Visual Detection Ability Research Articles

Testing the involvement of low-level visual representations during spoken word processing with non-Western students and meditators practicing Sudarshan Kriya Yoga

Previous studies, using the Continuous Flash Suppression (CFS) paradigm, observed that (Western) university students are better able to detect otherwise invisible pictures of objects when they are presented with the corresponding spoken word shortly before the picture appears. Here we attempted to replicate this effect with non-Western university students in Goa (India). A second aim was to explore the performance of (non-Western) meditators practicing Sudarshan Kriya Yoga in Goa in the same task. Some previous literature suggests that meditators may excel in some tasks that tap visual attention, for example by exercising better endogenous and exogenous control of visual awareness than non-meditators. The present study replicated the finding that congruent spoken cue words lead to significantly higher detection sensitivity than incongruent cue words in non-Western university students. Our exploratory meditator group also showed this detection effect but both frequentist and Bayesian analyses suggest that the practice of meditation did not modulate it. Overall, our results provide further support for the notion that spoken words can activate low-level category-specific visual features that boost the basic capacity to detect the presence of a visual stimulus that has those features. Further research is required to conclusively test whether meditation can modulate visual detection abilities in CFS and similar tasks.

Study on the Enrichment of Pavement Marking Width and Retroreflectivity on Elderly Drivers’ Safety

Drivers’ visual function and cognitive ability deteriorate with age, and road marking improvements can better meet the driving safety and comfort needs of elderly drivers. To provide an optimal solution for marking setup and management for a large elderly community, the specific enrichment of marking width and retroreflective luminance coefficient on the driving safety of elderly drivers is investigated through an outdoor real-vehicle experiment. Twelve elderly drivers were randomly selected as experimental participants to visually detect the markings under the illumination of the vehicle high beam, and the visible distance data of white 10, 15, and 20 cm wide markings with retroreflective luminance coefficients ranging from 33 to 420 mcd.m−2.lx−1 were collected. The results showed that the visual detection ability of elderly drivers to pavement markings was significantly affected by the width and the retroreflective luminance coefficient of the markings and the enrichment of width on the detection ability of elderly drivers gradually increased with the increase of the width of markings, but the enrichment of the retroreflective luminance coefficient on the detection ability of elderly drivers gradually decreased with the increase of the retroreflective luminance coefficient of markings. The logarithmic function models of the retroreflective luminance coefficient of markings and the detection distance of elderly drivers with different marking widths were obtained by fitting. The results can provide a technical reference for proposing alternative countermeasures for the design, maintenance, and updating of pavement markings based on meeting elderly drivers’ safety with respect to economic cost and low carbon.

Point-of-care detection of hydroxyurea drug in serum using a supramolecular enzyme mimetic

The sole approved therapeutic drug for sickle cell disease management is provided by hydroxyurea, requiring its precise detection and monitoring in biological matrices such as human blood serum for personalized treatment. Herein, we introduce a direct colorimetric detection method for hydroxyurea in serum using a metallo-supramolecular assembly called Vesi-ImCu that mimics the peroxidase enzyme. The Vesi-ImCu enzyme mimetic comprises a catalytically active copper center coordinated to synthetic imidazole containing surfactant and iminodiacetic acid capping moieties. By leveraging the peroxidase-like activity of Vesi-ImCu, we have demonstrated that it catalyzes the efficient production of nitric oxide from hydroxyurea that reacts with the Griess reagent, producing an intense pink color. This approach enables the naked-eye detection of hydroxyurea, with notable efficacy even in complex biological matrices such as human blood serum. The Vesi-ImCu suprazyme-based approach offers several advantages, including high sensitivity (limit of detection of 75 µM), clinically relevant dynamic range of hydroxyurea detection, minimum batch-to-batch variation, and the ability to perform mobile phone-based quantification. To our knowledge, this is the first report on direct colorimetric quantification of HU in serum. With its visual detection ability, high-end equipment-free quantification, user-friendliness and portability, the present enzyme mimetic holds great promise for point-of-care detection applications.

