Subjective Visual Experience Research Articles

Evaluating the Effect of a Myopia Control Spectacle Lens Among Children in Israel: 12-Month Results

To investigate the effectiveness of a novel spectacle lens designed to slow the progression of myopia in children. A prospective, randomized, double blind clinical trial. One hundred twenty-six Israeli children aged 6-13 years with spherical equivalent (SER) refractive errors of -0.5 to -6.25 diopters (D) were randomized into either the Shamir Myopia Control (SMC) lens design group or the conventional single-vision spectacle lenses (SVL), the control group. Outcomes measured were changes in axial length and cycloplegic refraction as well as subjective rating of visual experience over a period of 12 months. At 12 months, AL and SER progression were slowed by 0.11 mm (35%, P < .05) and 0.16 D (25%, P=.122), respectively. In the subgroup of 6-10-year-olds, AL and SER progression were slowed by 0.17 mm (41%, P < .05) and 0.31 D (43%, P < .05), respectively. Similarly, for the subgroup of children with 2 myopic parents AL and SER progression were slowed by 0.15 mm (45% P < .05) and 0.36 D (42%, P < .05), respectively. Subjective visual experience reported in the 12-month questionnaire revealed no difference between the SMC and SVL groups, and average daily wearing hours were also not different between the groups: 14 (±1.4) and 13.8 (±2.3) hours, respectively. The study continues to its second year. SMC lenses were effective in slowing the progression of SER and AL, especially for younger children and those having 2 myopic parents. The subjective rating of visual experience and the daily duration of use reported by the SMC group at 12 months were similar to the control group, indicating good lens tolerability.

Dissociable Neural Mechanisms Underlie the Effects of Attention on Visual Appearance and Response Bias.

A prominent theoretical framework spanning philosophy, psychology, and neuroscience holds that selective attention penetrates early stages of perceptual processing to alter the subjective visual experience of behaviorally relevant stimuli. For example, searching for a red apple at the grocery store might make the relevant color appear brighter and more saturated compared with seeing the exact same red apple while searching for a yellow banana. In contrast, recent proposals argue that data supporting attention-related changes in appearance reflect decision- and motor-level response biases without concurrent changes in perceptual experience. Here, we tested these accounts by evaluating attentional modulations of EEG responses recorded from male and female human subjects while they compared the perceived contrast of attended and unattended visual stimuli rendered at different levels of physical contrast. We found that attention enhanced the amplitude of the P1 component, an early evoked potential measured over visual cortex. A linking model based on signal detection theory suggests that response gain modulations of the P1 component track attention-induced changes in perceived contrast as measured with behavior. In contrast, attentional cues induced changes in the baseline amplitude of posterior alpha band oscillations (∼9-12 Hz), an effect that best accounts for cue-induced response biases, particularly when no stimuli are presented or when competing stimuli are similar and decisional uncertainty is high. The observation of dissociable neural markers that are linked to changes in subjective appearance and response bias supports a more unified theoretical account and demonstrates an approach to isolate subjective aspects of selective information processing.SIGNIFICANCE STATEMENT Does attention alter visual appearance, or does it simply induce response bias? In the present study, we examined these competing accounts using EEG and linking models based on signal detection theory. We found that response gain modulations of the visually evoked P1 component best accounted for attention-induced changes in visual appearance. In contrast, cue-induced baseline shifts in alpha band activity better explained response biases. Together, these results suggest that attention concurrently impacts visual appearance and response bias, and that these processes can be experimentally isolated.

