists and will use 2 EPSON Perfection V750 Pro scanners for the digitization, as well as Armenian Virtual Observatory (ArVO) database to accommodate all new data. The project will run during 3 years in 2015-2017 and the final result will be an electronic database and online interactive sky map to be used for further research projects.

  13. Supra-additive contribution of shape and surface information to individual face discrimination as revealed by fast periodic visual stimulation.

    PubMed

    Dzhelyova, Milena; Rossion, Bruno

    2014-12-24

    Face perception depends on two main sources of information--shape and surface cues. Behavioral studies suggest that both of them contribute roughly equally to discrimination of individual faces, with only a small advantage provided by their combination. However, it is difficult to quantify the respective contribution of each source of information to the visual representation of individual faces with explicit behavioral measures. To address this issue, facial morphs were created that varied in shape only, surface only, or both. Electrocephalogram (EEG) were recorded from 10 participants during visual stimulation at a fast periodic rate, in which the same face was presented four times consecutively and the fifth face (the oddball) varied along one of the morphed dimensions. Individual face discrimination was indexed by the periodic EEG response at the oddball rate (e.g., 5.88 Hz/5 = 1.18 Hz). While shape information was discriminated mainly at right occipitotemporal electrode sites, surface information was coded more bilaterally and provided a larger response overall. Most importantly, shape and surface changes alone were associated with much weaker responses than when both sources of information were combined in the stimulus, revealing a supra-additive effect. These observations suggest that the two kinds of information combine nonlinearly to provide a full individual face representation, face identity being more than the sum of the contribution of shape and surface cues. © 2014 ARVO.

  14. Analytic Approximations for Real-Time Area Light Shading.

    PubMed

    Lecocq, Pascal; Dufay, Arthur; Sourimant, Gael; Marvie, Jean-Eudes

    2017-05-01

    We introduce analytic approximations for accurate real-time rendering of surfaces lit by non-occluded area light sources. Our solution leverages the Irradiance Tensors developed by Arvo for the shading of Phong surfaces lit by a polygonal light source. Using a reformulation of the 1D boundary edge integral, we develop a general framework for approximating and evaluating the integral in constant time using simple peak shape functions. To overcome the Phong restriction, we propose a low cost edge splitting strategy that accounts for the spherical warp introduced by the half vector parametrization. Thanks to this novel extension, we accurately approximate common microfacet BRDFs, providing a practical method producing specular stretches that closely match the ground truth in real-time. Finally, using the same approximation framework, we introduce support for spherical and disc area light sources, based on an original polygon spinning method supporting non-uniform scaling operations and horizon clipping. Implemented on a GPU, our method achieves real-time performances without any assumption on area light shape nor surface roughness.

  15. Gestalt grouping via closure degrades suprathreshold depth percepts.

    PubMed

    Deas, Lesley M; Wilcox, Laurie M

    2014-08-19

    It is well known that the perception of depth is susceptible to changes in configuration. For example, stereoscopic precision for a pair of vertical lines can be dramatically reduced when these lines are connected to form a closed object. Here, we extend this paradigm to suprathreshold estimates of perceived depth. Using a touch-sensor, observers made quantitative estimates of depth between a vertical line pair presented in isolation or as edges of a closed rectangular object with different figural interpretations. First, we show that the amount of depth estimated within a closed rectangular object is consistently reduced relative to the vertical edges presented in isolation or when they form the edges of two segmented objects. We then demonstrate that the reduction in perceived depth for closed objects is modulated by manipulations that influence perceived closure of the central figure. Depth percepts were most disrupted when the horizontal connectors and vertical lines matched in color. Perceived depth increased slightly when the connectors had opposite contrast polarity, but increased dramatically when flankers were added. Thus, as grouping cues were added to counter the interpretation of a closed object, the depth degradation effect was systematically eliminated. The configurations tested here rule out explanations based on early, local interactions such as inhibition or cue conflict; instead, our results provide strong evidence of the impact of Gestalt grouping, via closure, on depth magnitude percepts from stereopsis. © 2014 ARVO.

  16. Substitution and pooling in visual crowding induced by similar and dissimilar distractors.

    PubMed

    Ester, Edward F; Zilber, Emma; Serences, John T

    2015-01-08

    Visual crowding refers to a phenomenon whereby objects that appear in the periphery of the visual field are more difficult to identify when embedded within clutter. Pooling models assert that crowding results from an obligatory averaging or other combination of target and distractor features that occurs prior to awareness. One well-known manifestation of pooling is feature averaging, with which the features of target and nontarget stimuli are combined at an early stage of visual processing. Conversely, substitution models assert that crowding results from binding a target and nearby distractors to incorrect spatial locations. Recent evidence suggests that substitution predominates when target-flanker feature similarity is low, but it is unclear whether averaging or substitution best explains crowding when similarity is high. Here, we examined participants' orientation report errors for targets crowded by similar or dissimilar flankers. In two experiments, we found evidence inconsistent with feature averaging regardless of target-flanker similarity. However, the observed data could be accommodated by a probabilistic substitution model in which participants occasionally "swap" a target for a distractor. Thus, we conclude that-at least for the displays used here-crowding likely results from a probabilistic substitution of targets and distractors, regardless of target-distractor feature similarity. © 2015 ARVO.

  17. Saccadic distractor effects: the remote distractor effect (RDE) and saccadic inhibition (SI): A response to McIntosh and Buonocore (2014).

    PubMed

    Walker, Robin; Benson, Valerie

    2015-02-04

    We (Walker & Benson, 2013) reported studies in which the spatial effects of distractors on the remote distractor effect (RDE) and saccadic inhibition (SI) were examined. Distractors remote from the target increased mean latency and the skew of the distractor-related distributions, without the presence of dips that are regarded as the hallmark of SI. We further showed that early onset distractors had similar effects although these would not be consistent with existing estimates of the duration of SI (of around 60-70 ms). McIntosh and Buonocore (2014) report a simulation showing that skewed latency distributions can arise from the putative SI mechanism and they also highlighted a number of methodological considerations regarding the RDE and SI as measures of saccadic distractor effects (SDEs). Here we evaluate these claims and note that the measures of SI obtained by subtracting latency distributions (specifically the decrease in saccade frequency--or dip duration) are no more diagnostic of a single inhibitory process, or more sensitive indicators of it, than is median latency. Furthermore the evidence of inhibitory influences of small distractors presented close to the target is incompatible with the explanations of both the RDE and SI. We conclude that saccadic distractor effects may be a more inclusive term to encompass the different characteristics of behavioral effects of underlying saccade target selection. © 2015 ARVO.