GABA and Glutamate in hMT+ Link to Individual Differences in Residual Visual Function After Occipital Stroke.

Damage to the primary visual cortex following an occipital stroke causes loss of conscious vision in the contralateral hemifield. Yet, some patients retain the ability to detect moving visual stimuli within their blind field. The present study asked whether such individual differences in blind field perception following loss of primary visual cortex could be explained by the concentration of neurotransmitters γ-aminobutyric acid (GABA) and glutamate or activity of the visual motion processing, human middle temporal complex (hMT+). We used magnetic resonance imaging in 19 patients with chronic occipital stroke to measure the concentration of neurotransmitters GABA and glutamate (proton magnetic resonance spectroscopy) and functional activity in hMT+ (functional magnetic resonance imaging). We also tested each participant on a 2-interval forced choice detection task using high-contrast, moving Gabor patches. We then measured and assessed the strength of relationships between participants' residual vision in their blind field and in vivo neurotransmitter concentrations, as well as visually evoked functional magnetic resonance imaging activity in their hMT+. Levels of GABA and glutamate were also measured in a sensorimotor region, which served as a control. Magnetic resonance spectroscopy-derived GABA and glutamate concentrations in hMT+ (but not sensorimotor cortex) strongly predicted blind-field visual detection abilities. Performance was inversely related to levels of both inhibitory and excitatory neurotransmitters in hMT+ but, surprisingly, did not correlate with visually evoked blood oxygenation level-dependent signal change in this motion-sensitive region. Levels of GABA and glutamate in hMT+ appear to provide superior information about motion detection capabilities inside perimetrically defined blind fields compared to blood oxygenation level-dependent signal changes-in essence, serving as biomarkers for the quality of residual visual processing in the blind-field. Whether they also reflect a potential for successful rehabilitation of visual function remains to be determined.

Reversible and Turn-On Fluorescence Detection of Phosphate in Aqueous Solution and Living Cell Imaging by Supramolecular Metallacycles with AIE-Active Ligands.

Luminescent supramolecular metallacycles have attracted great interest as a new promising class of sensing substrates. In this work, two tetraphenylethene (TPE)-based diimidazole and dipyrazole ligands with the aggregation-induced emission (AIE) feature were designed for the construction of supramolecular tetragonal metallacycles 1-4 with two 90° mononuclear [(bpy)M]2+ or dinuclear [(bpy)2M2]4+ acceptors (bpy = 2,2'-dipyridine; M = Pd, Pt), in which the fluorescence can be quenched to an "off" state due to the ligand-to-metal charge transfer (LMCT). Metallacycle 1 was utilized as a fluorescence sensor for phosphate (PO43-) detection in aqueous solution by means of disassembly, leading to the release of the ligand. Additionally, the metallacycle can be regenerated through self-assembly via the introduction of Pd(II) acceptors. PO43- was detected using TPE-based metallacycles over a wide concentration range, with a detection limit as low as 2.1 × 10-8 M. Furthermore, sensor 1 also presented the semiquantitative visual detection ability for PO43- in the test paper mode via fluorescence changes. The aforementioned studies not only enhance the current research on fluorescent materials but also offer a strategy for the creation of stimuli-responsive supramolecular coordination complexes.

Preparation of complex biological sample-compatible "turn-on"-type ratiometric fluorescent molecularly imprinted polymer microspheres via one-pot surface-initiated ATRP.

