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Hemispheric asymmetry of chromatic motion perception. Vision Res 2022; 196:108027. [DOI: 10.1016/j.visres.2022.108027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 02/01/2022] [Accepted: 02/02/2022] [Indexed: 11/17/2022]
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2
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Luo J, Chen Z, Lu Y, Spillmann L, Andolina IM, Wang W. The Serpentine Illusion: A Visual Motion Illusion Induced by Phase-Shifted Line Gratings. Front Neurosci 2020; 14:612153. [PMID: 33424543 PMCID: PMC7793819 DOI: 10.3389/fnins.2020.612153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/13/2020] [Indexed: 11/16/2022] Open
Abstract
In a pattern of horizontal lines containing ± 45° zigzagging phase-shifted strips, vivid illusory motion is perceived when the pattern is translated up or down at a moderate speed. Two forms of illusory motion are seen: [i] a motion "racing" along the diagonal interface between the strips and [ii] lateral (sideways) motion of the strip sections. We found the relative salience of these two illusory motions to be strongly influenced by the vertical spacing and length of the line gratings, and the period length of the zigzag strips. Both illusory motions are abolished when the abutting strips are interleaved, separated by a gap or when a real line is superimposed at the interface. Illusory motion is also severely weakened when equiluminant colored grating lines are used. Illusory motion perception is fully restored at < 20% luminance contrast. Using adaptation, we find that line-ends alone are insufficient for illusory motion perception, and that both physical carrier motion and line orientation are required. We finally test a classical spatiotemporal energy model of V1 cells that exhibit direction tuning changes that are consistent with the direction of illusory motion. Taking this data together, we constructed a new visual illusion and surmise its origin to interactions of spatial and temporal energy of the lines and line-ends preferentially driving the magnocellular pathway.
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Affiliation(s)
- Junxiang Luo
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China
| | - Zheyuan Chen
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China
| | - Yiliang Lu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China
| | - Lothar Spillmann
- Department of Neurology, University of Freiburg, Freiburg im Breisgau, Germany
| | - Ian Max Andolina
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China
| | - Wei Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
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3
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Pinna B, Deiana K. Material properties from contours: New insights on object perception. Vision Res 2015; 115:280-301. [PMID: 26072333 DOI: 10.1016/j.visres.2015.03.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 03/23/2015] [Accepted: 03/24/2015] [Indexed: 10/23/2022]
Abstract
In this work we explored phenomenologically the visual complexity of the material attributes on the basis of the contours that define the boundaries of a visual object. The starting point is the rich and pioneering work done by Gestalt psychologists and, more in detail, by Rubin, who first demonstrated that contours contain most of the information related to object perception, like the shape, the color and the depth. In fact, by investigating simple conditions like those used by Gestalt psychologists, mostly consisting of contours only, we demonstrated that the phenomenal complexity of the material attributes emerges through appropriate manipulation of the contours. A phenomenological approach, analogous to the one used by Gestalt psychologists, was used to answer the following questions. What are contours? Which attributes can be phenomenally defined by contours? Are material properties determined only by contours? What is the visual syntactic organization of object attributes? The results of this work support the idea of a visual syntactic organization as a new kind of object formation process useful to understand the language of vision that creates well-formed attribute organizations. The syntax of visual attributes can be considered as a new way to investigate the modular coding and, more generally, the binding among attributes, i.e., the issue of how the brain represents the pairing of shape and material properties.
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Affiliation(s)
- Baingio Pinna
- Dept. of Humanities and Social Sciences, University of Sassari, Italy.
