Contrast gain and power savings using local dimming backlights

2008 ◽  
Vol 16 (12) ◽  
pp. 1237 ◽  
Author(s):  
Erno H. A. Langendijk ◽  
Remco Muijs ◽  
William van Beek
Keyword(s):  
Contrast Gain ◽  
Local Dimming

scholarly journals Supersaturation of VEP in Migraine without Aura Patients Treated with Topiramate: An Anatomo-Functional Biomarker of the Disease

2021 ◽  
Vol 10 (4) ◽  
pp. 769
Author(s):  
Ciro De Luca ◽  
Sara Gori ◽  
Sonia Mazzucchi ◽  
Elisa Dini ◽  
Martina Cafalli ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Cortical Neurons ◽  
Migraine Without Aura ◽  
Inverse Correlation ◽  
Primary Headache ◽  
Contrast Gain ◽  
High Prevalence ◽  
Functional Pathway ◽  
Inhibitory Signaling ◽  
Potential Use

Migraine is a primary headache with high prevalence among the general population, characterized by functional hypersensitivity to both exogenous and endogenous stimuli particularly affecting the nociceptive system. The hyperresponsivity of cortical neurons could be due to a disequilibrium in the excitatory/inhibitory signaling. This study aimed to investigate the anatomo-functional pathway from the retina to the primary visual cortex using visual evoked potentials (VEP). Contrast gain protocol was used in 15 patients diagnosed with migraine without aura (at baseline and after 3 months of topiramate therapy) and 13 controls. A saturation (S) index was assessed to monitor the response of VEP’s amplitude to contrast gain. Non-linear nor monotone growth of VEP (S < 0.95) was defined as supersaturation. A greater percentage of migraine patients (53%) relative to controls (7%) showed this characteristic. A strong inverse correlation was found between the S index and the number of days separating the registration of VEP from the next migraine attack. Moreover, allodynia measured through the Allodynia Symptoms Check-list (ASC-12) correlates with the S index both at baseline and after 3 months of topiramate treatment. Other clinical characteristics were not related to supersaturation. Topiramate therapy, although effective, did not influence electrophysiological parameters suggesting a non-intracortical nor retinal origin of the supersaturation (with possible involvement of relay cells from the lateral geniculate nucleus). In conclusion, the elaboration of visual stimuli and visual cortex activity is different in migraine patients compared to controls. More data are necessary to confirm the potential use of the S index as a biomarker for the migraine cycle (association with the pain-phase) and cortical sensitization (allodynia).

EXPRESS: How the size of exogenous attentional cues alters visual performance: from response gain to contrast gain

2021 ◽  
pp. 174702182110248
Author(s):  
Xiaogang Wu ◽  
Aijun Wang ◽  
Ming Zhang
Keyword(s):  
Visual Selective Attention ◽  
Visual Performance ◽  
Target Size ◽  
Field Size ◽  
Gain Modulation ◽  
Absolute Size ◽  
Contrast Gain ◽  
Exogenous Cues ◽  
Exogenous Cue ◽  
Attentional Cues

The normalization model of attention (NMoA) predicts that the attention gain pattern is mediated by changes in the size of the attentional field and stimuli. However, existing studies have not measured gain patterns when the relative sizes of stimuli are changed. To investigate the NMoA, the present study manipulated the attentional field size, namely, the exogenous cue size. Moreover, we assessed whether the relative rather than the absolute size of the attentional field matters, either by holding the target size constant and changing the cue size (experiments 1-3) or by holding the cue size constant and changing the target size (experiment 4), in a spatial cueing paradigm of psychophysical procedures. The results show that the gain modulations changed from response gain to contrast gain when the precue size changed from small to large relative to the target size (experiments 1-3). Moreover, when the target size was once again made larger than the precue size, there was still a change in response gain (experiment 4). These results suggest that the size of exogenous cues plays an important role in adjusting the attentional field and that relative changes rather than absolute changes to exogenous cue size determine gain modulation. These results are consistent with the prediction of the NMoA and provide novel insights into gain modulations of visual selective attention.

scholarly journals Oscillatory Ca2+ Signaling in the Isolated Caenorhabditis elegans Intestine