Comparison of Subjective Visual Experiences and Ocular Symptoms After Wavefront-Guided and Wavefront-Optimized LASIK in a Prospective Fellow Eye Study

The purpose of this study was to compare the subjective visual experience and ocular symptoms of fellow eyes treated with wavefront-optimized (WFO-) laser-assisted in situ keratomileusis (LASIK) and wavefront-guided (WFG-) LASIK. Prospective randomized fellow eye, controlled study. Two hundred eyes of 100 subjects from a single academic center were enrolled and randomly assigned to treatment with WFO-LASIK in one eye and WFG-LASIK in the fellow eye. Subjects filled out a validated 14-part questionnaire for each eye at the preoperative visit and at postoperative months 1,3,6,12. In comparing the number of subjects who reported symptoms in the WFG- vs WFO- LASIK eyes, there was no difference in number reporting any visual experience (glare, halos, starbursts, hazy vision, blurred vision, distortion, double or multiple images, fluctuations in vision, focusing difficulties, and depth perception; all p>0.05) or ocular symptoms (photosensitivity, dry eye, foreign body sensation, ocular pain; all p>0.05). There was no preference for WFG-LASIK (28%) or the WFO-LASIK treated eye (29%) with most subjects reporting no preference (43%; Chi-squared p=0.972). Of the subjects who preferred one eye or the other, the preferred eye saw statistically better than the fellow eye (0.8 ± 1.4 Snellen line, p=0.0002). There was no other difference in subjective visual experience, ocular symptoms, refractive characteristics when taking into account eye preference. Most subjects had no eye preference; and for subjects who did have eye preference, the only detectable difference was better visual acuity in the preferred eye.

A case study in phenomenology of visual experience with retinal prosthesis versus visual-to-auditory sensory substitution

The phenomenology of the blind has provided an age-old, unparalleled means of exploring the enigmatic link between the brain and mind. This paper delves into the unique phenomenological experience of a man who became blind in adulthood. He subsequently underwent both an Argus II retinal prosthesis implant and training, and extensive training on the EyeMusic visual to auditory sensory substitution device (SSD), thereby becoming the first reported case to date of dual proficiency with both devices. He offers a firsthand account into what he considers the great potential of combining sensory substitution devices with visual prostheses as part of a complete visual restoration protocol. While the Argus II retinal prosthesis alone provided him with immediate visual percepts by way of electrically stimulated phosphenes elicited by the device, the EyeMusic SSD requires extensive training from the onset. Yet following the extensive training program with the EyeMusic sensory substitution device, our subject reports that the sensory substitution device allowed him to experience a richer, more complex perceptual experience, that felt more “second nature” to him, while the Argus II prosthesis (which also requires training) did not allow him to achieve the same levels of automaticity and transparency. Following long-term use of the EyeMusic SSD, our subject reported that visual percepts representing mainly, but not limited to, colors portrayed by the EyeMusic SSD are elicited in association with auditory stimuli, indicating the acquisition of a high level of automaticity. Finally, the case study indicates an additive benefit to the combination of both devices on the user's subjective phenomenological visual experience.

Eye Movement and Pupil Measures: A Review

Our subjective visual experiences involve complex interaction between our eyes, our brain, and the surrounding world. It gives us the sense of sight, color, stereopsis, distance, pattern recognition, motor coordination, and more. The increasing ubiquity of gaze-aware technology brings with it the ability to track gaze and pupil measures with varying degrees of fidelity. With this in mind, a review that considers the various gaze measures becomes increasingly relevant, especially considering our ability to make sense of these signals given different spatio-temporal sampling capacities. In this paper, we selectively review prior work on eye movements and pupil measures. We first describe the main oculomotor events studied in the literature, and their characteristics exploited by different measures. Next, we review various eye movement and pupil measures from prior literature. Finally, we discuss our observations based on applications of these measures, the benefits and practical challenges involving these measures, and our recommendations on future eye-tracking research directions.

Modelling visibility judgments using models of decision confidence

How can we explain the regularities in subjective reports of human observers about their subjective visual experience of a stimulus? The present study tests whether a recent model of confidence in perceptual decisions, the weighted evidence and visibility model, can be generalized from confidence to subjective visibility. In a postmasked orientation identification task, observers reported the subjective visibility of the stimulus after each single identification response. Cognitive modelling revealed that the weighted evidence and visibility model provided a superior fit to the data compared with the standard signal detection model, the signal detection model with unsystematic noise superimposed on ratings, the postdecisional accumulation model, the two-channel model, the response-congruent evidence model, the two-dimensional Bayesian model, and the constant noise and decay model. A comparison between subjective visibility and decisional confidence revealed that visibility relied more on the strength of sensory evidence about features of the stimulus irrelevant to the identification judgment and less on evidence for the identification judgment. It is argued that at least two types of evidence are required to account for subjective visibility, one related to the identification judgment, and one related to the strength of stimulation.