  18. Evolving the stimulus to fit the brain: a genetic algorithm reveals the brain's feature priorities in visual search.

    PubMed

    Van der Burg, Erik; Cass, John; Theeuwes, Jan; Alais, David

    2015-02-06

    How does the brain find objects in cluttered visual environments? For decades researchers have employed the classic visual search paradigm to answer this question using factorial designs. Although such approaches have yielded important information, they represent only a tiny fraction of the possible parametric space. Here we use a novel approach, by using a genetic algorithm (GA) to discover the way the brain solves visual search in complex environments, free from experimenter bias. Participants searched a series of complex displays, and those supporting fastest search were selected to reproduce (survival of the fittest). Their display properties (genes) were crossed and combined to create a new generation of "evolved" displays. Displays evolved quickly over generations towards a stable, efficiently searched array. Color properties evolved first, followed by orientation. The evolved displays also contained spatial patterns suggesting a coarse-to-fine search strategy. We argue that this behavioral performance-driven GA reveals the way the brain selects information during visual search in complex environments. We anticipate that our approach can be adapted to a variety of sensory and cognitive questions that have proven too intractable for factorial designs. © 2015 ARVO.

  19. Restoring accommodation: surgical technique and preliminary evaluation in rabbits

    NASA Astrophysics Data System (ADS)

    Tahi, Hassan; Chapon, Pascal F.; Hamaoui, Marie; Lee, William E.; Holden, Brien; Parel, Jean-Marie A.

    1999-06-01

    Purpose. To evaluate an innovative surgical technique for phaco-ersatz, a cataract surgery designed to restore accommodation. Techniques for very small capsulorhexis as well as the refilling procedure were developed. This study evaluates the feasibility and reproducibility of the surgical technique. Methods. The right eye of 8 NZW rabbits (~ 2 Kg) were operated following the ARVO Statements for the Use of Animals in Ophthalmic and Vision Research. The surgery is begun by making a small peripheral capsulorhexis of about 1 mm using. The lens content is then removed. The lens is then refilled with a novel in situ polymerizable gel and the corneal incision is closed using one 10/0 Nylon interrupted stitch. Results. The capsulorhexis technique was succesfully performed and reproducible in all animals. The average size of the capsulorhexis opening was 1. 2 mm (+/-0.14). Lens material removal and refilling of the capsular bag with an in situ polymerizable material was also performed in each trial study. Conclusion. This surgical technique seemed feasible and reproducible.

  20. Perception of physical stability and center of mass of 3-D objects.

    PubMed

    Cholewiak, Steven A; Fleming, Roland W; Singh, Manish

    2015-02-10

    Humans can judge from vision alone whether an object is physically stable or not. Such judgments allow observers to predict the physical behavior of objects, and hence to guide their motor actions. We investigated the visual estimation of physical stability of 3-D objects (shown in stereoscopically viewed rendered scenes) and how it relates to visual estimates of their center of mass (COM). In Experiment 1, observers viewed an object near the edge of a table and adjusted its tilt to the perceived critical angle, i.e., the tilt angle at which the object was seen as equally likely to fall or return to its upright stable position. In Experiment 2, observers visually localized the COM of the same set of objects. In both experiments, observers' settings were compared to physical predictions based on the objects' geometry. In both tasks, deviations from physical predictions were, on average, relatively small. More detailed analyses of individual observers' settings in the two tasks, however, revealed mutual inconsistencies between observers' critical-angle and COM settings. The results suggest that observers did not use their COM estimates in a physically correct manner when making visual judgments of physical stability. © 2015 ARVO.

  1. IAU South West Asian ROAD

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg; Azatyan, Naira; Farmanyan, Sona; Mikayelyan, Gor

    2016-10-01

    Armenia is hosting the IAU South West Asian (SWA) Regional Office of Astronomy for Development (ROAD). It is a county of ancient astronomy and is also rich in modern astronomical facilities and infrastructures, hence may successfully serve as a regional center for various activities. Byurakan Astrophysical Observatory (BAO) has 2.6m and 1m Schmidt, as well as a number of smaller telescopes that are an observational basis for joint projects and collaborations. Armenian Virtual Observatory (ArVO) is hosting astronomical databases, such as the Digitized First Byurakan Survey (DFBS) and may also serve as a basis for development of VO structures in this region. Recently we have conducted a number of new activities; a meeting on ``Relation of Astronomy to other Sciences, Culture and Society" (RASCS) was organized by BAO and Armenian Astronomical Society (ArAS) in Oct 2014 in Byurakan. Activities related to Archaeoastronomy and Astronomy in Culture (AAC) were initiated as well. Discussions on future Armenian-Iranian collaboration in astronomy were carried out, including an Armenian-Iranian Astronomical Workshop held in Oct 2015 in Byurakan. Similar workshops have been carried out between BAO and Abastumani Astronomical Observatory (AbAO, Georgia) since 1974.

  2. Vernier perceptual learning transfers to completely untrained retinal locations after double training: a "piggybacking" effect.

    PubMed

    Wang, Rui; Zhang, Jun-Yun; Klein, Stanley A; Levi, Dennis M; Yu, Cong

    2014-11-14

    Perceptual learning, a process in which training improves visual discrimination, is often specific to the trained retinal location, and this location specificity is frequently regarded as an indication of neural plasticity in the retinotopic visual cortex. However, our previous studies have shown that "double training" enables location-specific perceptual learning, such as Vernier learning, to completely transfer to a new location where an irrelevant task is practiced. Here we show that Vernier learning can be actuated by less location-specific orientation or motion-direction learning to transfer to completely untrained retinal locations. This "piggybacking" effect occurs even if both tasks are trained at the same retinal location. However, piggybacking does not occur when the Vernier task is paired with a more location-specific contrast-discrimination task. This previously unknown complexity challenges the current understanding of perceptual learning and its specificity/transfer. Orientation and motion-direction learning, but not contrast and Vernier learning, appears to activate a global process that allows learning transfer to untrained locations. Moreover, when paired with orientation or motion-direction learning, Vernier learning may be "piggybacked" by the activated global process to transfer to other untrained retinal locations. How this task-specific global activation process is achieved is as yet unknown. © 2014 ARVO.

  3. Separable effects of inversion and contrast-reversal on face detection thresholds and response functions: a sweep VEP study.