| | - Katia Deiana
- Dept. of Humanities and Social Sciences, University of Sassari, Italy
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4
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Dürsteler MR. A common framework for the analysis of complex motion? Standstill and capture illusions. Front Hum Neurosci 2015; 8:999. [PMID: 25566023 PMCID: PMC4270218 DOI: 10.3389/fnhum.2014.00999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 11/24/2014] [Indexed: 12/04/2022] Open
Abstract
A series of illusions was created by presenting stimuli, which consisted of two overlapping surfaces each defined by textures of independent visual features (i.e., modulation of luminance, color, depth, etc.). When presented concurrently with a stationary 2-D luminance texture, observers often fail to perceive the motion of an overlapping stereoscopically defined depth-texture. This illusory motion standstill arises due to a failure to represent two independent surfaces (one for luminance and one for depth textures) and motion transparency (the ability to perceive motion of both surfaces simultaneously). Instead the stimulus is represented as a single non-transparent surface taking on the stationary nature of the luminance-defined texture. By contrast, if it is the 2D-luminance defined texture that is in motion, observers often perceive the stationary depth texture as also moving. In this latter case, the failure to represent the motion transparency of the two textures gives rise to illusionary motion capture. Our past work demonstrated that the illusions of motion standstill and motion capture can occur for depth-textures that are rotating, or expanding / contracting, or else spiraling. Here I extend these findings to include stereo-shearing. More importantly, it is the motion (or lack thereof) of the luminance texture that determines how the motion of the depth will be perceived. This observation is strongly in favor of a single pathway for complex motion that operates on luminance-defines texture motion signals only. In addition, these complex motion illusions arise with chromatically-defined textures with smooth transitions between their colors. This suggests that in respect to color motion perception the complex motions' pathway is only able to accurately process signals from isoluminant colored textures with sharp transitions between colors, and/or moving at high speeds, which is conceivable if it relies on inputs from a hypothetical dual opponent color pathway.
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Affiliation(s)
- Max R Dürsteler
- Vestibulo-Oculomotor Lab., Department of Neurology, University Hospital Zürich Zürich, Switzerland
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5
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McKeefry DJ, Burton MP, Morland AB. The contribution of human cortical area V3A to the perception of chromatic motion: a transcranial magnetic stimulation study. Eur J Neurosci 2010; 31:575-84. [PMID: 20105228 DOI: 10.1111/j.1460-9568.2010.07095.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Area V3A was identified in five human subjects on both a functional and retinotopic basis using functional magnetic resonance imaging techniques. V3A, along with other visual areas responsive to motion, was then targeted for disruption by repetitive transcranial magnetic stimulation (rTMS) whilst the participants performed a delayed speed matching task. The stimuli used for this task included chromatic, isoluminant motion stimuli that activated either the L-M or S-(L+M) cone-opponent mechanisms, in addition to moving stimuli that contained only luminance contrast (L+M). The speed matching task was performed for chromatic and luminance stimuli that moved at slow (2 degrees/s) or faster (8 degrees/s) speeds. The application of rTMS to area V3A produced a perceived slowing of all chromatic and luminance stimuli at both slow and fast speeds. Similar deficits were found when rTMS was applied to V5/MT+. No deficits in performance were found when areas V3B and V3d were targeted by rTMS. These results provide evidence of a causal link between neural activity in human area V3A and the perception of chromatic isoluminant motion. They establish area V3A, alongside V5/MT+, as a key area in a cortical network that underpins the analysis of not only luminance but also chromatically-defined motion.
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Affiliation(s)
- D J McKeefry
- Bradford School of Optometry and Vision Science, University of Bradford, Bradford, W Yorks, UK.
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6
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The perception of speed based on L-M and S-(L+M) cone opponent processing. Vision Res 2009; 49:870-6. [PMID: 19285523 DOI: 10.1016/j.visres.2009.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 03/04/2009] [Accepted: 03/05/2009] [Indexed: 11/20/2022]
Abstract
We have measured perceived speed and speed discrimination thresholds for stimuli that selectively activate the L-M, S-(L+M) cone opponent and L+M (luminance) post-receptoral pathways. For low speeds and low contrasts speed discrimination thresholds for L-M and S-(L+M) are similar but are higher and have a greater dependency upon contrast than those for luminance motion. These differences between chromatic and luminance speed perception can be eliminated when stimuli are equated with respect to their individual motion detection thresholds (MDTs). For fast moving gratings speed perception based upon L-M, S-(L+M) and L+M signals is similar in terms of threshold performance and contrast dependency. These results are consistent with the view that there are separate mechanisms for the analysis of chromatic and luminance motion, the relative contributions of which may change as a function of stimulus contrast and speed. The similarity in performance for S-(L+M) and L+M chromatic stimuli across a range of stimulus parameters suggests that signals derived from the two cone opponent pathways can be used equally well. Our results argue against the idea that speed perception is compromised when it is based upon information derived from the S-(L+M) cone opponent pathway.