Zooming-in on higher-level vision: High-resolution fMRI for understanding visual perception and awareness.

One of the central questions in visual neuroscience is how the sparse retinal signals leaving our eyes are transformed into a rich subjective visual experience of the world. Invasive physiology studies, which offers the highest spatial resolution, have revealed many facts about the processing of simple visual features like contrast, color, and orientation, focusing on the early visual areas. At the same time, standard human fMRI studies with comparably coarser spatial resolution have revealed more complex, functionally specialized, and category-selective responses in higher visual areas. Although the visual system is the best understood among the sensory modalities, these two areas of research remain largely segregated. High-resolution fMRI opens up a possibility for linking them. On the one hand, it allows studying how the higher-level visual functions affect the fine-scale activity in early visual areas. On the other hand, it allows discovering the fine-scale functional organization of higher visual areas and exploring their functional connectivity with visual areas lower in the hierarchy. In this review, I will discuss examples of successful work undertaken in these directions using high-resolution fMRI and discuss where this method could be applied in the future to advance our understanding of the complexity of higher-level visual processing.

An Effective Progressive Image Transmission using Superpixel based Saliency Detection and Modified SPIHT Compression Algorithm

A new progressive image transmission system was proposed in this research paper for effective usage of communication bandwidth. At first, the superpixel based saliency detection method was used for segmenting the foreground region from the background region, because it gives more saliency information of an image with the benefit of color contrast. Then, Integer Wavelet Transform (IWT) was applied in the foreground image, which delivers A good quality of the image and also the compression ratio of the image was decent. Additionally, optimized neural network and modified Set Partitioned in Hierarchical Tree (SPIHT) algorithm were applied in the background image that delivers good rate distortion properties in the noise free environment and also enhances the image visual experience. In modified SPIHT, the sub-tree roots were not excluded that helps to encode and quantize the wavelet coefficients effectively. Also, it delivers more information to the image edges that effectively improves the subjective visual experience. Experiment report showed that the proposed work enhanced the Peak Signal to Noise Ratio (PSNR) upto 5dB compared to the existing work.

Low-Level Visual Information is Maintained Across Saccades by a 'Soft Hand-Off' between Visual Processing Areas

Subjective visual experience of a rich, detailed visual scene seems continuous despite us making several saccadic eye movements every second which radically change retinal input. Here, we investigated the time course of low-level visual information processing in the brain by decoding spatial frequency of an attended, stationary stimulus that changed from one visual hemifield to another due to a horizontal saccadic eye movement. Magneto-encephalography (MEG) was recorded while human participants made a large horizontal saccade and monitored the orientation of a grating stimulus, making spatial frequency task-irrelevant. Separate trials, in which participants maintained fixation, were used to train a classifier that was tested during saccade trials. Decoding performance showed that information about spatial frequency was present in the original retinotopic areas before, during and up to around 200 ms after the saccade. Post-saccadic information rapidly ramped up within a few tens of milliseconds, allowing for rapid decoding from the new retinotopic areas. There was an overlap of over 100 ms during which decoding was significant from both pre- and post-saccadic processing areas. These results suggest that the apparent richness of perception across saccades may be supported by the continuous availability of the low-level spatial frequency information that supports gist, object and ensemble perception, with a “soft hand-off” of this information during the initial visual processing sweep of the new fixation. Such a mechanism does not require remapping of low-level visual information before the saccade.