    PubMed

    Liu-Shuang, Joan; Ales, Justin; Rossion, Bruno; Norcia, Anthony M

    2015-02-10

    The human brain rapidly detects faces in the visual environment. We recently presented a sweep visual evoked potential approach to objectively define face detection thresholds as well as suprathreshold response functions (Ales, Farzin, Rossion, & Norcia, 2012). Here we determined these parameters are affected by orientation (upright vs. inverted) and contrast polarity (positive vs. negative), two manipulations that disproportionately disrupt the perception of faces relative to other object categories. Face stimuli parametrically increased in visibility through phase-descrambling while alternating with scrambled images at a fixed presentation rate of 3 Hz (6 images/s). The power spectrum and mean luminance of all stimuli were equalized. As a face gradually emerged during a stimulation sequence, EEG responses at 3 Hz appeared at ≈35% phase coherence over right occipito-temporal channels, replicating previous observations. With inversion and contrast-reversal, the 3-Hz amplitude decreased by ≈20%-50% and the face detection threshold increased by ≈30%-60% coherence. Furthermore, while the 3-Hz response emerged abruptly and saturated quickly for normal faces, suggesting a categorical neural response, the response profile for inverted and negative polarity faces was shallower and more linear, indicating gradual and continuously increasing activation of the underlying neural population. These findings demonstrate that inversion and contrast-reversal increase the threshold and modulate the suprathreshold response function of face detection. © 2015 ARVO.

  4. Intravitreal memantine retinal toxicity in rabbits.

    PubMed

    Moreno Páramo, D; Reyna Vielma, S; Rodríguez Reyes, A; Hernández Ayuso, I; Quiroz Mercado, H

    2016-02-01

    To histologically evaluate whether the intravitreal application of memantine produces retinal toxicity in rabbits. A cross-sectional design, experimental, descriptive study was performed on 16 eyes of 16 New Zealand rabbits of 3 kg, divided in 4 groups of 4 rabbits. A dose of 70 ng/ml of intravitreal memantine was administered in Group A, a dose of 150 ng/ml in Group B, a dose of 400 ng/ml in Group C, and Group D received 1 ml of balanced salt solution. The injected eye of half of each group was enucleated 15 days after the injection, and the rest within 30 days after injection. Following enucleation, each eye was placed in 10% formaldehyde. Histopathological analysis was performed on all enucleated eyes. The animals were treated according to the guidelines of the Association for Research on Vision and Ophthalmology (ARVO). Groups A, B and D did not show any histopathological changes after their enucleation at 15 and 30 days. Group C showed changes in the photoreceptor layer after enucleation at 15 and 30 days. In our study, it was observed that memantine concentrations at 70 ng/ml and 150 ng/ml are safe when administered intravitreally; however, doses of 400 ng/ml produced retinal structural changes. This research should continue to assess its clinical usefulness. Copyright © 2015 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

  5. Square wave jerks and anxiety as distinctive biomarkers for anorexia nervosa.

    PubMed

    Phillipou, Andrea; Rossell, Susan Lee; Castle, David Jonathan; Gurvich, Caroline; Abel, Larry Allen

    2014-12-02

    The factors contributing to the cause and maintenance of anorexia nervosa (AN) are poorly understood, though increasing interest surrounds the neurobiological underpinnings of the condition. The examination of saccadic eye movements has proven useful in our understanding of the neurobiology of some other psychiatric illnesses, as they utilize identifiable brain circuits. Square wave jerks (SWJs), which describe an involuntary saccade away and back to fixation, have been observed to occur at abnormally high rates in neurodegenerative disorders and some psychiatric illnesses, but have not been examined in AN. Therefore, the aim of this study was to investigate whether individuals with AN and healthy control (HC) individuals differ in SWJ rate during attempted fixation. Square wave jerk frequency was compared across 23 female participants with AN and 22 HC participants matched for age, sex, and premorbid intelligence. Anorexia nervosa participants were found to make SWJs at a significantly higher rate than HC participants. The rate of SWJs in AN was also found to negatively correlate with anxiety. Square wave jerk rate and anxiety were found to correctly classify groups, with an accuracy of 87% for AN participants and 95.5% for HCs. Given our current understanding of saccadic eye movements, the findings suggest a potential role of γ-aminobutyric acid (GABA) in the superior colliculus, frontal eye fields, or posterior parietal cortex in the psychopathology of AN. © ARVO.

  6. Why the long face? The importance of vertical image structure for biological "barcodes" underlying face recognition.

    PubMed

    Spence, Morgan L; Storrs, Katherine R; Arnold, Derek H

    2014-07-29

    Humans are experts at face recognition. The mechanisms underlying this complex capacity are not fully understood. Recently, it has been proposed that face recognition is supported by a coarse-scale analysis of visual information contained in horizontal bands of contrast distributed along the vertical image axis-a biological facial "barcode" (Dakin & Watt, 2009). A critical prediction of the facial barcode hypothesis is that the distribution of image contrast along the vertical axis will be more important for face recognition than image distributions along the horizontal axis. Using a novel paradigm involving dynamic image distortions, a series of experiments are presented examining famous face recognition impairments from selectively disrupting image distributions along the vertical or horizontal image axes. Results show that disrupting the image distribution along the vertical image axis is more disruptive for recognition than matched distortions along the horizontal axis. Consistent with the facial barcode hypothesis, these results suggest that human face recognition relies disproportionately on appropriately scaled distributions of image contrast along the vertical image axis. © 2014 ARVO.

  7. Development of Armenian-Georgian Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg; Kochiashvili, Nino; Astsatryan, Hrach; Harutyunian, Haik; Magakyan, Tigran; Chargeishvili, Ketevan; Natsvlishvili, Rezo; Kukhianidze, Vasil; Ramishvili, Giorgi; Sargsyan, Lusine; Sinamyan, Parandzem; Kochiashvili, Ia; Mikayelyan, Gor

    2009-10-01

    The Armenian-Georgian Virtual Observatory (ArGVO) project is the first initiative in the world to create a regional VO infrastructure based on national VO projects and regional Grid. The Byurakan and Abastumani Astrophysical Observatories are scientific partners since 1946, after establishment of the Byurakan observatory . The Armenian VO project (ArVO) is being developed since 2005 and is a part of the International Virtual Observatory Alliance (IVOA). It is based on the Digitized First Byurakan Survey (DFBS, the digitized version of famous Markarian survey) and other Armenian archival data. Similarly, the Georgian VO will be created to serve as a research environment to utilize the digitized Georgian plate archives. Therefore, one of the main goals for creation of the regional VO is the digitization of large amounts of plates preserved at the plate stacks of these two observatories. The total amount of plates is more than 100,000 units. Observational programs of high importance have been selected and some 3000 plates will be digitized during the next two years; the priority is being defined by the usefulness of the material for future science projects, like search for new objects, optical identifications of radio, IR, and X-ray sources, study of variability and proper motions, etc. Having the digitized material in VO standards, a VO database through the regional Grid infrastructure will be active. This partnership is being carried out in the framework of the ISTC project A-1606 "Development of Armenian-Georgian Grid Infrastructure and Applications in the Fields of High Energy Physics, Astrophysics and Quantum Physics".

