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Dopkins S. How is visual separation assessed? By counting distance units. Front Psychol 2024; 15:1410297. [PMID: 38873519 PMCID: PMC11169693 DOI: 10.3389/fpsyg.2024.1410297] [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: 03/31/2024] [Accepted: 05/14/2024] [Indexed: 06/15/2024] Open
Abstract
How does the human visual system assess the separation between pairs of stimuli in a frontal plane? According to the direct (or subtractive) view the system finds the difference between the positions of the stimuli in a localization system. According to the indirect (or additive) view the system finds the number of instances of a distance unit lying between representations of the stimuli. Critically, position is explicitly represented under the direct view, with separation being derived from position. Position is not explicitly represented under the indirect view; separation is consequently inferred by counting an internal unit of distance. Recent results favor the indirect over the direct view of separation assessment. Dissociations between assessments of separation and position, various context effects in the assessment of separation, and suggestions that position information is not cleanly accessed argue against the direct view. At the same time, various context effects in separation assessment argue for the indirect view. Recent findings regarding the brain bases of vision are consistent with the indirect view. In short, recent results suggest that assessing the separation between two frontal stimuli involves integrating distance units between representations of the stimuli.
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Affiliation(s)
- Stephen Dopkins
- Department of Psychological and Brain Sciences, George Washington University, Washington, DC, United States
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2
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Ryu J, Lee SH. Bounded contribution of human early visual cortex to the topographic anisotropy in spatial extent perception. Commun Biol 2024; 7:178. [PMID: 38351283 PMCID: PMC10864322 DOI: 10.1038/s42003-024-05846-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 01/23/2024] [Indexed: 02/16/2024] Open
Abstract
To interact successfully with objects, it is crucial to accurately perceive their spatial extent, an enclosed region they occupy in space. Although the topographic representation of space in the early visual cortex (EVC) has been favored as a neural correlate of spatial extent perception, its exact nature and contribution to perception remain unclear. Here, we inspect the topographic representations of human individuals' EVC and perception in terms of how much their anisotropy is influenced by the orientation (co-axiality) and radial position (radiality) of stimuli. We report that while the anisotropy is influenced by both factors, its direction is primarily determined by radiality in EVC but by co-axiality in perception. Despite this mismatch, the individual differences in both radial and co-axial anisotropy are substantially shared between EVC and perception. Our findings suggest that spatial extent perception builds on EVC's spatial representation but requires an additional mechanism to transform its topographic bias.
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Affiliation(s)
- Juhyoung Ryu
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sang-Hun Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
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3
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Yoo SA, Joo SJ. Behavioral examination of the role of the primary visual cortex in the perceived size representation. Sci Rep 2023; 13:21134. [PMID: 38036762 PMCID: PMC10689741 DOI: 10.1038/s41598-023-48632-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 11/28/2023] [Indexed: 12/02/2023] Open
Abstract
Previous research has shown that neural activity in the primary visual cortex (V1) and V1 surface area may be linked with subjective experience of size illusions. Here, we behaviorally measured the hallway illusion with experimental manipulations as a proxy of V1's influence on size perception. We first tested whether the hallway illusion can persist without further recurrent processing by using backward masking. Next, we examined relations among the hallway illusion magnitude and other perceptual measures that have been suggested to be correlated with V1 surface area. In Experiment 1, the magnitude of the hallway illusion was not affected by the stimulus duration and visual masking when the hallway context was previewed (i.e., complex depth information is already processed). It suggests that V1 activity could support the size illusion to some extent even when recurrent processing between V1 and higher areas is disturbed. In Experiment 2, the hallway illusion magnitude was correlated with the Vernier acuity threshold, but not with physical size discriminability. Our results provide converging evidence with the previous findings in that neural activity in V1 may contribute to size illusions and that V1 surface area is not the sole factor that mediates size perception and visual precision.
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Affiliation(s)
- Sang-Ah Yoo
- Department of Psychology, Pusan National University, Busan, Republic of Korea
| | - Sung Jun Joo
- Department of Psychology, Pusan National University, Busan, Republic of Korea.
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4
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Linton P. Minimal theory of 3D vision: new approach to visual scale and visual shape. Philos Trans R Soc Lond B Biol Sci 2023; 378:20210455. [PMID: 36511406 PMCID: PMC9745885 DOI: 10.1098/rstb.2021.0455] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Since Kepler and Descartes in the early-1600s, vision science has been committed to a triangulation model of stereo vision. But in the early-1800s, we realized that disparities are responsible for stereo vision. And we have spent the past 200 years trying to shoe-horn disparities back into the triangulation account. The first part of this article argues that this is a mistake, and that stereo vision is a solution to a different problem: the eradication of rivalry between the two retinal images, rather than the triangulation of objects in space. This leads to a 'minimal theory of 3D vision', where 3D vision is no longer tied to estimating the scale, shape, and direction of objects in the world. The second part of this article then asks whether the other aspects of 3D vision, which go beyond stereo vision, really operate at the same level of visual experience as stereo vision? I argue they do not. Whilst we want a theory of real-world 3D vision, the literature risks giving us a theory of picture perception instead. And I argue for a two-stage theory, where our purely internal 'minimal' 3D percept (from stereo vision) is linked to the world through cognition. This article is part of a discussion meeting issue 'New approaches to 3D vision'.
