Necker Cube Research Articles

A trained perceptual bias that lasts for weeks

Classical (Pavlovian) conditioning procedures can be used to bias the appearance of physical stimuli. Under natural conditions this form of perceptual learning could cause perception to become more accurate by changing prior belief to be in accord with what is statistically likely. However, for learning to be of functional significance, it must last until similar stimuli are encountered again. Here, we used the apparent rotation direction of a revolving wire frame (Necker) cube to test whether a learned perceptual bias is long lasting. Apparent rotation direction was trained to have a different bias at two different retinal locations by interleaving the presentation of ambiguous cubes with presentation of cubes that were disambiguated by disparity and occlusion cues. Four groups of eight subjects were subsequently tested either 1, 7, 14, or 28 days after initial training, respectively, using a counter-conditioning procedure. All four groups showed incomplete re-learning of the reversed contingency relationship during their second session. One group repeated the counter-conditioning and showed an increase in the reverse bias, showing that the first counter-conditioning session also had a long-lasting effect. The fact that the original learning was still evident four weeks after the initial training is consistent with the operation of a mechanism that ordinarily would improve the accuracy and efficiency of perception.

Event-related potential responses to perceptual reversals are modulated by working memory load

While viewing ambiguous figures, such as the Necker cube, the available perceptual interpretations alternate with one another. The role of higher level mechanisms in such reversals remains unclear. We tested whether perceptual reversals of discontinuously presented Necker cube pairs depend on working memory resources by manipulating cognitive load while recording event-related potentials (ERPs). The ERPs showed early enhancements of negativity, which were obtained in response to the first cube approximately 500ms before perceived reversals. We found that working memory load influenced reversal-related brain responses in response to the second cube over occipital areas at the 150–300ms post-stimulus and over central areas at P3 time window (300–500ms), suggesting that it modulates intermediate visual processes. Interestingly, reversal rates remained unchanged by the working memory load. We propose that perceptual reversals in discontinuous presentation of ambiguous stimuli are governed by an early (well preceding pending reversals) mechanism, while the effects of load on the reversal related ERPs may reflect general top-down influences on visual processing, possibly mediated by the prefrontal cortex.

In Search of Causal Mechanisms Underlying Bistable Perception

The visual system interprets most visual scenes according to a single best interpretation, thereby effectively disambiguating the inherently ambiguous information provided by retinal stimulation. The phenomenal instability of ambiguous figures like the Necker cube provides an especially dramatic and

The linear impact of concurrent working memory load on dynamics of Necker cube perceptual reversals

Ambiguous figures are visual stimuli that may be perceived in multistable interpretations. The role of attention in modulating perceptual reversals of ambiguous stimuli is not clear. We tested whether perceptual reversals depend on working memory by manipulating its load while the participants were viewing the Necker cube. Increasing working memory load delayed the latency and decreased the frequency of reversals. These effects followed a linear function of load. The findings imply shared resources of the mechanisms responsible for perceptual reversals and working memory maintenance. However, reversals were not completely abolished even with the hard seven-consonants load, suggesting that bottom-up processes continue to operate in the bistable perception dynamics when top-down mechanisms are attenuated.

Restorative effects of visits to urban and forest environments in patients with exhaustion disorder

This experimental study investigated differences in perceived restorativeness, mood, attention capacity and physiological reactions when visiting city and forest environments. Twenty female patients diagnosed with exhaustion disorder visited three different forest environments and one city environment in randomized order. They performed a standardized 90-min test procedure in each of these environments. Evaluation of the environments and psychological effects in mood were studied with self-administered questionnaires. Attention capacity was studied with Necker Cube Pattern Control task. Physiological responses were measured with regularly scheduled controls of heart rate and blood pressure, and a single test of heart rate recovery. Visits to the forest environments were perceived as significantly more restorative, enhancing mood and attention capacity compared to the city. This also applies to the results of heart rate and to some extent to the results of the diastolic blood pressure. The results from this experimental study support our hypothesis that short visits to forest environments enhance both psychological and physiological recovery and that visits to forest environments are likely to be beneficial when suffering from exhaustion disorder.