  8. A five-primary photostimulator suitable for studying intrinsically photosensitive retinal ganglion cell functions in humans.

    PubMed

    Cao, Dingcai; Nicandro, Nathaniel; Barrionuevo, Pablo A

    2015-01-26

    Intrinsically photosensitive retinal ganglion cells (ipRGCs) can respond to light directly through self-contained photopigment, melanopsin. IpRGCs also receive synaptic inputs from rods and cones. Thus, studying ipRGC functions requires a novel photostimulating method that can account for all of the photoreceptor inputs. Here, we introduced an inexpensive LED-based five-primary photostimulator that can control the excitations of rods, S-, M-, L-cones, and melanopsin-containing ipRGCs in humans at constant background photoreceptor excitation levels, a critical requirement for studying the adaptation behavior of ipRGCs with rod, cone, or melanopsin input. We described the theory and technical aspects (including optics, electronics, software, and calibration) of the five-primary photostimulator. Then we presented two preliminary studies using the photostimulator we have implemented to measure melanopsin-mediated pupil responses and temporal contrast sensitivity function (TCSF). The results showed that the S-cone input to pupil responses was antagonistic to the L-, M- or melanopsin inputs, consistent with an S-OFF and (L + M)-ON response property of primate ipRGCs (Dacey et al., 2005). In addition, the melanopsin-mediated TCSF had a distinctive pattern compared with L + M or S-cone mediated TCSF. Other than controlling individual photoreceptor excitation independently, the five-primary photostimulator has the flexibility in presenting stimuli modulating any combination of photoreceptor excitations, which allows researchers to study the mechanisms by which ipRGCs combine various photoreceptor inputs. © 2015 ARVO.

  9. What monitor can replace the cathode-ray tube for visual stimulation to elicit multifocal electroretinograms?

    PubMed

    Matsumoto, Celso Soiti; Shinoda, Kei; Matsumoto, Harue; Seki, Keisuke; Nagasaka, Eiichiro; Iwata, Takeshi; Mizota, Atsushi

    2014-08-05

    To compare a conventional cathode-ray tube (CRT) screen to organic light-emitting diode (OLED) and liquid crystal display (LCD) screens as visual stimulators to elicit multifocal electroretinograms (mfERGs), mfERGs were recorded from seven eyes of seven healthy volunteers (21 ± 2 years). The mfERGs elicited by a conventional CRT screen (S710, Compaq Computer Co.) were compared to those elicited by a studio-grade master OLED monitor (PVM-1741, Sony, Japan) and a conventional LCD (S1721, Flexscan, Eizo Nanao Corp., Japan). The luminance changes of each monitor were measured with a photodiode. CRT, OLED, and LCD screens with a frame frequency of 60 Hz were studied. A hexagonal stimulus array with 61 stimulus elements was created on each monitor. The serial white stimuli of the OLED screen at 60 Hz did not fuse, and that of the LCD screens fused. The amplitudes of P1 and P2 of the first-order kernels of the mfERGs were not significantly different from those elicited by the CRT and OLED screens, and the P1 amplitude of the first-order kernel elicited by the LCD stimuli was significantly smaller than that elicited by the CRT in all the groups of the averaged hexagonal elements. The implicit times were approximately 10 ms longer in almost all components elicited by the LCD screen compared to those elicited by the CRT screen. The mfERGs elicited by monitors other than the CRT should be carefully interpreted, especially those elicited by LCD screens. The OLED had good performance, and we conclude that it can replace the CRT as a stimulator for mfERGs; however, a collection of normative data is recommended. © 2014 ARVO.

  10. Pursuit Latency for Chromatic Targets

    NASA Technical Reports Server (NTRS)

    Mulligan, Jeffrey B.; Ellis, Stephen R. (Technical Monitor)

    1998-01-01

    The temporal dynamics of eye movement response to a change in direction of stimulus motion has been used to compare the processing speeds of different types of stimuli (Mulligan, ARVO '97). In this study, the pursuit response to colored targets was measured to test the hypothesis that the slow response of the chromatic system (as measured using traditional temporal sensitivity measures such as contrast sensitivity) results in increased eye movement latencies. Subjects viewed a small (0.4 deg) Gaussian spot which moved downward at a speed of 6.6 deg/sec. At a variable time during the trajectory, the dot's direction of motion changed by 30 degrees, either to the right or left. Subjects were instructed to pursue the spot. Eye movements were measured using a video ophthalmoscope with an angular resolution of approximately 1 arc min and a temporal sampling rate of 60 Hz. Stimuli were modulated in chrominance for a variety of hue directions, combined with a range of small luminance increments and decrements, to insure that some of the stimuli fell in the subjects' equiluminance planes. The smooth portions of the resulting eye movement traces were fit by convolving the stimulus velocity with an exponential having variable onset latency, time constant and amplitude. Smooth eye movements with few saccades were observed for all stimuli. Pursuit responses to stimuli having a significant luminance component are well-fit by exponentials having latencies and time constants on the order of 100 msec. Increases in pursuit response latency on the order of 100-200 msec are observed in response to certain stimuli, which occur in pairs of complementary hues, corresponding to the intersection of the stimulus section with the subjects' equiluminant plane. Smooth eye movements can be made in response to purely chromatic stimuli, but are slower than responses to stimuli with a luminance component.