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Affiliation(s)
- Paul Linton
- Presidential Scholars in Society and Neuroscience, Center for Science and Society, Columbia University, New York, NY 10027, USA,Italian Academy for Advanced Studies in America, Columbia University, New York, NY 10027, USA,Visual Inference Lab, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
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5
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Tamè L, Limbu S, Harlow R, Parikh M, Longo MR. Size Constancy Mechanisms: Empirical Evidence from Touch. Vision (Basel) 2022; 6:vision6030040. [PMID: 35893757 PMCID: PMC9326730 DOI: 10.3390/vision6030040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 06/10/2022] [Accepted: 06/14/2022] [Indexed: 11/30/2022] Open
Abstract
Several studies have shown the presence of large anisotropies for tactile distance perception across several parts of the body. The tactile distance between two touches on the dorsum of the hand is perceived as larger when they are oriented mediolaterally (across the hand) than proximodistally (along the hand). This effect can be partially explained by the characteristics of primary somatosensory cortex representations. However, this phenomenon is significantly attenuated relative to differences in acuity and cortical magnification, suggesting a process of tactile size constancy. It is unknown whether the same kind of compensation also takes place when estimating the size of a continuous object. Here, we investigate whether the tactile anisotropy that typically emerges when participants have to estimate the distance between two touches is also present when a continuous object touches the skin and participants have to estimate its size. In separate blocks, participants judged which of two tactile distances or objects on the dorsum of their hand felt larger. One stimulation (first or second) was aligned with the proximodistal axis (along the hand) and the other with the mediolateral axis (across the hand). Results showed a clear anisotropy for distances between two distinct points, with across distances consistently perceived as larger than along distances, as in previous studies. Critically, however, this bias was significantly reduced or absent for judgments of the length of continuous objects. These results suggest that a tactile size constancy process is more effective when the tactile size of an object has to be approximated compared to when the distance between two touches has to be determined. The possible mechanism subserving these results is described and discussed. We suggest that a lateral inhibition mechanism, when an object touches the skin, provides information through the distribution of the inhibitory subfields of the RF about the shape of the tactile RF itself. Such a process allows an effective tactile size compensatory mechanism where a good match between the physical and perceptual dimensions of the object is achieved.
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Affiliation(s)
- Luigi Tamè
- School of Psychology, University of Kent, Canterbury CT2 7NP, UK
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
- Correspondence: (L.T.); (M.R.L.)
| | - Suzuki Limbu
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
| | - Rebecca Harlow
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
| | - Mita Parikh
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
| | - Matthew R. Longo
- Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, UK; (S.L.); (R.H.); (M.P.)
- Correspondence: (L.T.); (M.R.L.)
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6
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Rohr JTD, Isaac CR, de Lima ADA, Garcia A, dos Santos PM, Tavares MCH. Study of Geometric Illusory Visual Perception – A New Perspective in the Functional Evaluation of Children With Strabismus. Front Hum Neurosci 2022; 16:769412. [PMID: 35496072 PMCID: PMC9043129 DOI: 10.3389/fnhum.2022.769412] [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: 09/03/2021] [Accepted: 03/23/2022] [Indexed: 11/17/2022] Open
Abstract
Despite the various perceptual-motor deficits documented in strabismus, there is a paucity of studies evaluating visual illusions in patients with strabismus. The aim of this study was to examine how the illusionary perception occurs in children/adolescents (10–15 years old) with strabismus with referral for surgery to correct ocular deviations. A controlled cross-sectional study was carried out in which 45 participants with strabismus and 62 healthy volunteers aged 10–15 years were evaluated. The behavioral response to three geometric illusions [Vertical-Horizontal illusion, Müller-Lyer illusion (Bretano version) and Ponzo illusion] and respective neutral stimuli (non-illusory images) regarding the estimation of image size and response time were measured using the Method of Adjustment. To analyze the influence of secondary factors: type of ocular deviation (convergent, divergent or associated with vertical deviation); amount of eye deviation; presence of amblyopia and stereopsis, a one-way ANOVA was performed. Among the tested illusions, children with strabismus showed greater susceptibility (p = 0.006) and response time (p = 0.004) to Ponzo’s illusory images. Children with strabismus and preserved stereopsis, on the other hand, showed similar susceptibility and response time to control group patients to the Ponzo illusion (p < 0.005). Patients with amblyopia showed overcorrection in the estimate of non-illusory Ponzo images (p = 0.046). Children with horizontal ocular deviation (esotropia or exotropia) associated with vertical deviation (hypertropia, DVD and/or alphabetical anisotropy) showed higher susceptibility to vertical adjustment images for the Müller-Lyer illusion (Brentano version) (p = 0.017). Individuals with strabismus tended to overcorrect the length of the straight-line segment adjusted for non-illusory images when testing non-illusory images in the Müller-Lyer test (Brentano version) (p = 0.009), as well as for the neutral images in the Vertical-Horizontal test (p = 0.000). The findings indicated impairment in the perception of geometric illusions and neutral figures, especially for the Ponzo illusion test by children with strabismus. As the behavioral response to illusory images may indirectly reflect the visual and morphofunctional alterations present in these individuals, we suggest that the investigation of visual illusory perception can be used as a new research strategy in the field of investigating the visual function in strabismus.
