Bistable Stimuli Research Articles

Balancing bistable perception during self-motion

In two experiments we investigated whether bistable visual perception is influenced by passive own body displacements due to vestibular stimulation. For this we passively rotated our participants around the vertical (yaw) axis while observing different rotating bistable stimuli (bodily or non-bodily) with different ambiguous motion directions. Based on previous work on multimodal effects on bistable perception, we hypothesized that vestibular stimulation should alter bistable perception and that the effects should differ for bodily versus non-bodily stimuli. In the first experiment, it was found that the rotation bias (i.e., the difference between the percentage of time that a CW or CCW rotation was perceived) was selectively modulated by vestibular stimulation: the perceived duration of the bodily stimuli was longer for the rotation direction congruent with the subject's own body rotation, whereas the opposite was true for the non-bodily stimulus (Necker cube). The results found in the second experiment extend the findings from the first experiment and show that these vestibular effects on bistable perception only occur when the axis of rotation of the bodily stimulus matches the axis of passive own body rotation. These findings indicate that the effect of vestibular stimulation on the rotation bias depends on the stimulus that is presented and the rotation axis of the stimulus. Although most studies on vestibular processing have traditionally focused on multisensory signal integration for posture, balance, and heading direction, the present data show that vestibular self-motion influences the perception of bistable bodily stimuli revealing the importance of vestibular mechanisms for visual consciousness.

A model for dynamical switching in tristable perception for visual plaids

When observers view for extended time an ambiguous visual scene with two or more different interpretations they report switching between different perceptions. We focus on a classical paradigmatic stimulus, the visual plaids, consisting of two superimposed drifting gratings with transparent intersections [1,2]. For visual plaids, tristable perception is experienced: one coherent percept (the gratings move together as a single pattern) and two transparent percepts (the gratings slide across one another) with alternating depth order [3]. In order to decipher the complex mechanisms of tristable perception, we gathered a large amount of psychophysical data on tristable plaids and developed a neural network, firing rate model of interaction between neural populations that could account for the experimental results. Nine subjects reported continuously the three possible percepts for 3 sessions of 10 stimuli each (3 minutes per stimulus). The angle between the vectors normal to gratings was equal to 80, 100 or 120 degrees. We collected enough percepts to compute statistics for each subject and parameter without collapsing data [4]. As opposed to bistable stimuli where the only possibility is the alternation between the two percepts, in the tristable case the results show that the next percept probability depends on the previous percepts. Indeed, the sequence of perceptual switches confirms that switches between two transparency states are typically interleaved by a coherent percept, especially for values of the angle equal to 80 and 100 [3,4]. Moreover, by examining triplets consisting of two transparent percepts interleaved by a coherent one, we observed that the probability of the two transparent percepts in the triplet having the same depth pattern decreases as the duration of the coherent percept shortens. These trends suggest that adaptation is implicated in perceptual alternations. For bistable alternations correlations are absent or insignificant. We propose inhibition-based competition along with adaptation and noise in a multi-state framework as plausible mechanisms for the dynamics of perceptual switching. Our model is a firing rate model consisting of three mutually coupled populations of cells, each one encoding a different percept. It is based on the firing rate models for alternations during perceptual bistability [5]. We can explain the dependence in perceptual history by introducing an inhibition imbalance in the interactions between neural populations (the two transparent percepts inhibit each other more strongly than they inhibit the coherent state, making the latter more dominant and more likely to switch to). Adjusting the relative strength of adaptation and noise we can account for the dominance duration distributions and the switching probability between depth percepts as a function of the coherent percept duration. Finally, we consider other possible architectures for the model and we show that a non-hierarchical architecture where motion is encoded together with depth fits better with the experimental results.