The efficient preparation of ratiometric fluorescent molecularly imprinted polymer (MIP) microspheres that can directly and selectively optosense a herbicide (i.e., 2,4-dichlorophenoxyacetic acid, 2,4-D) in undiluted pure milk is described. Thedual fluorescent MIP microparticles were readily obtained through grafting a green 4-nitrobenzo[c][1,2,5]oxadiazole (NBD)-labeled 2,4-D-MIP layer with hydrophilic polymer brushes onto the preformed uniform "living" red CdTe quantum dot (QD)-labeled SiO2 microspheres via one-pot surface-initiated atom transfer radical polymerization (SI-ATRP) in the presence of a polyethylene glycol macro-ATRP initiator. They proved to be highly promising "turn-on"-type fluorescent chemosensors with red CdTe QD (the maximum emission wavelength λe,max around 710nm) and green NBD (λe,max around 515nm) as the reference fluorophore and "turn-on"-type responsive fluorophore, respectively. The sensors showed excellent photostability and reusability, high 2,4-D selectivity and sensitivity (the limit of detection = 0.12μM), and direct visual detection ability (a fluorescent color change occurs from red to blue-green with the concentration of 2,4-D increasing from 0 to 100μM) in pure bovine milk. The sensorswere used for 2,4-D detection with high recoveries (96.0-104.0%) and accuracy (RSD ≤ 4.0%) in pure goat milk at three spiking levels of both 2,4-D and its mixtures with several analogues. This new strategy lays the foundation for efficiently developing diverse complex biological sample-compatible ratiometric fluorescent MIPs highly useful for real-world bioanalyses and diagnostics.

Aspartic acid assisted one-step synthesis of stable CsPbX3@Asp-Cs4PbX6 by in situ growth in NH2-MIL-53 for ratiometric fluorescence detection of 4-bromophenoxybenzene.

A molecularly imprinted ratiometric fluorescent sensor was synthesized for the detection of 4-bromophenoxybenzene (BDE-3) based on perovskite quantum dots and metal organic framework. First, aspartic acid (Asp) was introduced during the synthesis of perovskite CsPbX3 for the formation of a core-shell structure of CsPbX3@Asp-Cs4PbX6. Due to the protection of the shell layer Cs4PbX6, the stability of the core CsPbX3 was improved significantly. Compared to CsPb(BrI)3, the ultraviolet and thermal stabilities of CsPb(BrI)3@Asp-Cs4Pb(BrI)6 were increased by 26 times and 32 times, respectively, and, compared to CsPbBr3, these stabilities of CsPbBr3@Asp-Cs4PbBr6 were increased by 3 times and 13 times, respectively. The water stabilities of CsPb(BrI)3@Asp-Cs4Pb(BrI)6 and CsPbBr3@Asp-Cs4PbBr6 were greatly improved too. Then, a ratiometric fluorescence sensor was constructed by in situ growth of CsPb(BrI)3@Asp-Cs4Pb(BrI)6 in metal organic framework (NH2-MIL-53) for the detection of BDE-3, in which the orange fluorescence of CsPb(BrI)3@Asp-Cs4Pb(BrI)6 (614nm) was regarded as the reference signal and thecyan fluorescence of NH2-MIL-53 (494nm) was usedas the fluorescence response signal. To improve the selectivity of the sensor, the molecular imprinting polymer (MIP) was modified on the NH2-MIL-53 and an imprinting factor of 3.17 was obtained. Under 365nm light excitation, the fluorescent response signal at 494nm was quenched gradually by BDE-3 in the range 11.4 to 68.5nmol/L, while the reference signal at 614nm remained unchanged. The limit of detection and limit of quantification were 3.35 and 11.2nmol/L, respectively, and the fluorescent color of the sensor changed gradually from cyan to green to orange, which illustrated that the developed sensor has an ability to recognize BDE-3 specifically, a good anti-interference ability, and a sensitively visual detection ability. Moreover, the sensor was successfully applied to the BDE-3 detection in polyethylene terephthalate plastic bottle, polyvinyl chloride plastic bag, and circuit board with satisfactory recoveries (96.3-108.1%) and low relative standard deviations (5%). The preparation processes of NH2-MIL-53, NH2-MIL-53-CsPb(BrI)3@Asp-Cs4Pb(BrI)6, and the MIP-NH2-MIL-53-CsPb(BrI)3@Asp-Cs4Pb(BrI)6 composites.

