Luminance Changes Research Articles

Contributions of Luminance and Motion to Visual Escape and Habituation in Larval Zebrafish.

Animals from insects to humans perform visual escape behavior in response to looming stimuli, and these responses habituate if looms are presented repeatedly without consequence. While the basic visual processing and motor pathways involved in this behavior have been described, many of the nuances of predator perception and sensorimotor gating have not. Here, we have performed both behavioral analyses and brain-wide cellular-resolution calcium imaging in larval zebrafish while presenting them with visual loom stimuli or stimuli that selectively deliver either the movement or the dimming properties of full loom stimuli. Behaviorally, we find that, while responses to repeated loom stimuli habituate, no such habituation occurs when repeated movement stimuli (in the absence of luminance changes) are presented. Dim stimuli seldom elicit escape responses, and therefore cannot habituate. Neither repeated movement stimuli nor repeated dimming stimuli habituate the responses to subsequent full loom stimuli, suggesting that full looms are required for habituation. Our calcium imaging reveals that motion-sensitive neurons are abundant in the brain, that dim-sensitive neurons are present but more rare, and that neurons responsive to both stimuli (and to full loom stimuli) are concentrated in the tectum. Neurons selective to full loom stimuli (but not to movement or dimming) were not evident. Finally, we explored whether movement- or dim-sensitive neurons have characteristic response profiles during habituation to full looms. Such functional links between baseline responsiveness and habituation rate could suggest a specific role in the brain-wide habituation network, but no such relationships were found in our data. Overall, our results suggest that, while both movement- and dim-sensitive neurons contribute to predator escape behavior, neither plays a specific role in brain-wide visual habituation networks or in behavioral habituation.

Mindfulness Meditation Influences Implicit but Not Explicit Coding of Temporal Simultaneity

In the meditative state time appears to slow down and in the present moment it expands. However, to date, there is no investigation of the effect of meditative state on the structure of the “psychological moment”; this is the measurable, minimal duration of the moment “now.” In this study, we examined the effect on the psychological moment of a mindfulness intervention against an intervention in which participants listened to classical music. The psychological moment was measured using a simultaneity-detection paradigm from which the threshold between reports that two targets changed luminance simultaneously or with an asynchrony is normally taken as the duration of the moment. In line with previous research, this paradigm allowed for examination of the effects of the subthreshold synchronized, or asynchronized target onsets, which occurred prior to the luminance change of the targets. While there was no overall difference in the psychological moment pre- and post-, and as a function of the type of intervention, a bias against reporting simultaneity following presentation of a subthreshold asynchrony, which lowered thresholds and so shortened the psychological moment, was reduced after the mindfulness intervention. From this we conclude that even brief mindfulness meditation can encourage a more focalized attentional response, which can in turn be used to normalize psychological time.

Role of the frontal eye field in human microsaccade responses: A TMS study

Microsaccade is a type of fixational eye movements that is modulated by various sensory and cognitive processes, and impact our visual perception. Although studies in monkeys have demonstrated a functional role for the superior colliculus and frontal eye field (FEF) in controlling microsaccades, our understanding of the neural mechanisms underlying the generation of microsaccades is still limited. By applying continuous theta-burst stimulation (cTBS) over the right FEF and the vertex, we investigated the role of the FEF in generating human microsaccade responses evoked by salient stimuli or by changes in background luminance. We observed higher microsaccade rates prior to target appearance, and larger rebound in microsaccade occurrence following salient stimuli, when disruptive cTBS was applied over FEF compared to vertex stimulation. Moreover, the microsaccade direction modulation after changes in background luminance was disrupted with FEF stimulation. Together, our results constitute the first evidence of FEF modulation in human microsaccade responses.

