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Machida I, Shishikura M, Yamane Y, Sakai K. Representation of Natural Contours by a Neural Population in Monkey V4. eNeuro 2024; 11:ENEURO.0445-23.2024. [PMID: 38423791 PMCID: PMC10946029 DOI: 10.1523/eneuro.0445-23.2024] [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: 10/25/2023] [Revised: 02/18/2024] [Accepted: 02/22/2024] [Indexed: 03/02/2024] Open
Abstract
The cortical visual area, V4, has been considered to code contours that contribute to the intermediate-level representation of objects. The neural responses to the complex contour features intrinsic to natural contours are expected to clarify the essence of the representation. To approach the cortical coding of natural contours, we investigated the simultaneous coding of multiple contour features in monkey (Macaca fuscata) V4 neurons and their population-level representation. A substantial number of neurons showed significant tuning for two or more features such as curvature and closure, indicating that a substantial number of V4 neurons simultaneously code multiple contour features. A large portion of the neurons responded vigorously to acutely curved contours that surrounded the center of classical receptive field, suggesting that V4 neurons tend to code prominent features of object contours. The analysis of mutual information (MI) between the neural responses and each contour feature showed that most neurons exhibited similar magnitudes for each type of MI, indicating that many neurons showing the responses depended on multiple contour features. We next examined the population-level representation by using multidimensional scaling analysis. The neural preferences to the multiple contour features and that to natural stimuli compared with silhouette stimuli increased along with the primary and secondary axes, respectively, indicating the contribution of the multiple contour features and surface textures in the population responses. Our analyses suggested that V4 neurons simultaneously code multiple contour features in natural images and represent contour and surface properties in population.
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Affiliation(s)
- Itsuki Machida
- Department of Computer Science, University of Tsukuba, Tsukuba 305-8573, Japan
| | - Motofumi Shishikura
- Department of Computer Science, University of Tsukuba, Tsukuba 305-8573, Japan
| | - Yukako Yamane
- Neural Computation Unit, Okinawa Institute of Science and Technology, Okinawa 904-0495, Japan
| | - Ko Sakai
- Department of Computer Science, University of Tsukuba, Tsukuba 305-8573, Japan
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Haemodynamic Signatures of Temporal Integration of Visual Mirror Symmetry. Symmetry (Basel) 2022. [DOI: 10.3390/sym14050901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
EEG, fMRI and TMS studies have implicated the extra-striate cortex, including the Lateral Occipital Cortex (LOC), in the processing of visual mirror symmetries. Recent research has found that the sustained posterior negativity (SPN), a symmetry specific electrophysiological response identified in the region of the LOC, is generated when temporally displaced asymmetric components are integrated into a symmetric whole. We aim to expand on this finding using dynamic dot-patterns with systematically increased intra-pair temporal delay to map the limits of temporal integration of visual mirror symmetry. To achieve this, we used functional near-infrared spectroscopy (fNIRS) which measures the changes in the haemodynamic response to stimulation using near infrared light. We show that a symmetry specific haemodynamic response can be identified following temporal integration of otherwise meaningless dot-patterns, and the magnitude of this response scales with the duration of temporal delay. These results contribute to our understanding of when and where mirror symmetry is processed in the visual system. Furthermore, we highlight fNIRS as a promising but so far underutilised method of studying the haemodynamics of mid-level visual processes in the brain.
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Rampone G, Adam M, Makin ADJ, Tyson-Carr J, Bertamini M. Electrophysiological evidence of the amodal representation of symmetry in extrastriate areas. Sci Rep 2022; 12:1180. [PMID: 35064121 PMCID: PMC8783022 DOI: 10.1038/s41598-021-04501-3] [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: 08/05/2021] [Accepted: 12/14/2021] [Indexed: 11/09/2022] Open
Abstract
Extrastriate visual areas are strongly activated by image symmetry. Less is known about symmetry representation at object-level rather than image-level. Here we investigated electrophysiological responses to symmetry, generated by amodal completion of partially-occluded polygon shapes. We used a similar paradigm in four experiments (N = 112). A fully-visible abstract shape (either symmetric or asymmetric) was presented for 250 ms (t0). A large rectangle covered it entirely for 250 ms (t1) and then moved to one side to reveal one half of the shape hidden behind (t2, 1000 ms). Note that at t2 no symmetry could be extracted from retinal image information. In half of the trials the shape was the same as previously presented, in the other trials it was replaced by a novel shape. Participants matched shapes similarity (Exp. 1 and Exp. 2), or their colour (Exp. 3) or the orientation of a triangle superimposed to the shapes (Exp. 4). The fully-visible shapes (t0-t1) elicited automatic symmetry-specific ERP responses in all experiments. Importantly, there was an exposure-dependent symmetry-response to the occluded shapes that were recognised as previously seen (t2). Exp. 2 and Exp.4 confirmed this second ERP (t2) did not reflect a reinforcement of a residual carry-over response from t0. We conclude that the extrastriate symmetry-network can achieve amodal representation of symmetry from occluded objects that have been previously experienced as wholes.