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7
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Affiliation(s)
- Steven K. Shevell
- Departments of Psychology and Ophthalmology & Visual Science, University of Chicago, Chicago, Illinois 60637
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Michna ML, Yoshizawa T, Mullen KT. S-cone contributions to linear and non-linear motion processing. Vision Res 2007; 47:1042-54. [PMID: 17343890 DOI: 10.1016/j.visres.2007.01.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Revised: 12/21/2006] [Accepted: 01/25/2007] [Indexed: 11/30/2022]
Abstract
We investigated the characteristics of mechanisms mediating motion discrimination of S-cone isolating stimuli and found a double dissociation between the effects of luminance noise, which masks linear but not non-linear motion, and chromatic noise, which masks non-linear but not linear motion. We conclude that S-cones contribute to motion via two different pathways: a non-linear motion mechanism via a chromatic pathway and a linear motion mechanism via a luminance pathway. Additionally, motion discrimination and detection thresholds for drifting, S-cone isolating Gabors are unaffected by luminance noise, indicating that grating motion is mediated via chromatic mechanisms and based on higher-order motion processing.
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Affiliation(s)
- Magda L Michna
- Department of Ophthalmology, McGill Vision Research, McGill University, Montreal, Que., Canada H3A 1A1.
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9
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Abstract
The issue of whether there is a motion mechanism sensitive to purely chromatic stimuli has been pertinent for the past 30 or more years. The aim of this review is to examine why such different conclusions have been drawn in the literature and to reach some reconciliation. The review critically examines the behavioral evidence and concludes that there is a purely chromatic motion mechanism but that it is limited to the fovea. Examination of motion performance for chromatic and luminance stimuli provides convincing evidence that there are at least two different mechanisms for the two kinds of stimuli. The authors further argue that the chromatic mechanism may be at a particular disadvantage when the integration of multiple local motion signals is required. Finally, the authors present a descriptive model that may go some way toward explaining the reasons for the differences in collected data outlined in this article.
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10
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Cropper SJ. The detection of motion in chromatic stimuli: pedestals and masks. Vision Res 2005; 46:724-38. [PMID: 16112703 DOI: 10.1016/j.visres.2005.06.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 06/26/2005] [Accepted: 06/28/2005] [Indexed: 11/21/2022]
Abstract
This study seeks to clarify the reasons for some of the differences in the published data on chromatic motion perception, and to provide further support for the existence of a low-level motion mechanism sensitive to purely chromatic change. Observers discriminated the direction of motion of displaced sinusoidal gratings in the presence of a static grating mask (or pedestal). Each component of the stimulus was independently described in cardinal colour space and calibrated for subjective equiluminance using multiple methods. The motion structure, stimulus size, temporal frequency, contrast, relative phase and chromatic properties were all varied parametrically and the data cast in terms of predictions made by two different theoretical approaches to the test-mask combination. The vast majority of the data were well explained by a low-level motion mechanism sensitive to the motion of foveally-placed chromatic stimuli. Data consistent with either higher-level motion perception or a luminance-like signal were found outside the fovea and when the stimulus properties did not otherwise favour chromatic motion perception. There was some explanation of inconsistencies in previously published data and a strong suggestion that previous results showing pedestal-like behaviour for these stimulus combinations were a special case rather than a general result.
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Affiliation(s)
- Simon J Cropper
- Department of Psychology, University of Melbourne, Vic., Australia.
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11
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Cropper SJ. The detection of motion in chromatic stimuli: first-order and second-order spatial structure. Vision Res 2005; 45:865-80. [PMID: 15644227 DOI: 10.1016/j.visres.2004.09.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Revised: 08/31/2004] [Indexed: 11/17/2022]
Abstract
This study provides evidence for the existence of a low-level chromatic motion mechanism and further elucidates the conditions under which its operation becomes measurable in an experimental stimulus. Observers discriminated the direction of motion of amplitude modulated (AM) gratings that were defined by luminance or chromatic variation and masked with spatiotemporally broadband luminance or chromatic noise. The size and retinal location of the stimuli were varied and the effects of broadband noise and grating masks were both compared with the cohort of stimuli. Some significant disparities in the published literature were well explained by the results. In conclusion, evidence for a chromatically sensitive motion mechanism that evades the, detrimental effects of a luminance mask was found only at the fovea and only when the stimulus was small and centrally placed.
