julilili42/papers huggingface dataset:
Did you find it? Visual search tends to be faster when applying saliency-aware subtle scene modulation in VR-based realistic scenario
2021-09-01

Visual search as a daily task becomes particularly challenging when the time to find the target is limited. In a pilot study, we investigate whether a subtle modulation of visual content considering the scene saliency map can improve visual search performance in terms of the search time and proportion of failure to find the target within a limited time. To do so, a set of naturalistic omnidirectional images were displayed in virtual reality (VR) with a search target being overlaid on the visual scene at a random location. During the experiment, each of five participants performed a visual search task in this virtual environment with an ultimate goal to find the search target as soon as possible within 20 seconds. By subtle modulation of the visual content we intended to redirect the observer’s attention from salient regions of the scene, and, that way, enable the participant to find the search target faster. The scenes were modified applying blur, where blurring strength was spatially varied based on the saliency maps computed for the displayed omnidirectional images before the experiment. Specifically, the most salient regions of the scenes were blurred using a convolution of the original image with a Gaussian kernel. The maximal strength of blur was varied via different standard deviations of the Gaussian filter, defining three different experimental conditions. The mean search time, as well as the proportion of trials where participants failed to find the target, were compared among different strength values of a blur. Using linear mixed-effect model analysis, a significant decrease of search time as well as a significant reduction of the proportion of failed trials, as a function of blur strength, were found. Thus, this pilot study shows a possibility to improve visual search performance in realistic 3D scenes by applying a subtle saliency-aware scene modulation.
Feedforward-Feedback-verify-reWeight (FFVW) and perceptual impact of contrast-reversed binocular dot-pairs in random dot stereograms
2021-09-01

In a random-dot stereogram (RDS), depth is by images presented to left and right eyes that comprise interocularly corresponding random black and white dots. The spatial disparities between the binocularly corresponding dots determine the object depths. If the dots are contrast-reversed, such that a black dot in one eye corresponds to a white dot in the other, disparity-tuned neurons in the primary visual cortex (V1) respond as if their preferred disparities become non-preferred and vice versa, reversing the disparity sign reported to higher visual areas. Humans cannot perceive the reversed depth in central vision. We demonstrate that, in central vision, reversed depth signals can augment or degrade depth perception in noisy RDSs when contrast-reversed and contrast-matched dots are mixed. When the reversed depth signals and the normal depth signals from the (contrast-matched dots) are congruent with each other, augmentation occurs; when they are incongruent with each other and when the RDS images are sufficiently brief, degradation occurs. These findings are consistent with the FFVW process, its feedback-Verify-reWeight component disambiguates noisy and ambiguous inputs from V1. Through an analysis-by-synthesis computation, this top-down feedback vetoes misleading V1 signals, including, in certain situations, the reversed depth signals. When the RDS is viewed too briefly to allow time for feedback, augmentation or degradation works by adding, respectively, the congruent or incongruent, reversed signals to the normal signals in the feedforward direction. With a sufficient viewing duration for effective feedback, the feedback veto removes the degradation on the percept of the normal signals when the reversed and normal signals disagree, or, when the normal depth signals are absent, makes the reversed depth imperceptible. Meanwhile, the analysis-by-synthesis in the feedback process also fills in or corrects imperfect signals, allowing the reversed signals, when congruent with the normal depth signals, to augment the percept of the latter.
Object-context inconsistencies affect gaze behavior differently than predicted by contextualized meaning maps
2021-09-01

The role of semantic information in eye-movement control is increasingly recognized. One prototypical effect is particularly well studied: objects that are semantically inconsistent with their context (e.g., a shoe on a bathroom sink) attract more fixations than semantically consistent objects (e.g., a hair brush on the sink). The typical interpretation of this effect argues that fixations are driven towards inconsistent objects because they “contain greater meaning”. In the current study, we directly tested this explanation using contextualized meaning maps (cMMs), a method to quantify the spatial distribution of ‘meaning’ across an image. These maps aggregate crowd-sourced ratings of the meaningfulness of local images-patches into a distribution over an image. Importantly, patch-ratings are provided by raters who know the image, from which the patches originate. Therefore, when providing their ratings, raters can take into account the extent to which objects on the patches are consistent with the scene context. In our first experiment, we collected eye-tracking data and created cMMs for scenes, in which the consistency of objects with the scene was experimentally manipulated. As predicted, human observers fixated more on inconsistent vs. consistent objects. However, if anything, raters rated patches containing semantic inconsistencies as less meaningful, challenging the long-held notion that semantically inconsistent objects “contain greater meaning”. This finding was confirmed in Experiment 2, where 140 raters rated a carefully selected set of image-patches. Patches extracted from the same location within a scene were rated as less meaningful when the patch contained inconsistent, rather than consistent, objects. In summary, we demonstrated that, in contrast to a long-held view, semantically inconsistent objects might be experienced as less (not more) meaningful than their consistent counterparts, and that cMMs do not capture prototypical influences of image meaning on the guidance of human gaze.
Motor adaptations for object size perception and grasping
2021-09-01

