32 research outputs found

    Contextual effects in Bayesian inference of interval timing

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    Do we really need to write documentation for a system? CASE tool add-ons: generator+editor for a precise documentation

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    One of the common problems of system development projects is that the system documentation is often outdated and does not describe the latest version of the system. The situation is even more complicated if we are speaking not about a natural language description of the system, but about its formal specification. In this paper we discuss how the problem could be solved by updating the documentation automatically, by generating a new formal specification from the model if the model is frequently changed.Comment: In Proceedings International Conference on Model-Driven Engineering and Software Development (MODELSWARD'13

    Temporal bisection is influenced by ensemble statistics of the stimulus set

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    Although humans are well capable of precise time measurement, their duration judgments are nevertheless susceptible to temporal context. Previous research on temporal bisection has shown that duration comparisons are influenced by both stimulus spacing and ensemble statistics. However, theories proposed to account for bisection performance lack a plausible justification of how the effects of stimulus spacing and ensemble statistics are actually combined in temporal judgments. To explain the various contextual effects in temporal bisection, we develop a unified ensemble-distribution account (EDA), which assumes that the mean and variance of the duration set serve as a reference, rather than the short and long standards, in duration comparison. To validate this account, we conducted three experiments that varied the stimulus spacing (Experiment 1), the frequency of the probed durations (Experiment 2), and the variability of the probed durations (Experiment 3). The results revealed significant shifts of the bisection point in Experiments 1 and 2, and a change of the sensitivity of temporal judgments in Experiment 3-which were all well predicted by EDA. In fact, comparison of EDA to the extant prior accounts showed that using ensemble statistics can parsimoniously explain various stimulus set-related factors (e.g., spacing, frequency, variance) that influence temporal judgments

    Influences of luminance contrast and ambient lighting on visual context learning and retrieval

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    Invariant spatial context can guide attention and facilitate visual search, an effect referred to as “contextual cueing.” Most previous studies on contextual cueing were conducted under conditions of photopic vision and high search item to background luminance contrast, leaving open the question whether the learning and/or retrieval of context cues depends on luminance contrast and ambient lighting. Given this, we conducted three experiments (each contains two subexperiments) to compare contextual cueing under different combinations of luminance contrast (high/low) and ambient lighting (photopic/mesopic). With high-contrast displays, we found robust contextual cueing in both photopic and mesopic environments, but the acquired contextual cueing could not be transferred when the display contrast changed from high to low in the photopic environment. By contrast, with low-contrast displays, contextual facilitation manifested only in mesopic vision, and the acquired cues remained effective following a switch to high-contrast displays. This pattern suggests that, with low display contrast, contextual cueing benefited from a more global search mode, aided by the activation of the peripheral rod system in mesopic vision, but was impeded by a more local, fovea-centered search mode in photopic vision

    Duration reproduction under memory pressure: Modeling the roles of visual memory load in duration encoding and reproduction

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    Duration estimates are often biased by the sampled statistical context, yielding the classical central-tendency effect, i.e., short durations are over- and long duration underestimated. Most studies of the central-tendency bias have primarily focused on the integration of the sensory measure and the prior information, without considering any cognitive limits. Here, we investigated the impact of cognitive (visual working-memory) load on duration estimation in the duration encoding and reproduction stages. In four experiments, observers had to perform a dual, attention-sharing task: reproducing a given duration (primary) and memorizing a variable set of color patches (secondary). We found an increase in memory load (i.e., set size) during the duration-encoding stage to increase the central-tendency bias, while shortening the reproduced duration in general; in contrast, increasing the load during the reproduction stage prolonged the reproduced duration, without influencing the central tendency. By integrating an attentional-sharing account into a hierarchical Bayesian model, we were able to predict both the general over- and underestimation and the central-tendency effects observed in all four experiments. The model suggests that memory pressure during the encoding stage increases the sensory noise, which elevates the central-tendency effect. In contrast, memory pressure during the reproduction stage only influences the monitoring of elapsed time, leading to a general duration over-reproduction without impacting the central tendency.Competing Interest StatementThe authors have declared no competing interest

    Severe Biallelic Loss-of-function Mutations in Nicotinamide Mononucleotide Adenylyltransferase 2 (NMNAT2) in Two Fetuses with Fetal Akinesia Deformation Sequence

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    The three nicotinamide mononucleotide adenylyltransferase (NMNAT) family members synthesize the electron carrier nicotinamide adenine dinucleotide (NAD+) and are essential for cellular metabolism. In mammalian axons, NMNAT activity appears to be required for axon survival and is predominantly provided by NMNAT2. NMNAT2 has recently been shown to also function as a chaperone to aid in the refolding of misfolded proteins. Nmnat2 deficiency in mice, or in its ortholog dNmnat in Drosophila, results in axon outgrowth and survival defects. Peripheral nerve axons in NMNAT2-deficient mice fail to extend and innervate targets, and skeletal muscle is severely underdeveloped. In addition, removing NMNAT2 from established axons initiates axon death by Wallerian degeneration. We report here on two stillborn siblings with fetal akinesia deformation sequence (FADS), severely reduced skeletal muscle mass and hydrops fetalis. Clinical exome sequencing identified compound heterozygous NMNAT2 variant alleles in both cases. Both protein variants are incapable of supporting axon survival in mouse primary neuron cultures when overexpressed. In vitro assays demonstrate altered protein stability and/or defects in NAD+ synthesis and chaperone functions. Thus, both patient NMNAT2 alleles are null or severely hypo-morphic. These data indicate a previously unknown role for NMNAT2 in human neurological development and provide the first direct molecular evidence to support the involvement of Wallerian degeneration in a human axonal disorder.Funding for the project comes from the NIH (R.W.S. R01NS085023; R.G.Z. R56NS095893), the UK Medical Research Council grant (J.G. MR/N004582/1), the John and Lucille van Geest Foundation (M.C.) and the Taishan Scholar Project of Shandong Province, China (R.G.Z.)

