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Tekülve J, Schöner G. Neural Dynamic Principles for an Intentional Embodied Agent. Cogn Sci 2024; 48:e13491. [PMID: 39226219 DOI: 10.1111/cogs.13491] [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: 11/26/2023] [Revised: 06/26/2024] [Accepted: 08/02/2024] [Indexed: 09/05/2024]
Abstract
How situated embodied agents may achieve goals using knowledge is the classical question of natural and artificial intelligence. How organisms achieve this with their nervous systems is a central challenge for a neural theory of embodied cognition. To structure this challenge, we borrow terms from Searle's analysis of intentionality in its two directions of fit and six psychological modes (perception, memory, belief, intention-in-action, prior intention, desire). We postulate that intentional states are instantiated by neural activation patterns that are stabilized by neural interaction. Dynamic instabilities provide the neural mechanism for initiating and terminating intentional states and are critical to organizing sequences of intentional states. Beliefs represented by networks of concept nodes are autonomously learned and activated in response to desired outcomes. The neural dynamic principles of an intentional agent are demonstrated in a toy scenario in which a robotic agent explores an environment and paints objects in desired colors based on learned color transformation rules.
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Affiliation(s)
- Jan Tekülve
- Institute for Neural Computation, Ruhr-University Bochum
| | - Gregor Schöner
- Institute for Neural Computation, Ruhr-University Bochum
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2
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Hock HS, Schöner G. The stabilization of visibility for sequentially presented, low-contrast objects: Experiments and neural field model. J Vis 2023; 23:12. [PMID: 37585184 PMCID: PMC10434716 DOI: 10.1167/jov.23.8.12] [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: 12/31/2022] [Accepted: 07/06/2023] [Indexed: 08/17/2023] Open
Abstract
In any environment, events transpire in temporal sequences. The general principle governing such sequences is that each instance of the event is influenced by its predecessors. It is shown here that this principle is true for a fundamental aspect of visual perception: visibility. A series of nine psychophysical experiments and associated neural dynamic simulations provide evidence that two non-stimulus factors, self-excitation and short-term memory, stabilize the visibility of a simple low-contrast object (a line segment) as it moves over a sequence of unpredictable locations. Stabilization was indicated by the very low probability of visible-to-invisible switches, and dependence on preceding visibility states was indicated by hysteresis as the contrast of the object was gradually decreased or increased. The contribution of self-excitation to stabilization was indicated by increased visible-to-invisible switching (decreased hysteresis) following adaptation of the visibility state, and the contribution of memory to stabilization was indicated by visibility "bridging" long blank intervals separating each relocation of the object. Because of the unpredictability of the relocations of the object, its visibility at one location pre-shapes visibility at its next location via persisting subthreshold activation of detectors surrounding the low-contrast object. All effects were modeled, including contributions from adaptation and recurrent inhibition, with a single set of parameter values.
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Affiliation(s)
- Howard S Hock
- Department of Psychology and the Center for Complex Systems and Brain Sciences, Florida Atlantic University, Boca Raton, FL, USA
| | - Gregor Schöner
- Institute for Neural Computation, Ruhr-Universität Bochum, Bochum, Germany
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3
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Esposito A, Chiarella SG, Raffone A, Nikolaev AR, van Leeuwen C. Perceptual bias contextualized in visually ambiguous stimuli. Cognition 2023; 230:105284. [PMID: 36174260 DOI: 10.1016/j.cognition.2022.105284] [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: 11/22/2021] [Revised: 09/06/2022] [Accepted: 09/09/2022] [Indexed: 11/28/2022]
Abstract
The visual appearance of an object is a function of stimulus properties as well as perceptual biases imposed by the observer. The context-specific trade-off between both can be measured accurately in a perceptual judgment task, involving grouping by proximity in ambiguous dot lattices. Such grouping depends lawfully on a stimulus parameter of the dot lattices known as their aspect ratio (AR), whose effect is modulated by a perceptual bias representing the preference for a cardinal orientation. In two experiments, we investigated how preceding context can lead to bias modulation, either in a top-down fashion via visual working memory (VWM) or bottom-up via sensory priming. In Experiment 1, we embedded the perceptual judgment task in a change detection paradigm and studied how the factors of VWM load (complexity of the memory array) and content (congruency in orientation to the ensuing dot lattice) affect the prominence of perceptual bias. A robust vertical orientation bias was observed, which was increased by VWM load and modulated by congruent VWM content. In Experiment 2, dot lattices were preceded by oriented primes. Here, primes regardless of orientation elicited a vertical orientation bias in dot lattices compared to a neutral baseline. Taken together, the two experiments demonstrate that top-down context (VWM load and content) effectively controls orientation bias modulation, while bottom-up context (i.e., priming) merely acts as an undifferentiated trigger to perceptual bias. These findings characterize the temporal context sensitivity of Gestalt perception, shed light on the processes responsible for different perceptual outcomes of ambiguous stimuli, and identify some of the mechanisms controlling perceptual bias.