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Affiliation(s)
- Juliana Tessari Dias Rohr
- Department of Ophthalmology, Hospital de Base do Distrito Federal, Brasília, Brazil
- Department of Physiological Sciences, Institute of Biological Sciences, University of Brasília – UnB, Brasília, Brazil
- *Correspondence: Juliana Tessari Dias Rohr, ,
| | | | | | - Ana Garcia
- Department of Physiological Sciences, Institute of Biological Sciences, University of Brasília – UnB, Brasília, Brazil
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7
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The human primary visual cortex (V1) encodes the perceived position of static but not moving objects. Commun Biol 2022; 5:181. [PMID: 35233067 PMCID: PMC8888673 DOI: 10.1038/s42003-022-03136-y] [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: 09/01/2021] [Accepted: 02/03/2022] [Indexed: 11/09/2022] Open
Abstract
Brain activity in retinotopic cortex reflects illusory changes in stimulus position. Is this neural signature a general code for apparent position? Here we show that responses in primary visual cortex (V1) are consistent with perception of the Muller-Lyer illusion; however, we found no such signature for another striking illusion, the curveball effect. This demonstrates that V1 does not encode apparent position per se.
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8
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Linton P. V1 as an egocentric cognitive map. Neurosci Conscious 2021; 2021:niab017. [PMID: 34532068 PMCID: PMC8439394 DOI: 10.1093/nc/niab017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 05/21/2021] [Accepted: 06/08/2021] [Indexed: 01/20/2023] Open
Abstract
We typically distinguish between V1 as an egocentric perceptual map and the hippocampus as an allocentric cognitive map. In this article, we argue that V1 also functions as a post-perceptual egocentric cognitive map. We argue that three well-documented functions of V1, namely (i) the estimation of distance, (ii) the estimation of size, and (iii) multisensory integration, are better understood as post-perceptual cognitive inferences. This argument has two important implications. First, we argue that V1 must function as the neural correlates of the visual perception/cognition distinction and suggest how this can be accommodated by V1's laminar structure. Second, we use this insight to propose a low-level account of visual consciousness in contrast to mid-level accounts (recurrent processing theory; integrated information theory) and higher-level accounts (higher-order thought; global workspace theory). Detection thresholds have been traditionally used to rule out such an approach, but we explain why it is a mistake to equate visibility (and therefore the presence/absence of visual experience) with detection thresholds.
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Affiliation(s)
- Paul Linton
- Centre for Applied Vision Research, City, University of London, Northampton Square, London EC1V 0HB, UK
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9
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Abstract
We measured the pupil response to a light stimulus subject to a size illusion and found that stimuli perceived as larger evoke a stronger pupillary response. The size illusion depends on combining retinal signals with contextual 3D information; contextual processing is thought to vary across individuals, being weaker in individuals with stronger autistic traits. Consistent with this theory, autistic traits correlated negatively with the magnitude of pupil modulations in our sample of neurotypical adults; however, psychophysical measurements of the illusion did not correlate with autistic traits, or with the pupil modulations. This shows that pupillometry provides an accurate objective index of complex perceptual processes, particularly useful for quantifying interindividual differences, and potentially more informative than standard psychophysical measures.
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10
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Carther-Krone TA, Lawrence-Dewar JM, Shomstein S, Nah JC, Collegio AJ, Marotta JJ. Neural Correlates of Perceptual Grouping Under Conditions of Inattention and Divided Attention. Perception 2021; 49:495-514. [PMID: 32389095 DOI: 10.1177/0301006620912134] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Grouping local elements of the visual environment together is crucial for meaningful perception. While our attentional system facilitates perception, it is limited in that we are unaware of some aspects of our environment that can still influence how we experience it. In this study, the neural mechanisms underlying the Ponzo illusion were examined under inattention and divided-attention conditions using functional magnetic resonance imaging to investigate the brain regions responsible for accessing visual stimuli. A line discrimination task was performed in which two horizontal lines were superimposed on a background of black and white dots that, on occasion, induced the Ponzo illusion if perceptually grouped together. Our findings revealed activation for perceptual grouping in the frontal, parietal, and occipital regions of the brain and activation in the bilateral frontal, temporal, and cingulate gyrus in response to divided attention compared with inattention trials. A direct comparison between grouping and attention showed involvement of the right supramarginal gyrus in grouping specifically under conditions of inattention, suggesting that even during implicit grouping complex visual processing occurs. Given that much of the visual world is not represented in conscious perception, these findings provide crucial information about how we make sense of visual scenes in the world.
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Affiliation(s)
- Tiffany A Carther-Krone
- Perception and Action Lab, Department of Psychology, University of Manitoba, Winnipeg, Canada
| | | | | | | | - Andrew J Collegio
- Department of Psychology, George Washington University, Washington, USA
| | - Jonathan J Marotta
- Perception and Action Lab, Department of Psychology, University of Manitoba, Winnipeg, Canada
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11
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Zooming-in on higher-level vision: High-resolution fMRI for understanding visual perception and awareness. Prog Neurobiol 2021; 207:101998. [PMID: 33497652 DOI: 10.1016/j.pneurobio.2021.101998] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 11/11/2020] [Accepted: 01/16/2021] [Indexed: 12/24/2022]
Abstract
One of the central questions in visual neuroscience is how the sparse retinal signals leaving our eyes are transformed into a rich subjective visual experience of the world. Invasive physiology studies, which offers the highest spatial resolution, have revealed many facts about the processing of simple visual features like contrast, color, and orientation, focusing on the early visual areas. At the same time, standard human fMRI studies with comparably coarser spatial resolution have revealed more complex, functionally specialized, and category-selective responses in higher visual areas. Although the visual system is the best understood among the sensory modalities, these two areas of research remain largely segregated. High-resolution fMRI opens up a possibility for linking them. On the one hand, it allows studying how the higher-level visual functions affect the fine-scale activity in early visual areas. On the other hand, it allows discovering the fine-scale functional organization of higher visual areas and exploring their functional connectivity with visual areas lower in the hierarchy. In this review, I will discuss examples of successful work undertaken in these directions using high-resolution fMRI and discuss where this method could be applied in the future to advance our understanding of the complexity of higher-level visual processing.
