Complex Visual Scenes Research Articles

Ocular and extraocular expression of opsins in the rhopalium of Tripedalia cystophora (Cnidaria: Cubozoa).

A growing body of work on the neuroethology of cubozoans is based largely on the capabilities of the photoreceptive tissues, and it is important to determine the molecular basis of their light sensitivity. The cubozoans rely on 24 special purpose eyes to extract specific information from a complex visual scene to guide their behavior in the habitat. The lens eyes are the most studied photoreceptive structures, and the phototransduction in the photoreceptor cells is based on light sensitive opsin molecules. Opsins are photosensitive transmembrane proteins associated with photoreceptors in eyes, and the amino acid sequence of the opsins determines the spectral properties of the photoreceptors. Here we show that two distinct opsins (Tripedalia cystophora-lens eye expressed opsin and Tripedalia cystophora-neuropil expressed opsin, or Tc-leo and Tc-neo) are expressed in the Tripedalia cystophora rhopalium. Quantitative PCR determined the level of expression of the two opsins, and we found Tc-leo to have a higher amount of expression than Tc-neo. In situ hybridization located Tc-leo expression in the retinal photoreceptors of the lens eyes where the opsin is involved in image formation. Tc-neo is expressed in a confined part of the neuropil and is probably involved in extraocular light sensation, presumably in relation to diurnal activity.

The enigma of Bálint's syndrome: neural substrates and cognitive deficits

The enigma of Bálint's syndrome: neural substrates and cognitive deficits

Ensemble dictionary learning for saliency detection

The human visual system (HSV) is quite adept at swiftly detecting objects of interest in complex visual scene. Simulating human visual system to detect visually salient regions of an image has been one of the active topics in computer vision. Inspired by random sampling based bagging ensemble learning method, an ensemble dictionary learning (EDL) framework for saliency detection is proposed in this paper. Instead of learning a universal dictionary requiring a large number of training samples to be collected from natural images, multiple over-complete dictionaries are independently learned with a small portion of randomly selected samples from the input image itself, resulting in more flexible multiple sparse representations for each of the image patches. To boost the distinctness of salient patch from background region, we present a reconstruction residual based method for dictionary atom reduction. Meanwhile, with the obtained multiple probabilistic saliency responses for each of the patches, the combination of them is finally carried out from the probabilistic perspective to achieve better predictive performance on saliency region. Experimental results on several open test datasets and some natural images demonstrate that the proposed EDL for saliency detection is much more competitive compared with some existing state-of-the-art algorithms.

High-speed simulation of the dynamic neural responses of retinal and cortical simple neurons to complex visual scenes using general purpose computing on graphics processing units.

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Mechanisms Underlying the Attentional Guidance form Working Memory Representations

People had to select specific information from complex visual scene every time to avoid overloading the limited information processing system.When extracting relevant information from a complex visual environment,working memory(WM) representation would bias attention to stimuli that were the same or the similar to the search target,as to optimize target selection while ignoring the distractors.The present study systematically reviewed the emerging evidences on the attentional guidance from WM representations.After discussing the following three controversial issues: Could WM guide attention automatically? Could verbal WM guide attention? And did WM always guide attention? We concluded that the WM could top-down guide attention,but it was subjected to some constrains.

What Guides Visual Overt Attention under Natural Conditions? Past and Future Research.

In the last decade, overt attention under natural conditions became a prominent topic in neuroscientific and psychological research. In this context, one central question is “what guides the direction of gaze on complex visual scenes?” In the present review recent research on bottom-up influences on overt attention is presented first. Against this background, strengths and limitations of the bottom-up approach are discussed and future directions in this field are outlined. In addition to that, the current scope on top-down factors in visual attention is enlarged by discussing the impact of emotions and motivational tendencies on viewing behavior. Overall, this review highlights how behavioral and neurophysiological research on overt attention can benefit from a broader scope on influential factors in visual attention.

