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Yassin M, Lev M, Polat U. Space, time, and dynamics of binocular interactions. Sci Rep 2023; 13:21449. [PMID: 38052879 DOI: 10.1038/s41598-023-48380-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 11/25/2023] [Indexed: 12/07/2023] Open
Abstract
Binocular summation (BS), defined as the superiority of binocular over monocular visual performance, shows that thresholds are about 40% (a factor of 1.4) better in binocular than in monocular viewing. However, it was reported that different amounts of BS exist in a range from 1.4 to 2 values because BS is affected by the spatiotemporal parameters of the stimulus. Lateral interactions can be defined as the neuron's ability to affect the neighboring neurons by either inhibiting or exciting their activity. We investigated the effect of the spatial and temporal domains on binocular interactions and BS under the lateral masking paradigm and how BS would be affected by lateral interactions via a lateral masking experiment. The two temporal alternative forced-choice (2TAFC) method was used. The stimuli consisted of a central vertically oriented Gabor target and high-contrast Gabor flankers positioned in two configurations (orthogonal or collinear) with target-flanker separations of either 2 or 3 wavelengths (λ), presented at 4 different presentation times (40, 80, 120, and 200 ms) using a different order of measurements across the different experiments. Opaque lenses were used to control the monocular and binocular vision. BS is absent at close distances (2λ), depending on the presentation time's order, for the collinear but not for the orthogonal configuration. However, BS exists at more distant flankers (collinear and orthogonal, 3λ). BS is not uniform (1.4); it depends on the stimulus condition, the presentation times, the order, and the method that was used to control the monocular and binocular vision.
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Affiliation(s)
- Marzouk Yassin
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Maria Lev
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Uri Polat
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
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2
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Binocular fusion disorders impair basic visual processing. Sci Rep 2022; 12:12564. [PMID: 35869104 PMCID: PMC9307628 DOI: 10.1038/s41598-022-16458-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 07/11/2022] [Indexed: 11/18/2022] Open
Abstract
In an era of increasing screen consumption, the requirement for binocular vision is demanding, leading to the emergence of syndromes such as the computer vision syndrome (CVS) or visual discomfort reported by virtual reality (VR) users. Heterophoria (phoria) is a latent eye misalignment (with a prevalence up to 35%) that appears in conditions that disrupt binocular vision and may affect the quality of binocular fusion. Collinear facilitation (CF), the mechanism for grouping contour elements, is a process that reveals lateral interactions by improving the visibility of a target by flankers placed collinearly. An abnormal pattern of CF has been observed in strabismic amblyopia. We hypothesize that phoria may affect CF in the horizontal meridian (HM) due to latent eye misalignment and its impact on binocular fusion. Fully corrected participants (phoria group and controls) completed a standard CF experiment for horizontal and vertical meridians during binocular and monocular viewing. Phoric observers exhibited (1) an asymmetry and an abnormal pattern of CF only for the HM, during both monocular and binocular viewing, (2) poor binocular summation between the monocular inputs, and (3) no binocular advantage of the CF. Phoria affects the CF in a way that is reminiscent of meridional amblyopia without being attributed to abnormal refraction. The abnormal pattern of CF in monocular viewing suggests that phoria could be a binocular developmental disorder that affects monocular spatial interactions. We suggest that the results could contribute to explain the visual discomfort experienced with VR users or symptoms when presenting CVS.
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Pinchuk-Yacobi N, Sagi D. Contrast adaptation improves spatial integration. Vision Res 2021; 188:139-148. [PMID: 34333199 DOI: 10.1016/j.visres.2021.06.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 06/20/2021] [Accepted: 06/28/2021] [Indexed: 10/20/2022]
Abstract
The effects of contrast adaptation and contrast area summation (spatial integration) were investigated using a contrast discrimination task. The task consisted of a target of variable size, and a pedestal with a fixed base contrast. Discrimination performance was examined for a condition in which the pedestal size was fixed, equal to the largest target size, and for a condition in which the pedestal size matched the target size and thus varied with it. Repeated performance of the task produced rapid within-session improvements for both conditions. For stimuli with a matching size of target and pedestal, the performance improved only for the larger targets, indicating the development of spatial integration, which was initially absent for these stimuli. However, the improvements were mostly temporary, and were not fully retained between subsequent daily sessions. The temporary nature of the sensitivity gains implies that they resulted, at least in part, from rapid adaptation to the stimulus contrast. We suggest that adaptation decorrelates and thus reduces the spatial noise generated by a high-contrast pedestal, leading to improved spatial integration (area summation) and better contrast sensitivity. A decorrelation model successfully predicted our experimental results.
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Affiliation(s)
- Noga Pinchuk-Yacobi
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Dov Sagi
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 7610001, Israel.
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Doron R, Lev M, Wygnanski-Jaffe T, Moroz I, Polat U. Development of global visual processing: From the retina to the perceptive field. PLoS One 2020; 15:e0238246. [PMID: 32866203 PMCID: PMC7458325 DOI: 10.1371/journal.pone.0238246] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Accepted: 08/12/2020] [Indexed: 11/18/2022] Open
Abstract
Young children exhibit poorer visual performance than adults due to immaturity of the fovea and of the fundamental processing of visual functions such as masking and crowding. Recent studies suggest that masking and crowding are closely related to the size of the fundamental processing unit-the perceptive field (PF). However, while it is known that the retina and basic visual functions develop throughout childhood, it is not clear whether and how changes in the size of the PF affect masking and crowding. Furthermore, no retinal and perceptual development data have been collected from the same cohort and time. Here we explored the developmental process of the PF and the basic visual functions. Psychophysical and imaging methods were used to test visual functions and foveal changes in participants ranging from 3-17 years old. Lateral masking, crowding and contrast sensitivity were tested using computerized tasks. Foveal measurements were obtained from spectral-domain optical coherence tomography (OCT). The children patterns below 6 years exhibited high crowding, while the expected facilitation was found only at a larger target-flanker distance than required for children above 6 years, who exhibited the typical adult. Foveal thickness and macular volume for the children below 6 years were significantly lower than for the older group. Significant correlation was found for contrast sensitivity, foveal thickness and macular volume with age and between contrast sensitivity and foveal thickness. Our data suggest that the developmental processes at the retina and visual cortex occur in the same age range. Thus, in parallel to maturation of the PF, which enables reduction in crowding, foveal development contributes to increasing contrast sensitivity.
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Affiliation(s)
- Ravid Doron
- Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel
| | - Maria Lev
- The School of Optometry and Vision Science, The Mina & Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat-Gan, Israel
| | - Tamara Wygnanski-Jaffe
- Department of Ophthalmology, Sheba Medical Center, Tel Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Iris Moroz
- Department of Eye Imaging, Goldschleger Eye Research Institute, Sheba Medical Center, Tel Hashomer, Israel
| | - Uri Polat
- The School of Optometry and Vision Science, The Mina & Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat-Gan, Israel
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Andrei AR, Pojoga S, Janz R, Dragoi V. Integration of cortical population signals for visual perception. Nat Commun 2019; 10:3832. [PMID: 31444323 PMCID: PMC6707195 DOI: 10.1038/s41467-019-11736-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 07/31/2019] [Indexed: 11/09/2022] Open
Abstract
Visual stimuli evoke heterogeneous responses across nearby neural populations. These signals must be locally integrated to contribute to perception, but the principles underlying this process are unknown. Here, we exploit the systematic organization of orientation preference in macaque primary visual cortex (V1) and perform causal manipulations to examine the limits of signal integration. Optogenetic stimulation and visual stimuli are used to simultaneously drive two neural populations with overlapping receptive fields. We report that optogenetic stimulation raises firing rates uniformly across conditions, but improves the detection of visual stimuli only when activating cells that are preferentially-tuned to the visual stimulus. Further, we show that changes in correlated variability are exclusively present when the optogenetically and visually-activated populations are functionally-proximal, suggesting that correlation changes represent a hallmark of signal integration. Our results demonstrate that information from functionally-proximal neurons is pooled for perception, but functionally-distal signals remain independent.