Luminescent detection of pesticides by color changeable flexible coumarin-3-carboxylic acid/GdF3:Sm3+ composite film

The utilization and residue of pesticides exist multifaceted non-restrictive effects on food safety and ecological protection. Exploitation of rapid and sensitive pesticide detection technology is imperative and will be helpful to better control the detriment of pesticides. Here, a novel flexible film has been prepared based on organic-inorganic composite materials (coumarin-3-carboxylic acid and GdF3:Sm3+), which exhibits good optical performance and can well realize the timely and maneuverable detection for different pesticides. The spectra and luminescence properties of each composition in the composite have been analyzed systematically, and the coordinated fluorescence emission of Sm3+ and coumarin-3-carboxylic acid is revealed at an excitation wavelength of 373 nm. Besides, the energy transfer mechanism is also researched by both experiment and theoretical calculation. The actual detection of different pesticides reveals differential fluorescence influence degree. Meanwhile, the flexible film still possesses sensitive recognition in the presence of micro concentration of pesticides. Results indicate that the flexible film with good optical performance can produce visual detection ability and provide a promising strategy for wider detection applications.

A tetraphenylethylene-based aggregation-induced emission sensor: Ultrasensitive “turn-on” fluorescent sensing for phosphate anion in pure water

A new fluorescent sensor of tetraphenylethylene (TPE) derivate with four dimethylformamidine and four chloride anions, sensor 1, was resoundingly synthesized. Meanwhile, the structure of sensor 1 has been characterized by 1H NMR, 13C NMR, FT-IR and mass spectrum. Sensor 1 can dissolve in water completely and showed significant fluorescence enhancement response towards PO43− with selectivity and sensitivity in pure water. The results of fluorescence spectra, turbidity measurement, dynamic light scattering (DLS) and fluorescent micrographs elucidated that the distinct fluorescence enhancement of sensor 1 with PO43− anion can be attributed to the aggregation-induced emission (AIE) of TPE. The AIE of sensor 1 with PO43− anion was reversible, proved by the alternate addition of PO43− anion and calcium ion. The fluorescence intensity of sensor 1 at 510 nm gradually increased and was obviously augmented by 266% when the added concentration of PO43− was 150 μmol L−1 (15 equiv. of sensor 1). In addition, the fluorescence intensity also displayed a good linear relationship with PO43− ions in the large concentration range of 10–150 μmol L−1 with very low detection limit for PO43− of 6.56 × 10−8 mol L−1. Furthermore, sensor 1 also presented the semi-quantitative visual detection ability for PO43− in solutions and test paper mode via the fluorescence changes and quantitative detection potential for PO43− in actual water sample.

Engineered gold nanoparticles as multicolor labels for simultaneous multi-mycotoxin detection on the immunochromatographic test strip nanosensor

Herein, we report a multicolor immunochromatographic test strip (ICTS) nanosensor for the rapid and simultaneous visual detection of fumonisin B1 (FB1), zearalenone (ZEN), ochratoxin A (OTA), and aflatoxin B1 (AFB1). Four colored AuNPs, including gold nanospheres (red), gold nanocacti (purple), gold nanoflowers (blue), and hyperbranched Au plasmonic blackbodies (black), were synthesized and functionalized with the corresponding antibodies to target each analyte. The developed multicolor platform improved bare-eye-based visual detection ability with cut-off values of 120, 60, 2.5, and 5 ng/mL for FB1, ZEN, OTA, and AFB1, respectively. The limits of detection for FB1, ZEN, OTA, and AFB1 were calculated as 3.27, 0.70, 0.10, and 0.06 ng/mL, respectively, and the average recoveries of the four mycotoxins ranged from 82.36% to 116.23% with a small coefficient of variation (below 12.98%). Accuracy, stability, reliability, and practicability were demonstrated by analyzing artificially and naturally contaminated corn samples. In summary, the designed multicolor ICTS nanosensor can serve as an alternative rapid diagnostic platform enabling the sensitive, simultaneous, and on-site screening detection of mycotoxins and other analytes.

