Learning a Bayesian prior in interval timing

Behavioral studies on perceptual learning (PL) often attributed an improvement in task performance to an enhancement in sensory processing of stimuli. However, the framework of Bayesian inference suggests that perceptual improvements can arise from learning-induced changes either in a likelihood function or in a prior expectation for sensory input. We developed and adapted Bayesian observer models to long-term changes in interval timing (IT) performance by human subjects to assess relative contributions of the prior and likelihood to PL of IT.

While subjects were viewing a small bar that drifted for a while and disappeared, we estimated subjective time intervals ([DELTA]Ts) from subjects’ natural reactions to the reappearance of the invisible bar at a designated location, with the speed and distance of invisible motion varied trial to trial. Ten subjects performed this task over 10 daily sessions for [DELTA]Ts ranging from 0.5 to 6.5 sec. 

In terms of timing accuracy, the trend that short and long [DELTA]Ts were overestimated and underestimated, respectively, was evident in all subjects and became stronger over sessions. In contrast, timing precision gradually improved over session for the entire set of sampled [DELTA]Ts. These seemingly contradictory dynamics of PL in accuracy and precision were captured simultaneously by Bayesian models, in which subjective timing is determined jointly by the prior and likelihood function for IT. The best among several nested models was a simple model in which only a single Gaussian function and a single coefficient of variance were set free to describe the prior and the likelihood functions, respectively. Interestingly, it was the spread of the prior, not the likelihood, that changed steadily in the model fit to the across-session data, suggesting that the improvements in timing precision observed in our and previous studies arose as the prior became sharpened through massive training.
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Regulation of fast-spiking basket cell synapses by the chloride channel ClC-2.

Parvalbumin-expressing, fast-spiking basket cells are important for the generation of synchronous, rhythmic population activities in the hippocampus. We found that GABAA receptor-mediated synaptic inputs from murine parvalbumin-expressing basket cells were selectively modulated by the membrane voltage- and intracellular chloride-dependent chloride channel ClC-2. Our data reveal a previously unknown cell type-specific regulation of intracellular chloride homeostasis in the perisomatic region of hippocampal pyramidal neurons

Stimulus Fractionation by Interocular Suppression

Can human observers distinguish physical removal of a visible stimulus from phenomenal suppression of that stimulus during binocular rivalry? As so often happens, simple questions produce complex answers, and that is the case in the study reported here. Using continuous flash suppression to produce binocular rivalry, we were able to identify stimulus conditions where most – but not all – people utterly fail to distinguish physical from phenomenal stimulus removal, although we can be certain that those two equivalent perceptual states are accompanied by distinct neural events. More interestingly, we find subtle variants of the task where distinguishing the two states is trivially easy, even for people who utterly fail under the original conditions. We found that stimulus features are differentially vulnerable to suppression. Observers are able to be aware of existence/removal of some stimulus attributes (flicker) but not others (orientation), implying that interocular suppression breaks down the unitary awareness of integrated features belonging to a visual object. These findings raise questions about the unitary nature of awareness and, also, place qualifications on the utility of binocular rivalry as a tool for studying the neural concomitants of conscious visual awareness

Multi-Color Luminescence Transition of Upconversion Nanocrystals via Crystal Phase Control with SiO2 for High Temperature Thermal Labels

Upconversion nanocrystals (UCNs)-embedded microarchitectures with luminescence color transition capability and enhanced luminescence intensity under extreme conditions are suitable for developing a robust labeling system in a high-temperature thermal industrial process. However, most UCNs based labeling systems are limited by the loss of luminescence owing to the destruction of the crystalline phase or by a predetermined luminescence color without color transition capability. Herein, an unusual crystal phase transition of UCNs to a hexagonal apatite phase in the presence of SiO2 nanoparticles is reported with the enhancements of 130-fold green luminescence and 52-fold luminance as compared to that of the SiO2-free counterpart. By rationally combining this strategy with an additive color mixing method using a mask-less flow lithography technique, single to multiple luminescence color transition, scalable labeling systems with hidden letters-, and multi-luminescence colored microparticles are demonstrated for a UCNs luminescence color change-based high temperature labeling system

Reconstituting ring-rafts in bud-mimicking topography of model membranes.

During vesicular trafficking and release of enveloped viruses, the budding and fission processes dynamically remodel the donor cell membrane in a protein- or a lipid-mediated manner. In all cases, in addition to the generation or relief of the curvature stress, the buds recruit specific lipids and proteins from the donor membrane through restricted diffusion for the development of a ring-type raft domain of closed topology. Here, by reconstituting the bud topography in a model membrane, we demonstrate the preferential localization of cholesterol- and sphingomyelin-enriched microdomains in the collar band of the bud-neck interfaced with the donor membrane. The geometrical approach to the recapitulation of the dynamic membrane reorganization, resulting from the local radii of curvatures from nanometre-to-micrometre scales, offers important clues for understanding the active roles of the bud topography in the sorting and migration machinery of key signalling proteins involved in membrane budding