  11. Some Recent Developments in Structure and Glassy Behavior of Proteins

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2012-02-01

    We have used ARVO developed by us to find that the ratio of volume and surface area of proteins in Protein Data Bank distributed in a very narrow region [1]. Such result is useful for the determination of protein 3D structures. It has been widely known that a spin glass model can be used to understand the slow relaxation behavior of a glass at low temperatures [2]. We have used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that polymer chains with neighboring monomers connected by rigid bonds can relax very slowly and show glassy behavior [3]. We have also found that native collagen fibrils show glassy behavior at room temperatures [4]. The results of [3] and [4] about the glassy behavior of polymers or proteins are useful for understanding the mechanism for a biological system to maintain in a non-equilibrium state, including the ancient seed [5], which can maintain in a non-equilibrium state for a very long time. (1) M.-C. Wu, M. S. Li, W.-J. Ma, M. Kouza, and C.-K. Hu, EPL, in press (2011); (2) C. Dasgupta, S.-K. Ma, and C.-K. Hu. Phys. Rev. B 20, 3837-3849 (1979); (3) W.-J. Ma and C.-K. Hu, J. Phys. Soc. Japan 79, 024005, 024006, 054001, and 104002 (2010), C.-K. Hu and W.-J. Ma, Prog. Theor. Phys. Supp. 184, 369 (2010); S. G. Gevorkian, A. E. Allahverdyan, D. S. Gevorgyan and C.-K. Hu, EPL 95, 23001 (2011); S. Sallon, et al. Science 320, 1464 (2008).

  12. Dynamic interactions between visual working memory and saccade target selection.

    PubMed

    Schneegans, Sebastian; Spencer, John P; Schöner, Gregor; Hwang, Seongmin; Hollingworth, Andrew

    2014-09-16

    Recent psychophysical experiments have shown that working memory for visual surface features interacts with saccadic motor planning, even in tasks where the saccade target is unambiguously specified by spatial cues. Specifically, a match between a memorized color and the color of either the designated target or a distractor stimulus influences saccade target selection, saccade amplitudes, and latencies in a systematic fashion. To elucidate these effects, we present a dynamic neural field model in combination with new experimental data. The model captures the neural processes underlying visual perception, working memory, and saccade planning relevant to the psychophysical experiment. It consists of a low-level visual sensory representation that interacts with two separate pathways: a spatial pathway implementing spatial attention and saccade generation, and a surface feature pathway implementing color working memory and feature attention. Due to bidirectional coupling between visual working memory and feature attention in the model, the working memory content can indirectly exert an effect on perceptual processing in the low-level sensory representation. This in turn biases saccadic movement planning in the spatial pathway, allowing the model to quantitatively reproduce the observed interaction effects. The continuous coupling between representations in the model also implies that modulation should be bidirectional, and model simulations provide specific predictions for complementary effects of saccade target selection on visual working memory. These predictions were empirically confirmed in a new experiment: Memory for a sample color was biased toward the color of a task-irrelevant saccade target object, demonstrating the bidirectional coupling between visual working memory and perceptual processing. © 2014 ARVO.

  13. Attention modulates neuronal correlates of interhemispheric integration and global motion perception.

    PubMed

    Akin, Burak; Ozdem, Ceylan; Eroglu, Seda; Keskin, Dudu Taslak; Fang, Fang; Doerschner, Katja; Kersten, Daniel; Boyaci, Huseyin

    2014-10-27

    In early retinotopic areas of the human visual system, information from the left and right visual hemifields (VHFs) is processed contralaterally in two hemispheres. Despite this segregation, we have the perceptual experience of a unified, coherent, and uninterrupted single visual field. How exactly the visual system integrates information from the two VHFs and achieves this perceptual experience still remains largely unknown. In this study using fMRI, we explored candidate areas that are involved in interhemispheric integration and the perceptual experience of a unified, global motion across VHFs. Stimuli were two-dimensional, computer-generated objects with parts in both VHFs. The retinal image in the left VHF always remained stationary, but in the experimental condition, it appeared to have local motion because of the perceived global motion of the object. This perceptual effect could be weakened by directing the attention away from the global motion through a demanding fixation task. Results show that lateral occipital areas, including the medial temporal complex, play an important role in the process of perceptual experience of a unified global motion across VHFs. In early areas, including the lateral geniculate nucleus and V1, we observed correlates of this perceptual experience only when attention is not directed away from the object. These findings reveal effects of attention on interhemispheric integration in motion perception and imply that both the bilateral activity of higher-tier visual areas and feedback mechanisms leading to bilateral activity of early areas play roles in the perceptual experience of a unified visual field. © 2014 ARVO.

  14. Complementary effects of gaze direction and early saliency in guiding fixations during free viewing.

    PubMed

    Borji, Ali; Parks, Daniel; Itti, Laurent

    2014-11-04

    in constructing more predictive visual attention models in the future. © 2014 ARVO.

  15. The biomechanics of walking shape the use of visual information during locomotion over complex terrain.

    PubMed

    Matthis, Jonathan Samir; Barton, Sean L; Fajen, Brett R

    2015-03-18

    The aim of this study was to examine how visual information is used to control stepping during locomotion over terrain that demands precision in the placement of the feet. More specifically, we sought to determine the point in the gait cycle at which visual information about a target is no longer needed to guide accurate foot placement. Subjects walked along a path while stepping as accurately as possible on a series of small, irregularly spaced target footholds. In various conditions, each of the targets became invisible either during the step to the target or during the step to the previous target. We found that making targets invisible after toe off of the step to the target had little to no effect on stepping accuracy. However, when targets disappeared during the step to the previous target, foot placement became less accurate and more variable. The findings suggest that visual information about a target is used prior to initiation of the step to that target but is not needed to continuously guide the foot throughout the swing phase. We propose that this style of control is rooted in the biomechanics of walking, which facilitates an energetically efficient strategy in which visual information is primarily used to initialize the mechanical state of the body leading into a ballistic movement toward the target foothold. Taken together with previous studies, the findings suggest the availability of visual information about the terrain near a particular step is most essential during the latter half of the preceding step, which constitutes a critical control phase in the bipedal gait cycle. © 2015 ARVO.

