Flickering Light Research Articles

Triggering Factors for Breakthrough Seizures among Epileptic Patients. Cross Sectional Study in Epileptic Patients Attending Epilepsy Clinic Mansoura University Hospital, Egypt

Background: The prevalence of breakthrough seizures in persons with epilepsy is very high in developing countries. Consequently, patients and physicians should be aware of the possible factors that may cause breakthrough seizures.
 Objective: The aim of our study is to determine the possible factors that may be a precipitating cause for breakthrough seizures in patients with epilepsy.
 Methods: This cross-sectional study included 100 persons with epilepsy with idiopathic epilepsy receiving antiepileptic drugs (AEDs). They were divided into two groups. Group 1 included 50 persons with epilepsy with a history of recent breakthrough seizures. Group 2 included 50 persons with epilepsy who had not experienced any recent breakthrough seizures. Patients were subjected to a thorough questionnaire addressing precipitating factors. All participants were subjected to an electroencephalogram (EEG) and the Morisky Medication Adherence Scale (MMAS).
 Results: There was no significant differences between group 1 and group 2 regarding age, sex, age of onset of epilepsy, occupation and marital status (P value range 0.5 – 0.2). The patients in group 1 were found to have longer durations of epilepsy, lower adherence to AEDs (P = 0.001), more missed doses of AEDs (P = 0.0001), more side effects of AEDs (P = 0.0005), more sleep deprivation, lower level of AEDs (P = 0.0006), more frequently on AED polytherapy (P = 0.0002), and more flickering lights (P = 0.04) than the participants in group 2. In terms of the EEG, group 1 showed a higher percentage of abnormal EEGs and more frequent focal epileptiform discharges (P = 0.003). Also, pathological findings in MRI brain were associated with higher breakthrough seizures (P = 0.005). No significant difference was found in both group1 and group 2 regarding emotional stress (P = 0.55), substitution of brand AEDs by generic one (P = 0.83), concurrent illness (P = 1), or the use of non AEDs (P = 0.79).
 Conclusion: The precipitating factors of breakthrough seizures are multifactorial and it is very important to educate patients about these precipitating factors to achieve better control of epilepsy.

Clarifying frequency-dependent brightness enhancement: delta- and theta-band flicker, not alpha-band flicker, consistently seen as brightest.

Frequency-dependent brightness enhancement, a perceptual illusion in which a flickering light can appear twice as bright as a constant light, has historically been reported to produce maximum effects at a flicker rate within the alpha (8-12Hz) band (Bartley in J Exp Psychol 23(3):313-319, 1938). Our recent examinations of this phenomenon using brightness discrimination between two flickering stimuli, however, have instead revealed the brightest percepts from theta-band (4-7Hz) flicker (Bertrand et al. in Sci Rep8(1):6152, 2018). Two primary questions arise from these seemingly contradictory findings: first, could task differences between these studies have caused recruitment of discrete oscillatory processes? Second, could the reported theta-band flicker enhancement be the result of an aliased alpha rhythm, sequentially sampling two stimulus locations, resulting in an ~ 5Hz half-alpha rhythm? Here, we investigated these questions with two experiments: one replicating Bartley's (1938) adjustment paradigm, and one containing both Bartley's adjustment task and Bertrand's (2018) discrimination task, but presenting stimuli only sequentially (rather than concurrently). Examination of a range of frequencies (2-12Hz) revealed the greatest brightness enhancement arising from flicker in the delta- and theta-band across all conditions, regardless of the spatial or temporal configuration of the stimuli. We speculate that these slower rhythms play an integral role in complex visual operations (e.g., a discrimination decision) where the entrainment of the endogenous neural rhythm to matched exogenous rhythmic stimulation promotes more efficient processing of visual information and thus produces perceptual biases as seen in frequency-dependent brightness enhancement.

Age-related impairment of neurovascular coupling responses: a dynamic vessel analysis (DVA)-based approach to measure decreased flicker light stimulus-induced retinal arteriolar dilation in healthy older adults.