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12
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Wang A, Chen L, Jiang Y. Anodal Occipital Transcranial Direct Current Stimulation Enhances Perceived Visual Size Illusions. J Cogn Neurosci 2020; 33:528-535. [PMID: 33326330 DOI: 10.1162/jocn_a_01664] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Human early visual cortex has long been suggested to play a crucial role in context-dependent visual size perception through either lateral interaction or feedback projections from higher to lower visual areas. We investigated the causal contribution of early visual cortex to context-dependent visual size perception using the technique of transcranial direct current stimulation and two well-known size illusions (i.e., the Ebbinghaus and Ponzo illusions) and further elucidated the underlying mechanism that mediates the effect of transcranial direct current stimulation over early visual cortex. The results showed that the magnitudes of both size illusions were significantly increased by anodal stimulation relative to sham stimulation but left unaltered by cathodal stimulation. Moreover, the anodal effect persisted even when the central target and surrounding inducers of the Ebbinghaus configuration were presented to different eyes, with the effect lasting no more than 15 min. These findings provide compelling evidence that anodal occipital stimulation enhances the perceived visual size illusions, which is possibly mediated by weakening the suppressive function of the feedback connections from higher to lower visual areas. Moreover, the current study provides further support for the causal role of early visual cortex in the neural processing of context-dependent visual size perception.
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Affiliation(s)
- Anqi Wang
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University.,Key Laboratory of Brain and Cognitive Neuroscience, Dalian, China
| | - Lihong Chen
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University.,Key Laboratory of Brain and Cognitive Neuroscience, Dalian, China
| | - Yi Jiang
- State Key Laboratory of Brain and Cognitive Science, CAS Center for Excellence in Brain Science and Intelligence Technology, Institute of Psychology, Chinese Academy of Sciences.,University of Chinese Academy of Sciences.,Chinese Institute for Brain Research, Beijing, China.,Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, China
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13
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Yildiz GY, Sperandio I, Kettle C, Chouinard PA. Interocular transfer effects of linear perspective cues and texture gradients in the perceptual rescaling of size. Vision Res 2020; 179:19-33. [PMID: 33276195 DOI: 10.1016/j.visres.2020.11.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 10/30/2020] [Accepted: 11/13/2020] [Indexed: 12/29/2022]
Abstract
Our objective was to determine whether the influence of linear perspective cues and texture gradients in the perceptual rescaling of stimulus size transfers from one eye to the other. In experiment 1, we systematically added linear perspective cues and texture gradients in a background image of the corridor illusion. To determine whether perceptual size rescaling takes place at earlier or later stages, we tested how the perceived size of top and bottom rings changed under binocular (rings and background presented to both eyes), monocular (rings and background presented to the dominant eye only), and dichoptic (rings and background presented separately to the dominant and nondominant eyes, respectively) viewing conditions. We found differences between viewing conditions in the perceived size of the rings when linear perspective cues, but not texture gradients, were presented. Specifically, linear perspective cues produced a stronger illusion under the monocular compared to the dichoptic viewing condition. Hence, there was partial interocular transfer from the linear perspective cues, suggesting a dominant role of monocular neural populations in mediating the corridor illusion. In experiment 2, we repeated similar procedures with a more traditional Ponzo illusion background. Contrary to findings from experiment 1, there was a full interocular transfer with the presence of the converging lines, suggesting a dominant role of binocular neural populations. We conclude that higher order visual areas, which contain binocular neural populations, are more involved in the perceptual rescaling of size evoked by linear perspective cues in the Ponzo compared to the corridor illusion.
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Affiliation(s)
- Gizem Y Yildiz
- Department of Psychology and Counselling, School of Psychology and Public Health, La Trobe University, Melbourne, Australia
| | - Irene Sperandio
- Department of Psychology and Cognitive Science, University of Trento, Rovereto, TN, Italy
| | - Christine Kettle
- Department of Pharmacy and Biomedical Sciences, School of Molecular Sciences, La Trobe University, Melbourne, Australia
| | - Philippe A Chouinard
- Department of Psychology and Counselling, School of Psychology and Public Health, La Trobe University, Melbourne, Australia.
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14
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Abstract
We recently showed that motion dynamics greatly enhance the magnitude of certain size contrast illusions, such as the Ebbinghaus and Delboeuf illusions. Here, we extend our study of the effect of motion dynamics on size illusions through a novel dynamic corridor illusion, in which a single target translates along a corridor background. Across three psychophysical experiments, we quantify the effects of stimulus dynamics on the Ebbinghaus and corridor illusions across different viewing conditions. The results revealed that stimulus dynamics had opposite effects on these different classes of size illusions. Whereas dynamic motion enhanced the magnitude of the Ebbinghaus illusion, it attenuated the magnitude the corridor illusion. Our results highlight precision-driven weighting of visual cues by neural circuits computing perceived object size. This hypothesis is consistent with observations beyond size perception and may represent a more general principle of cue integration in the visual system.