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Affiliation(s)
- Ariana R Andrei
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas-Houston, Houston, TX, 77030, USA
| | - Sorin Pojoga
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas-Houston, Houston, TX, 77030, USA
| | - Roger Janz
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas-Houston, Houston, TX, 77030, USA
| | - Valentin Dragoi
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas-Houston, Houston, TX, 77030, USA.
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6
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The equivalent internal orientation and position noise for contour integration. Sci Rep 2017; 7:13048. [PMID: 29026194 PMCID: PMC5638929 DOI: 10.1038/s41598-017-13244-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 09/13/2017] [Indexed: 11/11/2022] Open
Abstract
Contour integration is the joining-up of local responses to parts of a contour into a continuous percept. In typical studies observers detect contours formed of discrete wavelets, presented against a background of random wavelets. This measures performance for detecting contours in the limiting external noise that background provides. Our novel task measures contour integration without requiring any background noise. This allowed us to perform noise-masking experiments using orientation and position noise. From these we measure the equivalent internal noise for contour integration. We found an orientation noise of 6° and position noise of 3 arcmin. Orientation noise was 2.6x higher in contour integration compared to an orientation discrimination control task. Comparing against a position discrimination task found position noise in contours to be 2.4x lower. This suggests contour integration involves intermediate processing that enhances the quality of element position representation at the expense of element orientation. Efficiency relative to the ideal observer was lower for the contour tasks (36% in orientation noise, 21% in position noise) compared to the controls (54% and 57%).
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Sang Q, Cai B, Chen H. Contour detection improved by context-adaptive surround suppression. PLoS One 2017; 12:e0181792. [PMID: 28759589 PMCID: PMC5536361 DOI: 10.1371/journal.pone.0181792] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Accepted: 07/09/2017] [Indexed: 11/19/2022] Open
Abstract
Recently, many image processing applications have taken advantage of a psychophysical and neurophysiological mechanism, called “surround suppression” to extract object contour from a natural scene. However, these traditional methods often adopt a single suppression model and a fixed input parameter called “inhibition level”, which needs to be manually specified. To overcome these drawbacks, we propose a novel model, called “context-adaptive surround suppression”, which can automatically control the effect of surround suppression according to image local contextual features measured by a surface estimator based on a local linear kernel. Moreover, a dynamic suppression method and its stopping mechanism are introduced to avoid manual intervention. The proposed algorithm is demonstrated and validated by a broad range of experimental results.
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Affiliation(s)
- Qiang Sang
- College of Information Science & Technology, Chengdu University of Technology, Chengdu, Sichuan, P.R.China
| | - Biao Cai
- Department of Digital Media Technology, Chengdu University of Technology, Chengdu, Sichuan, China
- * E-mail:
| | - Hao Chen
- Department of Computer Science and Technology, Southwest University for Nationalities, Chengdu, Sichuan, China
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8
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Abstract
Collinear facilitation is an enhancement in the visibility of a target by laterally placed iso-oriented flankers in a collinear (COL) configuration. Iso-oriented flankers placed in a non-collinear configuration (side-by-side, SBS) produce less facilitation. Surprisingly, presentation of both configurations simultaneously (ISO-CROSS) abolishes the facilitation rather than increases it - a phenomenon that can’t be fully explained by the spatial properties of the target and flankers. Based on our preliminary data and recent studies, we hypothesized that there might be a novel explanation based on the temporal properties of the excitation and inhibition, resulting in asynchrony between the lateral inputs received from COL and SBS, leading to cancelation of the facilitatory component in ISO-CROSS. We explored this effect using a detection task in humans. The results replicated the previous results showing that the preferred facilitation for COL and SBS was abolished for the ISO-CROSS configuration. However, presenting the SBS flankers, but not the COL flankers 20 msec before ISO-CROSS restored the facilitatory effect. We propose a novel explanation that the perceptual advantage of collinear facilitation may be cancelled by the delayed input from the sides; thus, the final perception is determined by the overall spatial-temporal integration of the lateral interactions.
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Freeman E, Sagi D, Driver J. Configuration-Specific Attentional Modulation of Flanker – Target Lateral Interactions. Perception 2016; 33:181-94. [PMID: 15109161 DOI: 10.1068/p3481] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Elements of a contour are often easier to detect when they possess collinearity, with their local orientations matching the global orientation of the contour. We recently reported attentional modulation of such lateral interactions between a central near-threshold target Gabor patch and flanking high-contrast patches (Freeman et al, 2001 Nature Neuroscience4 1032–1036). Here, we examined whether such attentional effects reflect specific modulation of mechanisms sensitive to collinear configurations, or instead more general modulation of sensitivity to either the global or local orientation-components of the stimulus. Thresholds for detecting a central Gabor target were measured, while observers also judged the Vernier alignment between one pair of flankers and ignored a second flanker pair (when present). Target contrast-thresholds were facilitated only when attending collinear flankers. There was no facilitation when attending flankers that shared only local orientation with the target, or flankers that fell on a global axis aligned with target orientation but having orthogonal local orientation. Ignored collinear flankers had no effect on target thresholds. These results demonstrate strong and specific attentional modulation of contour-integration mechanisms in early vision sensitive to collinear configurations.
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Affiliation(s)
- Elliot Freeman
- Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK.
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10
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Maniglia M, Pavan A, Aedo-Jury F, Trotter Y. The spatial range of peripheral collinear facilitation. Sci Rep 2015; 5:15530. [PMID: 26502834 PMCID: PMC5155702 DOI: 10.1038/srep15530] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 09/11/2015] [Indexed: 11/09/2022] Open
Abstract
Contrast detection thresholds for a central Gabor patch (target) can be modulated by the presence of co-oriented and collinear high contrast Gabors flankers. In foveal vision collinear facilitation can be observed for target-to-flankers relative distances beyond two times the wavelength (λ) of the Gabor’s carrier, while for shorter relative distances (<2λ) there is suppression. These modulatory influences seem to disappear after 12λ. In this study, we measured contrast detection thresholds for different spatial frequencies (1, 4 and 6 cpd) and target-to-flankers relative distances ranging from 6 to 16λ, but with collinear configurations presented in near periphery at 4° of eccentricity. Results showed that in near periphery collinear facilitation extends beyond 12λ for the higher spatial frequencies tested (4 and 6 cpd), while it decays already at 10λ for the lowest spatial frequency used (i.e., 1 cpd). In addition, we found that increasing the spatial frequency the peak of collinear facilitation shifts towards larger target-to-flankers relative distances (expressed as multiples of the stimulus wavelength), an effect never reported neither for near peripheral nor for central vision. The results suggest that the peak and the spatial extent of collinear facilitation in near periphery depend on the spatial frequency of the stimuli used.
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Affiliation(s)
- Marcello Maniglia
- Université de Toulouse-UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.,Centre National de la Recherche Scientifique, Toulouse Cedex, France
| | - Andrea Pavan
- University of Lincoln, Brayford Pool, Lincoln, Lincolnshire, LN6 7TS, United Kingdom
| | - Felipe Aedo-Jury
- Université de Toulouse-UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.,Centre National de la Recherche Scientifique, Toulouse Cedex, France
| | - Yves Trotter
- Université de Toulouse-UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France.,Centre National de la Recherche Scientifique, Toulouse Cedex, France
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11
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Abstract
Contour integration is a fundamental visual process. The constraints on integrating discrete contour elements and the associated neural mechanisms have typically been investigated using static contour paths. However, in our dynamic natural environment objects and scenes vary over space and time. With the aim of investigating the parameters affecting spatiotemporal contour path integration, we measured human contrast detection performance of a briefly presented foveal target embedded in dynamic collinear stimulus sequences (comprising five short ‘predictor’ bars appearing consecutively towards the fovea, followed by the ‘target’ bar) in four experiments. The data showed that participants' target detection performance was relatively unchanged when individual contour elements were separated by up to 2° spatial gap or 200 ms temporal gap. Randomising the luminance contrast or colour of the predictors, on the other hand, had similar detrimental effect on grouping dynamic contour path and subsequent target detection performance. Randomising the orientation of the predictors reduced target detection performance greater than introducing misalignment relative to the contour path. The results suggest that the visual system integrates dynamic path elements to bias target detection even when the continuity of path is disrupted in terms of spatial (2°), temporal (200 ms), colour (over 10 colours) and luminance (−25% to 25%) information. We discuss how the findings can be largely reconciled within the functioning of V1 horizontal connections.