Aging is a major risk factor for vascular cognitive impairment and dementia (VCID). Recent studies demonstrate that cerebromicrovascular dysfunction plays a causal role in the development of age-related cognitive impairment, in part via disruption of neurovascular coupling (NVC) responses. NVC (functional hyperemia) is responsible for adjusting cerebral blood flow to the increased energetic demands of activated neurons, and in preclinical animal models of aging, pharmacological restoration of NVC is associated with improved cognitive performance. To translate these findings, there is an increasing need to develop novel and sensitive tools to assess cerebromicrovascular function and NVC to assess risk for VCID and evaluate treatment efficacy. Due to shared developmental origins, anatomical features, and physiology, assessment of retinal vessel function may serve as an important surrogate outcome measure to study neurovascular dysfunction. The present study was designed to compare NVC responses in young (< 45years of age; n = 18) and aged (> 65years of age; n = 11) healthy human subjects by assessing flicker light-induced changes in the diameter of retinal arterioles using a dynamic vessel analyzer (DVA)-based approach. We found that NVC responses in retinal arterioles were significantly decreased in older adults as compared with younger subjects. We propose that the DVA-based approach can be used to assess NVC, as a surrogate cerebromicrovascular outcome measure, to evaluate the effects of therapeutic interventions in older individuals.

Fault diagnosis algorithm for LED lamp driven by segmented linear solution in indoor environment via illumination waveform fluctuation similarity calculation

In this paper, fault diagnosis (FD) algorithm for LED lamp driven by segmented linear solution via illumination waveform fluctuation similarity calculation is proposed for indoor environment application. The proposed FD algorithm can be divided into four steps: illumination signal pre-processing, illumination waveform fluctuation similarity calculation, similarity assessment, and fault recognition. In illumination signal pre-processing, smoothing the original illumination signal using average filter algorithm, and illumination data normalization with min-max normalization method. Calculating illumination waveform fluctuation similarity with euclidean distance between the illumination signal of detected-lamp and standard illumination templates. Diagnosing the detected-lamp whether occurs fault or not and confirming the fault-type with illumination waveform fluctuation similarity value. To validate the proposed FD algorithm, an experimental setup is established in indoor environment and illumination signal of LED lamps are captured using Light Flicker Analyzer. The experimental results demonstrate the proposed FD algorithm can effectively diagnose faulty LED lamps driven by segment linear solution in indoor environment. The proposed algorithm developed here can benefit the fault diagnosis technology of LED lamp driven by segmented linear solution.

Research Note: Visibility of temporal light artefact from flicker at 11 kHz

A flickering light can be seen during a saccadic eye movement as a pattern of contours known as a phantom array. On repeated pairs of trials, observers made saccades across a narrow (1 arc minutes), bright (10−4 cd/m2) source of flickering light and were required to detect the phantom array. On one of each pair of trials, chosen at random, the light flickered at 60 kHz and on the other at a frequency chosen in the range 1–11 kHz. In two such studies, a few observers were reliably able to discriminate 11 kHz from 60 kHz on the basis of the visibility of the phantom array. The average threshold at which the array was visible was about 6 kHz and therefore double that previously obtained with larger targets. Those observers who were able to see the phantom array tended reliably to report more symptoms of visual discomfort in everyday life.

The Diameter of Retinal Arterioles Is Unaffected by Intravascular Administration of the Adenosine A2A Receptor Agonist Regadenoson in Normal Persons