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Affiliation(s)
- Antonino Esposito
- Department of Psychology, Sapienza University of Rome, Italy; Brain and Cognition Research Unit, KU Leuven, Belgium.
| | - Salvatore Gaetano Chiarella
- Department of Psychology, Sapienza University of Rome, Italy; Brain and Cognition Research Unit, KU Leuven, Belgium
| | | | - Andrey R Nikolaev
- Brain and Cognition Research Unit, KU Leuven, Belgium; Department of Psychology, Lund University, Sweden
| | - Cees van Leeuwen
- Brain and Cognition Research Unit, KU Leuven, Belgium; Center for Cognitive Science, TU Kaiserslautern, Germany
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4
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Allen AK, Jacobs MT, Davidenko N. Subjective control of polystable illusory apparent motion: Is control possible when the stimulus affords countless motion possibilities? J Vis 2022; 22:5. [PMID: 35708685 PMCID: PMC9206494 DOI: 10.1167/jov.22.7.5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We investigate whether a new polystable illusion, illusory apparent motion (IAM), is susceptible to subjective perceptual control as has been shown in other polystable stimuli (e.g., the Necker cube, apparent motion quartets). Previous research has demonstrated that, although IAM shares some properties in common with other polystable stimuli, it also has some unique ones that make it unclear whether it should have similar susceptibility to subjective control. For example, IAM can be perceived in a countless number of directions and motion patterns (e.g., up–down, left–left, contracting–expanding, shear, diagonal). To explore perceptual control of IAM, in experiment 1 (n = 99) we used a motion persistence paradigm where participants are primed with different motion patterns and are instructed to control (change or hold) the initial motion pattern and indicate when the motion pattern changes. Building on experiment 1, experiment 2 (n = 76) brings the method more in line with previous subjective control research, testing whether participants can control their perception of IAM in a context without priming and while dynamically reporting their percepts throughout the trial. Findings from the two experiments demonstrate that participants were able to control their perception of IAM across paradigms. We explore the implications of these findings, strategies reported, and open questions for future research.
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Affiliation(s)
- Allison K Allen
- Department of Psychology, University of California Santa Cruz, Santa Cruz, CA, USA.,
| | - Matthew T Jacobs
- Open Mind School, Silicon Valley Social Innovation Lab, Menlo Park, CA, USA.,
| | - Nicolas Davidenko
- Department of Psychology, University of California Santa Cruz, Santa Cruz, CA, USA.,
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Gekas N, Mamassian P. Adaptation to one perceived motion direction can generate multiple velocity aftereffects. J Vis 2021; 21:17. [PMID: 34007990 PMCID: PMC8142737 DOI: 10.1167/jov.21.5.17] [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] [Indexed: 11/24/2022] Open
Abstract
Sensory adaptation is a useful tool to identify the links between perceptual effects and neural mechanisms. Even though motion adaptation is one of the earliest and most documented aftereffects, few studies have investigated the perception of direction and speed of the aftereffect at the same time, that is the perceived velocity. Using a novel experimental paradigm, we simultaneously recorded the perceived direction and speed of leftward or rightward moving random dots before and after adaptation. For the adapting stimulus, we chose a horizontally-oriented broadband grating moving upward behind a circular aperture. Because of the aperture problem, the interpretation of this stimulus is ambiguous, being consistent with multiple velocities, and yet it is systematically perceived as moving at a single direction and speed. Here we ask whether the visual system adapts to the multiple velocities of the adaptor or to just the single perceived velocity. Our results show a strong repulsion aftereffect, away from the adapting velocity (downward and slower), that increases gradually for faster test stimuli as long as these stimuli include some velocities that match some of the ambiguous ones of the adaptor. In summary, the visual system seems to adapt to the multiple velocities of an ambiguous stimulus even though a single velocity is perceived. Our findings can be well described by a computational model that assumes a joint encoding of direction and speed and that includes an extended adaptation component that can represent all the possible velocities of the ambiguous stimulus.
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Affiliation(s)
- Nikos Gekas
- School of Psychology, University of Nottingham, Nottingham, UK.,Laboratoire des Systèmes Perceptifs, Département d'études cognitives, École normale supérieure, PSL University, CNRS, Paris, France.,
| | - Pascal Mamassian
- Laboratoire des Systèmes Perceptifs, Département d'études cognitives, École normale supérieure, PSL University, CNRS, Paris, France.,
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Liaci E, Fischer A, Atmanspacher H, Heinrichs M, Tebartz van Elst L, Kornmeier J. Positive and negative hysteresis effects for the perception of geometric and emotional ambiguities. PLoS One 2018; 13:e0202398. [PMID: 30256789 PMCID: PMC6157843 DOI: 10.1371/journal.pone.0202398] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 08/02/2018] [Indexed: 12/21/2022] Open
Abstract
AIM The present study utilizes perceptual hysteresis effects to compare the ambiguity of Mona Lisa's emotional face expression (high-level ambiguity) and of geometric cube stimuli (low-level ambiguity). METHODS In two experiments we presented series of nine Mona Lisa variants and nine cube variants. Stimulus ambiguity was manipulated by changing Mona Lisa's mouth curvature (Exp. 1) and the cubes' back-layer luminance (Exp. 2). Each experiment consisted of three conditions, two with opposite stimulus presentation sequences with increasing and decreasing degrees of ambiguity, respectively, and a third condition with a random presentation sequence. Participants indicated happy or sad face percepts (Exp. 1) and alternative 3D cube percepts (Exp. 2) by key presses. We studied the influences of a priori perceptual biases (long-term memory) and presentation order (short-term memory) on perception. RESULTS Perception followed sigmoidal functions of the stimulus ambiguity morphing parameters. The morphing parameter for the functions' inflection points depended strongly on stimulus presentation order with similar effect sizes but different signs for the two stimulus types (positive hysteresis / priming for the cubes; negative hysteresis / adaptation for Mona Lisa). In the random conditions, the inflection points were located in the middle between those from the two directional conditions for the Mona Lisa stimuli. For the cube stimuli, they were superimposed on one sigmoidal function for the ordered condition. DISCUSSION The hysteresis effects reflect the influence of short-term memory during the perceptual disambiguation of ambiguous sensory information. The effects for the two stimulus types are of similar size, explaining up to 34% of the perceptual variance introduced by the paradigm. We explain the qualitative difference between positive and negative hysteresis with adaptation for Mona Lisa and with priming for the cubes. In addition, the hysteresis paradigm allows a quantitative determination of the impact of adaptation and priming during the resolution of perceptual ambiguities. The asymmetric shifts of inflection points in the case of the cube stimuli is likely due to an a priori perceptual bias, reflecting an influence of long-term memory. Whether corresponding influences also exist for the Mona Lisa variants is so far unclear.