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Affiliation(s)
- Simon J Cropper
- Department of Psychology, University of Melbourne, Victoria 3010, Australia.
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12
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Abstract
For over 30 years there has been a controversy over whether
color-defined motion can be perceived by the human visual system. Some
results suggest that there is no chromatic motion mechanism at all,
whereas others do find evidence for a purely chromatic motion
mechanism. Here we examine the chromatic input to global motion
processing for a range of color directions in the photopic luminance
range. We measure contrast thresholds for global motion identification
and simple detection using sparse random-dot kinematograms. The results
show a discrepancy between the two chromatic axes: whereas it is
possible for observers to perform the global motion task for stimuli
modulated along the red–green axis, we could not assess the
contrast threshold required for stimuli modulated along the
yellowish-violet axis. The contrast required for detection for both
axes, however, are well below the contrasts required for global motion
identification. We conclude that there is a significant red–green
input to global motion processing providing further evidence for the
involvement of the parvocellular pathway. The lack of S-cone input to
global motion processing suggests that the koniocellular pathway
mediates the detection but not the processing of complex motion for our
parameter range.
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Affiliation(s)
- Alexa I Ruppertsberg
- Eleanor Rathbone Building, Department of Psychology, University of Liverpool, Liverpool, L69 7ZA, UK.
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13
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Mullen KT, Yoshizawa T, Baker CL. Luminance mechanisms mediate the motion of red-green isoluminant gratings: the role of "temporal chromatic aberration". Vision Res 2003; 43:1235-47. [PMID: 12726830 DOI: 10.1016/s0042-6989(03)00115-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In this paper we use a dynamic noise-masking paradigm to explore the nature of the mechanisms mediating the motion perception of drifting isoluminant red-green gratings. We compare contrast thresholds for the detection and direction discrimination of drifting gratings (1.5 cpd), over a range of temporal frequencies (0.5-9 Hz) in the presence of variable luminance or chromatic noise. In the first experiment, we used dynamic luminance noise to show that direction thresholds for red-green grating motion are masked by luminance noise over the entire temporal range tested, whereas detection thresholds are unaffected. This result indicates that the motion of nominally isoluminant red-green gratings is mediated by luminance signals. We suggest that stimulus-based luminance artifacts are not responsible for this effect because there is no masking of the detection thresholds. Instead we propose that chromatic motion thresholds for red-green isoluminant gratings are mediated by dynamic luminance artifacts that have an internal, physiological origin. We have termed these "temporal chromatic aberration". In the second experiment, we used dynamic chromatic noise masking to test for a chromatic contribution to red-green grating motion. We were unable to find conclusive evidence for a contribution of chromatic mechanisms to the chromatic grating motion, although a contribution at very high chromatic contrasts cannot be ruled out. Our results add to a growing body of evidence indicating the presence of dynamic, internal luminance artifacts in the motion of chromatic stimuli and we show that these occur even at very low temporal rates. Our results are compatible with our previous work indicating the absence of a chromatic mechanism for first order (quasi-linear) apparent motion [Vision Res. 40 (2000) 1993]. We conclude that previous conclusions based on the motion of chromatic red-green gratings should be reassessed to determine the contribution of dynamic luminance artifacts.
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Affiliation(s)
- Kathy T Mullen
- McGill Vision Research, Department of Ophthalmology (H4-14), McGill University, 687 Pine Avenue West, Que., H3A 1A1, Montreal, Canada.