The role of eye movements in a contour detection task

Vision combines local feature integration with active viewing processes, such as eye movements, to perceive complex visual scenes. However, it is still unclear how these processes interact and support each other. Here, we investigated how the dynamics of saccadic eye movements interact with contour integration, focusing on situations in which contours are difficult to find or even absent. We recorded observers' eye movements while they searched for a contour embedded in a background of randomly oriented elements. Task difficulty was manipulated by varying the contour's path angle. An association field model of contour integration was employed to predict potential saccade targets by identifying stimulus locations with high contour salience. We found that the number and duration of fixations increased with the increasing path angle of the contour. In addition, fixation duration increased over the course of a trial, and the time course of saccade amplitude depended on the percept of observers. Model fitting revealed that saccades fully compensate for the reduced saliency of peripheral contour targets. Importantly, our model predicted fixation locations to a considerable degree, indicating that observers fixated collinear elements. These results show that contour integration actively guides eye movements and determines their spatial and temporal parameters.

Time-compressed spoken word primes crossmodally enhance processing of semantically congruent visual targets

Findings from three experiments support the conclusion that auditory primes facilitate the processing of related targets. In Experiments 1 and 2, we employed a crossmodal Stroop color identification task with auditory color words (as primes) and visual color patches (as targets). Responses were faster for congruent priming, in comparison to neutral or incongruent priming. This effect also emerged for different levels of time compression of the auditory primes (to 30 % and 10 % of the original length; i.e., 120 and 40 ms) and turned out to be even more pronounced under high-perceptual-load conditions (Exps. 1 and 2). In Experiment 3, target-present or -absent decisions for brief target displays had to be made, thereby ruling out response-priming processes as a cause of the congruency effects. Nevertheless, target detection (d') was increased by congruent primes (30 % compression) in comparison to incongruent or neutral primes. Our results suggest semantic object-based auditory-visual interactions, which rapidly increase the denoted target object's salience. This would apply, in particular, to complex visual scenes.

Motivational value and salience of images of infants

Researchers have typically reported relatively greater preferences for infants among females than among males, though this varies somewhat across samples and age groups. The mechanism by which this sex difference occurs is not well understood and many studies rely on participants' self-reported preferences rather than measuring motivated behavior or patterns of visual attention directly. The present research consists of two independent studies investigating attention to infants. The aim of these studies was to extend research on the characteristics associated with interest in infants by measuring motivation to view infant faces (Study 1) and visual attention to infants in a complex visual scene (Study 2). In Study 1, participants controlled the length of viewing time for different images. Women demonstrated motivation to extend viewing of infants. Men showed the opposite pattern, working to decrease the length of time they viewed infants. In Study 2, participants were shown complex scenes that contained infants. Patterns of visual attention were measured using eye-tracking technology. Infants did not receive a particularly high proportion of fixations from either sex. However, there were relationships between gender-linked traits, such as digit ratio and self-reported interest in infants, and the percentage of fixations on infants. Additionally, participants who reported being in a romantic relationship demonstrated greater interest in infants. This suggests the long-reported sex difference in interest in infants may relate more to current life circumstances and gender linked traits than an overwhelming tendency among all members of a sex.

How Lateral Connections and Spiking Dynamics May Separate Multiple Objects Moving Together

Over successive stages, the ventral visual system of the primate brain develops neurons that respond selectively to particular objects or faces with translation, size and view invariance. The powerful neural representations found in Inferotemporal cortex form a remarkably rapid and robust basis for object recognition which belies the difficulties faced by the system when learning in natural visual environments. A central issue in understanding the process of biological object recognition is how these neurons learn to form separate representations of objects from complex visual scenes composed of multiple objects. We show how a one-layer competitive network comprised of ‘spiking’ neurons is able to learn separate transformation-invariant representations (exemplified by one-dimensional translations) of visual objects that are always seen together moving in lock-step, but separated in space. This is achieved by combining ‘Mexican hat’ functional lateral connectivity with cell firing-rate adaptation to temporally segment input representations of competing stimuli through anti-phase oscillations (perceptual cycles). These spiking dynamics are quickly and reliably generated, enabling selective modification of the feed-forward connections to neurons in the next layer through Spike-Time-Dependent Plasticity (STDP), resulting in separate translation-invariant representations of each stimulus. Variations in key properties of the model are investigated with respect to the network’s ability to develop appropriate input representations and subsequently output representations through STDP. Contrary to earlier rate-coded models of this learning process, this work shows how spiking neural networks may learn about more than one stimulus together without suffering from the ‘superposition catastrophe’. We take these results to suggest that spiking dynamics are key to understanding biological visual object recognition.