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Affiliation(s)
- Emanuela Liaci
- Institute for Frontier Areas of Psychology and Mental Health, Freiburg, Germany
- Section for Experimental Neuropsychiatry, Department for Psychiatry & Psychotherapy, University of Freiburg, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Department of Psychology, University of Freiburg, Freiburg, Germany
| | - Andreas Fischer
- Institute for Frontier Areas of Psychology and Mental Health, Freiburg, Germany
| | - Harald Atmanspacher
- Institute for Frontier Areas of Psychology and Mental Health, Freiburg, Germany
- Collegium Helveticum, Zürich, Switzerland
| | - Markus Heinrichs
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Department of Psychology, University of Freiburg, Freiburg, Germany
| | - Ludger Tebartz van Elst
- Section for Experimental Neuropsychiatry, Department for Psychiatry & Psychotherapy, University of Freiburg, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jürgen Kornmeier
- Institute for Frontier Areas of Psychology and Mental Health, Freiburg, Germany
- Section for Experimental Neuropsychiatry, Department for Psychiatry & Psychotherapy, University of Freiburg, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Abstract
Eleven series of figures were studied, each series ranging from one extreme interpretation via five ambiguous intermediates to a second extreme interpretation. Triplets consisting of an ambiguous exemplar in the middle flanked on the left and right by its two extreme interpretations were presented to large groups of subjects. The initial aim was to establish the levels of perceptual ambiguity of each exemplar in a series, and normative data on the ambiguous figures are provided for future reference and use. However, several biases were encountered and these were examined in more detail. In experiment 1 the subject's task was to compare the middle figure with the flankers and draw an arrow from the middle figure towards the flanking extreme they judged the most similar. Here, an overall preference for the left extreme was found. Therefore the instructions were reversed in experiment 2; flankers had to be compared with the middle figure. The preference for the left extreme remained for figures of living objects, but for nonliving objects the preference switched to the right extreme. To do away with any effect of the arrows, in experiment 3 subjects were divided into two groups each receiving different instructions and were asked to circle one of the extremes. However, the pattern of biases remained the same. The bias found with figures of living objects may be explained on the basis of top–down processes. For nonliving figures, an hypothesis based on bottom–up processes like neural fatigue was considered but rejected.
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Affiliation(s)
- Ilse M Verstijnen
- Laboratory of Experimental Psychology, Department of Psychology, University of Leuven, Tiensestraat 102, B 3000 Leuven, Belgium.
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Abstract
Studies of perception usually emphasize processes that are largely universal across observers and--except for short-term fluctuations--stationary over time. Here we test the universality and stationarity assumptions with two families of ambiguous visual stimuli. Each stimulus can be perceived in two different ways, parameterized by two opposite directions from a continuous circular variable. A large-sample study showed that almost all observers have preferred directions or biases, with directions lying within 90 degrees of the bias direction nearly always perceived and opposite directions almost never perceived. The biases differ dramatically from one observer to the next, and although nearly every bias direction occurs in the population, the population distributions of the biases are nonuniform, featuring asymmetric peaks in the cardinal directions. The biases for the two families of stimuli are independent and have distinct population distributions. Following external perturbations and spontaneous fluctuations, the biases decay over tens of seconds toward their initial values. Persistent changes in the biases are found on time scales of several minutes to 1 hour. On scales of days to months, the biases undergo a variety of dynamical processes such as drifts, jumps, and oscillations. The global statistics of a majority of these long-term time series are well modeled as random walk processes. The measurable fluctuations of these hitherto unknown degrees of freedom show that the assumptions of universality and stationarity in perception may be unwarranted and that models of perception must include both directly observable variables as well as covert, persistent states.
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9
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Snyder JS, Schwiedrzik CM, Vitela AD, Melloni L. How previous experience shapes perception in different sensory modalities. Front Hum Neurosci 2015; 9:594. [PMID: 26582982 PMCID: PMC4628108 DOI: 10.3389/fnhum.2015.00594] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/12/2015] [Indexed: 11/13/2022] Open
Abstract
What has transpired immediately before has a strong influence on how sensory stimuli are processed and perceived. In particular, temporal context can have contrastive effects, repelling perception away from the interpretation of the context stimulus, and attractive effects (TCEs), whereby perception repeats upon successive presentations of the same stimulus. For decades, scientists have documented contrastive and attractive temporal context effects mostly with simple visual stimuli. But both types of effects also occur in other modalities, e.g., audition and touch, and for stimuli of varying complexity, raising the possibility that context effects reflect general computational principles of sensory systems. Neuroimaging shows that contrastive and attractive context effects arise from neural processes in different areas of the cerebral cortex, suggesting two separate operations with distinct functional roles. Bayesian models can provide a functional account of both context effects, whereby prior experience adjusts sensory systems to optimize perception of future stimuli.