  16. Naturally occurring circadian rhythm and sleep duration are related to executive functions in early adulthood.

    PubMed

    Kuula, Liisa; Pesonen, Anu-Katriina; Heinonen, Kati; Kajantie, Eero; Eriksson, Johan Gunnar; Andersson, Sture; Lano, Aulikki; Lahti, Jari; Wolke, Dieter; Räikkönen, Katri

    2017-07-20

    Experimental sleep deprivation studies suggest that insufficient sleep and circadian misalignment associates with poorer executive function. It is not known whether this association translates to naturally occurring sleep patterns. A total of 512 of full-term-born members of the Arvo Ylppö Longitudinal Study [mean age = 25.3, standard deviation (SD) = 0.65] (44.3% men) wore actigraphs to define sleep duration, its irregularity and circadian rhythm (sleep mid-point) during a 1-week period (mean 6.9 nights, SD = 1.7). Performance-based executive function was assessed with the Trail-Making Test, Conners' Continuous Performance Test and Stroop. The self-rated adult version of Behavior Rating Inventory of Executive Function was used to assess trait-like executive function. We found that performance-based and self-reported trait-like executive function correlated only modestly (all correlations ≤0.17). Shorter sleep duration associated with more commission errors. Later circadian rhythm associated with poorer trait-like executive function, as indicated by the Brief Metacognitive Index and the Behavior Regulation Index. Those belonging to the group with the most irregular sleep duration performed slower than others in the Trail-Making Test Part A. All associations were adjusted for sex, age, socioeconomic status and body mass index. In conclusion, naturally occurring insufficient sleep and later circadian rhythm showed modest associations with poorer executive function. Shorter habitual sleep duration was associated with lower scores of performance-based tests of executive function, and later circadian rhythm was associated mainly with poorer trait-like executive function characteristics. Our findings suggest additionally that sleep duration and circadian rhythm associate with different domains of executive function, and there are no additive effects between the two. © 2017 European Sleep Research Society.

  17. Preservation and maintenance of the astronomical sites in Armenia

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2008-01-01

    Astronomy in Armenia was popular since ancient times. There are signs of astronomical observations coming from a few thousands years ago. Two ancient observatories, Karahunge and Metzamor are especially well known. Karahunge is the Armenian twin of the Stonehenge and is even older. However, there is no proper attention from the state authorities and efforts are needed for preservation of such historical-astronomical monuments. The Byurakan Astrophysical Observatory (BAO) is the modern famous Armenian observatory founded in 1946 by the outstanding scientist Victor Ambartsumian. It was one of the world astronomical centres in 1950-s to 1970-s, and at present is the largest observatory in the Middle East area. As the ancient astronomical sites, Byurakan also needs a proper attitude from the state authorities and corresponding international organizations to preserve its values and importance for the present and future astronomical activities in the region, including its rich observational archive, telescopes, and human resources. Despite all the difficulties, the Armenian astronomers keep high international level of research and display various activities organizing international meetings and schools, preparing new young generation for the future research. The Armenian Astronomical Society (ArAS) is an affiliated member of EAS. Armenia has its Virtual Observatory project (ArVO) as well. The next Joint European and National Astronomy Meeting (JENAM-2007) will be held in Yerevan, Armenia, in August 2007. There are plans to organize astronomical tours to Armenia for making observations from various sites, including the ancient observatories. The future of astronomy in Armenia strongly depends on all of this activities and the proper attention both from state authorities and society.

  18. Foveal crowding differs in children and adults.

    PubMed

    Norgett, Yvonne; Siderov, John

    2014-10-23

    We used custom-designed acuity tests to compare the magnitude and extent of crowded letter recognition in children and adults. Visual acuity (logMAR) was measured monocularly in children and adults using five custom-designed letter tests with varying degrees of crowding: single letter, single letter surrounded by four flanking bars, single letter surrounded by four flanking letters, line of five letters surrounded by flanking bars, and line of five letters surrounded by flanking letters. The tests were constructed using Sloan letters and presented on an iPad (Apple Incorporated, Cupertino, CA) at 4 m using a standardized endpoint and instructions. Crowded logMAR was normalized to unflanked logMAR and results were analyzed in three groups: younger children aged 4-6 (n = 32), older children, aged 7-9 (n = 30), and adults (n = 27). Both groups of children showed a greater extent of crowding than the adults. The adult participants showed no difference in performance between single or linear presentation and letter or bar flankers. Letter flankers and linear presentation individually resulted in poorer performance in the younger children p < 0.001 and p = 0.003, respectively (mean normalized logMAR 0.17 in each case) and together had an additive effect (mean 0.24), p < 0.001. Crowding in the older children was adult-like except in the linear presentation with letter flankers, p < 0.001. These results indicate that both target-flanker similarity and linear presentation contribute more to foveal crowding in young children than in adults. © 2014 ARVO.

  19. Perceptual biases and cue weighting in perception of 3D slant from texture and stereo information.

    PubMed

    Saunders, Jeffrey A; Chen, Zhongting

    2015-02-10

    Multiple cues are typically available for perceiving the 3D slant of surfaces, and slant perception has been used as a test case for investigating cue integration. Previous evidence suggests that texture and stereo slant cues contribute in an optimal Bayesian manner. We tested whether a Bayesian model could also account for perceptual underestimation of slant from texture. One explanation proposed by Todd, Christensen, and Guckes (2010) is that slant from texture is based on an inaccurate optical variable. An alternative Bayesian explanation is that perceptual underestimation is due to the influence of frontal cues and/or a frontal prior, which is weighted according to the reliability of slant cues. We measured slant perception using a hand-alignment task for conditions that provided only texture, only stereo, or combined texture and stereo cues. Slant estimates from monocular texture showed large biases toward frontal, with proportionally more underestimation at low slants than high slants. Slant estimates from stereo alone were more accurate, and adding texture information did not reduce accuracy. These results are consistent with a frontal influence that is decreasingly weighted as slant information becomes more reliable. We also included conditions with small cue conflicts to measure the relative weighting of texture and stereo cues. Consistent with previous studies, texture had a significant effect on slant estimates in binocular conditions, and the relative weighting of texture increased with slant. In some cases, perceived slant from combined stereo and texture cues was higher than from either cue in isolation. Both the perceptual biases and the cue weights were generally consistent with a Bayesian model that optimally integrates texture and stereo slant cues with frontal cues and/or a frontal prior. © 2015 ARVO.