Sensorimotor contingency modulates breakthrough of virtual 3D objects during a breaking continuous flash suppression paradigm

To investigate how embodied sensorimotor interactions shape subjective visual experience, we developed a novel combination of Virtual Reality (VR) and Augmented Reality (AR) within an adapted breaking continuous flash suppression (bCFS) paradigm. In a first experiment, participants manipulated novel virtual 3D objects, viewed through a head-mounted display, using three interlocking cogs. This setup allowed us to manipulate the sensorimotor contingencies governing interactions with virtual objects, while characterising the effects on subjective visual experience by measuring breakthrough times from bCFS. We contrasted the effects of the congruency (veridical versus reversed sensorimotor coupling) and contingency (live versus replayed interactions) using a motion discrimination task. The results showed that the contingency but not congruency of sensorimotor coupling affected breakthrough times, with live interactions displaying faster breakthrough times. In a second experiment, we investigated how the contingency of sensorimotor interactions affected object category discrimination within a more naturalistic setting, using a motion tracker that allowed object interactions with increased degrees of freedom. We again found that breakthrough times were faster for live compared to replayed interactions (contingency effect). Together, these data demonstrate that bCFS breakthrough times for unfamiliar 3D virtual objects are modulated by the contingency of the dynamic causal coupling between actions and their visual consequences, in line with theories of perception that emphasise the influence of sensorimotor contingencies on visual experience. The combination of VR/AR and motion tracking technologies with bCFS provides a novel methodology extending the use of binocular suppression paradigms into more dynamic and realistic sensorimotor environments.

Remote sensing image compression based on binary tree and optimized truncation

The remote sensing image data is so vast that it requires compression by low-complexity algorithm on space-borne equipment. Binary tree coding with adaptive scanning order (BTCA) is an effective algorithm for the mission. However, for large-scale remote sensing images, BTCA requires a lot of memory, and does not provide random access property. In this paper, we propose a new coding method based on BTCA and optimize truncation. The wavelet image is first divided into several blocks which are encoded individually by BTCA. According the property of BTCA, we select the valid truncation points for each block carefully to optimize the ratio of rate-distortion, so that a higher compression ratio, lower memory requirement and random access property are attained. Without any entropy coding, the proposed method is simple and fast, which is very suitable for space-borne equipment. Experiments are conducted on three remote sensing image sets, and the results show that it can significantly improve PSNR, SSIM and VIF, as well as subjective visual experience.

Zerotree wavelet image compression with weighted sub-block-trees and adaptive coding order

Information distortion in regions of image edge is more perceptible for people than those in other regions. To improve the performance on the edge, we present an improved embedded zero-tree wavelet image compression algorithm with weighted sub-block-trees and adaptive coding order. First, we assign bigger weights to the sub-block-trees around image edge. The weights assigned to the sub-blocks in the same spatial location and the same orientation at different scales are equal so that the zero-tree structure of wavelet coefficients is maintained and only a little extra storage is needed. Then we prefer scanning the coefficients on the neighbor of previous significant coefficients and all of them are refined even they are not significant. Adaptive arithmetic coding is applied to the symbols of these coefficients and others respectively. The proposed method pays more attention to the edge and its neighborhood so that the decoded image on the edge is clearer. Compared with similar algorithms, experimental results show that the proposed method can improve the PSNR and SSIM, as well as the subjective visual experience. The proposed method is applicable to any genre of embedded wavelet image codec.

A global attentional scope setting prioritizes faces for conscious detection.

The scope of visual attention is known to affect conscious object perception, with recent studies showing that a global attentional scope boosts holistic face processing, relative to a local scope. Here we show that attentional scope settings can also modulate the availability of information for conscious visual awareness. In an initial experiment, we show that adopting a global attentional scope accelerates conscious detection of initially invisible faces, presented under continuous flash suppression (CFS). Furthermore, face detection time was not modulated by attentional scope in a nonrivalrous control condition, which emulated the experience of CFS without inducing binocular rivalry. In a follow-up experiment, we report an exact replication of the original effect, as well as data suggesting that this effect is specific to upright faces, and is abolished when using both inverted faces and images of houses in an otherwise identical task. Thus, attentional scope settings can modulate the availability of information to conscious awareness, fundamentally altering the contents of our subjective visual experience.