    Inhibition of 26S Protease Regulatory Subunit 7 (MSS1) Suppresses Neuroinflammation

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    Recently, researchers have focused on immunosuppression induced by rifampicin. Our previous investigation found that rifampicin was neuroprotective by inhibiting the production of pro-inflammatory mediators, thereby suppressing microglial activation. In this study, using 2-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS), we discovered that 26S protease regulatory subunit 7 (MSS1) was decreased in rifampicin-treated microglia. Western blot analysis verified the downregulation of MSS1 expression by rifampicin. As it is indicated that the modulation of the ubiquitin-26S proteasome system (UPS) with proteasome inhibitors is efficacious for the treatment of neuro-inflammatory disorders, we next hypothesized that silencing MSS1 gene expression might inhibit microglial inflammation. Using RNA interference (RNAi), we showed significant reduction of IkBα degradation and NF-kB activation. The production of lipopolysaccharides-induced pro-inflammatory mediators such as inducible nitric oxide synthase (iNOS), nitric oxide, cyclooxygenase-2, and prostaglandin E2 were also reduced by MSS1 gene knockdown. Taken together, our findings suggested that rifampicin inhibited microglial inflammation by suppressing MSS1 protein production. Silencing MSS1 gene expression decreased neuroinflammation. We concluded that MSS1 inhibition, in addition to anti-inflammatory rifampicin, might represent a novel mechanism for the treatment of neuroinflammatory disorders

    Crossmodal learning of target-context associations: When would tactile context predict visual search?

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    It is well established that statistical learning of visual target locations in relation to constantly positioned visual distractors facilitates visual search. In the present study, we investigated whether such a contextual-cueing effect would also work crossmodally, from touch onto vision. Participants responded to the orientation of a visual target singleton presented among seven homogenous visual distractors. Four tactile stimuli, two to different fingers of each hand, were presented either simultaneously with or prior to the visual stimuli. The identity of the stimulated fingers provided the crossmodal context cue: in half of the trials, a given visual target location was consistently paired with a given tactile configuration. The visual stimuli were presented above the unseen fingers, ensuring spatial correspondence between vision and touch. We found no evidence of crossmodal contextual cueing when the two sets of items (tactile, visual) were presented simultaneously (Experiment 1). However, a reliable crossmodal effect emerged when the tactile distractors preceded the onset of visual stimuli 700 ms (Experiment 2). But crossmodal cueing disappeared again when, after an initial learning phase, participants flipped their hands, making the tactile distractors appear at different positions in external space while their somatotopic positions remained unchanged (Experiment 3). In all experiments, participants were unable to explicitly discriminate learned from novel multisensory arrays. These findings indicate that search-facilitating context memory can be established across vision and touch. However, in order to guide visual search, the (predictive) tactile configurations must be remapped from their initial somatotopic into a common external representational format

    Polysaccharide monooxygenase-catalyzed oxidation of cellulose to glucuronic acid-containing cello-oligosaccharides

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    Abstract Background Polysaccharide monooxygenases (PMOs) play an important role in the enzymatic degradation of cellulose. They have been demonstrated to able to C6-oxidize cellulose to produce C6-hexodialdoses. However, the biological function of C6 oxidation of PMOs remains unknown. In particular, it is unclear whether C6-hexodialdoses can be further oxidized to uronic acid (glucuronic acid-containing oligosaccharides). Results A PMO gene, Hipmo1, was isolated from Humicola insolens and expressed in Pichia pastoris. This PMO (HiPMO1), belonging to the auxiliary activity 9 (AA9) family, was shown to able to cleave cellulose to yield non-oxidized and oxidized cello-oligosaccharides. The enzyme oxidizes C6 positions in cellulose to form glucuronic acid-containing cello-oligosaccharides, followed by hydrolysis with beta-glucosidase and beta-glucuronidase to yield glucose, glucuronic acid, and saccharic acid. This indicates that HiPMO1 can catalyze C6 oxidation of hydroxyl groups of cellulose to carboxylic groups. Conclusions HiPMO1 oxidizes C6 of cellulose to form glucuronic acid-containing cello-oligosaccharides followed by hydrolysis with beta-glucosidase and beta-glucuronidase to yield glucose, glucuronic acid, and saccharic acid, and even possibly by beta-eliminative cleavage to produce unsaturated cello-oligosaccharides. This study provides a new mechanism for cellulose cleavage by C6 oxidation of HiPMO1

    Anthraquinone dyes as photosensitizers for dye-sensitized solar cells

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    Three anthraquinone dyes with carboxylic acid as anchoring group are designed and synthesized as sensitizers for dye-sensitized solar cells (DSSCs). Preliminary photophys. and photoelectrochem. measurements show that these anthraquinone dyes have very low performance on DSSC applications, although they have broad and intense absorption spectra in the visible region (up to 800 nm). Transient absorption kinetics, fluorescence lifetime measurements and d. functional theory (DFT) calcns. are conducted to investigate the cause of such low DSSC performance for these dyes. The strong electron-withdrawing character of the two carbonyl groups on anthraquinone framework may lie behind the low performance by suppressing the efficient electron injection from the dye to the conduction band of TiO2
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