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Derpsch Y, Tyson-Carr J, Rampone G, Bertamini M, Makin ADJ. Event related potentials (ERP) reveal a robust response to visual symmetry in unattended visual regions. Neuroimage 2024; 290:120568. [PMID: 38499052 DOI: 10.1016/j.neuroimage.2024.120568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 03/05/2024] [Accepted: 03/07/2024] [Indexed: 03/20/2024] Open
Abstract
Visual symmetry at fixation generates a bilateral Event Related Potential (ERP) called the Sustained Posterior Negativity (SPN). Symmetry presented in the left visual hemifield generates a contralateral SPN over the right hemisphere and vice versa. The current study examined whether the contralateral SPN is modulated by the focus of spatial attention. On each trial there were two dot patterns, one to the left of fixation, and one to the right of fixation. A central arrow cue pointed to one of the patterns and participants discriminated its regularity (symmetry or random). We compared contralateral SPN amplitude generated by symmetry at attended and unattended spatial locations. While the response to attended symmetry was slightly enhanced, the response to unattended symmetry was still substantial. Although visual symmetry detection is a computational challenge, we conclude that the brain processes visual symmetry in unattended parts of the visual field.
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Affiliation(s)
- Yiovanna Derpsch
- School of Psychology, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom; Department of Psychological Sciences, Eleanor Rathbone Building, University of Liverpool, Liverpool L69 7ZA, United Kingdom.
| | - John Tyson-Carr
- Department of Psychological Sciences, Eleanor Rathbone Building, University of Liverpool, Liverpool L69 7ZA, United Kingdom
| | - Giulia Rampone
- Department of Psychological Sciences, Eleanor Rathbone Building, University of Liverpool, Liverpool L69 7ZA, United Kingdom
| | - Marco Bertamini
- Department of Psychological Sciences, Eleanor Rathbone Building, University of Liverpool, Liverpool L69 7ZA, United Kingdom; Department of General Psychology, University of Padova, Via Venezia, 8 - 35131, Padova, Italy
| | - Alexis D J Makin
- Department of Psychological Sciences, Eleanor Rathbone Building, University of Liverpool, Liverpool L69 7ZA, United Kingdom
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Mirror symmetry and aging: The role of stimulus figurality and attention to colour. Atten Percept Psychophys 2023; 85:99-112. [PMID: 36175763 PMCID: PMC9816266 DOI: 10.3758/s13414-022-02565-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2022] [Indexed: 01/11/2023]
Abstract
Symmetry perception studies have generally used two stimulus types: figural and dot patterns. Here, we designed a novel figural stimulus-a wedge pattern-made of centrally aligned pseudorandomly positioned wedges. To study the effect of pattern figurality and colour on symmetry perception, we compared symmetry detection in multicoloured wedge patterns with nonfigural dot patterns in younger and older adults. Symmetry signal was either segregated or nonsegregated by colour, and the symmetry detection task was performed under two conditions: with or without colour-based attention. In the first experiment, we compared performance for colour-symmetric patterns that varied in the number of wedges (24 vs. 36) and number of colours (2 vs. 3) and found that symmetry detection was facilitated by attention to colour when symmetry and noise signals were segregated by colour. In the second experiment, we compared performance for wedge and dot patterns on a sample of younger and older participants. Effects of attention to colour in segregated stimuli were magnified for wedge compared with dot patterns, with older and younger adults showing different effects of attention to colour on performance. Older adults significantly underperformed on uncued wedge patterns compared with dot patterns, but their performance improved greatly through colour cueing, reaching performance levels similar to young participants. Thus, while confirming the age-related decline in symmetry detection, we found that this deficit could be alleviated in figural multicoloured patterns by attending to the colour that carries the symmetry signal.
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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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Abstract
Recent studies have suggested that temporal dynamics rather than symmetrical motion-direction contribute to mirror-symmetry perception. Here we investigate temporal aspects of symmetry perception and implicitly, its temporal flexibility and limitations, by examining how symmetrical pattern elements are combined over time. Stimuli were dynamic dot-patterns consisting of either an on-going alternation of two images (sustained stimulus presentation) or just two images each presented once (transient stimulus presentation) containing different amounts of symmetry about the vertical axis. We varied the duration of the two images under five temporal-arrangement conditions: (a) whole patterns in which a symmetric pattern alternated with a noise pattern; (b) delayed halves—the halves of the symmetric and noise patterns were presented with temporal delay; (c) matched-pairs—two alternating images each containing equal amounts of symmetrical matched-pairs; (d) delayed matched-pairs—the same as arrangement (c), but with matched-pairs presented with delay; and (e) static—both images presented simultaneously as one. We found increased sensitivity in sustained compared to transient stimulus presentations and with synchronous compared to delayed matched-pairs stimuli. For the delayed conditions, sensitivity decreased gradually with longer image durations (>60 ms), prominently for the transient stimulus presentations. We conclude that spatial correlations across-the-symmetry-midline can be integrated over time (∼120 ms), and symmetry mechanisms can tolerate temporal delays between symmetric dot-pairs of up to ∼60 ms.