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Affiliation(s)
- Joel S. Snyder
- Department of Psychology, University of NevadaLas Vegas, Las Vegas, NV, USA
| | | | - A. Davi Vitela
- Department of Psychology, University of NevadaLas Vegas, Las Vegas, NV, USA
| | - Lucia Melloni
- Department of Neurophysiology, Max Planck Institute for Brain ResearchFrankfurt, Germany
- Department of Neurological Surgery, Columbia UniversityNew York, NY, USA
- Comprehensive Epilepsy Center, Department of Neurology, NYU Langone Medical Center, NYU School of Medicine, New York UniversityNew York, NY, USA
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10
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Kurylo DD, Bukhari F. Priming effects on the perceived grouping of ambiguous dot patterns. PSYCHOLOGICAL RESEARCH 2014; 79:872-81. [PMID: 25281427 DOI: 10.1007/s00426-014-0620-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 09/26/2014] [Indexed: 11/30/2022]
Abstract
For ambiguous stimuli, complex dynamics guide processes of perceptual grouping. Previous studies have suggested two opposing effects on grouping that are produced by the preliminary stimulus state: one that enhances grouping towards the existing structure, and another that opposes this structure. To examine effects of the preliminary state on grouping directly, measurements were made of perceived grouping of dot patterns that followed a visual prime. Three stimuli were presented in sequence: prime, target, and mask. Targets were composed of an evenly spaced dot grid in which grouping was established by similarity in luminance. Subjects indicated the dominant perceived grouping. The prime either corresponded to or opposed the prevailing organization of the target. Contrary to the hypothesis, solid-line primes biased grouping away from the structure of the prime, even when the prevailing organization of dot patterns strongly favored the primes' structure. This effect occurred, although to a lesser extent, when primes did not occupy the same location of targets, but were presented in a marginal area surrounding the grid. Priming effects did not occur for primes constructed of dot patterns. Effects found here may be attributed to a forward masking effect by primes, which more effectively disrupts grouping of patterns matched to the prime. Effects may also be attributed to a type of pattern contrast, in which a grouped pattern dissimilar to primes gains salience. For the pattern contrast model, the partial activation of multiple grouped configurations is compared to the pattern of the solid-line primes.
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Affiliation(s)
- Daniel D Kurylo
- Psychology Department, Brooklyn College CUNY, 2900 Bedford Avenue, Brooklyn, NY, 11210, USA,
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11
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Schwiedrzik CM, Ruff CC, Lazar A, Leitner FC, Singer W, Melloni L. Untangling perceptual memory: hysteresis and adaptation map into separate cortical networks. ACTA ACUST UNITED AC 2012; 24:1152-64. [PMID: 23236204 PMCID: PMC3977616 DOI: 10.1093/cercor/bhs396] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Perception is an active inferential process in which prior knowledge is combined with sensory input, the result of which determines the contents of awareness. Accordingly, previous experience is known to help the brain "decide" what to perceive. However, a critical aspect that has not been addressed is that previous experience can exert 2 opposing effects on perception: An attractive effect, sensitizing the brain to perceive the same again (hysteresis), or a repulsive effect, making it more likely to perceive something else (adaptation). We used functional magnetic resonance imaging and modeling to elucidate how the brain entertains these 2 opposing processes, and what determines the direction of such experience-dependent perceptual effects. We found that although affecting our perception concurrently, hysteresis and adaptation map into distinct cortical networks: a widespread network of higher-order visual and fronto-parietal areas was involved in perceptual stabilization, while adaptation was confined to early visual areas. This areal and hierarchical segregation may explain how the brain maintains the balance between exploiting redundancies and staying sensitive to new information. We provide a Bayesian model that accounts for the coexistence of hysteresis and adaptation by separating their causes into 2 distinct terms: Hysteresis alters the prior, whereas adaptation changes the sensory evidence (the likelihood function).
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Affiliation(s)
- Caspar M Schwiedrzik
- Department of Neurophysiology, Max Planck Institute for Brain Research, 60528 Frankfurt am Main, Germany
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12
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de Jong MC, Kourtzi Z, van Ee R. Perceptual experience modulates cortical circuits involved in visual awareness. Eur J Neurosci 2012; 36:3718-31. [PMID: 23031201 PMCID: PMC7611163 DOI: 10.1111/ejn.12005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 08/30/2012] [Indexed: 11/27/2022]
Abstract
Successful interactions with the environment entail interpreting ambiguous sensory information. To address this challenge it has been suggested that the brain optimizes performance through experience. Here we used functional magnetic resonance imaging (fMRI) to investigate whether perceptual experience modulates the cortical circuits involved in visual awareness. Using ambiguous visual stimuli (binocular rivalry or ambiguous structure-from-motion) we were able to disentangle the co-occurring influences of stimulus repetition and perceptual repetition. For both types of ambiguous stimuli we observed that the mere repetition of the stimulus evoked an entirely different pattern of activity modulations than the repetition of a particular perceptual interpretation of the stimulus. Regarding stimulus repetition, decreased fMRI responses were evident during binocular rivalry but weaker during 3-D motion rivalry. Perceptual repetition, on the other hand, entailed increased activity in stimulus-specific visual brain regions - for binocular rivalry in the early visual regions and for ambiguous structure-from-motion in both early as well as higher visual regions. This indicates that the repeated activation of a visual network mediating a particular percept facilitated its later reactivation. Perceptual repetition was also associated with a response change in the parietal cortex that was similar for the two types of ambiguous stimuli, possibly relating to the temporal integration of perceptual information. We suggest that perceptual repetition is associated with a facilitation of neural activity within and between percept-specific visual networks and parietal networks involved in the temporal integration of perceptual information, thereby enhancing the stability of previously experienced percepts.
