Processing Systems as Perceptual Systems
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Visual processing
Perceptual system
The perceptual visual quality evaluation of human visual system (HVS) is very complex. It concerns almost all aspects of visual processing in the vision path, from low-level neuron activities to high-level visual perception. Existing perceptual visual quality metrics (VQMs) only considered several of the mechanisms of HVS, and many others are ignored. In this paper, two global modulatory factors, visual attention and motion suppression, are modelled and combined to form a mathematic expression - perceptual quality significant level (PQSL). To a certain extent, it is believed that PQSL values reflect the processing ability of the human brain on local visual content. To evaluate their effects on visual quality evaluation, two VQMs are proposed. One is a MSE-like VQM based in a PQSL-modulated JND profile, which was proposed in (Z. K. Lu et al, Proc. ICASSP'2004, v.3, p.705-708, 2004); the other VQM is based on Wang's visual quality assessment (Sig. Proc.:Image Comm., v.19, n.2, p.121-132, 2004), PQSL values are used to adjust the weights of his structural similarity index. Experimental results show that introduction of the global modulatory factors can improve the performance of current visual quality metrics.
Visual processing
Similarity (geometry)
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The perceptual visual quality evaluation of Human Visual System (HVS) is very complex. It concerns almost all aspects of visual processing in vision path, from low-level neuron activities to high-level visual perception. Existing perceptual Visual Quality Metrics (VQMs) only considered several of the mechanisms of HVS and many others are ignored. In this paper, two global modulatory factors, visual attention and motion suppression, are modelled and combined to form a mathematic expression - Perceptual Quality Significant Level (PQSL). To a certain extent, it is believed that PQSL value reflect the processing ability of human brain on local visual contents. To evaluate their effects on visual quality evaluation, two VQMs are proposed. One is a MSE-like VQM based on PQSL-modulated JND profile, which was proposed in Z.K. Lu et al., (2004); the other VQM is based on Wang's visual quality assessment Zhou Wang et al., (2004) PQSL values are used to adjust the weights of his structural similarity index. Experimental results show that introducing of the global modulatory factors can improve the performance of current visual quality metrics.
Visual processing
Similarity (geometry)
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Norman's aim to reconcile two longstanding and seemingly opposed philosophies of perception, the constructivist and the ecological, by casting them as approaches to complementary subsystems within the visual brain is laudable. Unfortunately, Norman overreaches in attempting to equate direct perception with dorsal/unconscious visual processing and indirect perception with ventral/conscious visual processing. Even a cursory review suggests that the functional and neural segregation of direct and indirect perception is not as clear as the target article would suggest.
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According to Goodale and Milner, visual perception is mediated by the ventral stream and the visual control of action by the dorsal stream of cortical visual projections. The initial neuropsychological evidence for this idea was based strongly on a single case, DF, who has impaired object recognition but spared visual control of grasping, consistent with lesions to lateral occipital (LO) cortex but intact dorsal-stream processing. Here we present data from a new patient, MC, a 38-year-old woman who shows very similar behaviour to DF despite much more extensive bilateral occipitotemporal lesions that encompass not only LO but most of early visual cortex in the occipital lobe, except for a small tag of tissue in the rostral calcarine cortex (Culham et al., VSS 2008). MC shows some preserved motion perception, but is unable to identify line drawings (or real exemplars) of common objects or discriminate colours or visual textures. Not surprisingly, MC cannot discriminate between rectangular objects with different dimensions; nor can she indicate their width manually. Remarkably, however, when she reaches out to grasp such objects, her in-flight grasp scales to the object's size. Similarly, even though MC cannot discriminate between objects of varying shape, she chooses stable grasp points on those objects when she reaches out to pick them up. The case of MC not only reinforces the conclusions about separate visual processing for perception and action drawn from DF, but also suggests that visuomotor mechanisms in the dorsal stream are capable of mediating the processing of object features such as size, shape, and orientation for the control of visually guided grasping even with highly impoverished (or perhaps entirely absent) input from the ventral stream and early visual areas.
Visual processing
Occipital lobe
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Evidence reveals that visual processing speed decreases with age. The Motor-Free Visual Perception Test- Third Edition (MVPT-3) has an age-normed Response Time Index that measures visual processing speed. In 2015, a new version, Motor-Free Visual Perception Test- Fourth Edition (MVPT-4), was published. The new MVPT-4 does not yet demonstrate its utility in measuring visual processing speed. The purpose of this study was to explore if differences in visual processing speed between younger adults ages 20-35 years and older adults ages 70 years and older could be detected using the new MVPT-4. Results revealed a significant difference between older and younger adults’ time to complete the MVPT-4 (p <.05). This pilot study demonstrated that the MVPT-4 may be able to detect age-related changes in visual processing speed and therefore, a possible clinical tool for occupational therapists.
Visual processing
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Visual processing
Perceptual system
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This chapter starts out by contrasting the static image-processing tradition in vision research to the moving-observer tradition in ecological psychology. As visual neuroscience and computer vision began to test awake behaving monkeys and robots, respectively, instead of motionless observers, some of the most vexing problems of image processing melted away. Feedback projections from higher visual brain areas down to lower visual brain areas appear to exert a goal-oriented tuning of the perceptual process. Moreover, oculomotor processes are shown to play a role in perceptual decisions, suggesting a blurring of the lines between visual perception and visual cognition and visuomotor processes. The chapter focuses especially on visual search processes and simulations of linear increases in reaction time resulting from a parallel-processing model.
Visual processing
Observer (physics)
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Superior colliculus
Visual processing
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Scene statistics
Visual processing
Visual Search
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Abstract The human visual system is a remarkably versatile and powerful spatial image processor. The eye itself is only a small part of the visual mechanism. The task of analyzing and comprehending the visual world is so complex that the brain devotes between one‐third and one‐half of the entire cerebral cortex to solving it: all of the occipital lobe and large parts of the parietal, temporal, and frontal lobes as well. To appreciate the magnitude of the task of visual processing, it is useful to consider some of the problems that the visual system must address in the course of analyzing visual images. Solutions to initial problems are discussed. Details on the visual processing of the eye including visual analysis and coding strategies and cortical processing are given.
Visual processing
Gaze-contingency paradigm
Occipital lobe
N2pc
Parietal lobe
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