Binocular rivalry occurs when two eyes are presented with two conflicting stimuli. Although the physical stimulation stays the same, the conscious percept changes over time. This property makes it a unique paradigm in both vision science and consciousness research. Two key parameters, contrast and attention, were repeatedly shown to affect binocular rivalry dynamics in a similar manner. This was taken as evidence that attention acts by enhancing effective stimulus contrast. Brief transition periods between the two clear percepts have so far been much less investigated. In a previous study we demonstrated that transition periods can appear in different forms depending on the stimulus type and the observer. In the current study, we investigated how attention and contrast affect transition appearance. Observers viewed binocular rivalry and reported their perception of the four most common transition types by a button press while either the stimulus contrast or the locus of exogenous attention was manipulated. We show that contrast and attention similarly affect the overall binocular rivalry dynamics, but their effects on the appearance of transitions differ. These results suggest that the effect of attention is different from a simple enhancement of stimulus strength, which becomes evident only when different transition types are considered.

The role of temporal information in predicting human gaze in dynamic scenes remains a critical open question, underscored by the paradoxical finding that strong static models can outperform complex video-based models. This suggests that the true contribution of temporal cues has been obscured by confounding architectural variables. To resolve this, we present a rigorous, controlled experiment centered on a minimal architectural pair: a spatio-temporal saliency model (UniformerSal-ST) and its identical spatial-only counterpart (UniformerSal-S), designed to unambiguously isolate the impact of temporal feature integration. Our results demonstrate that principled temporal fusion yields a substantial Information Gain (IG) of +0.20 bits on temporally coherent datasets like LEDOV. Crucially, our controlled comparison also uncovers a key failure mode: on datasets with frequent hard cuts like DIEM, the same mechanism degrades performance, incurring a 0.07 bits IG deficit. We provide a mechanistic explanation for this dichotomy, revealing how certain visual scenarios (scene discontinuities, rapid camera zooms) can disrupt current temporal fusion approaches. By precisely quantifying both the benefits and drawbacks of temporal processing, our work provides the community with clear, actionable insights into when and why temporal information should be modeled for more robust and accurate video saliency prediction. The code will be made available at https: //github.com/peterjiz/uniformersal

The human claustrum is a small bilateral grey matter structure that is highly interconnected with cortical and subcortical regions. It has been implicated in different functions including sleep, multisensory integration, consciousness and attention, yet its exact function remains unclear. The primate claustrum is known to have distinct sensory regions, with the visual zone recently demonstrated in humans using high-resolution fMRI. In this study, we investigated stimulus properties that drive human visual claustrum activity. First, we tested the association of its response with various low- and mid-level physical stimulus features, including temporal and spatial contrast, color and motion. Second, we tested the association with subjective ratings of arousal, valence and interest. To compare the claustrum's responses with visual cortical regions, we performed the same analysis with the hV4 and hMT/V5+ complex. We found that the claustrum's visual response was associated with motion, as well as with arousal, interest and valence. The pattern of claustrum responses was similar to hMT/V5+. Given the well-established link between arousal and attentional allocation, as well as between saliency and motion, our results suggest that the visual claustrum may contribute to saliency detection and attention modulation during the sensory input.

Can knowledge influence perception? A central case suggesting it can, is evidence showing that knowledge about a color-diagnostic object’s typical color can influence its appearance. For example, a grey banana is allegedly perceived with a tint of yellow. However, methodological and conceptual considerations, leave it unclear whether the purported “memory-color” effect actually reflects changes in perception or changes in judgment and responses instead. Here, we combine memory-color with binocular rivalry to test if top-down influences affect the color an object is perceived in. We showed 24 participants familiar objects in their typical and opponent color and asked for concurrent reports of the perceived color. Consistent with Bayesian models of rivalry, we observed that conscious perception of identical spectral color pairs was biased towards the typical color of the presented object. Our results suggest that prior knowledge aids interpretation of ambiguous stimuli and biases conscious perception towards the most plausible interpretation.