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Affiliation(s)
- Maartje C de Jong
- Helmholtz Institute, Utrecht University, Heidelberglaan 2, 3584 CS, Utrecht, The Netherlands.
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13
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Abstract
Visual rivalry has been extensively characterized in the literature. It is thought to require spatial conflict between overlapping visual presentations, even in studies that have found nonspatial (i.e., nonretinal) influences on rivalry. Unexpectedly, we identified visual rivalry in the complete absence of spatial conflict. Participants experienced visual rivalry when we placed a nonambiguous motion stimulus in a nonspatial (in our case, object-based) reference frame. Moreover, a stimulus that was displaced within a nonspatial reference frame did not induce rivalry despite the presence of spatial conflict. This finding shows that nonspatial, object-based processing can overrule retinotopic processing and prevent rivalry from occurring when a perceived stimulus exists unambiguously in an object-based reference frame. Our results identify a potent high-level conflict-resolution stage independent of low-level spatial visual conflict. This independence of spatial overlap provides an advantage to the visual system, allowing conflict resolution when an object is nonstationary on the retina (e.g., during frequently occurring eye movements).
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Affiliation(s)
| | - Christof Koch
- Division of Biology, California Institute of Technology
- Allen Institute for Brain Science, Seattle, Washington
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14
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de Jong MC, Knapen T, van Ee R. Opposite influence of perceptual memory on initial and prolonged perception of sensory ambiguity. PLoS One 2012; 7:e30595. [PMID: 22295095 PMCID: PMC3266287 DOI: 10.1371/journal.pone.0030595] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 12/23/2011] [Indexed: 11/18/2022] Open
Abstract
Observers continually make unconscious inferences about the state of the world based on ambiguous sensory information. This process of perceptual decision-making may be optimized by learning from experience. We investigated the influence of previous perceptual experience on the interpretation of ambiguous visual information. Observers were pre-exposed to a perceptually stabilized sequence of an ambiguous structure-from-motion stimulus by means of intermittent presentation. At the subsequent re-appearance of the same ambiguous stimulus perception was initially biased toward the previously stabilized perceptual interpretation. However, prolonged viewing revealed a bias toward the alternative perceptual interpretation. The prevalence of the alternative percept during ongoing viewing was largely due to increased durations of this percept, as there was no reliable decrease in the durations of the pre-exposed percept. Moreover, the duration of the alternative percept was modulated by the specific characteristics of the pre-exposure, whereas the durations of the pre-exposed percept were not. The increase in duration of the alternative percept was larger when the pre-exposure had lasted longer and was larger after ambiguous pre-exposure than after unambiguous pre-exposure. Using a binocular rivalry stimulus we found analogous perceptual biases, while pre-exposure did not affect eye-bias. We conclude that previously perceived interpretations dominate at the onset of ambiguous sensory information, whereas alternative interpretations dominate prolonged viewing. Thus, at first instance ambiguous information seems to be judged using familiar percepts, while re-evaluation later on allows for alternative interpretations.
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15
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Wolf M, Hochstein S. High-level binocular rivalry effects. Front Hum Neurosci 2011; 5:129. [PMID: 22144953 PMCID: PMC3228233 DOI: 10.3389/fnhum.2011.00129] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 10/17/2011] [Indexed: 12/02/2022] Open
Abstract
Binocular rivalry (BR) occurs when the brain cannot fuse percepts from the two eyes because they are different. We review results relating to an ongoing controversy regarding the cortical site of the BR mechanism. Some BR qualities suggest it is low-level: (1) BR, as its name implies, is usually between eyes and only low-levels have access to utrocular information. (2) All input to one eye is suppressed: blurring doesn’t stimulate accommodation; pupilary constrictions are reduced; probe detection is reduced. (3) Rivalry is affected by low-level attributes, contrast, spatial frequency, brightness, motion. (4) There is limited priming due to suppressed words or pictures. On the other hand, recent studies favor a high-level mechanism: (1) Rivalry occurs between patterns, not eyes, as in patchwork rivalry or a swapping paradigm. (2) Attention affects alternations. (3) Context affects dominance. There is conflicting evidence from physiological studies (single cell and fMRI) regarding cortical level(s) of conscious perception. We discuss the possibility of multiple BR sites and theoretical considerations that rule out this solution. We present new data regarding the locus of the BR switch by manipulating stimulus semantic content or high-level characteristics. Since these variations are represented at higher cortical levels, their affecting rivalry supports high-level BR intervention. In Experiment I, we measure rivalry when one eye views words and the other non-words and find significantly longer dominance durations for non-words. In Experiment II, we find longer dominance times for line drawings of simple, structurally impossible figures than for similar, possible objects. In Experiment III, we test the influence of idiomatic context on rivalry between words. Results show that generally words within their idiomatic context have longer mean dominance durations. We conclude that BR has high-level cortical influences, and may be controlled by a high-level mechanism.