Perceptual memory drives learning of retinotopic biases for bistable stimuli

The visual system exploits past experience at multiple timescales to resolve perceptual ambiguity in the retinal image. For example, perception of a bistable stimulus can be biased toward one interpretation over another when preceded by a brief presentation of a disambiguated version of the stimulus (positive priming) or through intermittent presentations of the ambiguous stimulus (stabilization). Similarly, prior presentations of unambiguous stimuli can be used to explicitly “train” a long-lasting association between a percept and a retinal location (perceptual association). These phenonema have typically been regarded as independent processes, with short-term biases attributed to perceptual memory and longer-term biases described as associative learning. Here we tested for interactions between these two forms of experience-dependent perceptual bias and demonstrate that short-term processes strongly influence long-term outcomes. We first demonstrate that the establishment of long-term perceptual contingencies does not require explicit training by unambiguous stimuli, but can arise spontaneously during the periodic presentation of brief, ambiguous stimuli. Using rotating Necker cube stimuli, we observed enduring, retinotopically specific perceptual biases that were expressed from the outset and remained stable for up to 40 min, consistent with the known phenomenon of perceptual stabilization. Further, bias was undiminished after a break period of 5 min, but was readily reset by interposed periods of continuous, as opposed to periodic, ambiguous presentation. Taken together, the results demonstrate that perceptual biases can arise naturally and may principally reflect the brain's tendency to favor recent perceptual interpretation at a given retinal location. Further, they suggest that an association between retinal location and perceptual state, rather than a physical stimulus, is sufficient to generate long-term biases in perceptual organization.

Interpretation of contradictory images by means of systems of linear inequalities

We consider the problem of interpretation of three-dimensional images from their flat projections up to the set of visible faces. For projections of convex polyhedra, we present an interpretation algorithm based on maximal feasible subsystems of a certain infeasible system of linear inequalities modeling the visibility requirement for faces. A number of model examples are given; in particular, the algorithm is applied to the interpretation of the Necker cube.

Brain mechanisms for simple perception and bistable perception

When faced with ambiguous sensory inputs, subjective perception alternates between the different interpretations in a stochastic manner. Such multistable perception phenomena have intrigued scientists and laymen alike for over a century. Despite rigorous investigations, the underlying mechanisms of multistable perception remain elusive. Recent studies using multivariate pattern analysis revealed that activity patterns in posterior visual areas correlate with fluctuating percepts. However, increasing evidence suggests that vision--and perception at large--is an active inferential process involving hierarchical brain systems. We applied searchlight multivariate pattern analysis to functional magnetic resonance imaging signals across the human brain to decode perceptual content during bistable perception and simple unambiguous perception. Although perceptually reflective activity patterns during simple perception localized predominantly to posterior visual regions, bistable perception involved additionally many higher-order frontoparietal and temporal regions. Moreover, compared with simple perception, both top-down and bottom-up influences were dramatically enhanced during bistable perception. We further studied the intermittent presentation of ambiguous images--a condition that is known to elicit perceptual memory. Compared with continuous presentation, intermittent presentation recruited even more higher-order regions and was accompanied by further strengthened top-down influences but relatively weakened bottom-up influences. Taken together, these results strongly support an active top-down inferential process in perception.

Effects of alcohol on attentional mechanisms involved in figure reversals

The impairing effects of alcohol on attention are well documented and are thought to involve inhibitory mechanisms. We used ambiguous figures (Face-Vase and Necker cube) to test whether the intentional control mechanism is more vulnerable to the effects of alcohol than the automatic mechanism. Participants were assigned to an alcohol (Study 1, N = 15; Study 2, N = 18), placebo (Study 1, N = 15; Study 2, N = 20) or control (Study 1 only, N = 10) group. The doses of alcohol were 0.8 g/kg for men and 0.75 g/kg for women. Participants were shown the Face-Vase and Necker cube figures and two variants of each, which were biased in varying degrees towards one interpretation. Study 1 assessed the automatic control mechanism by asking participants to report spontaneous reversals. Study 2 assessed the intentional control mechanism by asking participants to increase reversal rate. In Study 1, reversal rate was similar for all groups, whereas in Study 2, the alcohol group reported more reversals than the control group, although this was true only for the biased versions of the Face-Vase illusion. The effect of alcohol on reversal rate is observed only during intentional reversals of semantically meaningful stimuli and only when the stimulus is biased.