Quantifying the effects of feature similarity on attentional selection using psychophysical scaling

The similarity between target and distractor features is a main factor determining the efficiency of attentional selection. Prior studies investigating the impact of target-distractor similarity on performance have mostly selected similarity levels in a categorical and qualitative way (e.g., by using discrete color or shape categories), or have used distance in physical stimulus space to quantify similarity. However, findings from psychophysics have shown that the physical stimulus space does not map linearly to psychological similarity. Thus, we here assessed psychological similarity using psychophysical scaling methods and tested how these similarity functions relate to attentional selection. We measured psychological similarity of colors chosen from CIELab space as a test case. Then, using a standard visual search task, we measured search times using a wide range of target-distractor similarity levels (Exp. 1) and also manipulated the number of distractors (2 or 7) to measure search efficiency (Exp. 2-3). In another sustained attention task (Exp. 4), participants continuously monitored a set of target dots among distractor dots to detect brief changes in luminance, and the color similarity between target and distractor dots was manipulated across trials, as in the visual search tasks. We found that performance in both tasks was comparably affected by target-distractor similarity, with search RTs and luminance discriminability plateauing at approximately 40°-50° around the CIELab color wheel. In contrast, the number of visual search distractors only affected performance when similarity was very high (below 20°). Interestingly, performance in each task was non-linearly related to both the physical and psychological similarity between targets and distractors. Overall, these findings suggest that there is no simple linear relationship between feature similarity and attentional selection, and point to the importance of understanding how the underlying perceptual organization of a given feature space interacts with mechanisms of attentional selection.

Abstract P473: Obstructive Sleep Apnea Results In Microbial Bile Acid Biotransformations To Promote Atherosclerosis

Obstructive sleep apnea (OSA) is an independent exacerbator of cardiovascular disease (CVD). However, it is unclear how OSA or it’s characteristic components, intermittent hypoxia and hypercapnia (IHC), increase CVD risk. Our previous work has shown that IHC reproducibly changes the gut microbiome dynamics in murine models of atherosclerosis and that these changes could affect host cardiovascular physiology through bile acids and phosphocholines. In our initial targeted metabolomics approach, changes in particular bile acids, such as taurocholic acid, taurodeoxycholic acid, and muricholic acid, were associated with and were predictive of IHC exposure in atherosclerotic Ldlr-/- mice. In a more recent study, we identified the formation of novel, microbially-synthesized conjugated bile acids by the gut microbiome that are more potent farnesoid X receptor agonists than other previously described bile acids, and thus, potentially can affect atherosclerosis formation. To determine whether these novel bile acids are associated with IHC-induced atherosclerosis, we characterized luminal bile acid changes in Ldlr-/- mice in an OSA model. We hypothesize that IHC alters the amount of microbially-synthesized novel bile acids and that these bile acids are associated with IHC-induced atherosclerosis. To test this hypothesis, we subjected atherogenic diet-fed Ldlr-/- mice to either room-air (control) or IHC conditions (n=10/condition) and assessed atherosclerotic lesion formation after 12 weeks post-diet. Mice under IHC conditions had significantly higher aortic lesion formation compared to controls. Assessment of fecal bile acid metabolites indicated changes in novel bile acid levels under IHC conditions. Moreover, correlational analysis showed that these novel bile acid changes were positively correlated with atherosclerotic lesion amounts, mainly driven by IHC conditions. Our results demonstrate that bile acid changes through microbial biotransformations occur under IHC conditions and could be the mechanistic link between OSA-induced microbiome changes and atherosclerosis.

Visual processing: Systematic variation in light–dark bias across visual space

Detecting changes in luminance is a fundamental property of the visual system. A new study shows that lights and darks are represented differently across visual space, with strong OFF bias in central vision and balanced ON/OFF in the periphery.

Change biases identify the features that drive time perception.

Time perception is malleable, and the perceived duration of stimuli can be strongly affected by the sensory response they evoke. Such "temporal illusions" provide a window on how different sensory systems contribute to our sense of time. Evidence suggests that the sensory response to different features affects time perception to different extents, mediated by the level of arousal or surprise that they evoke. This, however, makes it difficult to disentangle effects of the sensory response itself from the derived arousal or surprise effects. Here, we demonstrate that time perception is differentially affected by different stimulus features when arousal and surprise are kept constant. In four temporal discrimination experiments, participants were presented with empty intervals (1.25 s-2.25 s) marked by two briefly presented visual marker stimuli, and judged whether the duration was longer or shorter than a 1.75 s reference. Markers either repeated or changed along one of six feature dimensions, in a manner fully predictable to participants. Repetitions and changes would modulate sensory response magnitudes due to neural repetition suppression. Results showed that intervals were perceived as longer when markers changed in location, size, or numerosity. Conversely, changes in face identity, orientation or luminance did not affect time perception. These results point to neural and functional selectivity in the way different stimulus features affect time perception. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Rainbow color map distorts and misleads research in hydrology – guidance for better visualizations and science communication