Binocular rivalry is a visual phenomenon that occurs when two dissimilar stimuli are presented to each eye. The perception alternates between dominance periods when one of the stimuli is perceived with brief transition periods in between, providing a unique window into the dynamics of visual perception. While binocular rivalry dynamics are individually stable on a short time scale, they change with age. Previous research consistently showed that dominance durations increase with age while transition durations remain unchanged. However, the subjective appearance of transition periods can vary considerably even within an individual without any change in quantitative parameters. In the present study, we used a previously established methodology to investigate the change in subjective appearance of transitions in healthy adults across a continuous age range between 18 and 64. Consistent with prior studies, we found that dominance durations increased with age without any change in transition durations. Importantly, we observed age-related changes in transition appearance, which depended on the exact stimulus content used to induce binocular rivalry and were affecting only certain transition types. These results extend previous work by demonstrating that the qualitative experience of binocular rivalry can reflect important age-related changes which are not evident by conventional quantitative parameters.

Intriguing results from “choice blindness” (CB) experiments have shown that when people make choices, but are presented with a false outcome, many seem not to notice the mismatch and even provide reasons for choices they never made. They appear to be “blind” about their intentions. Yet, this effect goes against decision-making accounts and experience, in which we regularly notice outcomes that do not match our choices (e.g., when ordering food). Here, we ask whether participants really fail to detect the manipulation, or whether CB can be accounted for by covert detection, in that participants detect changes, but do not report them. To test this, we measured pupil dilation during the experiments to quantify objective responses in addition to reports by participants. In both experiments, we consistently observed that participants failed to report detected mismatches. Moreover, we observed increased pupil dilation during all manipulated trials, irrespective of whether they were reported or not. Thus, we provide conclusive evidence of covert detection in CB. In addition, we show that CB is strongly modulated by the idiosyncrasies of the experimental design. Our results cast doubt on the general validity of CB, and with that on key conclusions of previous studies. Instead, our results suggest no failure of detection, but instead higher-level, cognitively or socially driven hesitance of reporting. Our evidence leads us to a cautious discussion of CB and provides an account that no longer violates our intuitions about human intentionality and rationality, in that participants are less introspectively blind than originally portrayed.

Surprise responses signal both high-level cognitive alerts that information is missing, and increasingly specific back-propagating error signals that allow updates in processing nodes. Studying surprise is, hence, central for cognitive neuroscience to understand internal world representations and learning. Yet, only few prior studies used naturalistic stimuli targeting our high-level understanding of the world. Here, we use magic tricks in an fMRI experiment to investigate neural responses to violations of core assumptions held by humans about the world. We showed participants naturalistic videos of three types of magic tricks, involving objects appearing, changing color, or disappearing, along with control videos without any violation of expectation. Importantly, the same videos were presented with and without prior knowledge about the tricks' explanation. Results revealed generic responses in frontal and parietal areas, together with responses specific to each of the three trick types in posterior sensory areas. A subset of these regions, the midline areas of the default mode network (DMN), showed surprise activity that depended on prior knowledge. Equally, sensory regions showed sensitivity to prior knowledge, reflected in differing decoding accuracies. These results suggest a hierarchy of surprise signals involving generic processing of violation of expectations in frontal and parietal areas with concurrent surprise signals in sensory regions that are specific to the processed features.