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Schallmo MP, Sponheim SR, Olman CA. Abnormal contextual modulation of visual contour detection in patients with schizophrenia. PLoS One 2013; 8:e68090. [PMID: 23922637 PMCID: PMC3688981 DOI: 10.1371/journal.pone.0068090] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 05/25/2013] [Indexed: 11/19/2022] Open
Abstract
Schizophrenia patients demonstrate perceptual deficits consistent with broad dysfunction in visual context processing. These include poor integration of segments forming visual contours, and reduced visual contrast effects (e.g. weaker orientation-dependent surround suppression, ODSS). Background image context can influence contour perception, as stimuli near the contour affect detection accuracy. Because of ODSS, this contextual modulation depends on the relative orientation between the contour and flanking elements, with parallel flankers impairing contour perception. However in schizophrenia, the impact of abnormal ODSS during contour perception is not clear. It is also unknown whether deficient contour perception marks genetic liability for schizophrenia, or is strictly associated with clinical expression of this disorder. We examined contour detection in 25 adults with schizophrenia, 13 unaffected first-degree biological relatives of schizophrenia patients, and 28 healthy controls. Subjects performed a psychophysics experiment designed to quantify the effect of flanker orientation during contour detection. Overall, patients with schizophrenia showed poorer contour detection performance than relatives or controls. Parallel flankers suppressed and orthogonal flankers enhanced contour detection performance for all groups, but parallel suppression was relatively weaker for schizophrenia patients than healthy controls. Relatives of patients showed equivalent performance with controls. Computational modeling suggested that abnormal contextual modulation in schizophrenia may be explained by suppression that is more broadly tuned for orientation. Abnormal flanker suppression in schizophrenia is consistent with weaker ODSS and/or broader orientation tuning. This work provides the first evidence that such perceptual abnormalities may not be associated with a genetic liability for schizophrenia.
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Affiliation(s)
- Michael-Paul Schallmo
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA.
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Gilad A, Meirovithz E, Leshem A, Arieli A, Slovin H. Collinear stimuli induce local and cross-areal coherence in the visual cortex of behaving monkeys. PLoS One 2012. [PMID: 23185325 PMCID: PMC3501522 DOI: 10.1371/journal.pone.0049391] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Background Collinear patterns of local visual stimuli are used to study contextual effects in the visual system. Previous studies have shown that proximal collinear flankers, unlike orthogonal, can enhance the detection of a low contrast central element. However, the direct neural interactions between cortical populations processing the individual flanker elements and the central element are largely unknown. Methodology/Principal Findings Using voltage-sensitive dye imaging (VSDI) we imaged neural population responses in V1 and V2 areas in fixating monkeys while they were presented with collinear or orthogonal arrays of Gabor patches. We then studied the spatio-temporal interactions between neuronal populations processing individual Gabor patches in the two conditions. Time-frequency analysis of the stimulus-evoked VSDI signal showed power increase mainly in low frequencies, i.e., the alpha band (α; 7–14 Hz). Power in the α-band was more discriminative at a single trial level than other neuronal population measures. Importantly, the collinear condition showed an increased intra-areal (V1-V1 and V2-V2) and inter-areal (V1-V2) α-coherence with shorter latencies than the orthogonal condition, both before and after the removal of the stimulus contribution. α-coherence appeared between discrete neural populations processing the individual Gabor patches: the central element and the flankers. Conclusions/Significance Our findings suggest that collinear effects are mediated by synchronization in a distributed network of proximal and distant neuronal populations within and across V1 and V2.
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Affiliation(s)
- Ariel Gilad
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan, Israel.
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Gerhardstein P, Tse J, Dickerson K, Hipp D, Moser A. The human visual system uses a global closure mechanism. Vision Res 2012; 71:18-27. [PMID: 22940526 DOI: 10.1016/j.visres.2012.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Revised: 08/01/2012] [Accepted: 08/15/2012] [Indexed: 10/28/2022]
Abstract
Research asserting that the visual system instantiates a global closure heuristic in contour integration has been challenged by an argument that behaviorally-detected closure enhancement could be accounted for by low-level local mechanisms driven by collinearity or "good continuation" interacting with proximity. The present study investigated this issue in three experiments. Exp. 1 compared the visibility of closed and open contours using circles and S-contours from low to moderately high angles of path curvature in a temporal alternative-forced choice task. Circles were more detectable than S-contours, an effect that increased with curvature. The closure enhancement observed can, however, be explained by the fact that circles contain more 'contiguity' than S-contours. Additional tests added discontinuities to otherwise closed paths to control for the effects of good continuation and closure independently. Exp. 2 compared the visibility of incomplete circles (C-contours) and S-contours derived from the full circles and S-contours in Exp. 1. Exp. 3a compared the visibility of arc pairs arranged in an enclosed position similar to "()" and a non-enclosed position similar to ")(". Results consistently showed enhanced visibility of contour configurations enclosing a region even after controlling for differences in contiguity and changes of curvature direction. A control test (Exp. 3b) demonstrated that the gap in the contours of Exp. 3a was too large to be bridged by local-level collinearity/proximity alone. The combination of good continuation and proximity alone does not explain the closure effects observed across these tests, as demonstrated through the application of a Bayesian model of collinearity and proximity (Geisler et al., 2001) to the stimuli in Exps. 3a and 3b. These results argue for the presence of a global closure-driven contour enhancing mechanism in human vision.
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Affiliation(s)
- Peter Gerhardstein
- Department of Psychology, Binghamton University, State University of New York, Binghamton, NY 13902-6000, USA.
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15
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Bellacosa Marotti R, Pavan A, Casco C. The integration of straight contours (snakes and ladders): The role of spatial arrangement, spatial frequency and spatial phase. Vision Res 2012; 71:44-52. [PMID: 22902640 DOI: 10.1016/j.visres.2012.07.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Revised: 07/23/2012] [Accepted: 07/30/2012] [Indexed: 10/28/2022]
Abstract
In the present study we addressed the issue of whether the Gestalt principle of grouping by similarity (iso-orientation) subtends extraction of straight contours made up of disconnected, iso-oriented Gabor elements, whether collinear (snakes) or parallel (ladders). To prevent the use of the most obvious grouping principle of good continuation, which allows us to perceive the relation between local and global orientation along the contour, we manipulated the spatial arrangement of randomly oriented Gabors in the background: they were positioned on an ordered grid, and grouped on the basis of good continuation, or randomly positioned and not grouped. Grid-positioned backgrounds exert a suppressive contextual influence on detection of good continuation along the contour path. Results obtained in a two-interval forced choice task showed that the orderly-positioned background did not completely prevent detection of snakes and ladders. Detection of snakes was hampered at low spatial frequency whereas detection of ladders was improved by the randomly-positioned background at high spatial frequency. These contextual influences support the suggestion that both iso-orientation and good continuation rules are employed by the association field underlying the binding of straight contours. In addition, they are not compatible with integration of snakes and ladders elements within a single receptive field. In support of this suggestion we found that phase constancy within contour elements (as opposed to phase randomization) improved snake detectability at low spatial frequency, and, unexpectedly, impaired ladder detectability at high spatial frequency. This suggests that a low-level mechanism based on the balance between excitatory and inhibitory lateral interactions at a first stage may account for the detection of both straight contours.