Abstract. Nowadays color in scientific visualizations is standard and extensively used to group, highlight or delineate different parts of data in visualizations. The rainbow color map (also known as jet color map) is famous for its appealing use of the full visual spectrum with impressive changes in chroma and luminance. Besides attracting attention, science has for decades criticized the rainbow color map for its non-linear and erratic change of hue and luminance along the data variation. The missed uniformity causes a misrepresentation of data values and flaws in science communication. The rainbow color map is scientifically incorrect and hardly decodable for a considerable number of people due to color vision deficiency (CVD) or other vision impairments. Here we aim to raise awareness of how widely used the rainbow color map still is in hydrology. To this end, we perform a paper survey scanning for color issues in around 1000 scientific publications in three different journals including papers published between 2005 and 2020. In this survey, depending on the journal, 16 %–24 % of the publications have a rainbow color map and around the same ratio of papers (18 %–29 %) uses red–green elements often in a way that color is the only possibility to decode the visualized groups of data. Given these shares, there is a 99.6 % chance to pick at least one visual problematic publication in 10 randomly chosen papers from our survey. To overcome the use of the rainbow color maps in science, we propose some tools and techniques focusing on improvement of typical visualization types in hydrological science. We give guidance on how to avoid, improve and trust color in a proper and scientific way. Finally, we outline an approach how the rainbow color map flaws should be communicated across different status groups in science.

Plasma cells are essentially absent in the luminal gastrointestinal tract of patients with “complete” 22q11.2 deletion syndrome (DiGeorge syndrome)

Gastrointestinal symptoms are commonly reported in patients with 22q11.2 deletion syndrome or DiGeorge syndrome (DGS) in addition to the dominant cardiac manifestations and immunodeficiency. But literature providing specific morphologic details of the gastrointestinal tract pathology is very limited. Here, we provide the first comprehensive morphologic description of the luminal gastrointestinal tract changes in patients with DGS. Cytogenetically confirmed DGS patients were identified, clinical and laboratory data were reviewed to determine the severity of immunodeficiency, and patients were stratified into mildly immunocompromised, that is, partial DiGeorge anomaly or severely immunosuppressed, that is, complete DiGeorge anomaly groups. Gastrointestinal tract biopsies from these patients were retrospectively reviewed and compared with those from controls without the history of DGS. Patients with immunosuppressed DGS showed a near complete absence of plasma cells in the stomach, duodenum, and colon lamina propria by hematoxylin and eosin evaluation. Immunohistochemistry for CD138 used to highlight plasma cells confirmed this finding. The notable absence of plasma cells adds to the existing knowledge of the pathophysiology underlying DGSand expands the differential diagnostic considerations for this finding, which has been previously described in common variable immunodeficiency. It also provides a useful morphologic marker observable by the readily accessible light microscopy. Second, patients with DGS showed a mild increase in epithelial cell apoptosis in their colon. This finding is significant because of its overlap with morphologic features of gastrointestinal graft versus host disease as thymus transplantation is being used as a treatment option for patients with complete DGS.

P‐16.14: Research of Optical Influence on LCD by OGM Products

This paper aims to explore the influence mechanism and range of OGM (One Glass Solution, Metal Mesh) on LCD (Liquid Crystal Display) optical performance. Firstly, the basic concepts and calculation methods of color coordinates and other parameters are introduced; Then the laminated structure of TLCM is introduced, and the transmission spectrum of each layer is tested in different experiments, which points out that the most important influencing factor is the OC insulating layer due to the low light transmittance at low wavelength; Finally, the influence range of OGM on LCD's brightness, color coordinate, color temperature, color gamut and blue light proportion are pointed out, among them, the brightness and color temperature decrease by respectively about 6.0% and 6.25%. The above work analyzes the luminance and chromaticity changes of LCD products after OGM lamination, which provides theoretical and data reference for the design of new products in the future.