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Affiliation(s)
- Michal Wolf
- Neurobiology Department, Institute of Life Sciences, Interdisciplinary Center for Neural Computation, Hebrew University Jerusalem, Israel
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16
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Vanrie J, Verfaillie K. On the depth reversibility of point-light actions. VISUAL COGNITION 2011. [DOI: 10.1080/13506285.2011.614381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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17
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The temporal dynamics of global-to-local feedback in the formation of hierarchical motion patterns: psychophysics and computational simulations. Atten Percept Psychophys 2011; 73:1171-94. [DOI: 10.3758/s13414-011-0105-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Kaneoke Y, Urakawa T, Hirai M, Kakigi R, Murakami I. Neural basis of stable perception of an ambiguous apparent motion stimulus. Neuroscience 2009; 159:150-60. [PMID: 19138729 DOI: 10.1016/j.neuroscience.2008.12.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 12/08/2008] [Accepted: 12/09/2008] [Indexed: 10/21/2022]
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19
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Kohler A, Haddad L, Singer W, Muckli L. Deciding what to see: The role of intention and attention in the perception of apparent motion. Vision Res 2008; 48:1096-106. [PMID: 18279907 DOI: 10.1016/j.visres.2007.11.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Revised: 07/28/2007] [Accepted: 11/28/2007] [Indexed: 12/31/2022]
Affiliation(s)
- Axel Kohler
- Department of Neurophysiology, Max Planck Institute for Brain Research, Frankfurt am Main, Germany.
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20
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Hirahara M. Reduction in the motion coherence threshold for the same direction as that perceived during adaptation. Vision Res 2006; 46:4623-33. [PMID: 17092532 DOI: 10.1016/j.visres.2006.09.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Revised: 07/31/2006] [Accepted: 09/19/2006] [Indexed: 11/24/2022]
Abstract
When a stimulus of equally spaced parallel lines is displaced slightly in a direction perpendicular to the lines, low-speed motion toward the displacement direction can be perceived. Such a stimulus embodies both a low-speed and a high-speed component in opposite directions. The dominance of the former would result in the perception of low-speed motion. To see how the unperceived high-speed component is processed by the visual system, I measured coherence thresholds for random-dot test-motion with and without prior adaptation to the low-speed motion of the equally spaced parallel lines. The results depended on the test speeds. At low speeds, the coherence thresholds for the same direction as that perceived during the adaptation phase increased and the coherence thresholds for the opposite direction decreased. At high speeds, the same adaptation resulted in an opposite effect. The threshold reduction for high-speed motion in the same direction as that perceived during the adaptation phase and the threshold elevation in the opposite direction might be due to adaptation of a high-speed processing channel to the high-speed component that was not perceived but was nevertheless detected.
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21
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Nichols DF, Hock HS, Schöner G. Linking dynamical perceptual decisions at different levels of description in motion pattern formation: computational simulations. PERCEPTION & PSYCHOPHYSICS 2006; 68:515-33. [PMID: 16900841 DOI: 10.3758/bf03193694] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A two-level dynamical model of motion pattern formation is developed in which local motion/ nonmotion perceptual decisions are based on inhibitory competition between area V1 detectors responsive to motion-specifying versus motion-independent stimulus information, and pattern-level perceptual decisions are based on inhibitory competition between area MT motion detectors with orthogonal directional selectivity. The model accounts for the effects of luminance perturbations on the relative size of the pattern-level hysteresis effects reported by Hock and Ploeger (2006) and also accounts for related experimental results reported by Hock, Kelso, and Schöner (1993). Single-trial simulations demonstrated the crucial role of local motion/nonmotion bistability and activation-dependent future-shaping interactions in stabilizing perceived global motion patterns. Such interactions maintain currently perceived motion patterns by inhibiting the soon-to-be-stimulated motion detectors that otherwise would be the basis for the perception of an alternative pattern.
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22
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Maloney LT, Dal Martello MF, Sahm C, Spillmann L. Past trials influence perception of ambiguous motion quartets through pattern completion. Proc Natl Acad Sci U S A 2005; 102:3164-9. [PMID: 15710897 PMCID: PMC549457 DOI: 10.1073/pnas.0407157102] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Accepted: 01/07/2005] [Indexed: 11/18/2022] Open
Abstract
There are many celebrated examples of ambiguous perceptual configurations such as the Necker cube that abruptly and repeatedly "switch" among possible perceptual states. When such ambiguous configurations are presented intermittently, observers tend to see the same perceptual state on successive trials. The outcome of each trial apparently serves to "prime" the outcome of the following. We sought to determine how long the influence of a past trial persists by using ambiguous motion quartets as stimuli. We found large, significant effects of all four most recent trials, but the results were not consistent with any priming model. The results could be explained instead as perceptual completion of two kinds of temporal patterns, repeating and alternating. We conclude that the visual system does not passively remember perceptual state: it analyzes recent perceptual history and attempts to predict what will come next. These predictions can alter what is seen.
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Affiliation(s)
- L T Maloney
- Department of Psychology, Center for Neural Science, New York University, 6 Washington Place, New York, NY 10003, USA.
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23
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24
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Gepshtein S, Kubovy M. Stability and change in perception: spatial organization in temporal context. Exp Brain Res 2004; 160:487-95. [PMID: 15517224 DOI: 10.1007/s00221-004-2038-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2003] [Accepted: 06/29/2004] [Indexed: 10/26/2022]
Abstract
Perceptual multistability has often been explained using the concepts of adaptation and hysteresis. In this paper we show that effects that would typically be accounted for by adaptation and hysteresis can be explained without assuming the existence of dedicated mechanisms for adaptation and hysteresis. Instead, our data suggest that perceptual multistability reveals lasting states of the visual system rather than changes in the system caused by stimulation. We presented observers with two successive multistable stimuli and found that the probability that they saw the favored organization in the first stimulus was inversely related to the probability that they saw the same organization in the second. This pattern of negative contingency is orientation-tuned and occurs no matter whether the observer had or had not seen the favored organization in the first stimulus. This adaptation-like effect of negative contingency combines multiplicatively with a hysteresis-like effect that increases the likelihood of the just-perceived organization. Both effects are consistent with a probabilistic model in which perception depends on an orientation-tuned intrinsic bias that slowly (and stochastically) changes its orientation tuning over time.