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Affiliation(s)
- Giulia Rampone
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, Liverpool, L697ZA, UK. .,School of Psychology, University of Liverpool, Eleanor Rathbone Building, Liverpool, L7 7DL, UK.
| | - Martyna Adam
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, Liverpool, L697ZA, UK
| | - Alexis D J Makin
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, Liverpool, L697ZA, UK
| | - John Tyson-Carr
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, Liverpool, L697ZA, UK
| | - Marco Bertamini
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, Liverpool, L697ZA, UK.,Department of General Psychology, University of Padova, Via Venezia, 8, 35131, Padova, Italy
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Rampone G, Makin ADJ, Tyson-Carr J, Bertamini M. Spinning objects and partial occlusion: Smart neural responses to symmetry. Vision Res 2021; 188:1-9. [PMID: 34271291 DOI: 10.1016/j.visres.2021.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 06/04/2021] [Accepted: 06/19/2021] [Indexed: 11/18/2022]
Abstract
In humans, extrastriate visual areas are strongly activated by symmetry. However, perfect symmetry is rare in natural visual images. Recent findings showed that when parts of a symmetric shape are presented at different points in time the process relies on a perceptual memory buffer. Does this temporal integration need a retinotopic reference frame? For the first time we tested integration of parts both in the temporal and spatial domain, using a non-retinotopic frame of reference. In Experiment 1, an irregular polygonal shape (either symmetric or asymmetric) was partly occluded by a rectangle for 500 ms (T1). The rectangle moved to the opposite side to reveal the other half of the shape, whilst occluding the previously visible half (T2). The reference frame for the object was static: the two parts stimulated retinotopically corresponding receptive fields (revealed over time). A symmetry-specific ERP response from ~300 ms after T2 was observed. In Experiment 2 dynamic occlusion was combined with an additional step at T2: the new half-shape and occluder were rotated by 90°. Therefore, there was a moving frame of reference and the retinal correspondence between the two parts was disrupted. A weaker but significant symmetry-specific response was recorded. This result extends previous findings: global symmetry representation can be achieved in extrastriate areas non-retinotopically, through integration in both temporal and spatial domain.
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Affiliation(s)
- Giulia Rampone
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, L697ZA Liverpool, UK.
| | - Alexis D J Makin
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, L697ZA Liverpool, UK
| | - John Tyson-Carr
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, L697ZA Liverpool, UK
| | - Marco Bertamini
- Department of Psychology, University of Liverpool, Eleanor Rathbone Building, L697ZA Liverpool, UK; Department of General Psychology, Via Venezia, 8 - 35131, University of Padova, Padova, Italy
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Sakai K, Sakata Y, Kurematsu K. Interaction of surface pattern and contour shape in the tilt after effects evoked by symmetry. Sci Rep 2021; 11:8024. [PMID: 33850220 PMCID: PMC8044203 DOI: 10.1038/s41598-021-87429-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 03/12/2021] [Indexed: 11/22/2022] Open
Abstract
Integration of multiple properties of an object is a fundamental function of the visual cortex in object recognition. For instance, surface patterns and contour shapes are thought to be crucial characteristics that jointly contribute to recognition. However, the mechanisms of integration and corresponding cortical representations have not been fully clarified. We investigated the integration of surfaces and shapes by examining the tilt after effects (TAEs) evoked by the symmetry of patterns and contours. As symmetry in both pattern and contour evokes TAEs, we can directly measure the interaction between the two. The measured TAEs exhibited mutual transfer between the symmetry of the pattern (SP) and that of the contour shape (SS), i.e., adaptation by SP (SS) evoked TAEs when tested by SS (SP), suggesting the existence of an integrated representation. Next, we examined the interaction between SP and SS when both were simultaneously presented in adaptation. Congruent adaptors wherein their symmetry axes aligned evoked compressive interaction, whereas incongruent adaptors wherein the axes of SP and SS tilted to the opposite directions evoked subtractive interaction. These results suggest the existence of a cortical representation that integrates the properties of the surface and shape with suppressive interactions, which can provide crucial insights into the formation of object representation as well as the integration of visual information in the cortex.
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Affiliation(s)
- Ko Sakai
- Computational Vision Science Laboratory, Department of Computer Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan.
| | - Yui Sakata
- Computational Vision Science Laboratory, Department of Computer Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan
| | - Ken Kurematsu
- Computational Vision Science Laboratory, Department of Computer Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan
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Rampone G, Makin AD, Tatlidil S, Bertamini M. Representation of symmetry in the extrastriate visual cortex from temporal integration of parts: An EEG/ERP study. Neuroimage 2019; 193:214-230. [DOI: 10.1016/j.neuroimage.2019.03.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 02/17/2019] [Accepted: 03/04/2019] [Indexed: 10/27/2022] Open
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Speed tuning properties of mirror symmetry detection mechanisms. Sci Rep 2019; 9:3431. [PMID: 30837517 PMCID: PMC6400945 DOI: 10.1038/s41598-019-39064-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 01/15/2019] [Indexed: 11/08/2022] Open
Abstract
The human visual system is often tasked with extracting image properties such as symmetry from rapidly moving objects and scenes. The extent to which motion speed and symmetry processing mechanisms interact is not known. Here we examine speed-tuning properties of symmetry detection mechanisms using dynamic dot-patterns containing varying amounts of position and local motion-direction symmetry. We measured symmetry detection thresholds for stimuli in which symmetric and noise elements either drifted with different relative speeds, were relocated at different relative temporal frequencies or were static. We also measured percentage correct responses under two stimulus conditions: a segregated condition in which symmetric and noise elements drifted at different speeds, and a non-segregated condition in which the symmetric elements drifted at two different speeds in equal proportions, as did the noise elements. We found that performance (i) improved gradually with increasing the difference in relative speed between symmetric and noise elements, but was invariant across relative temporal frequencies/lifetime duration differences between symmetric and noise elements, (ii) was higher in the segregated compared to non-segregated conditions, and in the moving compared to the static conditions. We conclude that symmetry detection mechanisms are broadly tuned to speed, with speed-selective symmetry channels combining their outputs by probability summation.
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