Posterior brain lesions selectively alter alpha oscillatory activity and predict visual performance in hemianopic patients

Alpha oscillatory frequency and amplitude have been linked to visual processing and to the excitability of the visual cortex at rest. Therefore, posterior brain lesions, which damage the neural circuits of the visual system might induce alterations in the alpha oscillatory activity. To investigate this hypothesis, EEG activity was recorded during eyes-closed resting state in patients with hemianopia with posterior brain lesions, patients without hemianopia with anterior brain lesions and age-matched healthy controls. Patients with posterior lesions revealed a selective slowdown of individual alpha frequency in both the intact and the lesioned hemisphere and a reduction of alpha amplitude in the lesioned hemisphere, resulting in an interhemispheric imbalanced oscillatory alpha activity, while no significant alterations in the alpha range were found in patients with anterior lesions. This suggests a crucial role of posterior cortices in coordinating alpha oscillations in the visual system. Moreover, right posterior lesions had a more severe reduction of individual alpha frequency and altering of the interhemispheric distribution of the alpha amplitude, in line with the notion of the prominence of the right posterior cortices in balancing the interhemispheric functioning. Crucially, the duration of the in individual alpha frequency and the interhemispheric imbalance in alpha amplitude were directly linked to visuo-spatial performance across all participants and to impaired visual detection abilities in hemianopics, therefore supporting a functional role of alpha oscillations in visual processing and suggesting that activity in this frequency range at rest represents a neurophysiological marker reliably reflecting the integrity and the functionality of the visual system in humans.

Development and Implementation of a New Telerehabilitation System for Audiovisual Stimulation Training in Hemianopia.

Telerehabilitation, defined as the method by which communication technologies are used to provide remote rehabilitation, although still underused, could be as efficient and effective as the conventional clinical rehabilitation practices. In the literature, there are descriptions of the use of telerehabilitation in adult patients with various diseases, whereas it is seldom used in clinical practice with child and adolescent patients. We have developed a new audiovisual telerehabilitation (AVT) system, based on the multisensory capabilities of the human brain, to provide a new tool for adults and children with visual field defects in order to improve ocular movements toward the blind hemifield. The apparatus consists of a semicircular structure in which visual and acoustic stimuli are positioned. A camera is integrated into the mechanical structure in the center of the panel to control eye and head movements. Patients can use this training system with a customized software on a tablet. From hospital, the therapist has complete control over the training process, and the results of the training sessions are automatically available within a few minutes on the hospital website. In this paper, we report the AVT system protocol and the preliminary results on its use by three adult patients. All three showed improvements in visual detection abilities with long-term effects. In the future, we will test this apparatus with children and their families. Since interventions for impairments in the visual field have a substantial cost for individuals and for the welfare system, we expect that our research could have a profound socio-economic impact avoiding prolonged and intensive hospital stays.

Seabird distribution patterns observed with fishing vessel\u2019s radar reveal previously undescribed sub-meso-scale clusters

Seabirds are known to concentrate on prey patches or at predators aggregations standing for potential feeding opportunities. They may search for prey using olfaction or by detecting visually feeding con-specifics and sub-surface predators, or even boats. Thus, they might form a foraging network. We hypothesized that conditionally to the existence of a foraging network, the visual detection ability of seabirds should have a bearing on their medium-scale distribution at sea. Using a fishing-boat radar to catch the instantaneous distribution of seabirds groups within 30 km around the vessel, we conducted a spatial clustering of the seabird-echoes. We found 7,657 clusters (i.e. aggregations of echoes), lasting less than 15 minutes and measuring 9.2 km in maximum length (median). Distances between seabirds groups within clusters showed little variation (median: 2.1 km; CV: 0.5), while area varied largely (median: 21.9 km2; CV: 0.8). Given existing data on seabirds’ reaction distances to boats or other marine predators, we suggest that these structures may represent active foraging sequences of seabirds spreading themselves in space such as to possibly cue on each others. These seabird clusters were not previously described and are size compatible with the existence of a foraging network.

Individual differences in subitizing range predict visual detection ability.

Individual differences in subitizing range predict visual detection ability.