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14
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Abstract
We examined the role of color in the processing of motion of a luminance-varying pattern by alternating the color of a moving pattern and measuring the luminance contrast required for accurate discrimination of the motion direction. We report that the contrast threshold for perceiving the direction of motion of luminance-varying patterns is greatly elevated when the mean chromaticity of the moving luminance pattern alternates between two hues. Thus, color plays a critical role in the discrimination of luminance motion direction. The magnitude of the threshold elevation is directly related to the magnitude of the LM opponent color contrast produced by the color alternation. S-cone contrast produces little or no effect. The interference produced by color alternation was greatly reduced in the retinal periphery. Our results indicate that first-order luminance motion mechanisms are sensitive to the color of moving objects as coded by a differencing of the outputs of L and M cones. Contrary to the widely accepted notion that luminance-defined motion is processed primarily in the spectrally broadband magnocellular (M) pathway, our results suggest that the hue-selective parvocellular (P) mechanisms provide input to first-order motion detectors.
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Affiliation(s)
- Tatsuto Takeuchi
- NTT Communication Science Laboratories, Nippon Telegraph and Telephone Corporation, Japan.
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15
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Abstract
It has been suggested that there are two types of chromatic motion mechanisms: signed chromatic motion, in which correspondence across successive frames is based on chromatic content of image regions, and unsigned chromatic motion based on movement of chromatically-defined borders. We investigate whether signed and unsigned red-green chromatic motion are mediated by a genuinely chromatic mechanism. Direction discrimination of signed and unsigned red-green chromatic motion were measured in the presence of a dynamic luminance masking noise. Increasing the luminance noise contrast systematically impaired signed motion, regardless of contrast and speed. This result suggests that signed red-green chromatic motion is derived from a luminance-based signal, rather than a genuinely chromatic motion mechanism. In the case of unsigned chromatic motion, there is no effect of luminance masking noise, indicating there exists a genuine chromatic mechanism for second-order motion perception.
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Affiliation(s)
- Tatsuya Yoshizawa
- Department of Ophthalmology, McGill Vision Research, McGill University, 687 Pine Avenue West, Room H4-14, Que., H3A 1A1, Montreal, Canada
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Shioiri S, Ito S, Sakurai K, Yaguchi H. Detection of relative and uniform motion. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2002; 19:2169-2179. [PMID: 12413117 DOI: 10.1364/josaa.19.002169] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We measured the lowest velocity (velocity threshold) for discriminating motion direction in relative and uniform motion stimuli, varying the contrast and the spatial frequency of the stimulus gratings. The results showed significant differences in the effects of contrast and spatial frequency on the threshold, as well as on the absolute threshold level between the two motion conditions, except when the contrast was 1% or lower. Little effect of spatial frequency was found for uniform motion, whereas a bandpass property with a peak at approximately 5 cycles per degree was found for relative motion. It was also found that contrast had little effect on uniform motion, whereas the threshold decreased with increases in contrast up to 85% for relative motion. These differences cannot be attributed to possible differences in eye movements between the relative and the uniform motion conditions, because the spatial-frequency characteristics differed in the two conditions even when the presentation duration was short enough to prevent eye movements. The differences also cannot be attributed to detecting positional changes, because the velocity threshold was not determined by the total distance of the stimulus movements. These results suggest that there are two different motion pathways: one that specializes in relative motion and one that specializes in uniform or global motion. A simulation showed that the difference in the response functions of the two possible pathways accounts for the differences in the spatial-frequency and contrast dependency of the velocity threshold.
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Affiliation(s)
- Satoshi Shioiri
- Department of Information and Image Sciences, Chiba University, Japan.
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17
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Willis A, Anderson SJ. Colour and luminance interactions in the visual perception of motion. Proc Biol Sci 2002; 269:1011-6. [PMID: 12028757 PMCID: PMC1690987 DOI: 10.1098/rspb.2002.1985] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We sought to determine the extent to which red-green, colour-opponent mechanisms in the human visual system play a role in the perception of drifting luminance-modulated targets. Contrast sensitivity for the directional discrimination of drifting luminance-modulated (yellow-black) test sinusoids was measured following adaptation to isoluminant red-green sinusoids drifting in either the same or opposite direction. When the test and adapt stimuli drifted in the same direction, large sensitivity losses were evident at all test temporal frequencies employed (1-16 Hz). The magnitude of the loss was independent of temporal frequency. When adapt and test stimuli drifted in opposing directions, large sensitivity losses were evident at lower temporal frequencies (1-4 Hz) and declined with increasing temporal frequency. Control studies showed that this temporal-frequency-dependent effect could not reflect the activity of achromatic units. Our results provide evidence that chromatic mechanisms contribute to the perception of luminance-modulated motion targets drifting at speeds of up to at least 32 degrees s(-1). We argue that such mechanisms most probably lie within a parvocellular-dominated cortical visual pathway, sensitive to both chromatic and luminance modulation, but only weakly selective for the direction of stimulus motion.