Our subjective experience of the sensory information is rich and complex. Yet, typical cognitive and perception psychology paradigms reduce it to a few pre-defined discrete categories, like yes/no answers or the Likert scales. In the current study, we examined the complexity of subjective visual experience during binocular rivalry, a major experimental paradigm used to study conscious visual perception and its neural mechanisms. Binocular rivalry occurs when the two eyes are presented with two different images that cannot be fused into a uniform percept. As a result, the conscious perception alternates between the two images with brief transition phases in-between. Fifty-two subjects viewed binocular rivalry produced by pairs of stimuli with different visual information (images, orthogonal gratings or moving dots). After each rivalry period, they indicated how many different transition types they perceived and described their perception of each transition type. Using content analysis we identified 20 unique categories over all subjects, sessions, and stimuli. On average, participants reported 2-3 unique transition categories for each visual stimulus combination. The categories were consistent for each observer over time but varied across participants and stimulus content. Our results show that perceptual transitions during binocular rivalry appear in different forms and depend on the specific visual stimulus content that induces rivalry. Our findings have implications for neuroimaging studies of binocular rivalry, which may yield different results depending on the exact experience of transitions. They also demonstrate how the complexity of subjective visual experience may be underestimated in traditional perception paradigms.

Despite the functional specialization in visual cortex, there is growing evidence that the processing of chromatic and spatial visual features is intertwined. While past studies focused on visual field biases in retina and behavior, large-scale dependencies between coding of color and retinotopic space are largely unexplored in the cortex. Using a sample of male and female volunteers, we asked whether spatial color biases are shared across different human observers and whether they are idiosyncratic for distinct areas. We tested this by predicting the color a person was seeing using a linear classifier that has never been trained on chromatic responses from that same brain, solely by taking into account: (1) the chromatic responses in other individuals' brains and (2) commonalities between the spatial coding in brains used for training and the test brain. We were able to predict the color (and luminance) of stimuli seen by an observer based on other subjects' activity patterns in areas V1-V3, hV4, and LO1. In addition, we found that different colors elicited systematic, large-scale retinotopic biases that were idiosyncratic for distinct areas and common across brains. The area-specific spatial color codes and their conservation across individuals suggest functional or evolutionary organization pressures that remain to be elucidated.

The role of the parietal cortex in perceptual awareness and in resolving perceptual ambiguity is unsettled. Early influential transcranial magnetic stimulation studies have revealed differences in conscious perception following parietal stimulation, fuelling the notion that parietal cortex causally contributes to resolving perceptual ambiguity. However, central to this conclusion is the reliability of the method employed. Several prior studies have revealed opposing effects, such as shortening, lengthening, or no effect on multistable perceptual transitions following parietal stimulation. Here we addressed the reliability of continuous theta-burst stimulation (cTBS) on parietal cortex on the perception of bistable stimuli. We conducted three cTBS experiments that were matched to prior experiments in terms of stimuli, stimulation protocol, and target site, and used a higher number of participants. None of our cTBS experiments replicated prior cTBS results. The only experiment using individual functional localizers led to weak effects, while the two others led to null results. Individual variability of motor cortex cTBS did not predict parietal cTBS effects. In view of recent reports of highly variable cTBS effects over motor cortex, our results suggest that cTBS is particularly unreliable in modulating bistable perception when applied over parietal cortex.

Brightness illusions are a powerful tool in studying vision, yet their neural correlates are poorly understood. Based on a human paradigm, we presented illusory drifting gratings to mice. Primary visual cortex (V1) neurons responded to illusory gratings, matching their direction selectivity for real gratings, and they tracked the spatial phase offset between illusory and real gratings. Illusion responses were delayed compared to real gratings, in line with the theory that processing illusions requires feedback from higher visual areas (HVAs). We provide support for this theory by showing a reduced V1 response to illusions, but not real gratings, following HVAs optogenetic inhibition. Finally, we used the pupil response (PR) as an indirect perceptual report and showed that the mouse PR matches the human PR to perceived luminance changes. Our findings resolve debates over whether V1 neurons are involved in processing illusions and highlight the involvement of feedback from HVAs. The neural mechanisms underpinning visual illusions remains poorly understood. Here, the authors recorded the neural responses of mouse primary visual cortex to illusory grating and found delayed responses to illusory brightness, showing that optogenetic inhibition of higher visual areas reduced V1 response to illusions but not to real gratings.