Our research aimed to evaluate whether size perception and saccadic amplitude were affected before and after grasping a variable-size target under the presence (TF) or absence of tactile feedback (NoTF). Twenty-one volunteers (mean-age: 25.05±4.08years) participated. Volunteers were tested in four blocks of 30 trials. Each trial consisted of 3 consecutive phases: pre-grasping estimation, grasping and post-grasping estimation. During pre- and post-, participants were asked to perform a saccadic eye movement to a horizontal bar and manually indicate its horizontal size by extending index and thumb fingers. In the grasping phase, participants were instructed to make a grasping action towards the bar. While grasping, 30% of the trials had a random horizontal size perturbation, which meant a lengthening or shortening of 33% of the original size. In sixty trials, grasping action was assisted by TF implemented through mobile phone vibration motors. A motion caption system recorded and assessed participant’s hand position. Participant’s gaze was recorded by a mobile eye-tracker. During the post-estimation phase, the non-perturbation condition revealed an inverse relationship between saccadic amplitude and bar size (r=-0.69 and P=0.03, for both NoTF and TF). However, the same indirect relationship during shortening (NoTF: r=-0.17 and P=0.66; TF: r=-0.56 and P=0.15) and lengthening (NoTF: r=-0.46 and P=0.25; TF: r=-0.24 and P=0.50) conditions was not found. Grip aperture showed a significant correlation in all post-phase conditions for both NoTF and TF (r>0.93 and P<0.001). Comparing pre- and post-phase values, both NoTF and TF evidenced that lengthening condition caused a significant reduction in grip aperture (p=0.02 and p=0.04, respectively), whereas shortening did not reveal significant changes (P=0.74 and P=0.53). A significant increase in saccadic amplitude after shortening condition in TF was observed (P<0.001), but not in NoTF (P=0.22). Horizontal target size perturbation and tactile feedback during grasping execution modifies size perception and saccadic amplitude.
Aquaporin-4 Expression In The Human Choroid Plexus
2021-09-01

Abstract Background: The choroid plexus (CP) consists of specialized ependymal cells and underlying stroma and blood vessels, producing the bulk of the cerebrospinal fluid (CSF). CP epithelial cells are the site of the internal blood-cerebrospinal fluid barrier, show epithelial characteristics (basal lamina, tight junctions), and express aquaporin-1 (AQP1) apically. In contrast, ventricle-lining ependymal cells express aquaporin-4 (AQP4) basolaterallly. The initial purpose of this study was to analyze the expression of aquaporins in the ependyma – CP transition zone in the human brain to gain insights in aquaporin regulation. The results prompted us to investigate aquaporin expression in the mouse CP of different age groups. Methods: We analyzed the CP from eight body donors (age 74-91) applying immunofluorescence, qPCR, and freeze-fracture electron microscopy. We used antibodies against AQP1, AQP4, NKCC1, and Na/K-ATPase. In addition, we compared the CP from young (2 months), adult (12 months) and old (30 months) mice by qPCR and immunofluorescence. Results: Unexpectedly, many cells in the human CP were positive not only for AQP1 but also for AQP4, normally restricted to ependymal cells and astrocytes. Expression of AQP1 and AQP4 was found in the CP of all eight body donors. These results were confirmed by qPCR, and by electron microscopy detecting AQP4-specific orthogonal arrays of particles. To find out whether AQP4 expression correlated with relevant transport-related proteins we investigated expression of NKCC1 and Na/K-ATPase. Immunostaining for NKCC1 was similar to AQP1 and revealed no particular pattern related to AQP4. Co-staining of AQP4 and Na/K-ATPase indicated a trend for an inverse correlation of their expression. To test for the possibility of age-related changes causing AQP4 expression in the CP, we analyzed mouse brains from different age groups and found a significant increase of AQP4 on the mRNA level in old mice compared to young and adult animals. Conclusions : We provide evidence for AQP4 expression in the human and murine CP related to aging which likely contributes to the water flow through the CP epithelium and CSF production. In two alternative hypotheses, we discuss this as a beneficial compensatory, or a detrimental mechanism influencing the previously observed CSF changes during aging.
A vision for orienting in subcortical oculomotor control areas
2021-09-01

Ziad Hafed will review how an observation about fixational eye movements, first described about 20 years ago, led to a series of studies exploring the brain circuits that control both attention and saccades. We now have a much deeper understanding of the underlying roots and implications of the correlation between attention and microsaccades, the role of subcortical and cortical visual structures in this process, and the importance of approaching vision from an active, rather than passive, perspective.
Effects of visually masked numbers and lines on brain activity
2021-09-01