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15
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Chen L, Wu B, Qiao C, Liu DQ. Resting EEG in alpha band predicts individual differences in visual size perception. Brain Cogn 2020; 145:105625. [PMID: 32932108 DOI: 10.1016/j.bandc.2020.105625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 08/04/2020] [Accepted: 09/02/2020] [Indexed: 11/19/2022]
Abstract
Human visual size perception results from an interaction of external sensory information and internal state. The cognitive mechanisms involved in the processing of context-dependent visual size perception have been found to be innate in nature to some extent, suggesting that visual size perception might correlate with human intrinsic brain activity. Here we recorded human resting alpha activity (8-12 Hz), which is an inverse indicator of sustained alertness. Moreover, we measured an object's perceived size in a two-alternative forced-choice manner and the Ebbinghaus illusion magnitude which is a classic illustration of context-dependent visual size perception. The results showed that alpha activity along the ventral visual pathway, including left V1, right LOC and bilateral inferior temporal gyrus, negatively correlated with an object's perceived size. Moreover, alpha activity in the left superior temporal gyrus positively correlated with size discrimination threshold and size illusion magnitude. The findings provide clear evidence that human visual size perception scales as a function of intrinsic alertness, with higher alertness linking to larger perceived size of objects and better performance in size discrimination and size illusion tasks, and suggest that individual variation in resting-state brain activity provides a neural explanation for individual variation in cognitive performance of normal participants.
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Affiliation(s)
- Lihong Chen
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian, PR China; Key Laboratory of Brain and Cognitive Neuroscience, Liaoning Province, Dalian, PR China.
| | - Baoyu Wu
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian, PR China; Key Laboratory of Brain and Cognitive Neuroscience, Liaoning Province, Dalian, PR China
| | - Congying Qiao
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian, PR China; Key Laboratory of Brain and Cognitive Neuroscience, Liaoning Province, Dalian, PR China
| | - Dong-Qiang Liu
- Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian, PR China; Key Laboratory of Brain and Cognitive Neuroscience, Liaoning Province, Dalian, PR China.
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16
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Altan E, Boyaci H. Size aftereffect is non-local. Vision Res 2020; 176:40-47. [PMID: 32777588 DOI: 10.1016/j.visres.2020.07.006] [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: 05/17/2020] [Revised: 07/10/2020] [Accepted: 07/10/2020] [Indexed: 10/23/2022]
Abstract
It is well known that prolonged exposure to a certain size stimulus alters the perceived size of a subsequently presented stimulus at the same location. How the rest of the visual space is affected by this size adaptation, however, has not been systematically studied before. Here, to fill this gap in literature, we tested size adaptation at the adapter location as well as the rest of the visual space. We used peripherally presented solid discs (Experiment 1) and rings (Experiment 2) as adapter and target (test) stimuli. Observers adapted to a mid-sized stimulus and judged the size of the subsequently presented smaller or larger target stimuli. Results showed that the perceived sizes of target stimuli were repelled away from the adapter size, not only at the adapter location but also at other locations. These findings demonstrate that size adaptation causes widespread distortion of the visual space and alters perceived size. We discuss possible computational models that may underpin the perceptual effect.
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Affiliation(s)
- Ecem Altan
- A.S. Brain Research Center & National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey; Department of Psychology, Bilkent University, Ankara, Turkey.
| | - Huseyin Boyaci
- A.S. Brain Research Center & National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey; Department of Psychology, Bilkent University, Ankara, Turkey; Department of Psychology, JL Gießen University, Gießen, Germany
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17
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Visual Size Processing in Early Visual Cortex Follows Lateral Occipital Cortex Involvement. J Neurosci 2020; 40:4410-4417. [PMID: 32350038 DOI: 10.1523/jneurosci.2437-19.2020] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Revised: 04/06/2020] [Accepted: 04/06/2020] [Indexed: 11/21/2022] Open
Abstract
Neural activation in the early visual cortex (EVC) reflects the perceived rather than retinal size of stimuli, suggesting that feedback possibly from extrastriate regions modulates retinal size information in EVC. Meanwhile, the lateral occipital cortex (LOC) has been suggested to be critically involved in object size processing. To test for the potential contributions of feedback modulations on size representations in EVC, we investigated the dynamics of relevant processes using transcranial magnetic stimulation (TMS). Specifically, we briefly disrupted the neural activity of EVC and LOC at early, intermediate, and late time windows while participants performed size judgment tasks in either an illusory or neutral context. TMS over EVC and LOC allowed determining whether these two brain regions are relevant for generating phenomenological size impressions. Furthermore, the temporal order of TMS effects allowed inferences on the dynamics of information exchange between the two areas. Particularly, if feedback signals from LOC to EVC are crucial for generating altered size representations in EVC, then TMS effects over EVC should be observed simultaneously or later than the effects following LOC stimulation. The data from 20 humans (13 females) revealed that TMS over both EVC and LOC impaired illusory size perception. However, the strongest effects of TMS applied over EVC occurred later than those of LOC, supporting a functionally relevant feedback modulation from LOC to EVC for scaling size information. Our results suggest that context integration and the concomitant change of perceived size require LOC and result in modulating representations in EVC via recurrent processing.SIGNIFICANCE STATEMENT How we perceive an object's size is not entirely determined by its physical size or the size of its retinal representation but also the spatial context. Using transcranial magnetic stimulation, we investigated the role of the early visual cortex (EVC) and the higher-level visual area, lateral occipital cortex (LOC), known to be critically involved in object processing, in transforming an initial retinal representation into one that reflects perceived size. Transcranial magnetic stimulation altered size perception earlier over LOC compared with EVC, suggesting that context integration and the concomitant change in perceived size representations in EVC rely on feedback from LOC.