Varying Stimulus Duration Reveals Consistent Neural Activity and Behavior for Human Face Individuation

Establishing consistent relationships between neural activity and behavior is a challenge in human cognitive neuroscience research. We addressed this issue using variable time constraints in an oddball frequency-sweep design for visual discrimination of complex images (face exemplars). Sixteen participants viewed sequences of ascending presentation durations, from 25 to 333 ms (40–3 Hz stimulation rate) while their electroencephalogram (EEG) was recorded. Throughout each sequence, the same unfamiliar face picture was repeated with variable size and luminance changes while different unfamiliar facial identities appeared every 1 s (1 Hz). A neural face individuation response, tagged at 1 Hz and its unique harmonics, emerged over the occipito-temporal cortex at 50 ms stimulus duration (25–100 ms across individuals), with an optimal response reached at 170 ms stimulus duration. In a subsequent experiment, identity changes appeared non-periodically within fixed-frequency sequences while the same participants performed an explicit face individuation task. The behavioral face individuation response also emerged at 50 ms presentation time, and behavioral accuracy correlated with individual participants’ neural response amplitude in a weighted middle stimulus duration range (50–125 ms). Moreover, the latency of the neural response peaking between 180 and 200 ms correlated strongly with individuals’ behavioral accuracy in this middle duration range, as measured independently. These observations point to the minimal (50 ms) and optimal (170 ms) stimulus durations for human face individuation and provide novel evidence that inter-individual differences in the magnitude and latency of early, high-level neural responses are predictive of behavioral differences in performance at this function.

Osmium‐ and Cobalt‐Terpyridine‐Based Electrochromic Devices for “Smart” Signage Application: The Effect of Lighting on Color Perception

AbstractModern electrochromic devices (ECDs) have found a wide range of applications, which are not limited to the traditional design of “smart” windows and self‐dimming mirrors. Novel cutting‐edge applications in optoelectronics and particularly in low‐energy displays and “smart” signage require electrochromic materials (ECMs) that demonstrate significant changes in optical density, fast switching times, and color differences between the colored and bleached states that are visible to the naked eye. Here ECMs that are designed by the chemical deposition of electrochromic Co(II) and Os(II) complexes and their mixture on surface‐enhanced support fabricated by screen printing of indium–tin oxide (ITO‐50) nanoparticles are presented on an ITO/glass substrate. The oxidation state of the metal complexes is reversibly addressed by voltage switching between −1 and +3 V. Further assembly of the ECMs and ITO/glass counter electrode using gel electrolyte results in solid‐state ECDs. The changes in optical properties of these ECDs induced by the metal oxidation state alteration are tracked by recording UV–vis spectra. Moreover, here color differences (CDs) and changes in luminance of ECDs (ΔL) in the colored and bleached state are compared when illuminated with light‐emitting diodes (LEDs) of different colors.

Real time fall detection using infrared cameras and reflective tapes under day/night luminance

Falls are the leading cause of injuries and death in elderly individuals who live alone at home. The core service of assistive living technology is to monitor elders’ activities through wearable devices, ambient sensors, and vision systems. Vision systems are among the best solutions, as their implementation and maintenance costs are the lowest. However, current vision systems are limited in their ability to handle cluttered environments, occlusion, illumination changes throughout the day, and monitoring without illumination. To overcome these issues, this paper proposes a 24/7 monitoring system for elders that uses retroreflective tape fabricated as part of conventional clothing, monitored through low-cost infrared (IR) cameras fixed in the living environment. IR camera records video even when there are changes in illumination or zero luminance. For classification among clutter and occlusion, the tape is considered as a blob instead of a human silhouette; the orientation angle, fitted through ellipse modeling, of the blob in each frame allows classification that detects falls without pretrained data. System performance was tested using subjects in various age groups and “fall” or “non-fall” were detected with 99.01% accuracy.

HCN1 channels: A versatile tool for signal processing by primary sensory neurons

Most primary sensory neurons (PSNs) generate a slowly-activating inward current in response to membrane hyperpolarization (Ih) and express HCN1 along with additional isoforms coding for hyperpolarization-activated channels (HCN). Changes in HCN expression may affect the excitability and firing patterns of PSNs, but retinal and inner ear PSNs do not fire action potentials, suggesting HCN channel roles may extend beyond excitability and cell firing control. In patients taking Ih blockers, photopsia triggered in response to abrupt changes in luminance correlates with impaired visual signal processing via parallel rod and cone pathways. Furthermore, in a mouse model of inherited retinal degeneration, HCN blockers or Hcn1 genetic ablation may worsen photoreceptors' demise. PSN's use of HCN channels to adjust either their firing rate or process signals generated by sensory transduction in non-spiking PSNs indicates HCN1 channels as a versatile tool with a novel role in sensory processing beyond firing control.