2005 ◽  
Vol 126 (4) ◽  
pp. 379-392 ◽  
Author(s):  
Maria V. Espelt ◽  
Ana Y. Estevez ◽  
Xiaoyan Yin ◽  
Kevin Strange
Keyword(s):  
Caenorhabditis Elegans ◽  
Intestinal Epithelium ◽  
Oscillation Frequency ◽  
Gene Networks ◽  
Molecular Mechanisms ◽  
Apical Cell ◽  
Intestinal Cell ◽  
C Elegans ◽  
Contrast Gain ◽  
Behavioral Rhythm

Defecation in the nematode Caenorhabditis elegans is a readily observable ultradian behavioral rhythm that occurs once every 45–50 s and is mediated in part by posterior body wall muscle contraction (pBoc). pBoc is not regulated by neural input but instead is likely controlled by rhythmic Ca2+ oscillations in the intestinal epithelium. We developed an isolated nematode intestine preparation that allows combined physiological, genetic, and molecular characterization of oscillatory Ca2+ signaling. Isolated intestines loaded with fluo-4 AM exhibit spontaneous rhythmic Ca2+ oscillations with a period of ∼50 s. Oscillations were only detected in the apical cell pole of the intestinal epithelium and occur as a posterior-to-anterior moving intercellular Ca2+ wave. Loss-of-function mutations in the inositol-1,4,5-trisphosphate (IP3) receptor ITR-1 reduce pBoc and Ca2+ oscillation frequency and intercellular Ca2+ wave velocity. In contrast, gain-of-function mutations in the IP3 binding and regulatory domains of ITR-1 have no effect on pBoc or Ca2+ oscillation frequency but dramatically increase the speed of the intercellular Ca2+ wave. Systemic RNA interference (RNAi) screening of the six C. elegans phospholipase C (PLC)–encoding genes demonstrated that pBoc and Ca2+ oscillations require the combined function of PLC-γ and PLC-β homologues. Disruption of PLC-γ and PLC-β activity by mutation or RNAi induced arrhythmia in pBoc and intestinal Ca2+ oscillations. The function of the two enzymes is additive. Epistasis analysis suggests that PLC-γ functions primarily to generate IP3 that controls ITR-1 activity. In contrast, IP3 generated by PLC-β appears to play little or no direct role in ITR-1 regulation. PLC-β may function instead to control PIP2 levels and/or G protein signaling events. Our findings provide new insights into intestinal cell Ca2+ signaling mechanisms and establish C. elegans as a powerful model system for defining the gene networks and molecular mechanisms that underlie the generation and regulation of Ca2+ oscillations and intercellular Ca2+ waves in nonexcitable cells.

Sorted Sector Covering Combined with Image Condensation — An Efficient Method for Local Dimming of Direct-Lit and Edge-Lit LCDs

2010 ◽  
Vol E93-C (11) ◽  
pp. 1556-1563 ◽  
Author(s):  
Marc ALBRECHT ◽  
Andreas KARRENBAUER ◽  
Tobias JUNG ◽  
Chihao XU
Keyword(s):  
Efficient Method ◽  
Local Dimming

Contrast adaptation and contrast gain control

1991 ◽  
Vol 87 (1) ◽  
Author(s):  
L.M. M��tt�nen ◽  
J.J. Koenderink
Keyword(s):  
Gain Control ◽  
Contrast Gain ◽  
Contrast Gain Control ◽  
Contrast Adaptation

Effect of temporal sparseness and dichoptic presentation on multifocal visual evoked potentials

2005 ◽  
Vol 22 (1) ◽  
pp. 45-54 ◽  
Author(s):  
ANDREW C. JAMES ◽  
RASA RUSECKAITE ◽  
TED MADDESS
Keyword(s):  
Visual Field ◽  
Human Subjects ◽  
Signal To Noise ◽  
Recording Time ◽  
Contrast Gain ◽  
Upper Visual Field ◽  
Multifocal Vep ◽  
Normal Human ◽  
Time Decomposition ◽  
Peak Value