Learned bias for 3-D shape perception without object motion

Was the highlighted surface closer or farther? During “cue recruitment”, uninformative visual signals such as retinotopic location and object translation direction can come to bias the perceived rotation direction of a Necker cube (a bistable stimulus) after training [e.g. Haijiang et al., 2006; Harrison & Backus, 2010]. Studies to date used 3D rotating stimuli, so it is possible that the learning was peculiar to neurons in the motion sensitive areas, such as MT, that are jointly tuned to motion direction and disparity [DeAngelis, Cumming & Newsome, 1998]. We examined whether cue recruitment occurs when stimuli do not contain motion signals. Learned Bias for 3-D Shape Perception without Object Motion

Pattern of BOLD signal in auditory cortex relates acoustic response to perceptual streaming

BackgroundSegregating auditory scenes into distinct objects or streams is one of our brain's greatest perceptual challenges. Streaming has classically been studied with bistable sound stimuli, perceived alternately as a single group or two separate groups. Throughout the last decade different methodologies have yielded inconsistent evidence about the role of auditory cortex in the maintenance of streams. In particular, studies using functional magnetic resonance imaging (fMRI) have been unable to show persistent activity within auditory cortex (AC) that distinguishes between perceptual states.ResultsWe use bistable stimuli, an explicit perceptual categorization task, and a focused region of interest (ROI) analysis to demonstrate an effect of perceptual state within AC. We find that AC has more activity when listeners perceive the split percept rather than the grouped percept. In addition, within this ROI the pattern of acoustic response across voxels is significantly correlated with the pattern of perceptual modulation. In a whole-brain exploratory test, we corroborate previous work showing an effect of perceptual state in the intraparietal sulcus.ConclusionsOur results show that the maintenance of auditory streams is reflected in AC activity, directly relating sound responses to perception, and that perceptual state is further represented in multiple, higher level cortical regions.

Transient bold activity locked to perceptual reversals of auditory streaming in human auditory cortex and inferior colliculus

Our auditory system separates and tracks temporally interleaved sound sources by organizing them into distinct auditory streams. This streaming phenomenon is partly determined by physical stimulus properties but additionally depends on the internal state of the listener. As a consequence, streaming perception is often bistable and reversals between one- and two-stream percepts may occur spontaneously or be induced by a change of the stimulus. Here, we used functional MRI to investigate perceptual reversals in streaming based on interaural time differences (ITD) that produce a lateralized stimulus perception. Listeners were continuously presented with two interleaved streams, which slowly moved apart and together again. This paradigm produced longer intervals between reversals than stationary bistable stimuli but preserved temporal independence between perceptual reversals and physical stimulus transitions. Results showed prominent transient activity synchronized with the perceptual reversals in and around the auditory cortex. Sustained activity in the auditory cortex was observed during intervals where the ΔITD could potentially produce streaming, similar to previous studies. A localizer-based analysis additionally revealed transient activity time locked to perceptual reversals in the inferior colliculus. These data suggest that neural activity associated with streaming reversals is not limited to the thalamo-cortical system but involves early binaural processing in the auditory midbrain, already.

Structural and functional fractionation of right superior parietal cortex in bistable perception

SummaryWhen faced with ambiguous sensory input, conscious awareness may alternate between the different percepts that are consistent with the input. Visual phenomena leading to such multistable perception, where constant sensory input evokes different conscious percepts, are particularly useful for investigating the processes underlying perceptual awareness [1]. Understanding the role that high-level brain regions outside early visual cortex play in perceptual alternations could elucidate how top-down processes modulate conscious perception [2]. In two studies [3,4] published recently in Current Biology, different combinations of the present authors used repetitive transcranial magnetic stimulation (rTMS) to disrupt activity in human superior parietal cortex, and reported seemingly contradictory results [5] concerning the effect of disrupting the normal function of this area on bistable perception. Here we join forces to resolve this discrepancy.

Attention modulates spatio-temporal grouping

Dynamic stimuli are ubiquitous in natural viewing conditions implying that grouping operations need to operate, not only in space, but also jointly in space and time. Moreover, in natural viewing, attention plays an important role in controlling how resources are allocated. We investigated how attention interacts with spatio-temporal perceptual grouping by using a bistable stimulus, called the Ternus–Pikler display. Ternus–Pikler displays can give rise to two different motion percepts, called Element Motion (EM) and Group Motion (GM), the former dominating at short Inter-Stimulus Intervals (ISIs) and the latter at long ISIs. Our results indicate that GM grouping requires more attentional resources than EM grouping. Different theoretical accounts of perceptual grouping and attention are discussed and evaluated in the light of the current results.