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18
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Hataji Y, Kuroshima H, Fujita K. Dynamic Corridor Illusion in Pigeons: Humanlike Pictorial Cue Precedence Over Motion Parallax Cue in Size Perception. Iperception 2020; 11:2041669520911408. [PMID: 32269745 PMCID: PMC7093692 DOI: 10.1177/2041669520911408] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 02/14/2020] [Indexed: 11/20/2022] Open
Abstract
Depth information is necessary for perceiving the real size of objects at varying visual distances. To investigate to what extent this size constancy present in another vertebrate class, we addressed the two questions using pigeons: (a) whether pigeons see a corridor illusion based on size constancy and (b) whether pigeons prioritize pictorial cues over motion parallax cues for size constancy, like humans. We trained pigeons to classify target sizes on a corridor. In addition, we presented a dynamic version of corridor illusion in which the target and corridor moved side by side. Target speed was changed to manipulate motion parallax. With the static corridor, pigeons overestimated the target size when it was located higher, indicating that pigeons see a corridor illusion like humans. With the dynamic corridor, the pigeons overestimated the target size depending on target position, as in the static condition, but target speed did not affect their responses, indicating that the pictorial precedence also applies to pigeons. In a follow-up experiment using the same stimulus, we confirmed that humans perceive object size based on pictorial cues. These results suggest that size constancy characteristics are highly similar between pigeons and humans, despite the differences in their phylogeny and neural systems.
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Affiliation(s)
- Yuya Hataji
- Department of Psychology, Graduate School of
Letters,
Kyoto
University
| | - Hika Kuroshima
- Department of Psychology, Graduate School of
Letters,
Kyoto
University
| | - Kazuo Fujita
- Department of Psychology, Graduate School of
Letters,
Kyoto
University
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19
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Gayet S, Peelen MV. Scenes Modulate Object Processing Before Interacting With Memory Templates. Psychol Sci 2019; 30:1497-1509. [PMID: 31525114 PMCID: PMC6787763 DOI: 10.1177/0956797619869905] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 07/15/2019] [Indexed: 11/26/2022] Open
Abstract
When searching for relevant objects in our environment (say, an apple), we create a memory template (a red sphere), which causes our visual system to favor template-matching visual input (applelike objects) at the expense of template-mismatching visual input (e.g., leaves). Although this principle seems straightforward in a lab setting, it poses a problem in naturalistic viewing: Two objects that have the same size on the retina will differ in real-world size if one is nearby and the other is far away. Using the Ponzo illusion to manipulate perceived size while keeping retinal size constant, we demonstrated across 71 participants that visual objects attract attention when their perceived size matches a memory template, compared with mismatching objects that have the same size on the retina. This shows that memory templates affect visual selection after object representations are modulated by scene context, thus providing a working mechanism for template-based search in naturalistic vision.
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Affiliation(s)
- Surya Gayet
- Donders Institute for Brain, Cognition and
Behaviour, Radboud University
| | - Marius V. Peelen
- Donders Institute for Brain, Cognition and
Behaviour, Radboud University
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20
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The Critical Role of V2 Population Receptive Fields in Visual Orientation Crowding. Curr Biol 2019; 29:2229-2236.e3. [DOI: 10.1016/j.cub.2019.05.068] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 03/26/2019] [Accepted: 05/28/2019] [Indexed: 11/20/2022]
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21
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Chen J, Sperandio I, Henry MJ, Goodale MA. Changing the Real Viewing Distance Reveals the Temporal Evolution of Size Constancy in Visual Cortex. Curr Biol 2019; 29:2237-2243.e4. [PMID: 31257140 DOI: 10.1016/j.cub.2019.05.069] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 04/23/2019] [Accepted: 05/29/2019] [Indexed: 01/12/2023]
Abstract
Our visual system provides a distance-invariant percept of object size by integrating retinal image size with viewing distance (size constancy). Single-unit studies with animals have shown that some distance cues, especially oculomotor cues such as vergence and accommodation, can modulate the signals in the thalamus or V1 at the initial processing stage [1-7]. Accordingly, one might predict that size constancy emerges much earlier in time [8-10], even as visual signals are being processed in the thalamus. So far, the studies that have looked directly at size coding have either used fMRI (poor temporal resolution [11-13]) or relied on inadequate stimuli (pictorial illusions presented on a monitor at a fixed distance [11, 12, 14, 15]). Here, we physically moved the monitor to different distances, a more ecologically valid paradigm that emulates what happens in everyday life and is an example of the increasing trend of "bringing the real world into the lab." Using this paradigm in combination with electroencephalography (EEG), we examined the computation of size constancy in real time with real-world viewing conditions. Our study provides strong evidence that, even though oculomotor distance cues have been shown to modulate the spiking rate of neurons in the thalamus and in V1, the integration of viewing distance cues and retinal image size takes at least 150 ms to unfold, which suggests that the size-constancy-related activation patterns in V1 reported in previous fMRI studies (e.g., [12, 13]) reflect the later processing within V1 and/or top-down input from other high-level visual areas.