A frequently used paradigm to investigate unconscious processing of visual stimuli is masked priming. Traditionally, a direct task is compared to an indirect task: In the direct task, detection of a masked prime stimulus is typically found to be close to chance-level. In the indirect task, effects of the prime on reaction times to a subsequent target stimulus are analyzed (priming effects). Here, we focus on the indirect task and use event-related potentials (ERPs) to examine the effects of the masked primes on brain activity. Previous studies found that early deflections in the lateralized readiness potential (LRP), a measure of specific motor activation, reflect correct and incorrect response activations by the prime. This supports the idea of prime-induced covert motor activations that conflict with the responses required by the target. To test this, we performed two experiments using masked priming with numbers (Exp. 1) and simple line stimuli (Exp. 2). Additionally, in Exp. 1 prime contrast was varied to modulate visibility of the numbers. Preliminary results show that ERP onset latencies for congruent vs. incongruent trials measured at electrode Cz (Exp. 1: normal contrast: M=12 ms, p<.001 / high contrast: M=21 ms, p<.001; Exp. 2: M=51 ms, p<.001) closely matched the behavioral priming effects (Exp. 1: normal contrast: M=9 ms, p<.001 / high contrast: M=21 ms, p=.003; Exp. 2: M=46 ms, p=.001). In addition, we found more negative deflections in the early LRP phase for incongruent as compared to congruent trials in Exp. 2 (albeit not in Exp. 1). Overall, the results support the idea of prime-induced pre-activated motor responses. We discuss differences between the experiments and to which extend the behavioral results are related to the ERP effects.
Spatiotopic skew distortion adaptation with simultaneously present opposing stimuli
2021-09-01

Some optical elements, like corrective spectacle lenses with a progressive change in optical power, distort the visual field of the wearer. Optical distortions alter visual form and motion features, processed also up to higher areas of the visual system. Consequently, as has been shown, adaptation to distorted natural stimuli induces spatiotopic aftereffects: after a saccade subsequent to adaptation, aftereffects are present not only at the adapted retinal location, but also at the spatial location of adaptation stimulus. Because of the spatial variation of distortions in lenses, eye movements constantly modulate strength and orientation of the distortions present in the visual field. For progressive addition lenses, for example, left and right part of the lens skew distort the visual field in opposite directions. Switching gaze from one side to the other could stimulate adaptation with opposing retinotopic and spatiotopic aftereffects. For this study, 10 subjects were presented with two oppositely distorted adaptation stimuli simultaneously. To do so, a video with natural image content was skew distorted in opposite directions. Both distorted videos were shown simultaneously at distinct locations on the left and right side of a screen. Gaze was controlled by eye tracking and guided to repeatedly switch between the two stimuli during the 5 minutes of adaptation. Aftereffects of distortion adaptation were measured in a motion direction identification task. Before and after adaptation, the motion angle of a group of coherently moving dots perceived as horizontal was determined for both stimulus locations independently. A significant difference was found in the shift of perceived motion direction between the two stimulus locations. The direction agrees with the distortion direction shown during adaptation at the respective screen locations. Therefore, in case of prolonged adaptation with gaze switching between opposite skew distortions, retinotopic aftereffects of distortion adaptation are suppressed by the spatiotopic adaptation effects.
New enhancements to the DeepGaze models for a better understanding of human scanpaths
2021-09-01

The family of DeepGaze models comprises deep learning based computational models of freeviewing overt attention. DeepGaze II predicts freeviewing fixation locations (Kümmerer et al, ICCV 2017) and DeepGaze III (Kümmerer at al, CCN 2019) predicts freeviewing sequences of fixations. The models encode image information using deep features from pretrained deep neural networks to compute a spatial saliency map, which, in case of DeepGaze III, is then combined with information about the scanpath history to predict the next fixation. Both models have set the state of the art in their respective tasks in the last years. Here, we improve the performance of both models substantially. We replace the backbone deep neural network VGG-19 with better performing networks such as DenseNet. We also improve the architecture of the model and the training procedure. This results in a substantial performance improvement for both DeepGaze II and DeepGaze III and sets a new state of the art for freeviewing fixation prediction and freeviewing scanpath prediction across all commonly used metrics. We further use the improved DeepGaze III model to better understand human scanpaths. For example, we quantify the effects of scene content and scanpath history on human scanpaths. We find that, on the MIT1003 dataset, scene content has a substantially larger effect on fixation selection than scanpath history and that there are only very subtle but measurable interactions between scene content and scanpath history that go beyond a scalar saliency measure. Furthermore, we are able to disentangle the central fixation bias into contributions that are driven by image content, by the initial central fixation, and by a remaining effect that cannot be explained from these two sources. Taken together, the improved DeepGaze models allow us to analyze human scanpaths in ways that are not possible without high-performing deep learning models.
Self-motion cues in the natural habitats of zebrafish support lower visual field bias
2021-09-01