  20. Key characteristics of specular stereo.

    PubMed

    Muryy, Alexander A; Fleming, Roland W; Welchman, Andrew E

    2014-12-24

    Because specular reflection is view-dependent, shiny surfaces behave radically differently from matte, textured surfaces when viewed with two eyes. As a result, specular reflections pose substantial problems for binocular stereopsis. Here we use a combination of computer graphics and geometrical analysis to characterize the key respects in which specular stereo differs from standard stereo, to identify how and why the human visual system fails to reconstruct depths correctly from specular reflections. We describe rendering of stereoscopic images of specular surfaces in which the disparity information can be varied parametrically and independently of monocular appearance. Using the generated surfaces and images, we explain how stereo correspondence can be established with known and unknown surface geometry. We show that even with known geometry, stereo matching for specular surfaces is nontrivial because points in one eye may have zero, one, or multiple matches in the other eye. Matching features typically yield skew (nonintersecting) rays, leading to substantial ortho-epipolar components to the disparities, which makes deriving depth values from matches nontrivial. We suggest that the human visual system may base its depth estimates solely on the epipolar components of disparities while treating the ortho-epipolar components as a measure of the underlying reliability of the disparity signals. Reconstructing virtual surfaces according to these principles reveals that they are piece-wise smooth with very large discontinuities close to inflection points on the physical surface. Together, these distinctive characteristics lead to cues that the visual system could use to diagnose specular reflections from binocular information. © 2014 ARVO.

  1. Fast periodic presentation of natural images reveals a robust face-selective electrophysiological response in the human brain.

    PubMed

    Rossion, Bruno; Torfs, Katrien; Jacques, Corentin; Liu-Shuang, Joan

    2015-01-16

    We designed a fast periodic visual stimulation approach to identify an objective signature of face categorization incorporating both visual discrimination (from nonface objects) and generalization (across widely variable face exemplars). Scalp electroencephalographic (EEG) data were recorded in 12 human observers viewing natural images of objects at a rapid frequency of 5.88 images/s for 60 s. Natural images of faces were interleaved every five stimuli, i.e., at 1.18 Hz (5.88/5). Face categorization was indexed by a high signal-to-noise ratio response, specifically at an oddball face stimulation frequency of 1.18 Hz and its harmonics. This face-selective periodic EEG response was highly significant for every participant, even for a single 60-s sequence, and was generally localized over the right occipitotemporal cortex. The periodicity constraint and the large selection of stimuli ensured that this selective response to natural face images was free of low-level visual confounds, as confirmed by the absence of any oddball response for phase-scrambled stimuli. Without any subtraction procedure, time-domain analysis revealed a sequence of differential face-selective EEG components between 120 and 400 ms after oddball face image onset, progressing from medial occipital (P1-faces) to occipitotemporal (N1-faces) and anterior temporal (P2-faces) regions. Overall, this fast periodic visual stimulation approach provides a direct signature of natural face categorization and opens an avenue for efficiently measuring categorization responses of complex visual stimuli in the human brain. © 2015 ARVO.

  2. Gaze direction affects the magnitude of face identity aftereffects.

    PubMed

    Kloth, Nadine; Jeffery, Linda; Rhodes, Gillian

    2015-02-20

    The face perception system partly owes its efficiency to adaptive mechanisms that constantly recalibrate face coding to our current diet of faces. Moreover, faces that are better attended produce more adaptation. Here, we investigated whether the social cues conveyed by a face can influence the amount of adaptation that face induces. We compared the magnitude of face identity aftereffects induced by adaptors with direct and averted gazes. We reasoned that faces conveying direct gaze may be more engaging and better attended and thus produce larger aftereffects than those with averted gaze. Using an adaptation duration of 5 s, we found that aftereffects for adaptors with direct and averted gazes did not differ (Experiment 1). However, when processing demands were increased by reducing adaptation duration to 1 s, we found that gaze direction did affect the magnitude of the aftereffect, but in an unexpected direction: Aftereffects were larger for adaptors with averted rather than direct gaze (Experiment 2). Eye tracking revealed that differences in looking time to the faces between the two gaze directions could not account for these findings. Subsequent ratings of the stimuli (Experiment 3) showed that adaptors with averted gaze were actually perceived as more expressive and interesting than adaptors with direct gaze. Therefore it appears that the averted-gaze faces were more engaging and better attended, leading to larger aftereffects. Overall, our results suggest that naturally occurring facial signals can modulate the adaptive impact a face exerts on our perceptual system. Specifically, the faces that we perceive as most interesting also appear to calibrate the organization of our perceptual system most strongly. © 2015 ARVO.

  3. Experience moderates overlap between object and face recognition, suggesting a common ability.

    PubMed

    Gauthier, Isabel; McGugin, Rankin W; Richler, Jennifer J; Herzmann, Grit; Speegle, Magen; Van Gulick, Ana E

    2014-07-03

    Some research finds that face recognition is largely independent from the recognition of other objects; a specialized and innate ability to recognize faces could therefore have little or nothing to do with our ability to recognize objects. We propose a new framework in which recognition performance for any category is the product of domain-general ability and category-specific experience. In Experiment 1, we show that the overlap between face and object recognition depends on experience with objects. In 256 subjects we measured face recognition, object recognition for eight categories, and self-reported experience with these categories. Experience predicted neither face recognition nor object recognition but moderated their relationship: Face recognition performance is increasingly similar to object recognition performance with increasing object experience. If a subject has a lot of experience with objects and is found to perform poorly, they also prove to have a low ability with faces. In a follow-up survey, we explored the dimensions of experience with objects that may have contributed to self-reported experience in Experiment 1. Different dimensions of experience appear to be more salient for different categories, with general self-reports of expertise reflecting judgments of verbal knowledge about a category more than judgments of visual performance. The complexity of experience and current limitations in its measurement support the importance of aggregating across multiple categories. Our findings imply that both face and object recognition are supported by a common, domain-general ability expressed through experience with a category and best measured when accounting for experience. © 2014 ARVO.

  4. How saliency, faces, and sound influence gaze in dynamic social scenes.

    PubMed

    Coutrot, Antoine; Guyader, Nathalie

    2014-07-03

    Conversation scenes are a typical example in which classical models of visual attention dramatically fail to predict eye positions. Indeed, these models rarely consider faces as particular gaze attractors and never take into account the important auditory information that always accompanies dynamic social scenes. We recorded the eye movements of participants viewing dynamic conversations taking place in various contexts. Conversations were seen either with their original soundtracks or with unrelated soundtracks (unrelated speech and abrupt or continuous natural sounds). First, we analyze how auditory conditions influence the eye movement parameters of participants. Then, we model the probability distribution of eye positions across each video frame with a statistical method (Expectation-Maximization), allowing the relative contribution of different visual features such as static low-level visual saliency (based on luminance contrast), dynamic low level visual saliency (based on motion amplitude), faces, and center bias to be quantified. Through experimental and modeling results, we show that regardless of the auditory condition, participants look more at faces, and especially at talking faces. Hearing the original soundtrack makes participants follow the speech turn-taking more closely. However, we do not find any difference between the different types of unrelated soundtracks. These eyetracking results are confirmed by our model that shows that faces, and particularly talking faces, are the features that best explain the gazes recorded, especially in the original soundtrack condition. Low-level saliency is not a relevant feature to explain eye positions made on social scenes, even dynamic ones. Finally, we propose groundwork for an audiovisual saliency model. © 2014 ARVO.