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Affiliation(s)
- Sergei Gepshtein
- Vision Science, University of California at Berkeley, 360 Minor Hall, Berkeley, CA 94720-2020, USA.
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25
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Rajimehr R, Vaziri-Pashkam M, Afraz SR, Esteky H. Adaptation to apparent motion in crowding condition. Vision Res 2004; 44:925-31. [PMID: 14992836 DOI: 10.1016/j.visres.2003.11.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2003] [Revised: 10/17/2003] [Indexed: 10/26/2022]
Abstract
Visual adaptation has been successfully used for studying the neural activity of different cortical areas in response to visual stimuli when observers do not have explicit conscious access to those stimuli. We compared the orientation selective adaptation to apparent motion and its effect on the perception of stimuli with bistable apparent motion in crowded and non-crowded conditions. In the crowding paradigm conscious access to a visual stimulus is severely impaired when it is flanked by other similar stimuli in the peripheral visual field. As expected, adaptation to the target stimulus occurred in the non-crowded condition in all of the individual subjects (n=4; P<0.001). Although in the crowded condition subjects were not able to discriminate the target stimulus, adaptation to that stimulus was still preserved (P<0.001). There was no significant difference between the adaptations in the two conditions of the apparent motion (P>0.05). Imaging studies have shown that V5 cortex is the earliest visual area that specifically responds to apparent motion. Our results suggest that in certain conditions V5 may be activated while there is no explicit conscious access to the apparent motion.
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Affiliation(s)
- Reza Rajimehr
- School of Cognitive Sciences, Institute for Studies in Theoretical Physics and Mathematics (IPM), Niavaran, P.O. Box 19395-5746, Tehran, Iran.
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26
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Hock HS, Schöner G, Giese M. The dynamical foundations of motion pattern formation: stability, selective adaptation, and perceptual continuity. PERCEPTION & PSYCHOPHYSICS 2003; 65:429-57. [PMID: 12785073 DOI: 10.3758/bf03194574] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A dynamical model is used to show that global motion pattern formation for several different apparent motion stimuli can be embodied in the stable distribution of activation over a population of concurrently activated, directionally selective motion detectors. The model, which is based on motion detectors being interactive, noisy, and self-stabilizing, accounts for such phenomena as bistability, spontaneous switching, hysteresis, and selective adaptation. Simulations show that dynamical solutions to the motion correspondence problem for a bistable stimulus (two qualitatively different patterns are formed) apply as well to the solution for a monostable stimulus (only one pattern is formed) and highlight the role of interactions among sequentially stimulated detectors in establishing the state dependence and, thereby, the temporal persistence of percepts.
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Affiliation(s)
- Howard S Hock
- Department of Psychology, Florida Atlantic University, Boca Raton, Florida 33431, USA.
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27
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Abstract
We propose that explicit vision advances in reverse hierarchical direction, as shown for perceptual learning. Processing along the feedforward hierarchy of areas, leading to increasingly complex representations, is automatic and implicit, while conscious perception begins at the hierarchy's top, gradually returning downward as needed. Thus, our initial conscious percept--vision at a glance--matches a high-level, generalized, categorical scene interpretation, identifying "forest before trees." For later vision with scrutiny, reverse hierarchy routines focus attention to specific, active, low-level units, incorporating into conscious perception detailed information available there. Reverse Hierarchy Theory dissociates between early explicit perception and implicit low-level vision, explaining a variety of phenomena. Feature search "pop-out" is attributed to high areas, where large receptive fields underlie spread attention detecting categorical differences. Search for conjunctions or fine discriminations depends on reentry to low-level specific receptive fields using serial focused attention, consistent with recently reported primary visual cortex effects.
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Affiliation(s)
- Shaul Hochstein
- Department of Neurobiology, Neural Computation Center, Hebrew University, Jerusalem, Israel.
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28
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Hock HS, Park CL, Schöner G. Self-organized pattern formation: experimental dissection of motion detection and motion integration by variation of attentional spread. Vision Res 2002; 42:991-1003. [PMID: 11934451 DOI: 10.1016/s0042-6989(02)00026-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The formation of global motion patterns depends on the stimulus activation of local motion detectors as well as integrative excitatory and/or inhibitory interactions among the activated detectors. The counterphase row-of-elements [Vis. Res. 34 (1994) 1843] is an ideal stimulus for examining the relationship between the activational/energizing effect of the stimulus and interaction among the activated detectors. This is because the formation of the alternative unidirectional and oscillatory motion patterns for this stimulus requires the stimulation of local motion detectors, but there is no information in the stimulus that specifies either of the patterns. Their formation depends instead on the relative contributions of excitatory and inhibitory interactions to detector activation; the temporal patterns are self-organized. Broadly spread attention affects motion integration by changing the balance of excitatory versus inhibitory interactions, increasing the perception of unidirectional compared with oscillatory motion. (It likewise increases the perception of group compared with element motion for the Ternus stimulus.) There is, however, little if any effect of attentional spread on the luminance contrast required for the perception of single-element motion. The results indicate that the balance of integrative excitatory and/or inhibitory detector interactions can be modified by the perceiver's spread of attention, and further, that such changes need not be mediated by changes in the local, stimulus activation of the detectors.
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Affiliation(s)
- Howard S Hock
- Department of Psychology, Florida Atlantic University, Boca Raton 33431, USA.