Non-3D pattern of copying the Necker cube as a risk of dementia among a nondemented population: Reanalysis from the Tajiri project

cerebral blood flow and altered cerebrovascular reactivity (CVR).Methods: To determine changes in cerebral vascular reactivity in adults over 65 with MCI Subcortical Vascular (MCI -VS) and without MCI -VS.Prospective, case-control. DCL-VS was defined for those subjects with memory complaints and objective cognitive impairment, detected by neuropsychological test. Were obtained data and vascular risk factors. Evaluation of cerebrovascular reactivity in middle cerebral arteries to hypercapnia was measured with transcranial Doppler ultrasonography using the breath-holding index (BHI); pulsatility index (PI) was also recorded.Was considered abnormal, an apnea index of 0.8% (p<0.005). In addition, we found a significant negative correlation between the values V‘V‘of CVR in the right MCA with age, suggesting that at an older age, lower the CVR (r test, p<0.008). Conclusions: The cerebral vascular reactivity, is impaired in subjects with vascularMCI. Likewise, we also observed a decrease in CVRwithi ncreasing age,in both groups.This study shows that transcranial Doppler can be a useful tool to confirm vascular cognitive profile.

How intermittent presentation affects conscious perceptual reversals of ambiguous figures

Continually observing an ambiguous figure, we can perceive reversals between different interpretations. How perceptual reversals change when an ambiguous stimulus is presented intermittently? Since no reversal can be consciously perceived during off-periods, we use net Average Reversal Interval (netARI) but not usual average reversal interval to measure the perceptual reversal rate. NetARI is calculated by dividing accumulated time of on-periods by the number of reversals. The results are: (1) presenting an ambiguous figure intermittently increased the perceptual reversal rate; (2) the longer the exposure of Necker cube, the slower the perceptual reversal rate was, and when on-periods were longer as 15 s, the perceptual reversal rate was slowed down and was almost same to that in the continuous case; (3) the length of off-periods (which ranged from 1 s to 5 s in the present study) did not affect the reversal rate.

Ambient GABA Responsible for Age-Related Changes in Multistable Perception

Multistable perception is a psychophysical phenomenon in which one unique interpretation alternates spontaneously every few seconds between two or more interpretations of the same sensory input. Well-known examples include the Necker cube and face-vase illusions in vision. Interestingly, young adults generally see more perceptual switches than do elderly people. To understand the underlying neuronal mechanism of age-related multistable perception, we simulated a cortical neural network model that consists of multiple cell assemblies. In the network, a specific population of noncore cells and a common population of core cells form a cell assembly that represents a single object (or event). Every dynamic cell assembly, activated by a given sensory input, involves the common (overlapping) population of core cells. Ambient GABA-mediated intracortical tonic inhibition via extrasynaptic GABAa receptors destabilized the currently appearing dynamic cell assembly and terminated its burst firing. This allowed another dynamic cell assembly to emerge one after the other. Namely, multistable perception took place. Transporters, which were embedded in axon terminal membranes of interneurons, regulated levels of ambient GABA. For elderly people, we assumed a decline in transporter. This decelerated GABA augmentation and resulted in prolonging the durations of burst firing and thus in slowing perceptual switches. We suggest that poor control of ambient GABA levels due to age-related decline in GABA transporter may be responsible for the slowing of perceptual switches in elderly people.

A Tentative Nonlinear Model for Explanation of a Perceptual Alternation Phenomenon

We present a simple three-neuron Hopfield neural network as a tentative model to illustrate the perspective alternation of Necker cube. This neural network has a chaotic attractor with two “leaves", each leaf can be regarded as a dynamic process corresponding a feature of the Necker cube. This tentative model suggests another manifestation of the role of chaos in information processing.