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Affiliation(s)
- Alexandra Willis
- School of Psychology and Sociology, Napier University, Craighouse Road, Edinburgh EH10 5LG, UK.
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18
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Abstract
Motion-onset visual evoked potentials (VEPs) were elicited by low spatial frequency chromatic isoluminant gratings presented in a central 7 degrees circular field. The chromatic composition of the stimuli was varied so as to modulate along different axes in colour space. For slow speeds (<5 degrees/s) changing the chromatic axis induced large response differences between the S- and L/M-cone VEPs. At faster speeds (5-12 degrees/s) the effects were not as marked. A dichotomy between the slow and fast responses was also shown to exist in terms of their contrast dependencies, the former exhibiting a stronger dependency on contrast than the latter. These findings suggest that neural substrates with chromatic sensitivity are involved in the generation of S- and L/M-cone mediated motion-onset VEPs at low velocities. At higher velocities, responses are generated by different mechanisms that possess little or no chromatic sensitivity.
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Affiliation(s)
- D J McKeefry
- Vision Science Research Group, School of Biomedical Sciences, University of Ulster, Coleraine, N. Ireland, BT52 1SA, UK.
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19
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Abstract
In this study, we have compared foveal SF discriminations for luminance and color-defined stimuli using two different tasks (criteria): in criterion-A, the discrimination is based on spatial (size of the stimuli) and/or spatial frequency; in criterion-B, it is based on apparent motion (contraction/expansion). We used high contrast (75%) spatially localized D6 stimuli and cosine gratings (0.25-9.5 cpd). The SF discrimination was measured by the method of constant stimuli with a two-interval forced-choice procedure. Data show that: (i) for criterion-A, the discrimination thresholds for color stimuli were lower than that for luminance stimuli at low SFs, but similar or higher at higher SFs; for criterion-B, the thresholds to chromatic stimuli were higher than that to achromatic stimuli for all SFs; (ii) SF discrimination was best at inter-stimulus-interval (ISI) of about 200 ms for color stimuli and at ISI of 0 ms for luminance stimuli; (iii) SF discrimination got better with stimulus duration and reached to plateau at 200 ms (or more) for color stimuli and at 67 ms (or more) for luminance stimuli; (iv) SF discrimination threshold (mean Delta(f)=0.19 octaves) is about one-tenth of the full bandwidth (mean=1.96 octaves) of SF tuned mechanisms and is in hyperacuity range; both (discrimination and hyperacuity) can be explained by the relative activities within a population of tuned mechanisms. We conclude that color and luminance SF discrimination thresholds have a different SF dependence. While color appears to perform better than luminance vision at low SFs, this effect is lost or even reversed at high SFs. Data imply that color and form interact, but color and motion are largely segregated (i.e. they weakly interact).
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20
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Baker CL, Mareschal I. Processing of second-order stimuli in the visual cortex. PROGRESS IN BRAIN RESEARCH 2002; 134:171-91. [PMID: 11702543 DOI: 10.1016/s0079-6123(01)34013-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Naturally occurring visual stimuli are rich in examples of objects delineated from their backgrounds simply by differences in luminance, so-called first-order stimuli, as well as those defined by differences of contrast or texture, referred to as second-order stimuli. Here we provide a brief overview of visual cortical processing of second-order stimuli, as well as some comparative background on first-order processing, concentrating on single-unit neurophysiology, but also discussing relationships to human psychophysics and to neuroimaging. The selectivity of visual cortical neurons to orientation, spatial frequency, and direction of movement of first-order, luminance-defined stimuli is conventionally understood in terms of simple linear filter models, albeit with some minor nonlinearities such as thresholding and gain control. However, these kinds of models fail entirely to account for responses of neurons to second-order stimuli such as contrast envelopes, illusory contours, or texture borders. Second-order stimuli constructed from sinusoidal components have been used to analyze the neurophysiological mechanisms of such responses; these experiments demonstrate that the same neuron can exhibit three distinct kinds of tuning to spatial frequency, and also to orientation. These results can be understood in terms of a type of nonlinear 'filter-->rectify-->filter' model, which has been widely used in human psychophysics. Finally, several general issues will be discussed, including potential artifacts in experiments with second-order stimuli, and strategies for avoiding or controlling for them; caveats about definitions of first- vs. second-order mechanisms and stimuli; the concept of form-cue invariance; and the functional significance of second-order processing.