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Affiliation(s)
- Juan Chen
- Center for the Study of Applied Psychology, Guangdong Key Laboratory of Mental Health and Cognitive Science and the School of Psychology, South China Normal University, Guangzhou, Guangdong Province 510631, China; The Brain and Mind Institute, The University of Western Ontario, London, ON N6A 5B7, Canada.
| | - Irene Sperandio
- The School of Psychology, University of East Anglia, Norwich NR4 7TJ, UK.
| | - Molly J Henry
- The Brain and Mind Institute, The University of Western Ontario, London, ON N6A 5B7, Canada
| | - Melvyn A Goodale
- The Brain and Mind Institute, The University of Western Ontario, London, ON N6A 5B7, Canada; Department of Psychology, The University of Western Ontario, London, ON N6A 5C2, Canada
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22
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Chen J, McManus M, Valsecchi M, Harris LR, Gegenfurtner KR. Steady-state visually evoked potentials reveal partial size constancy in early visual cortex. J Vis 2019; 19:8. [DOI: 10.1167/19.6.8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Jing Chen
- School of Psychology, Shanghai University of Sport, Shanghai, China
- Abteilung Allgemeine Psychologie, Justus-Liebig-Universität Gießen, Gießen, Germany
- ://orcid.org/0000-0002-3038-1786
| | - Meaghan McManus
- Centre for Vision Research, York University, Toronto, Ontario, Canada
| | - Matteo Valsecchi
- Abteilung Allgemeine Psychologie, Justus-Liebig-Universität Gießen, Gießen, Germany
- ://valsecchimat.altervista.org/
| | - Laurence R. Harris
- Centre for Vision Research, York University, Toronto, Ontario, Canada
- ://www.yorku.ca/harris/
| | - Karl R. Gegenfurtner
- Abteilung Allgemeine Psychologie, Justus-Liebig-Universität Gießen, Gießen, Germany
- ://www.allpsych.uni-giessen.de/karl/
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23
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Dumoulin SO, Knapen T. How Visual Cortical Organization Is Altered by Ophthalmologic and Neurologic Disorders. Annu Rev Vis Sci 2018; 4:357-379. [DOI: 10.1146/annurev-vision-091517-033948] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Receptive fields are a core property of cortical organization. Modern neuroimaging allows routine access to visual population receptive fields (pRFs), enabling investigations of clinical disorders. Yet how the underlying neural circuitry operates is controversial. The controversy surrounds observations that measurements of pRFs can change in healthy adults as well as in patients with a range of ophthalmological and neurological disorders. The debate relates to the balance between plasticity and stability of the underlying neural circuitry. We propose that to move the debate forward, the field needs to define the implied mechanism. First, we review the pRF changes in both healthy subjects and those with clinical disorders. Then, we propose a computational model that describes how pRFs can change in healthy humans. We assert that we can correctly interpret the pRF changes in clinical disorders only if we establish the capabilities and limitations of pRF dynamics in healthy humans with mechanistic models that provide quantitative predictions.
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Affiliation(s)
- Serge O. Dumoulin
- Spinoza Centre for Neuroimaging, 1105 BK Amsterdam, Netherlands
- Department of Experimental and Applied Psychology, VU University Amsterdam, 1181 BT Amsterdam, Netherlands
- Department of Experimental Psychology, Helmholtz Institute, Utrecht University, 3584 CS Utrecht, Netherlands
| | - Tomas Knapen
- Spinoza Centre for Neuroimaging, 1105 BK Amsterdam, Netherlands
- Department of Experimental and Applied Psychology, VU University Amsterdam, 1181 BT Amsterdam, Netherlands
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24
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Image identification from brain activity using the population receptive field model. PLoS One 2017; 12:e0183295. [PMID: 28922355 PMCID: PMC5603170 DOI: 10.1371/journal.pone.0183295] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 08/02/2017] [Indexed: 11/19/2022] Open
Abstract
A goal of computational models is not only to explain experimental data but also to make new predictions. A current focus of computational neuroimaging is to predict features of the presented stimulus from measured brain signals. These computational neuroimaging approaches may be agnostic about the underlying neural processes or may be biologically inspired. Here, we use the biologically inspired population receptive field (pRF) approach to identify presented images from fMRI recordings of the visual cortex, using an explicit model of the underlying neural response selectivity. The advantage of the pRF-model is its simplicity: it is defined by a handful of parameters, which can be estimated from fMRI data that was collected within half an hour. Using 7T MRI, we measured responses elicited by different visual stimuli: (i) conventional pRF mapping stimuli, (ii) semi-random synthetic images and (iii) natural images. The pRF mapping stimuli were used to estimate the pRF-properties of each cortical location in early visual cortex. Next, we used these pRFs to identify which synthetic or natural images was presented to the subject from the fMRI responses. We show that image identification using V1 responses is far above chance, both for the synthetic and natural images. Thus, we can identify visual images, including natural images, using the most fundamental low-parameter pRF model estimated from conventional pRF mapping stimuli. This allows broader application of image identification.