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Affiliation(s)
- Rebecca J Sharman
- University of Stirling, Department of Psychology, Stirling, Scotland, UK
| | | | - Elena Gheorghiu
- University of Stirling, Department of Psychology, Stirling, Scotland, UK
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Bertamini M, Silvanto J, Norcia AM, Makin ADJ, Wagemans J. The neural basis of visual symmetry and its role in mid- and high-level visual processing. Ann N Y Acad Sci 2018; 1426:111-126. [PMID: 29604083 DOI: 10.1111/nyas.13667] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/05/2018] [Accepted: 02/13/2018] [Indexed: 01/18/2023]
Abstract
Symmetry is an important and prominent feature of the visual world. It has been studied as a basis for image segmentation and perceptual organization, but it also plays a role in higher level processes, such as face and object perception. Over the past decade, there has been progress in the study of the neural mechanisms of symmetry perception in humans and other animals. There is extended activity in the ventral stream, including the lateral occipital complex (LOC) and VO1; this activity starts in V3 and it occurs independently of the task (automatic response). Additionally, when the task requires processing of symmetry, the activation may emerge for objects that are symmetrical, even though they do not project a symmetrical image. There is also some evidence of hemispheric lateralization, especially for the LOC. We review the studies on the cortical basis of visual symmetry processing and its links to encoding of other aspects of the visual world, such as faces and objects.
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Affiliation(s)
- Marco Bertamini
- Department of Psychological Science, University of Liverpool, Liverpool, United Kingdom
| | - Juha Silvanto
- Department of Psychology, University of Westminster, London, United Kingdom
| | - Anthony M Norcia
- Department of Psychology, Stanford University, Stanford, California
| | - Alexis D J Makin
- Department of Psychological Science, University of Liverpool, Liverpool, United Kingdom
| | - Johan Wagemans
- Laboratory of Experimental Psychology, Brain & Cognition, KU Leuven, Leuven, Belgium
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Wright D, Mitchell C, Dering BR, Gheorghiu E. Luminance-polarity distribution across the symmetry axis affects the electrophysiological response to symmetry. Neuroimage 2018; 173:484-497. [PMID: 29427849 PMCID: PMC5929902 DOI: 10.1016/j.neuroimage.2018.02.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 01/25/2018] [Accepted: 02/05/2018] [Indexed: 11/03/2022] Open
Abstract
Electrophysiological studies of symmetry have found a difference wave termed the Sustained Posterior Negativity (SPN) related to the presence of symmetry. Yet the extent to which the SPN is modulated by luminance-polarity and colour content is unknown. Here we examine how luminance-polarity distribution across the symmetry axis, grouping by luminance polarity, and the number of colours in the stimuli, modulate the SPN. Stimuli were dot patterns arranged either symmetrically or quasi-randomly. There were several arrangements: 'segregated'-symmetric dots were of one polarity and randomly-positioned dots were of the other; 'unsegregated'-symmetric dots were of both polarities in equal proportions; 'anti-symmetric'-dots were of opposite polarity across the symmetry axis; 'polarity-grouped anti-symmetric'-this is the same as anti-symmetric but with half the pattern of one polarity and the other half of opposite polarity; multi-colour symmetric patterns made of two, three to four colours. We found that the SPN is: (i) reduced by the amount of position-symmetry, (ii) sensitive to luminance-polarity mismatch across the symmetry axis, and (iii) not modulated by the number of colours in the stimuli. Our results show that the sustained nature of the SPN coincides with the late onset of a topographic microstate sensitive to symmetry. These findings emphasise the importance of not only position symmetry, but also luminance polarity matching across the symmetry axis.
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Affiliation(s)
- Damien Wright
- University of Stirling, Department of Psychology, Stirling, FK9 4LA, Scotland, United Kingdom.
| | - Claire Mitchell
- University of Stirling, Department of Psychology, Stirling, FK9 4LA, Scotland, United Kingdom
| | - Benjamin R Dering
- University of Stirling, Department of Psychology, Stirling, FK9 4LA, Scotland, United Kingdom
| | - Elena Gheorghiu
- University of Stirling, Department of Psychology, Stirling, FK9 4LA, Scotland, United Kingdom
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