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Affiliation(s)
- C L Baker
- Department of Ophthalmology, McGill University, 687 Pine Ave. W. H4-14, Montreal, PQ H3A 1A1, Canada.
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Li HC, Kingdom FA. Motion-surface labeling by orientation, spatial frequency and luminance polarity in 3-D structure-from-motion. Vision Res 2001; 41:3873-82. [PMID: 11738453 DOI: 10.1016/s0042-6989(01)00227-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A compelling percept of three-dimensionality is attainable from a purely motion-defined simulation of a transparent rotating cylinder, referred to as 3-D structure-from-motion (SFM). Interestingly, subjects rarely perceive reversals of the cylinder's direction of rotation when they are introduced. Treue, Andersen, Ando, and Hildreth (Vision Res. 35 (1995) 139-148) have argued that this reflects the visual system's insensitivity to the textural detail on the cylinder's motion surfaces. We have recently shown however that with cylinders made from oriented micropatterns, motion reversals are perceived when the orientations of the micropatterns are different on the cylinder's front/back surfaces, suggesting that the visual system is sensitive to the type of feature in these stimuli (Vision Res. 39 (1999) 881-886). In the present study we extended this finding by testing for feature-sensitivity along other dimensions besides orientation, specifically spatial frequency, colour and luminance polarity. We found that subjects perceived more rotation direction reversals when the front/back surfaces of the cylinder were segregated, as opposed to non-segregated by feature-type, along all of these dimensions except, notably, colour. We also investigated the stage at which the feature-sensitivity is incorporated in 3-D SFM. We reasoned that if 3-D SFM mechanisms were tuned, or labeled for feature-type, swapping of features during the cylinder's rotation would result in illusory reversals in just the feature-segregated condition, whereas if grouping of like-features preceded the formation of 3-D motion surfaces, no such illusory reversals would be expected. We found that feature-swapping resulted in more illusory reversals in the feature-segregated compared to non-segregated conditions, supporting the mechanism tuning, or labeling, hypothesis.
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Affiliation(s)
- H C Li
- Department of Industrial Psychology, Kwangwoon University, Nowon-Gu, Wolgae-Dong, 447-1 Seoul, South Korea.
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Li HC, Kingdom FA. Segregation by color/luminance does not necessarily facilitate motion discrimination in the presence of motion distractors. PERCEPTION & PSYCHOPHYSICS 2001; 63:660-75. [PMID: 11436736 DOI: 10.3758/bf03194428] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Under what circumstances is the common motion of a group of elements more easily perceived when the elements differ in color and/or luminance polarity from their surround? Croner and Albright (1997), using a conventional global motion paradigm, first showed that motion coherence thresholds fell when target and distractor elements were made different in color. However, in their paradigm, there was a cue in the static view of the stimulus as to which elements belonged to the target. Arguably, in order to determine whether the visual system automatically groups, or prefilters, the image into different color maps for motion processing, such static form cues should be eliminated. Using various arrangements of the global motion stimulus in which we eliminated all static form cues, we found that global motion thresholds were no better when target and distractors differed in color than when they were identical, except under certain circumstances in which subjects had prior knowledge of the specific target color. We conclude that, in the absence of either static form cues or the possibility of selective attention to the target color, features with similar colors/luminance-polarities are not automatically grouped for global motion analysis.
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Affiliation(s)
- H C Li
- Department of Industrial Psychology, Kwangwoon University, Nowon-Gu, Wolgae-Dong, 447-1, Seoul, Korea.
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