Background: The neurotransmitter adenosine has been proposed to be involved in the pathogenesis of diabetic retinopathy, which may be due to the vasoactive properties of the compound. Previous studies have shown that adenosine can affect the tone of retinal arterioles in vitro to induce dilatation mediated by A_2A and A_2Breceptors and constriction mediated by A₁ and A₃ receptors. Purpose: To investigate effects of intravenous administration of the adenosine A_2A receptor agonist regadenoson on the diameter of retinal vessels in vivo. Method: The diameter responses of larger retinal arterioles and venules were evaluated using the dynamic vessel analyser in 20 normal persons (age 22–31 years) after intravenous administration of the adenosine A_2A receptor agonist regadenoson during exposure to systemic normoxia and hypoxia. Results: The diameter of retinal arterioles and venules increased significantly during stimulation with flickering light (p < 0.0001). Regadenoson reduced the flicker-induced dilatation of venules during normoxia (p = 0.0006), but otherwise had no effect on vessel diameters (p > 0.08 for all comparisons). Conclusions:Intravenous administration of the adenosine A_2A receptor agonist regadenoson had no significant effect on the diameter of retinal arterioles. Future studies should investigate differential effects of intra- and extravascular administration of adenosine receptor agonists on retinal vessels.

Marine larval vision suffers in low oxygen

Human brains don't do well without oxygen. When mountaineer Thomas Hornbein ascended Everest in 1963, he described his vision dimming when his oxygen regulator jarred loose. Fortunately, few of us experience hypoxia in such dramatic situations, but Lillian McCormick, from the Scripps Institution of Oceanography, explains that many aquatic creatures routinely encounter potentially threatening oxygen levels. ‘In nearshore areas of the Pacific Ocean off southern California, organisms can be exposed to reduced oxygen even in 0–50 m depth,’ she says. And when she reviewed the literature, it was clear that species with complex eyes would be most at risk of visual impairment. However, she and her colleagues Lisa Levin and Nicholas Oesch noticed that little was known about the ill effects of hypoxia on the larvae of many of these species.To rectify the situation, McCormick went trawling for plankton. ‘I hand-sorted each tow to set aside the larvae that we were interested in’, says McCormick, who decided to test the vision of larvae of the two spot octopus (Octopus bimaculatus), the tuna crab (Pleuroncodes planipes) and the graceful rock crab (Metacarcinus gracilis). However, she had to wait for the first and new moons of each month, when the market squid (Doryteuthis opalescens) spawn, to collect freshly laid egg sacs, which she took back to the lab to wait for the youngsters to hatch. Then, she painstakingly inserted a minute electrode into the retina of each tiny larva to record the eye's responses to light. Gradually decreasing and then increasing the concentration of oxygen dissolved in the water, McCormick recorded the response of each larva's retina to 1 s flashes of light. And when the oxygen was at ∼21, ∼10 and ∼3%, she shone a series of increasingly dimmer 1 s flashes into their eyes. In addition, McCormick shone a flickering light that gradually speeded up until the flashes blurred into one into the eyes of the squid and tuna crab larvae to find out how well the tiny animals could see fast-moving objects as the oxygen dwindled.Shockingly, all of the larvae lost some or all of their vision as the oxygen declined, with the market squid and graceful rock crab larvae unexpectedly beginning to suffer vision loss as soon as the oxygen began dropping. In contrast, the light response of the two spot octopus and tuna crab larval retinas held out reasonably well until the oxygen fell to ∼13%. By the time the oxygen had dipped to ∼3%, most of the squid, octopus and graceful rock crab larvae had completely lost their vision, although the retinal response of the tuna crab larvae only dipped to 60%. And while the speed of the tuna crab larvae's vision barely faltered at the lower oxygen levels, the response time of the squid larvae's retina reduced significantly, suggesting that they may really struggle to see the fast-moving copepods, upon which they dine, when oxygen is scarce.‘We calculate that the decline in retinal function due to decreased oxygen availability in larvae that move from 0 to 30 m depth in spring in southern California would be 15–59%’, says McCormick; which means that these minute creatures may already be experiencing visual loss in their natural environment. And she is concerned that additional declines in oxygen availability could place the larvae at further risk. ‘If larvae are unable to detect small changes in light intensity, or the swimming movements of their prey, they may not survive’, she warns.