A Comparison of Closed Loop vs. Fixed Frequency tACS on Modulating Brain Oscillations and Visual Detection.

Transcranial alternating current stimulation has emerged as an effective tool for the exploration of brain oscillations. By applying a weak alternating current between electrodes placed on the scalp matched to the endogenous frequency, tACS enables the specific modulation of targeted brain oscillations This results in alterations in cognitive functions or persistent physiological changes. Most studies that utilize tACS determine a fixed stimulation frequency prior to the stimulation that is kept constant throughout the experiment. Yet it is known that brain rhythms can encounter shifts in their endogenous frequency. This could potentially move the ongoing brain oscillations into a frequency region where it is no longer affected by the stimulation, thereby decreasing or negating the effect of tACS. Such an effect of a mismatch between stimulation frequency and endogenous frequency on the outcome of stimulation has been shown before for the parietal alpha-activity. In this study, we employed an intermittent closed loop stimulation protocol, where the stimulation is divided into short epochs, between which an EEG is recorded and rapidly analyzed to determine a new stimulation frequency for the next stimulation epoch. This stimulation protocol was tested in a three-group study against a classical fixed stimulation protocol and a sham-treatment. We targeted the parietal alpha rhythm and hypothesized that this setup will ensure a constant close match between the frequencies of tACS and alpha activity. This closer match should lead to an increased modulation of detection of visual luminance changes depending on the phase of the tACS and an increased rise in alpha peak power post stimulation when compared to a protocol with fixed pre-determined stimulation frequency. Contrary to our hypothesis, our results show that only a fixed stimulation protocol leads to a persistent increase in post-stimulation alpha power as compared to sham. Furthermore, in none of the stimulated groups significant modulation of detection performance occurred. While the lack of behavioral effects is inconclusive due to the short selection of different phase bins and trials, the physiological results suggest that a constant stimulation with a fixed frequency is actually beneficial, when the goal is to produce persistent synaptic changes.

Role of Intestinal Ultrasound in the Management of Patients with Inflammatory Bowel Disease.

Intestinal ultrasound (IUS) has gained popularity as a first line technique for the diagnosis and monitoring of patients with inflammatory bowel diseases (IBD) due to its many advantages. It is a non-invasive imaging technique with non-ionizing radiation exposure. It can be easily performed not only by radiologists but also by trained gastroenterologists at outpatient clinics. In addition, the cost of IUS equipment is low when compared with other imaging techniques. IUS is an accurate technique to detect inflammatory lesions and complications in the bowel in patients with suspected or already known Crohn’s disease (CD). Recent evidence indicates that IUS is a convenient and accurate technique to assess extension and activity in the colon in patients with ulcerative colitis (UC), and can be a non-invasive alternative to endoscopy. In patients with IBD, several non-specific pathological ultrasonographic signs can be identified: bowel wall thickening, alteration of the bowel wall echo-pattern, loss of bowel stratification, increased vascularization, decreased bowel peristalsis, fibro-fatty proliferation, enlarged lymph nodes, and/or abdominal free fluid. Considering the transmural CD inflammation, CD complications such as presence of strictures, fistulae, or abscesses can be detected. In patients with UC, where inflammation is limited to mucosa, luminal inflammatory ultrasonographic changes are similar to those of CD. As the technique is related to the operator’s experience, adequate IUS training, performance in daily practice, and a generalized use of standardized parameters will help to increase its reproducibility.