Strength of the zwicker tone illusion is reflected by induced and evoked brain responses following stimulus offset

Event Abstract Back to Event Strength of the zwicker tone illusion is reflected by induced and evoked brain responses following stimulus offset Sabine Jatzev1*, Ada Tse1 and Nathan Weisz1 1 Universität Konstanz, Germany Studies investigating brain processes giving rise to conscious perception often involve bistable stimuli or illusions, but are mostly restricted to the visual domain (Blake, 2002). The Zwicker tone (ZT) (Zwicker, 1964) is an interesting illusion of the auditory domain that has not been in the center of investigation in this area. The ZT is an auditory afterimage induced by and following to the presentation of notched noise. The perception is a sinusoidal tone with a pitch falling in the frequency range of the noise that is suppressed (Franosch, 2003). The ZT has also been discussed as a theoretical model explaining tinnitus (Norena, 2000). The objective of the current study was to manipulate the ZT illusion in parametrical way, inducing auditory illusions of different loudness. For this white noise with three different notch widths of 0.4, 0.6 and 0.8 or 0.6, 0.8 and 1 octaves were presented and white noise as a control condition. The notch center frequency was chosen according to the subjects ZT detection curves. EEG was measured for thirteen participants from 128 channels. Subjective ratings show a parametric modulation of the participant’s perceived loudness of the ZT according to notch bandwidth. This parametrical modulation is mirrored in EEG measures. Linear trend tests reveal a parametrical enhanced N1 and gamma activity relatively increasing with notch bandwidth and perceived loudness following the offset of the sound, i.e. at the moment of the actual ZT perception. At the same time activity in the alpha band shows the reverse pattern. These EEG patterns might reveal neural processes involved the conscious processing of tones, noise and phenomena in the auditory domain. Keywords: Awareness, EEG Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Consciousness and Awareness Citation: Jatzev S, Tse A and Weisz N (2011). Strength of the zwicker tone illusion is reflected by induced and evoked brain responses following stimulus offset. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00056 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Nov 2011; Published Online: 25 Nov 2011. * Correspondence: Mrs. Sabine Jatzev, Universität Konstanz, Konstanz, Germany, sabine.jatzev@googlemail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sabine Jatzev Ada Tse Nathan Weisz Google Sabine Jatzev Ada Tse Nathan Weisz Google Scholar Sabine Jatzev Ada Tse Nathan Weisz PubMed Sabine Jatzev Ada Tse Nathan Weisz Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Dynamic coupling of bistable stimuli reveals long-range connectivity

Dynamic coupling of bistable stimuli reveals long-range connectivity

Attention mediates learned perceptual bias for bistable stimuli

Attention mediates learned perceptual bias for bistable stimuli

Preexposure disrupts learning of location-contingent perceptual biases for ambiguous stimuli

The perception of a bistable stimulus as one or the other interpretation can be biased by prior presentations of that stimulus. Such learning effects have been found to be long lasting even after small amounts of training. The effectiveness of training may be influenced by preexposure to the ambiguous stimulus. Here we investigate the role of preexposure for learning a position-dependent perceptual bias. We used rotating Necker Cubes as the bistable stimuli, which were presented at two locations: above or below fixation. On training trials, additional depth cues disambiguated the rotation direction contingent on the location. On test trials, the rotating cube was presented without disambiguation cues. Without preexposure to the ambiguous stimulus, subjects learned to perceive the cube to be rotating in the trained direction for both locations. However, subjects that were preexposed to the ambiguous stimulus did not learn the trained percept-location contingency, even though the preexposure was very short compared to the subsequent training. Preexposure to the disambiguated stimulus did not interfere with learning. This indicates a fundamental difference between ambiguous test and disambiguated training trials for learning a perceptual bias. In short, small variations in paradigm can have huge effects for the learning of perceptual biases for ambiguous stimuli.

Reversal negativity and bistable stimuli: Attention, awareness, or something else?