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Lev M, Polat U. Collinear facilitation and suppression at the periphery. Vision Res 2011; 51:2488-98. [DOI: 10.1016/j.visres.2011.10.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 10/09/2011] [Accepted: 10/10/2011] [Indexed: 11/16/2022]
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Reducing crowding by weakening inhibitory lateral interactions in the periphery with perceptual learning. PLoS One 2011; 6:e25568. [PMID: 22065990 PMCID: PMC3204963 DOI: 10.1371/journal.pone.0025568] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Accepted: 09/07/2011] [Indexed: 12/02/2022] Open
Abstract
We investigated whether lateral masking in the near-periphery, due to inhibitory lateral interactions at an early level of central visual processing, could be weakened by perceptual learning and whether learning transferred to an untrained, higher-level lateral masking known as crowding. The trained task was contrast detection of a Gabor target presented in the near periphery (4°) in the presence of co-oriented and co-aligned high contrast Gabor flankers, which featured different target-to-flankers separations along the vertical axis that varied from 2λ to 8λ. We found both suppressive and facilitatory lateral interactions at target-to-flankers distances (2λ - 4λ and 8λ, respectively) that were larger than those found in the fovea. Training reduces suppression but does not increase facilitation. Most importantly, we found that learning reduces crowding and improves contrast sensitivity, but has no effect on visual acuity (VA). These results suggest a different pattern of connectivity in the periphery with respect to the fovea as well as a different modulation of this connectivity via perceptual learning that not only reduces low-level lateral masking but also reduces crowding. These results have important implications for the rehabilitation of low-vision patients who must use peripheral vision to perform tasks, such as reading and refined figure-ground segmentation, which normal sighted subjects perform in the fovea.
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Amiaz R, Zomet A, Polat U. Excitatory repetitive transcranial magnetic stimulation over the dorsolateral prefrontal cortex does not affect perceptual filling-in in healthy volunteers. Vision Res 2011; 51:2071-6. [PMID: 21855560 DOI: 10.1016/j.visres.2011.08.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 08/01/2011] [Accepted: 08/02/2011] [Indexed: 11/19/2022]
Affiliation(s)
- Revital Amiaz
- Psychiatry Clinic, Sheba Medical Center, Tel-Aviv University, Israel
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19
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Schumacher JF, Quinn CF, Olman CA. An exploration of the spatial scale over which orientation-dependent surround effects affect contour detection. J Vis 2011; 11:12. [PMID: 21778251 DOI: 10.1167/11.8.12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Contour detection is a crucial component of visual processing; however, performance on contour detection tasks can vary depending on the context of the visual scene. S. C. Dakin and N. J. Baruch (2009) showed that detection of a contour in an array of distracting elements depends on the orientation of flanking elements. Here, using a line of five collinear Gabor elements ("target contour") in a field of distractor Gabor elements, we systematically measured the effects of eccentricity, spacing, and spatial frequency on contour detection performance in three different contexts: randomly oriented distractors (control condition), flanking distractors (on either side of the collinear Gabors) aligned approximately parallel to the target contour, and flanking distractors aligned approximately orthogonal to the target contour. In the control condition, contour detection performance was best for larger Gabors (2 cpd) spaced farther apart (1.2°). Parallel flankers reduced performance for intermediate and large spacings and sizes compared to the control condition, while orthogonal flankers increased performance for the smallest spacing and size compared to the control condition. The results are fit by a model in which collinear facilitation, which is size-dependent but can persist for several degrees of visual angle, competes with orientation-dependent suppression from the flanking context when elements are separated by less than a degree of visual angle.
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Affiliation(s)
- Jennifer F Schumacher
- Graduate Program in Neuroscience, University of Minnesota, St. Paul, MN 55144-1000, USA.
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20
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Yeotikar NS, Khuu SK, Asper LJ, Suttle CM. Configuration specificity of crowding in peripheral vision. Vision Res 2011; 51:1239-48. [DOI: 10.1016/j.visres.2011.03.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 02/08/2011] [Accepted: 03/24/2011] [Indexed: 11/30/2022]
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21
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Lateral facilitation – No effect on the target noise level. Vision Res 2010; 50:2486-94. [DOI: 10.1016/j.visres.2010.08.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 07/07/2010] [Accepted: 08/10/2010] [Indexed: 11/22/2022]
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22
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Hall S, Pollux PM, Guo K. Exploitation of natural geometrical regularities facilitates target detection. Vision Res 2010; 50:2411-20. [DOI: 10.1016/j.visres.2010.09.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 07/21/2010] [Accepted: 09/09/2010] [Indexed: 11/26/2022]
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23
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Peeling plaids apart: context counteracts cross-orientation contrast masking. PLoS One 2009; 4:e8123. [PMID: 19956546 PMCID: PMC2780729 DOI: 10.1371/journal.pone.0008123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Accepted: 09/25/2009] [Indexed: 11/19/2022] Open
Abstract
Background Contrast discrimination for an image is usually harder if another image is superimposed on top. We asked whether such contrast masking may be enhanced or relieved depending on cues promoting integration of both images as a single pattern, versus segmentation into two independent components. Methodology & Principal Findings Contrast discrimination thresholds for a foveal test grating were sharply elevated in the presence of a perfectly overlapping orthogonally-oriented mask grating. However thresholds returned to the unmasked baseline when a surround grating was added, having the same orientation and phase of either the test or mask grating. Both such masking and ‘unmasking’ effects were much stronger for moving than static stimuli. Conclusions & Significance Our results suggest that common-fate motion reinforces the perception of a single coherent plaid pattern, while the surround helps to identify each component independently, thus peeling the plaid apart again. These results challenge current models of early vision, suggesting that higher-level surface organization influences contrast encoding, determining whether the contrast of a grating may be recovered independently from that of its mask.
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24
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Meirovithz E, Ayzenshtat I, Bonneh YS, Itzhack R, Werner-Reiss U, Slovin H. Population response to contextual influences in the primary visual cortex. ACTA ACUST UNITED AC 2009; 20:1293-304. [PMID: 19759123 DOI: 10.1093/cercor/bhp191] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Collinear proximal flankers can facilitate the detection of a low-contrast target or generate false-alarm target detection in the absence of a target. Although these effects are known to involve subthreshold neuronal interactions beyond the classical receptive field, the underlying neuronal mechanisms are not fully understood. Here, we used voltage-sensitive dye imaging that emphasizes subthreshold population activity, at high spatial and temporal resolution and imaged the visual cortex of fixating monkeys while they were presented with a low-contrast Gabor target, embedded within collinear or orthogonal flankers. We found that neuronal activity at the target site in area primary visual cortex increased and response latency decreased due to spatial spread of activation from the flankers' site. This increased activity was smaller than expected by a linear summation. The presentation of flankers alone induced strong spatial filling-in at the target site. Importantly, the increased neuronal activity at the target site was synchronized over time, both locally and with neuronal population at the flanker's site. This onset synchronization was higher for collinear than for orthogonal flankers. We further show that synchrony is a superior code over amplitude, for discriminating collinear from orthogonal pattern. These results suggest that population synchrony can serve as a code to discriminate contextual effects.