The amygdala encodes level of perceived fear but not emotional ambiguity in visual scenes

There are two current models of amygdala functioning with regard to identification of emotional expression. Classic models propose that the amygdala contributes to emotional expression recognition and empathy by encoding the level of threat or distress, and as such, responds greatest to more potent fearful cues. However, recent evidence suggests that the amygdala directs attention to relevant object features to disambiguate the stimulus (e.g., the eyes of a fearful face). The present study used fMRI to investigate amygdala functioning during the perception and identification of emotion in complex visual scenes. Participants later rated the images on levels of fear, disgust and arousal. These ratings were used to identify stimuli that were emotionally-ambiguous, emotionally-discrete, and non-emotional for each individual. A whole-brain and ROI approach was used to identify the nature of the amygdala response to visual scenes. Amygdala activity was associated with higher levels of fear in stimuli and was found to reflect the level of arousal in complex visual scenes. In contrast, no activity was observed that would indicate that the amygdala was modulated by emotional ambiguity when discriminating between fearful and disgusting visual scenes. These results are consistent with models that implicate the amygdala in the evaluation and representation of the intensity of fear, and imply that the functional contribution of the amygdala to deciphering threat in visual scenes likely extends beyond the search for emotionally salient features. The results also suggest that using attention to remedy emotion recognition abnormalities in at-risk populations with amygdala dysfunction may not address all key deficits associated with contributions of the amygdala to emotion and empathy.

Professional athletes have extraordinary skills for rapidly learning complex and neutral dynamic visual scenes

Evidence suggests that an athlete's sports-related perceptual-cognitive expertise is a crucial element of top-level competitive sports1. When directly assessing whether such experience-related abilities correspond to fundamental and non-specific cognitive laboratory measures such as processing speed and attention, studies have shown moderate effects leading to the conclusion that their special abilities are context-specific2. We trained 308 observers on a complex dynamic visual scene task void of context and motor control requirements3 and demonstrate that professionals as a group dramatically differ from high-level amateur athletes, who dramatically differ from non-athlete university students in their capacity to learn such stimuli. This demonstrates that a distinguishing factor explaining the capacities of professional athletes is their ability to learn how to process complex dynamic visual scenes. This gives us an insight as to what is so special about the elite athletes' mental abilities, which allows them to express great prowess in action.

Viewing the dynamics and control of visual attention through the lens of electrophysiology

How we find what we are looking for in complex visual scenes is a seemingly simple ability that has taken half a century to unravel. The first study to use the term visual search showed that as the number of objects in a complex scene increases, observers’ reaction times increase proportionally (Green & Anderson, 1956). This observation suggests that our ability to process the objects in the scenes is limited in capacity. However, if it is known that the target will have a certain feature attribute, for example, that it will be red, then only an increase in the number of red items increases reaction time. This observation suggests that we can control which visual inputs receive the benefit of our limited capacity to recognize the objects, such as those defined by the color red, as the items we seek. The nature of the mechanisms that underlie these basic phenomena in the literature on visual search have been more difficult to definitively determine. In this paper, I discuss how electrophysiological methods have provided us with the necessary tools to understand the nature of the mechanisms that give rise to the effects observed in the first visual search paper. I begin by describing how recordings of event-related potentials from humans and nonhuman primates have shown us how attention is deployed to possible target items in complex visual scenes. Then, I will discuss how event-related potential experiments have allowed us to directly measure the memory representations that are used to guide these deployments of attention to items with target-defining features.