Ambiguous (or bistable) figures are visual stimuli that have two mutually exclusive perceptual interpretations that spontaneously alternate with each other. Perceptual reversals, as compared with non-reversals, typically elicit a negative difference called reversal negativity (RN), peaking around 250 ms from stimulus onset. The cognitive interpretation of RN remains unclear: it may reflect either bottom-up processes, attentional processes that select between the alternative views of the stimulus, or it may reflect the change in the contents of subjective awareness. In the present study, event-related potentials in response to endogenous unilateral and bilateral reversals of two Necker lattices were compared with exogenously induced reversals of unambiguous lattices. The RN neither resembled the attention-related N2pc response, nor did it correlate with the content of subjective visual awareness. Thus, we conclude that RN is a non-attentional ERP correlate of the changes in the perceptual configuration of the presented object.

Uninformative visual experience establishes long term perceptual bias

Visual appearance depends upon the resolution of ambiguities that arise when 2D retinal images are interpreted as 3D scenes. This resolution may be characterized as a form of Bayesian perceptual inference, whereby retinal sense data combine with prior belief to yield an interpretation. Under this framework, the prior reflects environmental statistics, so an efficient system should learn by changing its prior after exposure to new statistics. We conjectured that a prior would only be modified when sense data contain disambiguating information, such that it is clear what bias is appropriate. This conjecture was tested by using a perceptually bistable stimulus, a rotating wire-frame cube, as a sensitive indicator of changes in the prior for 3D rotation direction, and by carefully matching perceptual experience of ambiguous and unambiguous versions of the stimulus across three groups of observers. We show for the first time that changes in the prior—observed as a change in bias that resists reverse learning the next day—is affected more by ambiguous stimuli than by disambiguated stimuli. Thus, contrary to our conjecture, modification of the prior occurred preferentially when the observer actively resolved ambiguity rather than when the observer was exposed to environmental contingencies. We propose that resolving stimuli that are not easily interpreted by existing visual rules must be a valid method for establishing useful perceptual biases in the natural world.

Electrophysiological correlates of perceptual reversals for three different types of bistable images

Bistable stimuli, i.e. stable visual images that can be perceived in two mutually exclusive ways, offer unique tools for dissociating perceptual from stimulus-driven changes in visual processing. Recently, event-related potentials (ERPs) have been employed to investigate the time-course of these endogenous changes in visual perception. For example, using a variant of the Necker cube, Kornmeier & Bach (2004, 2005) identified a ‘reversal negativity’ ERP component, i.e. a broad increase in negative potential extending from 200–400msec post-stimulus, for trials in which observers reported perceptual reversals. To further investigate the reversal negativity, as well as possible earlier influences on bistability, the current study employed three different types of bistable stimuli: a modified Rubin's face/vase, a modified Schröder's staircase, and a novel stimulus, Lemmo's cheetahs. Using a 128-channel system, 21 observers viewed flashing bistable stimuli, time-locked to the EEG recording, and indicated reversals by a button-press. Results show clear reversal negativities for all three bistable stimuli. In addition, an effect of early visual spatial attention on figure reversals was implicated by an analysis of the early occipital P1 & N1 ERP components. The P1 & N1 were enhanced for trials in which the observer reported perceptual reversals as compared to trials in which no reversals were reported for the face/vase and staircase, but not for the cheetahs. Taken together these results support a model of bistable perception in which changes in early spatial attention (indicated by P1 & N1 enhancement) modulate reversals (indicated by the reversal negativity).

Short-term dynamics of perceptual bias for bistable stimuli

Short-term dynamics of perceptual bias for bistable stimuli

What factors determine the stabilization of a bi-stable stimulus?

What factors determine the stabilization of a bi-stable stimulus?

Bistable stereoscopic 3D percepts: Will-power, flip frequency, eye movements and blinks