Neural processing around 200 ms after stimulus-onset correlates with subjective visual awareness

Does visual awareness correlate with early activity in visual cortex or with later wide-spread neural activation? This question was studied by presenting liminal targets in one of the four quadrants of the screen and asking the participants to make forced-choice localization responses and to rate their subjective visual awareness of each target, while electroencephalography was measured. In the analyses of event-related potential (ERP) correlates of awareness, response accuracy was kept constant so that only the subjectively rated awareness varied between high-awareness (‘seen’ rating) and low-awareness (‘unseen’ rating) targets. High-awareness-correct trials were associated with enhanced contralateral N200 at 180–280ms as compared with low-awareness-correct trials. This effect (visual awareness negativity, VAN) also correlated with aware sensitivity to the presence vs. absence of the stimulus (d’). In addition, high-awareness-correct trials were associated with later enhanced P3 amplitudes (after 350ms), but this effect correlated only with the response bias (c). ERPs to low-awareness-correct trials elicited larger contralateral N200 than ERPs to low-awareness-incorrect trials, and this effect correlated with conservative response bias, suggesting that it reflected weak awareness rather than unconscious processing. The results suggest that the enhanced N200 correlates with graded awareness. The results support theories of visual awareness in which early activity in visual cortex gives rise to subjective visual experiences.

Retrospective Attention Gates Discrete Conscious Access to Past Sensory Stimuli.

Cueing attention after the disappearance of visual stimuli biases which items will be remembered best. This observation has historically been attributed to the influence of attention on memory as opposed to subjective visual experience. We recently challenged this view by showing that cueing attention after the stimulus can improve the perception of a single Gabor patch at threshold levels of contrast. Here, we test whether this retro-perception actually increases the frequency of consciously perceiving the stimulus, or simply allows for a more precise recall of its features. We used retro-cues in an orientation-matching task and performed mixture-model analysis to independently estimate the proportion of guesses and the precision of non-guess responses. We find that the improvements in performance conferred by retrospective attention are overwhelmingly determined by a reduction in the proportion of guesses, providing strong evidence that attracting attention to the target’s location after its disappearance increases the likelihood of perceiving it consciously.

Behavioral and electrophysiological evidence for fast emergence of visual consciousness.

A fundamental unsettled dispute concerns how fast the brain generates subjective visual experiences. Both early visual cortical activation and later activity in fronto-parietal global neuronal workspace correlate with conscious vision, but resolving which of the correlates causally triggers conscious vision has proved a methodological impasse. We show that participants can report whether or not they consciously perceived a stimulus in just over 200 ms. These fast consciousness reports were extremely reliable, and did not include reflexive, unconscious responses. The neural events that causally generate conscious vision must have occurred before these behavioral reports. Analyses on single-trial neural correlates of consciousness revealed that the late cortical processing in fronto-parietal global neuronal workspace (∼300 ms) started after the fastest consciousness reports, ruling out the possibility that this late activity directly reflects the emergence of visual consciousness. The consciousness reports were preceded by a negative amplitude difference (∼160–220 ms) that spread from occipital to frontal cortex, suggesting that this correlate underlies the emergence of conscious vision.

The Research of Illumination Uniformity Assessment Technology

In precision machining field,lighting quality has an important influence on subjective visual experience and job performance. Therefore,it has great significance that the effective assessment of illumination uniformity.In connection with illumination uniformity assessment which is a nonlinear optimization problem, a evaluation method of illuminance uniformity based on improved particle swarm optimization algorithm is proposed.under the premise of elaborate the basic principles of the algorithm and implementation steps. The paper has given its optimized objective function and fitness function of the algorithm.what’s more, the feasibility and accuracy of the algorithm is verified.The results that illumination uniformity function of the simulation show that this method not only improves the calculation accuracy and reduces the possibility of local convergence.