The optomotor response (OMR) behavior in larval zebrafish comprises swimming prompted by visual motion cues. This behavior is likely key to self-stabilization in moving aquatic environments. Larval zebrafish collect visual information from a very large field of view (>120 degrees both horizontally and vertically), but they preferentially respond to motion in the lower and posterior visual field with OMR (Wang et al., Cell Reports, 2020). We hypothesized that this preference reflects an adaptation to gather sensory signals from regions in the visual field where optical flow is most reliably informative about self-motion. To test this hypothesis, a video dataset was collected in nine natural shallow-water habitats located across the ecological range of the species. The videos were recorded using a 360-degree underwater camera, attached to a robotic gantry that moved through a series of controlled trajectories, including rotations and translations at multiple speeds. The total dataset includes several minutes of data for each trajectory, collected at 100 frames per second. Using an optical flow analysis on this dataset, we mapped the spatial distribution of several metrics of motion cue quality. We show that the lower visual field contains more texture information, produces more accurate motion cues over the dataset, and provides lower variance estimates of image motion from frame to frame. These factors likely contribute to more accurate and reliable self-motion estimates from the lower visual field compared to the upper visual field. The motion statistics found in our dataset both explain the lower-field bias seen in zebrafish OMR behavior and suggest practical design strategies for visual guidance systems in underwater robotics applications.
Measuring the saliency of an invisible visual feature and its interaction with visible features
2021-09-01

A single object presented to one eye among many other identical objects presented to the other eye – an ocularity singleton – is salient to attract visual attention automatically. Saliency from ocularity contrast helps rapidly localize the foreground, especially in 3D visual scenes. However, unlike saliency by other feature dimensions, e.g., color (C) and orientation (O), uniqueness by ocularity (E, eye-of-origin) alone is perceptually invisible, making it difficult to be quantified. I.e., the reaction time to detect an ocularity singleton – RT(E) – remains unknown. Quantitative measures could help further investigate the interaction between saliency by ocularity and by other features, unfolding its neural mechanisms. In the current study, RTs were measured in a search task for a unique bar among many background bars with identical C, O and E features. The target bar was unique in either C or O alone, or unique simultaneously in two or three feature dimensions: CO, CE, EO, CEO. Importantly, with a quantitative model derived from the V1 Saliency Hypothesis (V1SH), which links saliency with neural activities of primate V1, RT(E) was then robustly calculated from RT(C), RT(O), RT(CO), RT(CE), RT(EO) and RT(CEO). Furthermore, by V1SH, whether RT(CE) is shorter than the RTs of the winner of a race model involving RT(E) and RT(C) reflects whether there are V1 neurons tuned conjunctively to both E and C – monocular neurons tuned to color – that contribute to saliency. Analogously, RT(EO) sheds light on monocular neurons tuned to orientation. We show that RT(CE) and RT(EO) are shorter than that of the race winner between single-feature RTs, suggesting a contribution by CE and EO neurons. However, this applies only to search among red rather than green background bars, suggesting an intrinsic color asymmetry for saliency interaction with ocularity.
Is Contextual Cueing Unconscious? The Indirect Task Advantage in Implicit Learning
2021-09-01

We have recently shown that typical results from the unconscious priming paradigm suffer from serious methodological flaws that call into question the conclusions of many unconscious priming studies. Here, we describe a similar problem in the contextual cueing literature. In the priming paradigm, participants perform close to chance when directly attempting to identify or discriminate prime stimuli (direct task). Nevertheless, the same stimuli indirectly affect responses (e.g., priming effects on reaction times). From this pattern of results, researchers typically infer better sensitivity for the stimuli in the indirect than direct task, which is further interpreted as processing outside of conscious awareness. However, we have shown that this inference is flawed (Meyen et al., 2020). Similar to the priming paradigm, the contextual cueing paradigm follows the same logic: Participants show close to chance sensitivity in a direct task. In an indirect task, clear cueing effects on reaction times are found. This pattern of results is again used to infer better sensitivity in the indirect than direct task, which is then the basis for further-reaching inferences about unconscious processing. We generalized our methods to the typical contextual cueing paradigm (which often utilizes more response alternatives than the priming paradigm) and estimated the sensitivities of responses in the direct and indirect tasks based on the typically reported results. To do so, we present a model that relates participants’ sensitivity in the direct task to the size of cueing effects in the indirect task. This allows us to compare sensitivities between the two tasks and test for a difference, which is required to make further inferences on unconscious processing. We reanalyzed multiple studies showing that some fail to provide evidence for better sensitivity in the indirect task, thereby calling into question the corresponding inferences about conscious/unconscious processing.