Conscious perception can be influenced by the observer's intention. Insights in conscious perception stem mainly from binocular rivalry studies in which the alternative percepts flip without clear voluntary control. We studied voluntary control in perception by exposing the visual system to a novel ambiguous 3D stimulus. In our paradigm observers estimate the orientation of a grid in 3D space (a metrical task). Perspective- and disparity-specified grid orientations can be independently varied across stimulus presentations, enabling us to do quantitative signal processing analysis. We have previously reported that observers are able to attentively select either a perspective- or a disparity-dominated percept when the two specified orientations had opposite signs (van Ee et al., Journal of Vision, 2002, 2, 597–607). Here we measured (i) the duration that an observer is able to voluntarily keep one percept over the alternative percept and (ii) the normal percept-dominance duration when the observer does not try to keep one over the other percept. We examined the increase in percept-dominance duration due to voluntary control, for both our stimuli and the classical binocular rivalry stimuli (horizontal/vertical bars and the house/face). Although spontaneous flips could not be prevented, we found a clear increase in percept-dominance duration for our stimulus relative to the classical stimuli. For a number of subjects the increase was almost ten-fold. We also measured eye movements and found that perceptual flips were neither correlated with eye movements, nor with blinks. Thus, will-power seems to have a relatively large influence in our bistable stimulus providing conditions for well-controlled conscious perception experiments.

Tri-stable stimuli reveal interactions among subsequent percepts: Rivalry is biased by perceptual history

In rivalry, constant stimuli allow several interpretations (“percepts”). Percepts are characterized by their probability to occur and by the duration of their dominance. During continuous presentation of bi-stable stimuli, both percept probabilities are trivially 50%. To disentangle the processes triggering a percept from those stabilizing it, we introduce tri-stable stimuli having three percepts. We find the probability and dominance duration of a percept independently adjustable. Percept probabilities and dominance durations show mutual dependencies across several perceptual switches. Consequently, the current perceptual experience depends on perceptual history; therefore, rivalry – even for continuous presentation – is not a memory-less process.

Perceptual ambiguity of bistable visual stimuli causes no or little increase in perceptual latency

Cognitive ambiguity, such as found in categorical judgments, increases behavioral response latency. Here we examined whether perceptual ambiguity for bistable stimuli, stimuli in which two perceptual interpretations were mutually competitive, also increased perceptual latency. We presented a bistable stimulus and measured the observer's reaction time to judge which of two possible percepts was seen. Perceptual ambiguity was systematically manipulated and how it affected the response latency was examined. The first experiment used a motion-defined rotating cylinder. The observers judged the rotation direction, and the perceptual ambiguity was controlled by binocular disparity. The second experiment used Rubin's vase. The observers judged whether the figure was a vase or faces, and the perceptual ambiguity was controlled by luminance of the surround. In both experiments, we found that the perceptual ambiguity caused only a small or no increase in reaction time and, presumably, in the perceptual latency included in the reaction time. These findings suggest that perceptual competition does not have a strong effect on the latency of the initial perception of bistable stimuli. Given that many perceptual problems are under-constrained as in the cases of bistable stimuli, it is presumably ecologically functional for the brain to establish perception as quickly as possible regardless of the presence of potential alternatives.

Spatiotemporal Neural Integration for Bistable Perception in a Response-Time Structure-From-Motion Task

The question of how perception arises from neuronal activity in the visual cortex is of fundamental importance to many issues in cognitive neuroscience. To address this question, we adopt a unique experimental paradigm in which bistable stimuli, namely structure from motion (SFM), are employed to dissociate the visual input from perception while monitoring cortical neural activity. In this paper, we analyze the dynamic responses of the multiunit activity, simultaneously collected from multiple channels in the middle temporal visual cortex of awake behaving macaque monkeys, for decoding the bistable percepts of SFM in a response-time (RT) perceptual discrimination task. Our goal is to understand how the perceptual discriminative information of neuronal population activity evolves and accumulates over time to mediate behaviors. Here, we used a discriminative classifier called the logistic regression and contrasted it with two generative classifiers, namely the quadratic discriminant analysis (QDA) and linear discriminant analysis (LDA), to achieve the spatiotemporal integration of neural activity and dynamically decode the perceptual reports on a single-trial basis. We found that the logistic regression outperforms both QDA and LDA in terms of decoding accuracy for both single-channel and multichannel decoding of bistable percepts. Subsequent analysis of the temporal profile of neural population decoding in relation to RT revealed that the amplitude and latency of the decoding accuracy are highly correlated with the RT, thus indicating that the monkeys respond faster when the decoding accuracy is higher and has shorter latency. These findings suggest that enhanced neuronal discrimination ability and shortened neuronal discrimination latency may impact monkeys' behaviors.