The role of the early visual cortex in visual working memory (VWM) is a matter of current debate. Neuroimaging studies have consistently shown that visual areas encode the content of working memory, while transcranial magnetic stimulation (TMS) studies have presented incongruent results. Thus, we lack conclusive evidence supporting the causal role of early visual areas in VWM. In a recent registered report, Phylactou et al. (Phylactou P, Shimi A, Konstantinou N 2023 R. Soc. Open Sci. 10, 230321 (doi:10.1098/rsos.230321)) sought to tackle this controversy via two well-powered TMS experiments, designed to correct possible methodological issues of previous attempts identified in a preceding systematic review and meta-analysis (Phylactou P, Traikapi A, Papadatou-Pastou M, Konstantinou N 2022 Psychon. Bull. Rev. 29, 1594–1624 (doi:10.3758/s13423-022-02107-y)). However, a key part of their critique and experimental design was based on a misunderstanding of the visual system. They disregarded two important anatomical facts, namely that early visual areas of each hemisphere represent the contralateral visual hemifield, and that each hemisphere receives equally strong input from each eye—both leading to confounded conditions and artefactual effects in their studies. Here, we explain the correct anatomy, describe why their experiments failed to address current issues in the literature and perform a thorough reanalysis of their TMS data revealing important null results. We conclude that the causal role of the visual cortex in VWM remains uncertain.

The role of the early visual cortex in visual working memory is a matter of current debate (Christophel et al., 2017; Xu 2017). Neuroimaging research has consistently shown that early visual areas (V1, V2 and V3) encode the content of VWM (e.g., Harrison and Tong 2009; Serences et al., 2009). However, we are lacking conclusive evidence supporting the causal role of sensory areas in VWM, not at least because previous transcranial magnetic stimulation (TMS) studies provided incongruent results (e.g., van de Ven et al., 2012; van Lamsweerde et al., 2017; Rademaker et al., 2017). In a recent registered report, Phylactou et al., (2023), sought to tackle this controversy via two well powered TMS experiments, designed to correct possible methodological issues of previous attempts. Unfortunately, a key part of their experimental design was based on the wrong anatomical assumption that a given eye projects input from the center of gaze (i.e., from the central retina) primarily to one hemisphere. They hence disregarded two important anatomical facts, namely that early visual areas of each hemisphere represent the contralateral visual hemifield, and that each hemisphere receives equally strong input from each eye. In what follows, we explain the correct anatomy and describe why their main approach failed to address current issues in the literature.

Illusions are a powerful tool for studying the single neuron correlates of perception. Here, we introduce the neon color spreading (NCS) illusion in mice and report the neuronal correlates of illusory brightness, which has heretofore only been studied using human fMRI. We designed a novel NCS paradigm to evoke the percept of an illusory drifting grating and analyzed the activity of 520 single units in the mouse primary visual cortex (V1). A substantial proportion of V1 single units (60.5%) responded to illusory gratings with direction tuning matched to their preferred direction, which was determined using physically presented luminance-defined gratings (LDG). Moreover, by presenting LDG gratings with a 180° phase shift relative to NCs gratings, we show that spatial phase tuning shifted 180° for most single units. This finding conclusively demonstrates that V1 single units respond to illusory brightness. Using this novel mouse paradigm, we show that responses to illusory gratings have a lower magnitude and are delayed relative to physical gratings. We determined where V1 single units fell in the V1 cellular hierarchy (based on their susceptibility to surround suppression, their putative classification as interneuron or pyramidal neuron, and designation as a simple or complex cell) and found that higher-level V1 single units are more responsive to NCS stimuli. These findings resolve the debate of whether V1 is involved in illusory brightness processing and reveal a V1 hierarchical organization in which higher-level neurons are pivotal to the processing of illusory qualities, such as brightness.

In visual cortex, anatomically distinct patches respond to distinct categories, such as faces or text. New research confirms this parcellation using unsupervised analysis of functional magnetic resonance imaging data obtained from humans viewing tens of thousands of images, discovering one more preference: for food.