Efficiently evaluating the effect of color gamut and spectral bandwidth on observer metamerism in high dynamic range displays

AbstractObserver metamerism (OM), which likely causes potential issues in high dynamic range (HDR) displays due to those formidable peak luminance and color gamut required, is examined in this work using simulations. The simulations focus on investigating how OM in HDR displays would vary with chromaticity gamut and peak luminance level changes, proposing a new OM index, OMM. The effects of additional factors noteworthy on OM, such as reference white level, age, and spectral characteristics, are discussed. Finally, a simple metric capable of predicting observer metamerism between displays with less computational complexity, OMMN, is introduced. The simulation results showed that observer metamerism magnitudes between displays tend to depend on the similarity in spectral bandwidth between paired displays, in addition to the fact that narrow‐band primary displays generally cause larger metameric failures. Besides, the effect of changes in peak luminance on observer metamerism was found to be relatively small, increasing OMM by 7%–8% when peak luminance doubles. Notably, the proposed efficient metric OMMN outperforms metrics based on spectral similarity by also factoring in inter‐observer variability. In addition, the proposed metric's performance with 10 categorical observers, OMMN, 10, is nearly as good as that with thousands more computations. OMMN, 10 is recommended as a reliable and efficient metric to evaluate OM between HDR displays.

Algorithms underlying flexible phototaxis in larval zebrafish.

To thrive, organisms must maintain physiological and environmental variables in suitable ranges. Given that these variables undergo constant fluctuations over varying time scales, how do biological control systems maintain control over these values? We explored this question in the context of phototactic behavior in larval zebrafish. We demonstrate that larval zebrafish use phototaxis to maintain environmental luminance at a set point, that the value of this set point fluctuates on a time scale of seconds when environmental luminance changes, and that it is determined by calculating the mean input across both sides of the visual field. These results expand on previous studies of flexible phototaxis in larval zebrafish; they suggest that larval zebrafish exert homeostatic control over the luminance of their surroundings, and that feedback from the surroundings drives allostatic changes to the luminance set point. As such, we describe a novel behavioral algorithm with which larval zebrafish exert control over a sensory variable.

Short-latency ocular following responses to motion stimuli are strongly affected by temporal modulations of the visual content during the initial fixation period.

Neuronal and psychophysical responses to a visual stimulus are known to depend on the preceding history of visual stimulation, but the effect of stimulation history on reflexive eye movements has received less attention. Here, we quantify these effects using short-latency ocular following responses (OFRs), a valuable tool for studying early motion processing. We recorded, in human subjects, the horizontal OFRs induced by drifting vertical 1D pink noise. The stimulus was preceded by 600 to 1000 ms of maintained fixation (on a visible cross), and we explored the effect of different stimuli (“fixation patterns”) presented during the fixation period. We found that any temporal modulation present during the fixation period reduced the magnitude of the subsequent OFRs. Even changes in the overall luminance during the fixation period induced significant suppression. The magnitude of the effect was a function of both spatial and temporal structure of the fixation pattern. Suppression that was selective for both relative orientation and relative spatial frequency accounted for a considerable fraction of total suppression. Finally, changes in stimulus temporal structure alone (i.e. “flicker” versus “transparent motion”) led to changes in the spatial frequency tuning of suppression. In the time domain, the suppression developed quickly: 100 ms of temporal modulation in the fixation pattern produced up to 80% of maximal suppression. Recovery from suppression was instead more gradual, taking up to several seconds. By presenting transparent motion during the fixation period, with opposite motion signals having different spatial frequency content, we also discovered a direction-selective component of suppression, which depended on both the frequency and the direction of the moving stimulus.

Different roles of subcortical inputs in V1 responses to luminance and contrast.

Cells in the primary visual cortex (V1) generally respond weakly to large uniform luminance stimuli. Only a subset of V1 cells is thought to encode uniform luminance information. In natural scenes, local luminance is an important feature for defining an object that varies and coexists with local spatial contrast. However, the strategies used by V1 cells to encode local mean luminance for spatial contrast stimuli remain largely unclear. Here, using extracellular recordings in anesthetized cats, we investigated the responses of V1 cells by comparing with those of retinal ganglion (RG) cells and lateral geniculate nucleus (LGN) cells to simultaneous and rapid changes in luminance and spatial contrast. Almost all V1 cells exhibited a strong monotonic increasing luminance tuning when they were exposed to high spatial contrast. Thus, V1 cells encode the luminance carried by spatial contrast stimuli with the monotonically increasing response function. Moreover, high contrast decreased luminance tuning of OFF cells but increased that of in ON cells in RG and LGN. The luminance and contrast tunings of LGN ON cells were highly separable as V1 cells, whereas those of LGN OFF cells were lowly separable. These asymmetrical effects of spatial contrast on ON/OFF channels might underlie the robust ability of V1 cells to perform luminance tuning when exposed to spatial contrast stimuli.