Perceptual Hypotheses in Drosophila Vision

Event Abstract Back to Event Perceptual Hypotheses in Drosophila Vision Reinhard Wolf1*, Franziska Töpfer1 and Martin Heisenberg1 1 Rudolf-Virchow-Center for Experimental Biomedicine, University of Wuerzburg, Germany Vision is an active process. One way to demonstrate activity in visual behavior is to present ambiguous visual stimuli that elicit several equally adaptive responses. A well-known example from psychophysics is the Necker cube (a) which is seen in two rivaling perspectives. The brain is said to respond to one of two equally valid perceptual hypotheses which subsequently may be confirmed (or not) by further sensory information possibly caused by the response. If a hypothesis is not confirmed, the brain tries the alternative one. We use the flight simulator to expose Drosophila to ambiguous stimuli. The fly is suspended at a torque meter in the center of a 360° random dot pattern. The fly’s yaw torque is negatively proportional to the angular velocity of the panorama. If the fly intends to turn clockwise, the pattern rotates counterclockwise, and vice versa. If a constant rotatory bias is added to the panorama, the fly instantly adjusts its mean yaw torque to compensate for it (optomotor balance). In free flight, optomotor balance would correspond to a straight trajectory and a rotatory bias to the injury of one wing. In (b) the fly is surrounded by two identical, concentric random dot patterns (shown flat). Both are driven by the fly’s yaw torque. We now add to the angular velocity of one pattern a constant clockwise rotatory bias [w(cw)], and to the angular velocity of the other pattern an equally fast constant counterclockwise bias [w(ccw)]. If the fly brain would simply process the summed output of its motion detectors, it would have only one yaw torque value (T=0) to obtain optomotor balance. However, Drosophila occasionally adjusts its mean yaw torque to the two yaw torque levels which compensate for the rotatory bias of one of the two patterns separately [w(cw) or w(ccw)]. This finding implies that from each set of dots moving coherently the fly can derive a separate 'hypothesis' about self-rotation, and tries to confirm it with the corresponding behavior. Figure 1 Keywords: Drosophila vision, Brain activity, Visual Perception, active vision, visual control of movement Conference: International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013. Presentation Type: Oral presentation preferred Topic: Motion vision Citation: Wolf R, Töpfer F and Heisenberg M (2019). Perceptual Hypotheses in Drosophila Vision. Front. Physiol. Conference Abstract: International Conference on Invertebrate Vision. doi: 10.3389/conf.fphys.2013.25.00089 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: 27 Feb 2013; Published Online: 09 Dec 2019. * Correspondence: Mr. Reinhard Wolf, Rudolf-Virchow-Center for Experimental Biomedicine, University of Wuerzburg, Wuerzburg, Germany, reinhard.wolf@virchow.uni-wuerzburg.de 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 Reinhard Wolf Franziska Töpfer Martin Heisenberg Google Reinhard Wolf Franziska Töpfer Martin Heisenberg Google Scholar Reinhard Wolf Franziska Töpfer Martin Heisenberg PubMed Reinhard Wolf Franziska Töpfer Martin Heisenberg 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.

Antecedent occipital alpha band activity predicts the impact of oculomotor events in perceptual switching.

Oculomotor events such as blinks and saccades transiently interrupt the visual input and, even though this mostly goes undetected, these brief interruptions could still influence the percept. In particular, both blinking and saccades facilitate switching in ambiguous figures such as the Necker cube. To investigate the neural state antecedent to these oculomotor events during the perception of an ambiguous figure, we measured the human scalp electroencephalogram (EEG). When blinking led to perceptual switching, antecedent occipital alpha band activity exhibited a transient increase in amplitude. When a saccade led to switching, a series of transient increases and decreases in amplitude was observed in the antecedent occipital alpha band activity. Our results suggest that the state of occipital alpha band activity predicts the impact of oculomotor events on the percept.