Study of Electroencephalogram Pattern from Eye Response to Flickering Light

Electroencephalograph (EEG) has been widely used in brain wave mapping studies with several subject conditions, such as in evaluations of dementia and encephalopathy, screening for possible epileptic spikes, investigational for clinical use in mental disorders. In addition, the EEG has also been used to investigate the response of human brain in listening to music, movement of arm, and turning of neck. In this study, electroencephalograph was used to study the eye response to a 20 Hz flickering light. Brain waves recorded during the subject watching flickering light by using wireless electroencephalograph 14 channels. By recording the brain waves of the subject in the “Edf’s” format, the electroencephalogram was then analyzed using tools such as centering, filtering, and Welch’s power spectral density estimation. Using Power Spectra Density (PSD) graph, we can assess the active part of the lobes as eye responds to flickering light, i.e. parietal and occipital lobes. We found that the occipital lobe of six subjects from 9 subjects has higher average intensity in the right side than in the left. Parietal lobe of all subjects also has higher average intensity in the right side than in the left.

Multi-sensory Gamma Stimulation Ameliorates Alzheimer’s-Associated Pathology and Improves Cognition

We previously reported that inducing gamma oscillations with a non-invasive light flicker (gamma entrainment using sensory stimulus or GENUS) impacted pathology in the visual cortex of Alzheimer's disease mouse models. Here, we designed auditory tone stimulation that drove gamma frequency neural activity in auditory cortex (AC) and hippocampal CA1. Seven days of auditory GENUS improved spatial and recognition memory and reduced amyloid in AC and hippocampus of 5XFAD mice. Changes in activation responses were evident in microglia, astrocytes, and vasculature. Auditory GENUS also reduced phosphorylated tau in the P301S tauopathy model. Furthermore, combined auditory and visual GENUS, but not either alone, produced microglial-clustering responses, and decreased amyloid in medial prefrontal cortex. Whole brain analysis using SHIELD revealed widespread reduction of amyloid plaques throughout neocortex after multi-sensory GENUS. Thus, GENUS can be achieved through multiple sensory modalities with wide-ranging effects across multiple brain areas to improve cognitive function.

Retinal vasodilatation in the affected eye but reduced pressure autoregulation of both eyes in unilateral Coats' disease.

Coats' disease is characterized by vascular hyperpermeability, oedema and accumulation of exudates related to impairment of retinal vascular function. The background for the development of the disease is unknown, but it is likely that the study of diameter changes of retinal vessels may contribute to understanding the pathophysiology of the disease. In seven patients with unilateral Coats' disease (mean age=34.7years, range: 11-69years), the baseline diameter and reactivity of retinal vessels during an increase in the arterial blood pressure by isometric exercise and in the metabolism by flicker stimulation were measured on video recordings of the retina obtained with the Dynamic Vessel Analyzer. The baseline diameter of retinal vessels was larger in the affected than in the unaffected eyes which was significant for the arterioles (p=0.02), but not for the venules (p=0.15). During an increase in the arterial blood pressure induced by isometric exercise, the normal contraction of arterioles was absent in both eyes (p>0.7), whereas there was a significant dilatation of the venules in the unaffected eyes (p=0.04). Stimulation with flickering light induced normal dilatation of retinal vessels in both affected and unaffected eyes. Unilateral Coats' disease is accompanied by vasodilatation in the affected eye but impaired pressure autoregulation in both eyes. A further investigation of the disease should include an elucidation of the background for dilatation of retinal vessels in affected eyes and whether impaired pressure autoregulation can be found in vessels elsewhere in the body.