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25
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Zeidman P, Silson EH, Schwarzkopf DS, Baker CI, Penny W. Bayesian population receptive field modelling. Neuroimage 2017; 180:173-187. [PMID: 28890416 PMCID: PMC7417811 DOI: 10.1016/j.neuroimage.2017.09.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 06/28/2017] [Accepted: 09/05/2017] [Indexed: 12/25/2022] Open
Abstract
We introduce a probabilistic (Bayesian) framework and associated software toolbox for mapping population receptive fields (pRFs) based on fMRI data. This generic approach is intended to work with stimuli of any dimension and is demonstrated and validated in the context of 2D retinotopic mapping. The framework enables the experimenter to specify generative (encoding) models of fMRI timeseries, in which experimental stimuli enter a pRF model of neural activity, which in turns drives a nonlinear model of neurovascular coupling and Blood Oxygenation Level Dependent (BOLD) response. The neuronal and haemodynamic parameters are estimated together on a voxel-by-voxel or region-of-interest basis using a Bayesian estimation algorithm (variational Laplace). This offers several novel contributions to receptive field modelling. The variance/covariance of parameters are estimated, enabling receptive fields to be plotted while properly representing uncertainty about pRF size and location. Variability in the haemodynamic response across the brain is accounted for. Furthermore, the framework introduces formal hypothesis testing to pRF analysis, enabling competing models to be evaluated based on their log model evidence (approximated by the variational free energy), which represents the optimal tradeoff between accuracy and complexity. Using simulations and empirical data, we found that parameters typically used to represent pRF size and neuronal scaling are strongly correlated, which is taken into account by the Bayesian methods we describe when making inferences. We used the framework to compare the evidence for six variants of pRF model using 7 T functional MRI data and we found a circular Difference of Gaussians (DoG) model to be the best explanation for our data overall. We hope this framework will prove useful for mapping stimulus spaces with any number of dimensions onto the anatomy of the brain. We introduce a Bayesian toolbox for population receptive field (pRF) mapping. Neuronal and haemodynamic parameters are estimated per voxel or per region. Hypotheses can be tested by comparing pRF models based on their evidence. The uncertainty over parameters (such as pRF size) is estimated and visualised. We establish face validity using simulations and test-rest reliability with 7 T fMRI.
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Affiliation(s)
- Peter Zeidman
- The Wellcome Trust Centre for Neuroimaging, University College London, 12 Queen Square, London, WC1N 3BG, UK.
| | - Edward Harry Silson
- Laboratory of Brain and Cognition, National Institute of Mental Health, Bethesda, MD, 20892-1366, USA
| | - Dietrich Samuel Schwarzkopf
- Experimental Psychology, University College London, 26 Bedford Way, London, WC1H 0AP, UK; UCL Institute of Cognitive Neuroscience, 17-19 Queen Square, London, WC1N 3AR, UK
| | - Chris Ian Baker
- Laboratory of Brain and Cognition, National Institute of Mental Health, Bethesda, MD, 20892-1366, USA
| | - Will Penny
- The Wellcome Trust Centre for Neuroimaging, University College London, 12 Queen Square, London, WC1N 3BG, UK
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26
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Mikellidou K, Gouws AD, Clawson H, Thompson P, Morland AB, Keefe BD. An Orientation Dependent Size Illusion Is Underpinned by Processing in the Extrastriate Visual Area, LO1. Iperception 2016; 7:2041669516667628. [PMID: 27733896 PMCID: PMC5040199 DOI: 10.1177/2041669516667628] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We use the simple, but prominent Helmholtz's squares illusion in which a vertically striped square appears wider than a horizontally striped square of identical physical dimensions to determine whether functional magnetic resonance imaging (fMRI) BOLD responses in V1 underpin illusions of size. We report that these simple stimuli which differ in only one parameter, orientation, to which V1 neurons are highly selective elicited activity in V1 that followed their physical, not perceived size. To further probe the role of V1 in the illusion and investigate plausible extrastriate visual areas responsible for eliciting the Helmholtz squares illusion, we performed a follow-up transcranial magnetic stimulation (TMS) experiment in which we compared perceptual judgments about the aspect ratio of perceptually identical Helmholtz squares when no TMS was applied against selective stimulation of V1, LO1, or LO2. In agreement with fMRI results, we report that TMS of area V1 does not compromise the strength of the illusion. Only stimulation of area LO1, and not LO2, compromised significantly the strength of the illusion, consistent with previous research that LO1 plays a role in the processing of orientation information. These results demonstrate the involvement of a specific extrastriate area in an illusory percept of size.
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Affiliation(s)
- Kyriaki Mikellidou
- Department of Psychology, University of York, UK; University of Pisa, Italy
| | - André D Gouws
- York Neuroimaging Centre, Department of Psychology, University of York, UK
| | | | | | - Antony B Morland
- York Neuroimaging Centre, Department of Psychology, University of York, UK; Centre for Neuroscience, Hull-York Medical School, UK
| | - Bruce D Keefe
- York Neuroimaging Centre, Department of Psychology, University of York, UK
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27
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Cortical idiosyncrasies predict the perception of object size. Nat Commun 2016; 7:12110. [PMID: 27357864 PMCID: PMC4931347 DOI: 10.1038/ncomms12110] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 06/01/2016] [Indexed: 11/13/2022] Open
Abstract
Perception is subjective. Even basic judgments, like those of visual object size, vary substantially between observers and also across the visual field within the same observer. The way in which the visual system determines the size of objects remains unclear, however. We hypothesize that object size is inferred from neuronal population activity in V1 and predict that idiosyncrasies in cortical functional architecture should therefore explain individual differences in size judgments. Here we show results from novel behavioural methods and functional magnetic resonance imaging (fMRI) demonstrating that biases in size perception are correlated with the spatial tuning of neuronal populations in healthy volunteers. To explain this relationship, we formulate a population read-out model that directly links the spatial distribution of V1 representations to our perceptual experience of visual size. Taken together, our results suggest that the individual perception of simple stimuli is warped by idiosyncrasies in visual cortical organization. Perceiving the size of objects is subjective. Here the authors show that these subjective differences in size perception can be explained by the individual variance in spatial tuning of neuronal populations in the primary visual cortex.
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