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29
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Gilroy LA, Hock HS, Ploeger A. Differential activation solution to the motion correspondence problem. PERCEPTION & PSYCHOPHYSICS 2001; 63:847-61. [PMID: 11521851 DOI: 10.3758/bf03194442] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The correspondence problem arises in motion perception when more than one motion path is possible for discontinuously presented visual elements. Ullman's (1979) "minimal mapping" solution to the correspondence problem, for which costs are assigned to competing motion paths on the basis of element affinities (e.g., greater affinity for elements that are closer together), is distinguished from a solution based on the differential activation of directionally selective motion detectors. The differential activation account was supported by evidence that path length affects detector activation in a paradignm for which motion correspondence is not a factor. Effects on detector activation in this paradigm also were the basis for the successful prediction of path luminance effects on solutions to the motion correspondence problem. Finally, the differential activation account was distinguished from minimal mapping theory by an experiment showing that the perception of an element moving simultaneously in two directions does not depend on whether the two motions are matched in path-length determined affinity; it is sufficient that the activation of detectors responding to each of the two motion directions is above the threshold level required for the motions to be perceived. Implications of the differential activation solution are discussed for the stability of perceived motions once they are established, and the adaptation of perceived and unperceived motions.
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Affiliation(s)
- L A Gilroy
- Florida Atlantic University, Boca Raton 33431, USA
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30
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Strüber D, Stadler M. Differences in top-down influences on the reversal rate of different categories of reversible figures. Perception 2000; 28:1185-96. [PMID: 10694967 DOI: 10.1068/p2973] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Understanding the mechanisms underlying the multistability of reversible figures may provide valuable insights into the normal functioning of our visual system. The proposed factors that control the perceptual alternations of reversible figures can be classified into bottom-up and top-down processes. In the present study, we report differences in top-down effects on the reversal rate depending on whether a structural perspective (Necker cube, Schröder staircase) or a meaningful content (duck/rabbit figure, chef/dog figure) is subject to the reversal phenomenon. In order to activate top-down mechanisms explicitly the subjects had the instruction to bring the reversal rate under voluntary control. The results indicated that both slowing down and speeding up the rate of alternations was more effective for the content-reversal figures (duck/rabbit, chef/dog) than for the rather abstract perspective-reversal figures (Necker cube, Schröder staircase). In order to investigate the effect of meaningfulness in figure/ground reversals, the effect of the same instructional variable was also determined for Rubin's vase/faces and the Maltese cross. The results showed a similar tendency as in the case of the comparison between perspective reversals and content reversals. Possible cognitive processes that may play a role in top-down influences on figure reversal and theoretical implications of these findings for the interaction of bottom-up and top-down processes are discussed.
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Affiliation(s)
- D Strüber
- Institute of Psychology and Cognition Research & Center for Cognitive Sciences, University of Bremen, Germany.
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31
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Oyama T, Simizu M, Tozawa J. Effects of similarity on apparent motion and perceptual grouping. Perception 2000; 28:739-48. [PMID: 10664768 DOI: 10.1068/p2799] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Effects of similarity in colour, luminance, size, and shape on apparent motion and perceptual grouping were examined in part 1 in two parallel experiments on the same seven subjects. In both experiments, the effect of similarity was compared with that of proximity in competitive, bistable stimulus situations. A combination of a larger horizontal separation between the homogeneous stimulus elements and a smaller constant vertical separation between heterogeneous stimulus elements produced two kinds of apparent motion (or perceptual grouping) with equal probabilities. Such matched separations between homogeneous stimulus elements were obtained by the double staircase method in various stimulus conditions. In both experiments on apparent motion and perceptual grouping matched separation was found to increase as the difference between the heterogeneous stimulus elements increased. High correlations (0.71 to 0.94) of matched separations were found between apparent motion and perceptual grouping in four stimulus series: colour, luminance, size, and shape. Six of the seven subjects were also tested in part 2. Here, the effects of differences were found to work additively across different perceptual attributes in both phenomena, when multiple differences were combined in heterogeneous elements. The experimental results are discussed from the point of view that apparent motion is an example of perceptual constancy.
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Affiliation(s)
- T Oyama
- Department of Psychology, Nihon University, Tokyo, Japan.
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32
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Hock HS, Schöner G, Voss A. The influence of adaptation and stochastic fluctuations on spontaneous perceptual changes for bistable stimuli. PERCEPTION & PSYCHOPHYSICS 1997; 59:509-22. [PMID: 9158326 DOI: 10.3758/bf03211860] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Spontaneous perceptual change was studied by measuring the probabilities of the first two spontaneous pattern switches as a function of time following the onset of a bistable apparent quartet for which either horizontal or vertical motion is perceived. Contrary to the classical satiation hypothesis (Köhler & Wallach, 1944), differential time-dependent adaptation of the perceived compared with the unperceived motion directions was not necessary to account for the first spontaneous switch. In addition, adaptation of the perceived motion accompanied by recovery from adaptation of the unperceived motion was not necessary to account for the increased probability of the second spontaneous switch. It was concluded that regardless of possible adaptation effects, stochastic fluctuations are necessary for the actual reversal of activation levels that produces the spontaneous switch. When the difference in detector activation is reduced by differential adaptation of competing motion detectors (or by the occurrence of a prior spontaneous pattern change), smaller stochastic fluctuations are sufficient to reverse the relative activation of competing detectors. Thus, adaptation can increase the probability of spontaneous switches without directly causing them.
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Affiliation(s)
- H S Hock
- Department of Psychology, Florida Atlantic University, Boca Raton 33431, USA.
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