Multifocal VEP (mfVEP) responses were obtained from 13 normal human subjects for nine test conditions, covering three viewing conditions (dichoptic and left and right monocular), and three different temporal stimulation forms (rapid contrast reversal, rapid pattern pulse presentation, and slow pattern pulse presentation). The rapid contrast reversal stimulus had pseudorandomized reversals of checkerboards in each visual field region at a mean rate of 25 reversals/s, similar to most mfVEP studies to date. The rapid pattern pulse presentation had pseudorandomized presentations of a checkerboard for one frame, interspersed with uniform grey frames, with a mean rate of 25 presentations/s per region per eye. The slow pattern pulse stimulus had six presentations/s per region per eye. Recording time was 5.3 min/condition. For dichoptic presentation slow pattern pulse responses were 4.6 times larger in amplitude than the contrast reversal responses. Binocular suppression was greatest for the contrast reversal stimulus. Consideration of the signal-to-noise ratios indicated that to achieve a given level of reliability, slow pattern pulse stimuli would require half the recording time of contrast reversal stimuli for monocular viewing, and 0.4 times the recording time for dichoptically presented stimuli. About half the responses to the slow pattern pulse stimuli had peak value exceeding five times their estimated standard error. Responses were about 20% smaller in the upper visual field locations. Space–time decomposition showed that responses to slow pattern pulse were more consistent across visual field locations. We conclude that the pattern pulse stimuli, which we term temporally sparse, maintain the visual system in a high contrast gain state. This more than compensates for the smaller number of presentations in the run, and provides signal-to-noise advantages that may be valuable in clinical application.

How to reduce light leakage and clipping in local-dimming liquid-crystal displays

2009 ◽  
Vol 17 (12) ◽  
pp. 1051 ◽  
Author(s):  
Seong-Eun Kim ◽  
Joo-Young An ◽  
Jong-Ju Hong ◽  
Tae Wook Lee ◽  
Chang Gone Kim ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystal Displays ◽  
Local Dimming

scholarly journals Contrast Gain Reduction in Fly Motion Adaptation

Neuron ◽  
2000 ◽  
Vol 28 (2) ◽  
pp. 595-606 ◽  
Author(s):  
Robert A. Harris ◽  
David C. O'Carroll ◽  
Simon B. Laughlin
Keyword(s):  
Motion Adaptation ◽  
Contrast Gain ◽  
Gain Reduction

Contrast Adaptation in a Nonadapting LGN Model

2007 ◽  
Vol 98 (3) ◽  
pp. 1287-1296 ◽  
Author(s):  
Kate S. Gaudry ◽  
Pamela Reinagel
Keyword(s):  
Information Transmission ◽  
Detailed Comparison ◽  
Spike Timing ◽  
Physiological Data ◽  
Model Parameters ◽  
Transient Effects ◽  
Full Field ◽  
Contrast Gain ◽  
Contrast Adaptation ◽  
Contrast Normalization

Sensory neurons appear to adapt their gain to match the variance of signals along the dimension they encode, a property we shall call “contrast normalization.” Contrast normalization has been the subject of extensive physiological and theoretical study. We previously found that neurons in the lateral geniculate nucleus (LGN) exhibit contrast normalization in their responses to full-field flickering white-noise stimuli, and that neurons with the strongest contrast normalization best preserved information transmission across a range of contrasts. We have also shown that both of these properties could be reproduced by nonadapting model cells. Here we present a detailed comparison of this nonadapting model to physiological data from the LGN. First, the model cells recapitulated other contrast dependencies of LGN responses: decreasing stimulus contrast resulted in an increase in spike-timing jitter and spike-number variability. Second, we find that the extent of contrast normalization in this model depends on model parameters related to refractoriness and to noise. Third, we show that the model cells exhibit rapid, transient changes in firing rate just after changes in contrast, and that this is sufficient to produce the transient changes in information transmission that have been reported in other neurons. It is known that intrinsic properties of neurons change during contrast adaptation. Nevertheless the model demonstrates that the spiking nonlinearity of neurons can produce many of the temporal aspects of contrast gain control, including normalization to input variance and transient effects of contrast change.

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