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Affiliation(s)
- Elhanan Meirovithz
- Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan, Israel
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25
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Sterkin A, Yehezkel O, Bonneh YS, Norcia A, Polat U. Backward masking suppresses collinear facilitation in the visual cortex. Vision Res 2009; 49:1784-94. [PMID: 19383510 DOI: 10.1016/j.visres.2009.04.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2008] [Revised: 04/02/2009] [Accepted: 04/06/2009] [Indexed: 11/28/2022]
Affiliation(s)
- Anna Sterkin
- Goldschleger Eye Research Institute, Sheba Medical Center, Tel Aviv University, Tel Hashomer 52621, Israel
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26
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Pei F, Baldassi S, Procida G, Igliozzi R, Tancredi R, Muratori F, Cioni G. Neural correlates of texture and contour integration in children with autism spectrum disorders. Vision Res 2009; 49:2140-50. [PMID: 19523974 DOI: 10.1016/j.visres.2009.06.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 06/05/2009] [Accepted: 06/05/2009] [Indexed: 10/20/2022]
Abstract
In this study, we have used an electrophysiological paradigm to investigate the neural correlates of the visual integration of local signals across space to generate global percepts in a group of low functioning autistic kids. We have analyzed the amplitude of key harmonics of the Visual Evoked Potentials (VEPs) recorded while participants observed orientation-based texture and contour stimuli, forming coherent global patterns, alternating with visual patterns in which the same number of local elements were randomly oriented in order to loose any globally organized feature. Comparing the results of the clinical sample with those obtained in an age-matched control group, we have observed that in the texture conditions the 1st and 3rd harmonics, containing signature of global form processing (Norcia, Pei, Bonneh, Hou, Sampath, & Pettet, 2005), were present in the control group, while in the experimental group only the 1st harmonic was present. In the Contour condition the 1st harmonic was not present for both groups while the 3rd harmonic was significantly present in the control group but absent in the group with autism. Moreover, the amount of organization required to elicit significant 1st harmonic response in the texture condition was higher in the clinical group. The present results bring additional support to the idea that texture and contour processing are supported by independent mechanisms in normal vision. Autistic vision would thus be characterized by a preserved, perhaps weaker texture mechanism, possibly mediated by feedback interactions between visual areas, and by a disfunction of the mechanism supporting contour processing, possibly mediated by long-range intra-cortical connections. Within this framework, the residual ability to detect contours shown in psychophysical studies could be due to the contribution of the texture mechanism to contour processing.
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Affiliation(s)
- Francesca Pei
- Associazione Italiana di Scienze della Visione, Cascina, Pisa, Italy
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27
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Abstract
Perception of global patterns requires the integration of local orientation information across space. The present study examined whether this integration ability declines in older age. We measured contrast thresholds for discriminating the global orientation of a "C" shaped contour against a blank background in younger and older subjects. Performance of younger subjects improved when the elements composing the "C" were aligned along the contour path, as opposed to being orthogonal to it or of mixed orientations. However, older subjects' performance was not affected by the orientation of the local elements. This indicates an age-related decline in contour integration.
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28
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To M, Lovell PG, Troscianko T, Tolhurst DJ. Summation of perceptual cues in natural visual scenes. Proc Biol Sci 2008; 275:2299-308. [PMID: 18628119 PMCID: PMC2495046 DOI: 10.1098/rspb.2008.0692] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Natural visual scenes are rich in information, and any neural system analysing them must piece together the many messages from large arrays of diverse feature detectors. It is known how threshold detection of compound visual stimuli (sinusoidal gratings) is determined by their components' thresholds. We investigate whether similar combination rules apply to the perception of the complex and suprathreshold visual elements in naturalistic visual images. Observers gave magnitude estimations (ratings) of the perceived differences between pairs of images made from photographs of natural scenes. Images in some pairs differed along one stimulus dimension such as object colour, location, size or blur. But, for other image pairs, there were composite differences along two dimensions (e.g. both colour and object-location might change). We examined whether the ratings for such composite pairs could be predicted from the two ratings for the respective pairs in which only one stimulus dimension had changed. We found a pooling relationship similar to that proposed for simple stimuli: Minkowski summation with exponent 2.84 yielded the best predictive power (r=0.96), an exponent similar to that generally reported for compound grating detection. This suggests that theories based on detecting simple stimuli can encompass visual processing of complex, suprathreshold stimuli.
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Affiliation(s)
- M To
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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29
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Huckauf A, Knops A, Nuerk HC, Willmes K. Semantic processing of crowded stimuli? PSYCHOLOGICAL RESEARCH 2008; 72:648-56. [PMID: 18841386 DOI: 10.1007/s00426-008-0171-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Accepted: 01/28/2008] [Indexed: 11/29/2022]
Abstract
Effects of semantic processing of crowded characters were investigated using numbers as stimuli. In an identification task, typical spacing effects in crowding were replicated. Using the same stimuli in a magnitude comparison task, a smaller effect of spacing was observed as well as an effect of response congruency. These effects were replicated in a second experiment with varying stimulus-onset asynchronies. In addition, decreasing performance with increasing onset-asynchrony (so-called type-B masking) for incongruent flankers indicates semantic processing of target and flankers. The data show that semantic processing takes place even in crowded stimuli. This argues strongly against common accounts of crowding in terms of early stimulus-driven impairments of processing.
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Affiliation(s)
- Anke Huckauf
- Faculty of Media, Bauhaus-University of Weimar, Bauhausstr. 11, 99423, Weimar, Germany.
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30
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Spatio-temporal low-level neural networks account for visual masking. Adv Cogn Psychol 2008; 3:153-65. [PMID: 20517505 PMCID: PMC2864984 DOI: 10.2478/v10053-008-0021-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Accepted: 02/07/2007] [Indexed: 11/21/2022] Open
Abstract
T emporal masking is a paradigm that is widely used to study visual information
processing. When a mask is presented, typically within less than 100 msec before
or after the target, the response to the target is reduced. The results of our
psychophysical and visual evoked potential (VEP) experiments show that the
masking effect critically depends on a combination of several factors: (1) the
processing time of the target, (2) the order of presentation of the target and
the mask, and (3) the spatial arrangement of the target and the mask. Thus, the
masking effect depends on the spatial-temporal combination of these factors.
Suppression was observed when the mask was positioned within a spatial range
that was found to evoke inhibition, and when the temporal separation between the
target and the mask was short. In contrast, lateral facilitation was observed
when the mask was presented at a spatial separation that did not evoke
inhibition from the target’s vicinity and with a temporal sequence that preceded
the target, or when it was presented simultaneously with it, but not when the
target preceded the mask. We propose that masking effects, either suppression or
facilitation, reflect integration into the spatial and the temporal domains of
the feedforward response to the target and the lateral inputs evoked by the mask
(excitatory and/or inhibitory). Because the excitation evoked by the mask
develops and propagates slowly from the mask’s location to the target’s
location, it lags behind the response to the target. On the other hand,
inhibition that is produced in the vicinity of the target evolves more rapidly
and follows the onset and offset of the stimulus more closely. Thus, lateral
excitation that overcomes the inhibition may facilitate the grouping of local
elements into a global percept by increasing the survivability of the object and
its accessibility for perceptual awareness.
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31
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Sterkin A, Yehezkel O, Bonneh YS, Norcia A, Polat U. Multi-component correlate for lateral collinear interactions in the human visual cortex. Vision Res 2008; 48:1641-7. [DOI: 10.1016/j.visres.2008.04.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 04/14/2008] [Accepted: 04/16/2008] [Indexed: 10/22/2022]
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32
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Polat U, Sagi D. The relationship between the subjective and objective aspects of visual filling-in. Vision Res 2007; 47:2473-81. [PMID: 17655907 DOI: 10.1016/j.visres.2007.06.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 06/13/2007] [Accepted: 06/15/2007] [Indexed: 11/21/2022]
Abstract
We explored the relationship between filling-in processes and the known increase in detection sensitivity observed for targets presented between collinear flankers. Filling-in was probed using a Yes/No detection task by measuring the false-positive reports (false-alarm, FA) and hit rate (Hit) for a low-contrast Gabor target with different target-flankers distances. Observers increased the number of reports on the presence of a target (FA and Hit) when the flankers' distance was within the known range of facilitatory lateral interactions. This bias in reporting was reduced with blocked stimulation, when the target-flanker distance was kept fixed across trials. When different distances were mixed by trials the bias followed the pattern of lateral interactions across distance. The effect was maximal when flankers and targets were aligned. These false perceptions are most likely the result of a filling-in process by lateral excitation that produces illusory contours.
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Affiliation(s)
- Uri Polat
- Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel-Hashomer, Israel.