Quantitative analysis of unconsciousness in extremely low frequency-inducing flickering light sensation

A flickering light sensation induced by the extremely low frequency stimulus to retina is known as the one and only phenomenon that the human body can vividly perceive with a biological effect with the use of very weak magnetic fields. Because the flicker sensation can be made visible by direct stimulus to retina, deliberations for details in the retinal receptivity of the sensation are of great importance. In this paper, we examined the several flows of retinal capacities with the extremely low frequency-inducing flicker, employing a functional brain-imaging technique as well as an original human reliability test equipped with spot-detections at irregular intervals. In the results of our functional brain-imaging analyses, the occipital hemodynamics corresponding to the spot-detections were enhanced noticeably when compared with a control experiment. On the other hand, the error rates in the correct spot-detections at the threshold for the flicker perception were significantly poorer in most of eight subjects. The error rates at 80% of the threshold were decreased in no more than five among the subjects; of particular note is, the rates at 70% of the threshold were maintained in two of them. Our experimental results support the fact that extremely low frequency stimuli can reveal definite subliminal effects – – human error, unconsciousness, synaptic plasticity, etc. – – to the human visual perceptions.

Hemodynamic Response of the Three Macular Capillary Plexuses in Dark Adaptation and Flicker Stimulation Using Optical Coherence Tomography Angiography.

PurposeTo assess retinal microvascular reactivity during dark adaptation and the transition to ambient light and after flicker stimulation using optical coherence tomography angiography (OCTA).MethodsFifteen eyes of 15 healthy participants were dark adapted for 45 minutes followed by OCTA imaging in the dark-adapted state. After 5 minutes of normal lighting, subjects underwent OCTA imaging. Participants were then subjected to a flashing light-emitting diode (LED) light and repeat OCTA. Parafoveal vessel density and adjusted flow index (AFI) were calculated for superficial (SCP), middle (MCP), and deep capillary plexuses (DCP), and then compared between conditions after adjusting for age, refractive error, and scan quality. SCP vessel length density (VLD) was also evaluated. Between-condition capillary images were aligned and subtracted to identify differences. We then analyzed images from 10 healthy subjects during the transition from dark adaptation to ambient light.ResultsSCP vessel density was significantly higher while SCP VLD was significantly lower during ambient light and flicker compared to dark adaptation. There was a significant positive mean value for DCP “flicker minus dark or light,” suggesting more visible vessels during flicker due to changes in flow, dilation, or vessel recruitment. We found a significant, transient increase in SCP and decrease in both MCP and DCP vessel density during the transition from dark to light.ConclusionsWe show evidence suggesting constriction of deeper vessels and dilation of large SCP vessels during the transition from dark to light. This contrasts to redistribution of blood flow to deeper layers during dark adaptation and flicker stimulation.

Light Emitting Diode Lighting Flicker, its Impact on Health and the Need to Minimise it

Light Emitting Diode Lighting Flicker, its Impact on Health and the Need to Minimise it

Bit-Shuffle Coding for Flicker Mitigation in Visible Light Communication

Visible light communication (VLC) is a promising technology for both wireless communications and illumination via light-emitting diodes (LEDs). Although conventional run-length-limited (RLL) codes are employed to mitigate modulation-induced flickers, they can suffer from data rate reduction, worst-case bit sequences, and hardware overheads, resulting in a performance bottleneck. In this paper, we introduce a novel VLC data-encoding algorithm using bit shuffling to resolve these problems while alleviating light flickers. In contrast to existing RLL coding approaches, bit shuffling with an Omega network can generate codewords dynamically, which guarantees short runs of consecutive 0’s or 1’s, avoidance of worst-case bit sequences, and a relatively short code length. To illustrate the performance of hardware implementations, we discuss the hardware designs of the proposed bit-shuffle coding scheme. Our simulation results demonstrate the effectiveness of the bit-shuffle coding approach in terms of mitigation of flickering, transmission efficiency, and hardware overheads.