Numbers reorient visuo-spatial attention during cancellation tasks

Numbers induce shifts of spatial attention on the left or the right sides of external space as a function of their magnitude. However, whether this number-space association is restricted to the linear horizontal extensions, or extends to the whole visual scene, is still an open question. This study investigates, by means of a cancellation paradigm, the influence of numerical magnitude during scanning tasks in which participants freely explore complex visual scenes unconstrained towards either the horizontal or the vertical unidimensional axes. Five cancellation tasks were adapted in which Arabic digits were used as targets or distracters, in structured (lines and columns) or unstructured visual displays, with a smaller (2 or 3 types of distracters) or larger (10 or more types of distracters) sets of stimuli. Results show that the participants' hits distribution was a function of number magnitude: shifted on the left for small and on the right for large numbers. This effect was maximised when numerical cues were sparse, randomly arranged and, critically, irrelevant to the task. Overall, this study provides novel evidence from visuo-spatial exploratory cancellation tasks for an attentional shift induced by number magnitude.

Lateralization of spatial relation processing in natural scenes.

Spatial relations between objects can be represented in a categorical and in a coordinate manner. Categorical representations reflect abstract relations, like ‘left of’ or ‘under’, whereas coordinate representations concern exact metric distances between objects. These two types of spatial relations are thought to be linked to a left hemisphere and a right hemisphere advantage, respectively. This lateralization pattern was examined in a visual search task, making use of natural scenes, in patients with unilateral brain damage and healthy controls. In addition, all participants performed a low-level spatial relation processing task. The results suggest that the lateralization pattern commonly found for spatial relation processing in low-level perceptual tasks is also applicable to the processing of complex visual scenes.

Lateralization of Spatial Relation Processing in Natural Scenes

Spatial relations between objects can be represented in a categorical and in a coordinate manner. Categorical representations reflect abstract relations, like ‘left of’ or ‘under’, whereas coordinate representations concern exact metric distances between objects. These two types of spatial relations are thought to be linked to a left hemisphere and a right hemisphere advantage, respectively. This lateralization pattern was examined in a visual search task, making use of natural scenes, in patients with unilateral brain damage and healthy controls. In addition, all participants performed a low-level spatial relation processing task. The results suggest that the lateralization pattern commonly found for spatial relation processing in low-level perceptual tasks is also applicable to the processing of complex visual scenes.

A map of visual space in the primate entorhinal cortex

Place-modulated activity among neurons in the hippocampal formation presents a means to organize contextual information in the service of memory formation and recall. One particular spatial representation, that of grid cells, has been observed in the entorhinal cortex (EC) of rats and bats, but has yet to be described in single units in primates. Here we examined spatial representations in the EC of head-fixed monkeys performing a free-viewing visual memory task. Individual neurons were identified in the primate EC that emitted action potentials when the monkey fixated multiple discrete locations in the visual field in each of many sequentially presented complex images. These firing fields possessed spatial periodicity similar to a triangular tiling with a corresponding well-defined hexagonal structure in the spatial autocorrelation. Further, these neurons showed theta-band oscillatory activity and changing spatial scale as a function of distance from the rhinal sulcus, which is consistent with previous findings in rodents. These spatial representations may provide a framework to anchor the encoding of stimulus content in a complex visual scene. Together, our results provide a direct demonstration of grid cells in the primate and suggest that EC neurons encode space during visual exploration, even without locomotion.

O1‐10‐06: Encoding of novel complex visual scenes in presymptomatic Alzheimer's disease

O1‐10‐06: Encoding of novel complex visual scenes in presymptomatic Alzheimer's disease

IC‐P‐058: Encoding of novel complex visual scenes in presymptomatic Alzheimer's disease

IC‐P‐058: Encoding of novel complex visual scenes in presymptomatic Alzheimer's disease

Am I seeing my hand? Visual appearance and knowledge of controllability both contribute to the visual capture of a person's own body

When confronted with complex visual scenes in daily life, how do we know which visual information represents our own hand? We investigated the cues used to assign visual information to one's own hand. Wrist tendon vibration elicits an illusory sensation of wrist movement. The intensity of this illusion attenuates when the actual motionless hand is visually presented. Testing what kind of visual stimuli attenuate this illusion will elucidate factors contributing to visual detection of one's own hand. The illusion was reduced when a stationary object was shown, but only when participants knew it was controllable with their hands. In contrast, the visual image of their own hand attenuated the illusion even when participants knew that it was not controllable. We suggest that long-term knowledge about the appearance of the body and short-term knowledge about controllability of a visual object are combined to robustly extract our own body from a visual scene.