  5. Armenian Astronomical Archives and Databases

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Astsatryan, H. V.; Knyazyan, A. V.; Mikayelyan, G. A.

    2017-01-01

    interactive sky map and scientific usage of this material. The Armenian Virtual Observatory (ArVO) is based on the DFBS database and other large-area surveys and catalogue data, as well as the data coming from other BAO digitization projects.

  6. Childhood cognitive ability and body composition in adulthood

    PubMed Central

    Kumpulainen, S M; Heinonen, K; Salonen, M K; Andersson, S; Wolke, D; Kajantie, E; Eriksson, J G; Raikkonen, K

    2016-01-01

    Background: Childhood cognitive ability has been identified as a novel risk factor for adulthood overweight and obesity as assessed by adult body mass index (BMI). BMI does not, however, distinguish fat-free and metabolically harmful fat tissue. Hence, we examined the associations between childhood cognitive abilities and body fat percentage (BF%) in young adulthood. Methods: Participants of the Arvo Ylppö Longitudinal Study (n=816) underwent tests of general reasoning, visuomotor integration, verbal competence and language comprehension (M=100; s.d.=15) at the age of 56 months. At the age of 25 years, they underwent a clinical examination, including measurements of BF% by the InBody 3.0 eight-polar tactile electrode system, weight and height from which BMI (kg m−2) was calculated and waist circumference (cm). Results: After adjustments for sex, age and BMI-for-age s.d. score at 56 months, lower general reasoning and visuomotor integration in childhood predicted higher BMI (kg m−2) increase per s.d. unit decrease in cognitive ability (−0.32, 95% confidence interval −0.60,−0.05; −0.45, −0.75,−0.14, respectively) and waist circumference (cm) increase per s.d. unit decrease in cognitive ability (−0.84, −1.56,−0.11; −1.07,−1.88,−0.26, respectively) in adulthood. In addition, lower visuomotor integration predicted higher BF% per s.d. unit decrease in cognitive ability (−0.62,−1.14,−0.09). Associations between general reasoning and BMI/waist were attenuated when adjusted for smoking, alcohol consumption, intake of fruits and vegetables and physical activity in adulthood, and all associations, except for visuomotor integration and BMI, were attenuated when adjusted for parental and/or own attained education and/or birth weight. Conclusions: Of the measured childhood cognitive abilities, only lower visuomotor integration was associated with BF% in adulthood. This challenges the view that cognitive ability, at least when measured in

  7. PREFACE: International Conference on Functional Materials and Nanotechnologies 2013 (FM&NT2013)

    NASA Astrophysics Data System (ADS)

    Nõmmiste, Ergo; Kirm, Marco; Plank, Toomas

    2013-12-01

    oral, and 5 commercial talks were delivered and more than 200 posters were presented. In the framework of conference more than 20 papers were submitted to a topical issue of Physica Scripta. Based on the work presented at the conference, 62 articles are included in this volume of IOP Conference Series: Materials Science and Engineering. Additional information about FM&NT-2013 is available at its homepage http://fmnt.ut.ee/. The Organizing Committee would like to thank all the speakers, contributors, session chairs, referees and other involved staff for their efforts in making FM&NT-2013 successful. Special thanks for their hard work dealing with the conference papers goes to the Guest Editors: Professor Mikhail Brik, Dr Svetlana Zazubovits, Dr Arvo Kikas, Dr Rainer Pärna. The Organizing Committee hopes that Conference gave participants good insight into recent developments in nanotechnology, sustainable energetics, processing and modelling of multifunctional materials and research done using synchrotron radiation or other novel light sources. We sincerely hope that conference has provided support for the sharing of information and has brought together many young and experienced scientists from different fields, leading to fruitful discussions. We hope that all participants had good and memorable time in Tartu. On the behalf of organising committee Professor Ergo Nõmmiste Dr Marco Kirm Dr Toomas Plank The PDF also contains lists of the committees, the conference photograph and the sponsor's logos.

  8. Vitrectomy with internal limiting membrane (ILM) peeling versus vitrectomy with no peeling for idiopathic full-thickness macular hole (FTMH).

    PubMed

    Spiteri Cornish, Kurt; Lois, Noemi; Scott, Neil; Burr, Jennifer; Cook, Jonathan; Boachie, Charles; Tadayoni, Ramin; la Cour, Morten; Christensen, Ulrik; Kwok, Alvin

    2013-06-05

    (ASRS), Annual Meeting of the Retina Society, Congress of the Asia-Pacific Academy of Ophthalmology (APAO), European Association for Vision and Eye Research (EVER) Annual Congress, European Vitreoretinal Society (EVRS) Annual Meeting, Association for Research in Vision and Ophthalmology (ARVO) Meeting, International Vitreoretinal Meeting, and World Ophthalmology Congress. Only randomised controlled trials (RCTs) comparing ILM peeling with the no-peeling counterpart were included. Two review authors (KSC and NL) independently assessed the titles and abstracts of all RCTs identified by electronic and manual searches.We obtained Individual patient data (IPD) from three of the four identified eligible trials. The fourth identified RCT had only been published in abstract form and no IPD were available; we included data from this published abstract for one outcome (macular hole closure).The primary outcome was distance visual acuity at six months. Secondary outcomes included distance and near  visual acuity at three and 12 months postoperatively, near visual acuity at six months postoperatively, primary (after a single surgery) and final (following more than one surgery) macular hole closure, need for additional surgical interventions, vision-related quality of life and intraoperative and postoperative complications.We performed meta-analysis using standard techniques (the Mantel-Haenszel odds ratio (OR) for binary outcomes, mean difference (MD) for continuous outcomes) using a fixed-effect model. For two outcomes we also used the IPD to perform adjusted analyses using regression methods. We identified and included four RCTs; these were conducted in Denmark, France, Hong Kong and the United Kingdom/Republic of Ireland and randomised 47, 80, 49 and 141 participants respectively.There was no evidence of a difference in the primary outcome (distance visual acuity at six months), nor in distance visual acuity at 12 months between randomised groups. However, there was evidence