Crossmodal enhancement of visual orientation discrimination by looming sounds requires functional activation of primary visual areas: A case study

Approaching or looming sounds are salient, potentially threatening stimuli with particular impact on visual processing. The early crossmodal effects by looming sounds (Romei, Murray, Cappe, & Thut, 2009) and their selective impact on visual orientation discrimination (Leo, Romei, Freeman, Ladavas, & Driver, 2011) suggest that these multisensory interactions may take place already within low-level visual cortices. To investigate this hypothesis, we tested a patient (SDV) with bilateral occipital lesion and spared residual portions of V1/V2. Accordingly, SDV׳s visual perimetry revealed blindness of the central visual field with some residual peripheral vision. In two experiments we tested for the influence of looming vs. receding and stationary sounds on SDV׳s line orientation discrimination (orientation discrimination experiment) and visual detection abilities (detection experiment) in the preserved or blind portions of the visual field, corresponding to spared and lesioned areas of V1, respectively. In the visual orientation discrimination experiment we found that SDV visual orientation sensitivity significantly improved for visual targets paired with looming sounds but only for lines presented in the partially preserved visual field. In the visual detection experiment, where SDV was required to simply detect the same stimuli presented in the orientation discrimination experiment, a generalised sound-induced visual improvement both in the intact and in blind portion of the visual field was observed. These results provide direct evidence that early visual areas are critically involved in crossmodal modulation of visual orientation sensitivity by looming sounds. Thus, a lesion in V1 prevents the enhancement of visual orientation sensitivity. In contrast, the same lesion does not prevent the visual detection enhancement by a sound, probably due to alternative visual pathways (e.g. retino-colliculo-extrastriate) which are usually spared in these patients and able to mediate the crossmodal enhancement of basic visual abilities such as detection.

Observers are inconsistent and inaccurate in judging their own visual detection ability at different retinal locations

Observers are inconsistent and inaccurate in judging their own visual detection ability at different retinal locations

Long-term learning of visual functions in patients after brain damage

Purpose Systematic vision restoration training has been shown to improve the detection performance of brain-damaged patients with visual-field defects. So far, patients have been trained daily up to 6 months. We wished to determine whether intensive long-term training of 12 months further increases visual detection abilities. Methods Retrospective comparison of 17 patients with visual-field defects using vision restoration training for 12 months with a group of patients training for 6 months. Computer-based home training was completed for 6 months (about 195,000 stimuli presentations) or for 12 months (about 390,000 stimuli presentations). Visual fields were measured at baseline with Rodenstock Perimat 206 (monocular) at 90° eccentricity and at 54° eccentricity with high resolution perimetry (HRP) (binocular) after 6 months (post-6) and after 12 months (post-12) of training. Results Near-threshold perimetry revealed minor training effects, beyond 6 months, of 3.5% ( p = 0.099) in the right eye and of 1.5% ( p = 0.57) in the left eye. No effects of long-term training were evident in above threshold testing (0.8% detection improvement, n.s.). Conclusions Learning to detect above-threshold stimuli in patients with post-retinal lesions is completed after 6 months of practice with only marginal improvements thereafter. Near-threshold testing reveals that peripheral areas of the visual-field benefit from long-term training even if they are not trained.

Assessing visual detection ability for mobility in individuals with low vision

We investigated the mobility performance of legally blind patients with age-related maculopathy (ARM) as assessed by their ability to visually detect hazards in their travel path. The three types of hazards were: drop-offs (a curb), obstacle on the travel surface (a small wastebasket), and a head-height obstacle (a piece of foam insulation projecting across the travel path at head height). We also recorded the patient’s logMAR visual acuity and Pelli-Robson contrast sensitivity. Three distinct daylight assessments were made in a naturalistic outdoor environment: an initial assessment of distance to visually detect each of the three types of hazards; an assessment designed to assess the subject’s maximum potential visual detection distance; and a final assessment following training and fitting with filters to reduce glare to determine the increase, if any, in visual detection distance for the three types of hazards. The inter-rater and test/retest reliabilities of the assessment procedure were studied. The results indicated that many ARM patients are unable to visually detect some hazards at a safe distance, that their ability to improve can be predicted from the assessment, and that most subjects can improve their ability to visually detect obstacles if provided appropriate training and filters. The limitations of this study and their implications are discussed.