Perceptual reversals of Necker stimuli during intermittent presentation with limited attentional resources

During prolonged viewing of ambiguous stimuli, such as Necker cubes, sudden perceptual reversals occur from one perceptual interpretation to another. The role of attention in such reversals is not clear. We tested whether perceptual reversals depend on attentional resources by manipulating perceptual load and recording event-related potentials (ERPs) during intermittent presentation of Necker stimuli. The results did not reveal any influence for perceptual load on the frequency of reversals. The ERPs showed that perceptual load influenced electrophysiological activity over parieto-central areas in the P1 time window (110-140 ms), but load did not modify the early enhancements of positivity (30-140 ms), which correlated with perceptual reversals at occipito-temporal sites. We conclude that disambiguation of ambiguous figures is based on early mechanisms that can work efficiently with only a minimal amount of attentional resources.

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.

Rotating the Necker cube: A bioeconomic approach to cooperation and the causal role of synergy in evolution

The paradox of widespread cooperation in an intensely competitive natural world has been a major focus of theory and research in evolutionary biology and related disciplines over the past several decades. While much of the earlier work in this vein was gene-centered and grounded in inclusive fitness (or kin selection) theory, more recent developments suggest that it might also be useful to view cooperation (and biological complexity) from a bioeconomic perspective. Here I will briefly explore the case for a paradigm shift, with special reference to the role of functional synergy as a distinct class of interdependent causal influences in evolution. I will argue that synergies of various kinds have been important drivers for cooperation in living systems at all levels. From this perspective, inclusive fitness and other factors may be enablers for cooperation, but the many exceptions show that genetic relatedness is neither necessary nor sufficient for the emergence of cooperative phenomena.

Slower adaptation to driving simulator and simulator sickness in older adults Aging Clinical and Experimental Research

Methods of assessing driving abilities in the elderly are urgently needed. Although the driving simulator (DS) appears to be a safe and cost-effective method of objectively evaluating driving performance, it may pose adaptation problems for elderly adults. In this study, we examined age-related adaptation deficits on the DS. Healthy young adults (n=15) and healthy elderly persons (n=17) completed some neuropsychological tests, and then performed a road-tracking task with the DS, which was repeated four times (Trials 1-4). After simulated driving in DS, simulator sickness (SS) was observed in 18.8% of participants. The frequency of SS was 29.4% in elderly adults and 6.7% in young adults, and 17.6% of the elderly participants dropped out of the experiment. Performance on the Necker cube copying task was significantly correlated with the onset of SS. Driving performance also showed a significant interaction between group and trial, for both driving accuracy and vehicle speed. In addition, the performance of elderly adults significantly improved between trials 1 and 4, reaching a plateau in trial 4, whereas that of young adults did not change across trials. This study provides preliminary evidence of slower adaptation to a DS-based driving task by older adults, which was associated with cognitive aging. Age affected driving accuracy and velocity when a road-tracking task was simply repeated. It is concluded that the capacity of elderly people to adapt to DS environments should be taken into consideration when evaluating their performance on DS tasks.

Traveling EEG slow oscillation along the dorsal attention network initiates spontaneous perceptual switching

An ambiguous figure such as the Necker cube causes spontaneous perceptual switching (SPS). The mechanism of SPS in multistable perception has not yet been determined. Although early psychological studies suggested that SPS may be caused by fatigue or satiation of orientation, the neural mechanism of SPS is still unknown. Functional magnetic resonance imaging (fMRI) has shown that the dorsal attention network (DAN), which mainly controls voluntary attention, is involved in bistable perception of the Necker cube. To determine whether neural dynamics along the DAN cause SPS, we performed simultaneous electroencephalography (EEG) and fMRI during an SPS task with the Necker cube, with every SPS reported by pressing a button. This EEG–fMRI integrated analysis showed that (a) 3–4 Hz spectral EEG power modulation at fronto-central, parietal, and centro-parietal electrode sites sequentially appeared from 750 to 350 ms prior to the button press; and (b) activations correlating with the EEG modulation traveled along the DAN from the frontal to the parietal regions. These findings suggest that slow oscillation initiates SPS through global dynamics along the attentional system such as the DAN.