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33
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Bonneh YS, Sagi D, Polat U. Spatial and temporal crowding in amblyopia. Vision Res 2007; 47:1950-62. [PMID: 17502115 DOI: 10.1016/j.visres.2007.02.015] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Revised: 02/06/2007] [Accepted: 02/06/2007] [Indexed: 10/23/2022]
Abstract
Spatial crowding is a well-known deficit in amblyopia. We have previously reported evidence suggesting that the inability to isolate stimuli in space in crowded displays (spatial crowding) is a largely independent component of the amblyopic deficit in visual acuity, which is typically found in strabismic amblyopia [Bonneh, Y., Sagi, D., & Polat, U. (2004a). Local and non-local deficits in amblyopia: Acuity and spatial interactions. Vision Research, 44, 3009-3110]. Here, we extend this result to the temporal domain by measuring visual acuity (VA) for a single pattern in a rapid serial visual presentation (RSVP-VA, N=15) for fast ("crowded") and slow ("uncrowded") presentations. We found that strabismic amblyopes but not anisometropic amblyopes or normal controls exhibited a significant difference between VA under the fast and slow conditions. We further compared the "temporal crowding" measure to two measures of spatial crowding: (1) static Tumbling-E acuity in multi-pattern crowded displays (N=26) and (2) Gabor alignment with lateral flankers (N=20). We found that all three measures of crowding (one temporal and two spatial) were highly correlated across subjects while being largely independent of the visual acuity for a single isolated pattern, with both spatial and temporal crowding being high and correlated in strabismus and low in anisometropia. This suggests that time and space are related in crowding, at least in amblyopia.
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Affiliation(s)
- Yoram S Bonneh
- Department of Neurobiology, Brain Research, The Weizmann Institute of Science, Rehovot 76100, Israel.
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34
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Tanaka Y, Miyauchi S, Misaki M. Bilateral long-range interaction between right and left visual hemifield. Vision Res 2007; 47:1490-503. [PMID: 17416397 DOI: 10.1016/j.visres.2007.01.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 11/08/2006] [Accepted: 01/21/2007] [Indexed: 10/23/2022]
Abstract
Long-range interaction has been reported to be limited in space within a few degrees. Here, we present a new type of interaction by means of a bilateral configuration using two Gabor signals (GSs). Two horizontally oriented GSs, the first defined as a cue and the second as a probe, appeared in the right and left peripheral visual fields in mirror symmetrical regions. The detection threshold of the GS probe was found to decrease significantly up to cue-probe separations of 10 degrees tested. Since the interaction was sensitive to symmetrical locus, as well as specific to the direction of the horizontal axis, the results suggest novel long-range interaction extending toward the periphery with a mirror-symmetrical configuration. This may be acquired by neuronal communication, which directly connects bilateral receptive fields in the right and left visual cortices.
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Affiliation(s)
- Yasuto Tanaka
- Brain Information Group, National Institute of Information and Communications Technology (NICT), 588 Iwaoka-cho Iwaoka, Nishi-ku, Kobe 651-2492, Japan.
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35
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Sukumar S, Waugh SJ. Separate first- and second-order processing is supported by spatial summation estimates at the fovea and eccentrically. Vision Res 2007; 47:581-96. [PMID: 17275063 DOI: 10.1016/j.visres.2006.10.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 10/03/2006] [Accepted: 10/10/2006] [Indexed: 11/30/2022]
Abstract
We estimated spatial summation areas for the detection of luminance-modulated (LM) and contrast-modulated (CM) blobs at the fovea, 2.5, 5 and 10 deg eccentrically. Gaussian profiles were added or multiplied to binary white noise to create LM and CM blob stimuli and these were used to psychophysically estimate detection thresholds and spatial summation areas. The results reveal significantly larger summation areas for detecting CM than LM blobs across eccentricity. These differences are comparable to receptive field size estimates made in V1 and V2. They support the notion that separate spatial processing occurs for the detection of LM and CM stimuli.
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Affiliation(s)
- Subash Sukumar
- University of Manchester, Department of Ophthalmology, Manchester Royal Eye Hospital, Oxford Road, M13 9WH, UK.
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36
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Levi DM, Yu C, Kuai SG, Rislove E. Global contour processing in amblyopia. Vision Res 2007; 47:512-24. [PMID: 17223155 PMCID: PMC1851910 DOI: 10.1016/j.visres.2006.10.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Revised: 10/19/2006] [Accepted: 10/23/2006] [Indexed: 11/19/2022]
Abstract
The purpose of the experiments described here was to investigate global image processing using methods that require global processing while eliminating or compensating for low level abnormalities: visibility, shape perception and positional uncertainty. In order to accomplish this we used a closed figure made up of Gabor patches either in noise or on a blank field. The stimuli were circular or elliptical contours, formed by N equally spaced Gabor patches. We performed two separate experiments: In one experiment we fixed N and varied the aspect ratio using a staircase to determine the threshold aspect ratio; in the second experiment we held the aspect ratio constant (at twice the threshold aspect ratio) and varied N in order to measure the threshold number of elements required to judge the shape. Our results confirm and extend previous studies showing that humans with naturally occurring amblyopia show deficits in contour processing. Our results show that the deficits depend strongly on spatial scale (target size and spatial frequency). The deficit in global contour processing is substantially greater in noise (where contour-linking is required) than on a blank field. The magnitude of the deficits is modest when low-level deficits (reduced visibility, increased positional uncertainty, and abnormal shape perception) are minimized, and does not seem to depend much on acuity, crowding or stereoacuity. The residual deficits reported here cannot be simply ascribed to reduced visibility or increased positional uncertainty, and we therefore conclude that these are genuine deficits in global contour segregation and integration.
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Affiliation(s)
- Dennis M Levi
- School of Optometry and Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720-2020, USA.
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37
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Pei F, Pettet MW, Norcia AM. Sensitivity and configuration-specificity of orientation-defined texture processing in infants and adults. Vision Res 2006; 47:338-48. [PMID: 17188321 PMCID: PMC1994821 DOI: 10.1016/j.visres.2006.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Revised: 10/01/2006] [Accepted: 10/12/2006] [Indexed: 11/16/2022]
Abstract
Here we use textures made up of widely spaced Gabor patches to compare infant and adult sensitivity to the global organization of the elements comprising the textures. Visual Evoked Potentials (VEPs) were recorded to alterations between random images and images containing varying proportions of patches that were of the same orientation. The patches were placed on rectangular, hexagonal or random lattices. Texture-specific responses were robust in adults and their VEP threshold was reached when 1-17% of the patches had the same orientation in the structured image. Infant thresholds were approximately 20-60%. While infants are capable of detecting the global structure of our textures, their sensitivity is low. In adults we found, unexpectedly, that sensitivity and response gain were higher for horizontal compared to vertical global orientations. Infant sensitivity was the same for the two orientations. Comparable orientation anisotropies have not been previously reported for gratings, suggesting that the Gabor-defined textures are tapping different mechanisms. There were small, but measurable effects of the lattice type in adults, with the rectangular lattice producing the largest responses.
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Affiliation(s)
- Francesca Pei
- Department of Physiology and Biochemistry, University of Pisa, Italy
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38
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Li W, Piëch V, Gilbert CD. Contour saliency in primary visual cortex. Neuron 2006; 50:951-62. [PMID: 16772175 DOI: 10.1016/j.neuron.2006.04.035] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Revised: 10/31/2005] [Accepted: 04/17/2006] [Indexed: 10/24/2022]
Abstract
Contour integration is an important intermediate stage of object recognition, in which line segments belonging to an object boundary are perceptually linked and segmented from complex backgrounds. Contextual influences observed in primary visual cortex (V1) suggest the involvement of V1 in contour integration. Here, we provide direct evidence that, in monkeys performing a contour detection task, there was a close correlation between the responses of V1 neurons and the perceptual saliency of contours. Receiver operating characteristic analysis showed that single neuronal responses encode the presence or absence of a contour as reliably as the animal's behavioral responses. We also show that the same visual contours elicited significantly weaker neuronal responses when they were not detected in the detection task, or when they were unattended. Our results demonstrate that contextual interactions in V1 play a pivotal role in contour integration and saliency.