Neural mechanisms underlying a stable perception of the world during pursuit eye movements are not fully understood. Both, perceptual stability as well as perception of real (i.e. objective) motion are the product of integration between motion signals on the retina and efference copies of eye movements. Human areas V3A and V6 have previously been shown to have strong objective (‘real’) motion responses. Here we used high-resolution laminar fMRI at ultra-high magnetic field (9.4T) in human subjects to examine motion integration across cortical depths in these areas. We found an increased preference for objective motion in areas V3A and V6+ i.e. V6 and possibly V6A towards the upper layers. When laminar responses were detrended to remove the upper-layer bias present in all responses, we found a unique, condition-specific laminar profile in V6+, showing reduced mid-layer responses for retinal motion only. The results provide evidence for differential, motion-type dependent laminar processing in area V6+. Mechanistically, the mid-layer dip suggests a special contribution of retinal motion to integration, either in the form of a subtractive (inhibitory) mid-layer input, or in the form of feedback into extragranular or infragranular layers. The results show that differential laminar signals can be measured in high-level motion areas in the human occipitoparietal cortex, opening the prospect of new mechanistic insights using non-invasive brain imaging. Significance Statement Visual stability and our ability to differentiate between self-induced and real motion are central to our visual sense. Both require the integration of two signals – retinal motion and copies of muscle commands used for eye movements (efference copies). A reasonable assumption is that either the efference copy or the result of integration will be conveyed to high-level visual regions along with visual retinal input, possibly differentially across cortical depth as the input sources differ. Our ultra-high field recordings present the first laminar evidence of differential signal processing of retinal and objective motion signals in area V6+, and present a first window into a mechanistic understanding of visual high-level motion processing.

Consciousness, its neural underpinnings, and the role of frontal cortex are highly debated topics. New evidence shows that human frontal cortex can bias conscious perception. What does this really mean about its contribution to consciousness?

Magic tricks have enjoyed an increasing interest by scientists. However, most research in magic focused on isolated aspects of it and a conceptual understanding of magic, encompassing its distinct components and varieties, is missing. Here, we present an account of magic within the theory of Bayesian predictive coding. We present the “wow” effect of magic as an increase in surprise evoked by the prediction error between expected and observed data. We take into account prior knowledge of the observer, attention, and (mis-)direction of perception and beliefs by the magician to bias the observer’s predictions and present a simple example for the modelling of the evoked surprise. The role of misdirection is described as everything that aims to maximize the surprise a trick evokes by the generation of novel beliefs, the exploitation of background knowledge and attentional control of the incoming information. Understanding magic within Bayesian predictive coding allows unifying all aspects of magic tricks within one framework, making it tractable, comparable and unifiable with other models in psychology and neuroscience.

Recognising a person's identity often relies on face and body information, and is tolerant to changes in low-level visual input (e.g., viewpoint changes). Previous studies have suggested that face identity is disentangled from low-level visual input in the anterior face-responsive regions. It remains unclear which regions disentangle body identity from variations in viewpoint, and whether face and body identity are encoded separately or combined into a coherent person identity representation. We trained participants to recognise three identities, and then recorded their brain activity using fMRI while they viewed face and body images of these three identities from different viewpoints. Participants' task was to respond to either the stimulus identity or viewpoint. We found consistent decoding of body identity across viewpoint in the fusiform body area, right anterior temporal cortex, middle frontal gyrus and right insula. This finding demonstrates a similar function of fusiform and anterior temporal cortex for bodies as has previously been shown for faces, suggesting these regions may play a general role in extracting high-level identity information. Moreover, we could decode identity across fMRI activity evoked by faces and bodies in the early visual cortex, right inferior occipital cortex, right parahippocampal cortex and right superior parietal cortex, revealing a distributed network that encodes person identity abstractly. Lastly, identity decoding was consistently better when participants attended to identity, indicating that attention to identity enhances its neural representation. These results offer new insights into how the brain develops an abstract neural coding of person identity, shared by faces and bodies.