Temporal Aspects of Subjective Visual Experience: Evidence from Stimulus-evoked Hallucination

Our understanding of human visual perception generally rests on the assumption that conscious visual states represent, in some qualitative fashion, the complex interaction between spatially structured variations in the ambient optic array and our visual nervous systems. The existence of visual hallucinations (or purely subjective visual experience) in a number of pathologies as well as in experimental contexts questions the assumption that what we see in the environment is necessarily determined by spatial structure in the distal stimulus. The experimental data go further by showing that conscious states of apparent vision (i.e., apperception) are triggered by temporal stimulation that does not ultimately relate to what the observer ‘sees’ in the apperceptive field. We have shown that the subjective experience of complex colour and forms is evoked by flickering light and, critically that the incidence and type of subjective experience varies with flicker frequency and phase (Becker & Elliott, 2006; Becker et al., 2008; Elliott et al., 2012). In this contribution, I shall outline evidence that subjective experiences, perhaps also hallucinations, arise from dynamic systems states with very well defined temporal structure. This structure is both measurable and refers to well- known perceptual timing quanta – leading in turn to novel and perhaps radical conclusions about the relationship between dynamic systems and perceptual (and perhaps more generally psychological) experience.

Visual Quality of Life in Veterans With Blast-Induced Traumatic Brain Injury

Traumatic brain injury (TBI) is an important cause of morbidity worldwide, with increasing awareness of the role of blast exposure in military and civilian casualties. Visual problems have been reported in TBI and may affect functioning and quality of life. To evaluate the 25-item National Eye Institute Visual Functioning Questionnaire and Neuro-Ophthalmic Supplement for utility in assessing the effect of blast exposure on perceived visual functioning among veterans with TBI. Observational cohort study from a tertiary care Veterans Health Administration hospital. Reported visual quality of life was compared with existing norms, and relationships between perceived visual quality and ocular injury, diplopia, visual performance, and blast exposure characteristics were examined. Participants included inpatients with blast-induced TBI who underwent baseline examination between December 7, 2006, and January 11, 2012, at a multiple-trauma rehabilitation center and who had at least 1 intact eye and were able to undergo psychometric testing and ocular examination. Among 64 sequentially eligible patients, 60 completed visual quality testing, 1 declined study participation, and 3 were evaluated prior to inclusion of visual quality testing in the protocol. Thirty-nine patients returned for outpatient follow-up, with a median test-retest interval of 11 months. Combat blast exposure with documented TBI. Composite and subscale scores on the 25-item National Eye Institute Visual Functioning Questionnaire and Neuro-Ophthalmic Supplement. Both tests had high test-retest reliability. Blast-exposed veterans reported significantly poorer visual quality compared with healthy samples and some patient samples with known eye disease. Scores tended to be worse for participants with identified visual performance deficits (poorer visual acuity or spatial contrast sensitivity, visual field depression or defects). Scores were not related to the extent of ocular injury or to blast exposure characteristics such as use of protective eyewear or TBI severity level. Individuals with blast-induced TBI reliably completed both tests and reported significant decrements in their subjective visual experiences. Measures of subjective visual quality may be useful to identify patients needing additional visual or neurologic evaluation and to monitor the effect of visual rehabilitation on patients with blast-related visual disabilities.

Characterising eye movement dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome

People who suffer from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) often report that their eye movements are sluggish and that they have difficulties tracking moving objects. However, descriptions of these visual problems are based solely on patients' self-reports of their subjective visual experiences, and there is a distinct lack of empirical evidence to objectively verify their claims. This paper presents the first experimental research to objectively examine eye movements in those suffering from ME/CFS. Patients were assessed for ME/CFS symptoms and were compared to age, gender, and education matched controls for their ability to generate saccades and smooth pursuit eye movements. Patients and controls exhibited similar error rates and saccade latencies (response times) on prosaccade and antisaccade tasks. Patients showed relatively intact ability to accurately fixate the target (prosaccades), but were impaired when required to focus accurately in a specific position opposite the target (antisaccades). Patients were most markedly impaired when required to direct their gaze as closely as possible to a smoothly moving target (smooth pursuit). It is hypothesised that the effects of ME/CFS can be overcome briefly for completion of saccades, but that continuous pursuit activity (accurately tracking a moving object), even for a short time period, highlights dysfunctional eye movement behaviour in ME/CFS patients. Future smooth pursuit research may elucidate and improve diagnosis of ME/CFS.