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Affiliation(s)
- Wu Li
- The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
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39
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Polat U, Sagi D. Temporal asymmetry of collinear lateral interactions. Vision Res 2006; 46:953-60. [PMID: 16274724 DOI: 10.1016/j.visres.2005.09.031] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Revised: 09/18/2005] [Accepted: 09/20/2005] [Indexed: 11/19/2022]
Abstract
The visibility of a target improves when the target is presented simultaneously or with a delay between two collinear flankers. Here we tested the temporal properties of lateral facilitation by manipulating the timing of both onsets and offsets of the target and flankers. The results show that lateral facilitation critically depends on the order of presentation of the target and flankers. A typical pattern of lateral interactions was observed when the flankers preceded the target, or were presented simultaneously with it, but not when the target preceded the flankers. This result is incompatible with a feedforward account of lateral interactions, according to which the two temporal effects are linearly summed within a higher level receptive field. We propose that both facilitation and masking are the result of excitatory and inhibitory interactions within neuronal networks. The temporal asymmetry can be accounted for by assuming different time courses for the excitatory and the inhibitory interactions. Although the excitation is slow to develop, lagging behind the stimulus both in onset and offset, inhibition is rapid and follows the onset and offset of the stimulus more closely. Such a network exhibits fast transitions between slow processes.
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Affiliation(s)
- Uri Polat
- Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel-Hashomer, Israel.
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40
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Nikolaev AR, Leeuwen CV. Collinearity, curvature interpolation, and the power of perceptual integration. PSYCHOLOGICAL RESEARCH 2005; 71:427-37. [PMID: 16215743 DOI: 10.1007/s00426-005-0026-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Accepted: 09/06/2005] [Indexed: 10/25/2022]
Abstract
In three experiments, participants determined the orientation of a global triangle formed by three Gabor patches of a target spatial frequency in a field of distracters. The orientation of the target patches and their proximity were varied between conditions. When all the target patches had the same orientation this facilitated the response compared to random orientations. This effect occurred only when the patches were in close proximity. When the orientations of the target patches were different but aligned to the global triangle, facilitation occurred regardless of proximity. These contrasting types of facilitation were attributed to different early perceptual integration mechanisms that enable the perception of holistic structure.
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Affiliation(s)
- Andrey R Nikolaev
- Laboratory for Perceptual Dynamics, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
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41
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Olzak LA, Laurinen PI. Contextual effects in fine spatial discriminations. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2005; 22:2230-8. [PMID: 16277291 PMCID: PMC1808345 DOI: 10.1364/josaa.22.002230] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The context in which a pattern is viewed can greatly affect its apparent contrast, a phenomenon commonly attributed to pooled contrast gain control processes. A low-contrast surround may slightly enhance apparent contrast, whereas increasing the contrast of the surround leads to a monotonic decline in contrast appearance. We ask here how the presence of a patterned surround affects the ability to perform fine, suprathreshold orientation, contrast, and spatial frequency discriminations as a function of surround contrast and phase. Our results revealed an unexpected dip in performance when center and surround were in phase and similar in contrast. These results suggest that additional processes, perhaps those involved in scene segregation, play a role in contextual effects on discrimination.
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Affiliation(s)
- Lynn A Olzak
- Department of Psychology, Miami University of Ohio, Oxford 45056, USA.
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42
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Shani R, Sagi D. Eccentricity effects on lateral interactions. Vision Res 2005; 45:2009-24. [PMID: 15820518 DOI: 10.1016/j.visres.2005.01.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2004] [Revised: 08/16/2004] [Accepted: 01/25/2005] [Indexed: 11/25/2022]
Abstract
We attempted to resolve an apparent conflict between the lack of psychophysical evidence of collinear facilitation at the near-periphery and physiological evidence from the monkey showing collinear effects extra-fovealy. We compared collinear and orthogonal configurations to discount facilitation due to reduced positional uncertainty. Detection thresholds were measured for Gabor targets at eccentricities of 0 degrees - 4 degrees, flanked by collinear or orthogonal flankers. Like in previous reports in the literature, results varied among subjects when the stimulus position was off-fixation. We found reduced facilitation at eccentricities as small as 1 degrees - 2 degrees. Moreover, facilitation did not increase when the stimuli were M-scaled or when observers received more practice. However, a larger proportion of subjects showed collinear facilitation when attention was directed to the tested configurations. The results suggest that differences in allocation of attention along the visual field may affect the underlying lateral interactions, consequently resulting in eccentricity effects as well as inter-observer variability.
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Affiliation(s)
- Revital Shani
- Department of Neurobiology, The Weizmann Institute of Science, Rehovot 76100, Israel
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43
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Polat U, Bonneh Y, Ma-Naim T, Belkin M, Sagi D. Spatial interactions in amblyopia: Effects of stimulus parameters and amblyopia type. Vision Res 2005; 45:1471-9. [PMID: 15743616 DOI: 10.1016/j.visres.2004.12.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Revised: 11/25/2004] [Accepted: 12/02/2004] [Indexed: 11/16/2022]
Abstract
Adults with amblyopia were recently shown to perform abnormally in tasks requiring integration of local features into global percepts. Moreover, spatial interactions in amblyopic patients, though often found to be abnormal, showed marked variability. Here we measured collinear lateral interactions using Gabor patches in a large number of amblyopic (N=75) and normal subjects (N=25), testing four spatial frequencies (1.5, 3, 6, 9 cpd). We used the lateral masking paradigm, in which the contrast-detection threshold is measured in the presence of high-contrast flankers at different distances from a central target. Whereas in normal subjects spatial interaction patterns were evident across all spatial frequencies, amblyopic subjects showed abnormal spatial interactions and increasing deficiencies with increasing spatial frequencies. These abnormalities depended on the axis of astigmatism (in meridional amblyopia) and were more pronounced in strabismic than in anisometropic amblyopia. Spatial interactions were independent on the contrast-detection thresholds. Thus, adults with amblyopia might perform as well as normal observers for some stimulus parameters and abnormally for others. Our results indicate a close relationship between abnormal visual input to the visual cortex during development and abnormal functionality of the collinear spatial interactions in adults with amblyopia.
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Affiliation(s)
- U Polat
- Department of Medicine, Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel-Hashomer, Israel.
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44
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Bonneh YS, Sagi D, Polat U. Local and non-local deficits in amblyopia: acuity and spatial interactions. Vision Res 2004; 44:3099-110. [PMID: 15482798 DOI: 10.1016/j.visres.2004.07.031] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Revised: 07/24/2004] [Indexed: 11/27/2022]
Abstract
Amblyopic vision is thought to be limited by abnormal long-range spatial interactions, but their exact mode of action and relationship to the main amblyopic deficit in visual acuity is largely unknown. We studied this relationship in a group (N=59) of anisometropic (N=21) and strabismic (or combined, N=38) subjects, using (1) a single and multi-pattern (crowded) computerized static Tumbling-E test with scaled spacing of two pattern widths (TeVA), in addition to an optotype (ETDRS chart) acuity test (VA) and (2) contrast detection of Gabor patches with lateral flankers (lateral masking) along the horizontal and vertical axes as well as in collinear and parallel configurations. By correlating the different measures of visual acuity and contrast suppression, we found that (1) the VA of the strabismic subjects could be decomposed into two uncorrelated components measured in TeVA: acuity for isolated patterns and acuity reduction due to flanking patterns. The latter comprised over 60% of the VA magnitude, on the average and accounted for over 50% of its variance. In contrast, a slight reduction in acuity was found in the anisometropic subjects, and the acuity for a single pattern could account for 70% of the VA variance. (2) The lateral suppression (contrast threshold elevation) in a parallel configuration along the horizontal axis was correlated with the VA (R2=0.7), as well as with the crowding effect (TeVA elevation, R2=0.5) for the strabismic group. Some correlation with the VA was also found for the collinear configuration in the anisometropic group, but less suppression and no correlation were found for all the vertical configurations in all the groups. The results indicate the existence of a specific non-local component of the strabismic deficit, in addition to the local acuity deficit in all amblyopia types. This deficit might reflect long-range lateral inhibition, or alternatively, an inaccurate and scattered top-down attentional selection mechanism.