Dissensus, Irony, Dialectic

Dissensus, Irony, Dialectic

Evaluation of critical flicker-fusion frequency measurement methods using a touchscreen-based visual temporal discrimination task in the behaving mouse

The critical flicker-fusion frequency (CFF), defined as the frequency at which a flickering light is indistinguishable from a continuous light, is a useful measure of visual temporal resolution. The mouse CFF has been studied by electrophysiological approaches such as recordings of the electroretinogram (ERG) and the visually evoked potential (VEP), but it has not been measured behaviorally. Here we estimated the mouse CFF by using a touchscreen based operant system. The test with ascending series of frequencies and that with randomized frequencies resulted in about 17 and 14 Hz, respectively, as the frequency which could not be distinguished from steady lights. Since the ascending method of limits tend to overestimate the threshold than the descending method, we estimated the mouse CFF to be about 14 Hz. Our results highlight usefulness of the operant conditioning method in measurement of the mouse visual temporal resolution.

Evaluation of sex differences in flicker light induced vasodilation and central retinal thickness in healthy young subjects.

Evaluation of sex differences in flicker light induced vasodilation and central retinal thickness in healthy young subjects.

Effect of green flickering light on myopia development and expression of M1 muscarinic acetylcholine receptor in guinea pigs.

To investigate the effects of green flickering light on refractive development and expression of muscarinic acetylcholine receptor (mAChR) M1 in the eyes of guinea pigs. Thirty guinea pigs (15-20 days old) were randomly divided into three groups (n=10/group). Animals in group I were raised in a completely closed carton with green flickering light illumination. Those in group II were kept in the open top closed carton under normal natural light. Guinea pigs were raised in a sight-widen cage under normal natural light in group III. The refractive status and axial length were measured before and after 8 weeks' illumination. Moreover, total RNA extracted from retinal, choroidal, and scleral tissues were determined by real-time reverse transcription polymerase chain reaction (RT-PCR). The expressions of the receptor M1 were also explored in the retina, choroid, and sclera using immunohistochemistry. There was a remarkable reduction in refractive error and increase in axial length after 8-weeks' green flickering light stimulation (P<0.001). The expression of M1 receptor mRNA in sclera and retina in myopia group were remarkably lower than that in group II and III (P<0.01). Significant reduced expression of M1 receptor stimulated by green flickering light in retina and sclera tissues were also observed (P<0.05). However, there was no M1 receptor expression in choroid in 3 groups. Myopia can be induced by 8 weeks' green flickering light exposure in the animal model. M1 receptor may be involved causally or protectively in myopia development.

Feed-Forward Control Circuit for CFL Ballast Compatible with TRIAC Based Dimmer

Conventional triac based dimmer for light dimming of compact fluorescent lamps (CFLs) results in poor power factor (PF) and light flickering. In this paper a feed-forward control circuit based on phase-cut dimmer capable of regulating lamp power from 10% to full power with high PF and without flickering is proposed. The control circuit detects the firing angle (α) of the triac based dimmer and determines the duty cycle of the switch of CFL ballast circuit. The control circuit is located inside the CFL as part of its electronic ballast and then the relevant lighting circuit of the CFL does not need any additional wiring to the triac based dimmer. The lamp power is regulated by both the duty cycle of the ballast single switch and the input voltage cut. The proposed control circuit offers simplicity, high PF, low crest factor (CF) and zero voltage switching over the whole dimming range. To verify proper operation of the proposed control circuit, a laboratory prototype of the proposed control circuit compatible with an electronic ballast topology is implemented for a 42 W CFL lamp tube. Experimental results confirm the analysis and design of the proposed control circuit.

Os limites do modelo de cidade turística de Cabo Frio, RJ: quando a luz acende e apaga.

O turismo e uma atividade economica importante e diretamente articulada ao poder publico e ao mercado imobiliario, produzindo a mercantilizacao dos elementos do meio ambiente, a ocupacao e dominio do litoral brasileiro, e, o processo de reestruturacao urbana de muitas cidades do litoral brasileiro. A cidade de Cabo Frio (interior do Rio de Janeiro) transforma-se em uma cidade de turismo e estadia temporaria a partir da segunda metade do seculo XX, contudo, o modelo de cidade turistica e de estadia temporaria produzido na cidade apresenta limites e conflitos.