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Affiliation(s)
- Yoram S Bonneh
- Department of Neurobiology, Brain Research, The Weizmann Institute of Science, Rehovot 76100, Israel.
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45
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Khoe W, Freeman E, Woldorff MG, Mangun GR. Electrophysiological correlates of lateral interactions in human visual cortex. Vision Res 2004; 44:1659-73. [PMID: 15136002 DOI: 10.1016/j.visres.2004.02.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2003] [Revised: 02/04/2004] [Indexed: 11/25/2022]
Abstract
Detection thresholds for visually presented targets can be influenced by the nature of information in adjacent regions of the visual field. For example, detection thresholds for low-contrast Gabor patches decrease when flanked by patches that are oriented collinearly rather than orthogonally with the target. Such results are consistent with the known microanatomy of primary visual cortex, where long-range horizontal connections link cortical columns with common orientation preferences. To investigate the neural bases of collinearity effects, we recorded event-related brain potentials (ERPs) together with psychophysical measures for targets flanked by collinear vs. orthogonal gratings. Human volunteers performed a contrast discrimination task on a target grating presented at a perifoveal location. For targets flanked by collinear stimuli, we observed an increased positive polarity voltage deflection in the occipital scalp-recorded ERPs between 80 to 140 ms after stimulus onset. Such a midline occipital scalp voltage distribution of this ERP collinearity effect is consistent with a generator in primary visual cortex. Two later negative voltage ERP deflections (latencies of 245-295 and 300-350 ms) were focused at lateral occipital scalp sites, a pattern consistent with activity in extrastriate visual cortex. These ERP effects were correlated with improved contrast discrimination for central targets presented with collinear flanks. These results demonstrate that the integration of local flanking elements with a central stimulus can occur as early as 80 ms in human visual cortex, but this includes processes occurring at longer latencies and appears to involve both striate and extrastriate visual areas.
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Affiliation(s)
- W Khoe
- Center for Cognitive Research, Duke University, Durham, NC 27708, USA.
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46
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Silver MA, Logothetis NK. Grouping and segmentation in binocular rivalry. Vision Res 2004; 44:1675-92. [PMID: 15136003 DOI: 10.1016/j.visres.2003.12.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2003] [Revised: 11/03/2003] [Indexed: 11/30/2022]
Abstract
Dichoptic presentation of dot arrays produces binocular rivalry if the arrays are of opposite contrast relative to background. Rivalry can occur even if individual dots in one eye's array do not overlap with the dots in the contralateral eye's array. The amount of unitary perception of only one array is a measure of the probability that the stimuli rival as textured surfaces rather than as portions of arrays or as individual dot elements. In accordance with Gestalt grouping principles, arrays of uniform brightness or color produced more unitary perception than mixed arrays. However, experiments with parametric variation of dot motion coherence suggested that segmentation mechanisms based on detection of collinearity can also influence perceptual selection and suppression in binocular rivalry.
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Affiliation(s)
- Michael A Silver
- Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, D 72076 Tübingen, Germany.
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47
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Polat U, Ma-Naim T, Belkin M, Sagi D. Improving vision in adult amblyopia by perceptual learning. Proc Natl Acad Sci U S A 2004; 101:6692-7. [PMID: 15096608 PMCID: PMC404107 DOI: 10.1073/pnas.0401200101] [Citation(s) in RCA: 292] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Practicing certain visual tasks leads, as a result of a process termed "perceptual learning," to a significant improvement in performance. Learning is specific for basic stimulus features such as local orientation, retinal location, and eye of presentation, suggesting modification of neuronal processes at the primary visual cortex in adults. It is not known, however, whether such low-level learning affects higher-level visual tasks such as recognition. By systematic low-level training of an adult visual system malfunctioning as a result of abnormal development (leading to amblyopia) of the primary visual cortex during the "critical period," we show here that induction of low-level changes might yield significant perceptual benefits that transfer to higher visual tasks. The training procedure resulted in a 2-fold improvement in contrast sensitivity and in letter-recognition tasks. These findings demonstrate that perceptual learning can improve basic representations within an adult visual system that did not develop during the critical period.
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Affiliation(s)
- Uri Polat
- Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel Hashomer, Israel.
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48
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Abstract
Contextual elements can fundamentally change the perception of an embedded target. A recently discovered masking effect, shine-through, allows one to investigate the precise dynamics of contextual modulation of the human visual system. In this shine-through effect, a vernier precedes a grating comprising more than seven elements for display times as short as 10 ms. The vernier appears as a "shine-through" element superimposed on the grating. However, if additional single lines are presented above and below the grating, visibility of the shine-through element dramatically diminishes. Recent publications focused mainly on the spatial aspects of this contextual modulation. Here, we investigate its temporal characteristics. We show that contextual suppression can occur for context durations of 5-10 ms, even if contextual elements appear 100 ms before target onset. This contextual suppression is not due to the presentation of the contextual elements themselves since without the grating contextual elements exert only weak masking power. Only the combination of contextual elements and grating causes the contextual suppression.
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Affiliation(s)
- Michael H Herzog
- Human Neurobiology, Center for Advanced Imaging, University of Bremen, Argonnenstr. 3, D-28211, Bremen, Germany.
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49
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Levi DM, Wing-Hong Li R, Klein SA. "Phase capture" in the perception of interpolated shape: cue combination and the influence function. Vision Res 2003; 43:2233-43. [PMID: 12885377 DOI: 10.1016/s0042-6989(03)00310-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This study was concerned with what stimulus information observers use to judge the shape of simple objects. We used a string of four Gabor patches to define a contour. A fifth, center patch served as a test pattern. The observers' task was to judge the location of the test pattern relative to the contour. The contour was either a straight line, or an arc with positive or negative curvature (the radius of curvature was either 2 or 6 deg). We asked whether phase shifts in the inner or outer pairs of patches distributed along the contour influence the perceived shape. That is, we measured the phase shift influence function. We found that shifting the inner patches of the string by 0.25 cycle results in almost complete phase capture (attraction) at the smallest separation (2 lambda), and the capture effect falls off rapidly with separation. A 0.25 cycle shift of the outer pair of patches has a much smaller effect, in the opposite direction (repulsion). In our experiments, the contour is defined by two cues--the cue provided by the Gabor carrier (the 'feature' cue) and that defined by the Gaussian envelope (the 'envelope' cue). Our phase shift influence function can be thought of as a cue combination task. An ideal observer would weight the cues by the inverse variance of the two cues. The variance in each of these cues predicts the main features of our results quite accurately.
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Affiliation(s)
- Dennis M Levi
- School of Optometry, University of California, Berkeley, CA 94720-2020, USA
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50
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Chandler DM, Hemami SS. Effects of natural images on the detectability of simple and compound wavelet subband quantization distortions. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2003; 20:1164-1180. [PMID: 12868624 DOI: 10.1364/josaa.20.001164] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Quantization of the coefficients within a discrete wavelet transform subband gives rise to distortions in the reconstructed image that are localized in spatial frequency and orientation and are spatially correlated with the image. We investigated the detectability of these distortions: Contrast thresholds were measured for both simple and compound distortions presented in the unmasked paradigm and against two natural-image maskers. Simple and compound distortions were generated through uniform scalar quantization of one or two subbands. Unmasked detection thresholds for simple distortions yielded contrast sensitivity functions similar to those reported for 1-octave Gabor patches. Detection thresholds for simple distortions presented against two natural-image backgrounds revealed that thresholds were elevated across the frequency range of 1.15-18.4 cycles per degree with the greatest elevation for low-frequency distortions. Unmasked thresholds for compound distortions revealed relative sensitivities of 1.1-1.2, suggesting that summation of responses to wavelet distortions is similar to summation of responses to gratings. Masked thresholds for compound distortions revealed relative sensitivities of 1.5-1.7, suggesting greater summation when distortions are masked by natural images.
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Affiliation(s)
- Damon M Chandler
- Visual Communications Laboratory, School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.
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