Brightness change is optimal stimulus for parasol retinal ganglion cells

Magnocellular-projecting retinal ganglion cells show spike response in two cases. Firstly, as a result of presentation of the optimal stimulus. Secondly, rebound excitation when removing the opposite stimulus. Also, there are studies suggesting that rebound excitation meets conditions to participate in visual perception at the same sensitivity and reaction speed as a response to the optimal stimulus. Thus, white noise stimulation creates possibility to catch the form of a smooth transition from one type of response to another. Using freely available data, a spike-triggered behavior map was built that does not show the area of silence between those two types of spike triggers. Moreover, linear filter with biphasic temporal properties which work as the derivative kernel demonstrate that both responses are two sides of the same coin. Thus, it is suggested to determine the optimal stimulus for magnocellular-projecting retinal ganglion cells as brightness change according to concentric center–surround receptive field structure.

Unsupervised Learning of Depth and Camera Pose with Feature Map Warping

Estimating the depth of image and egomotion of agent are important for autonomous and robot in understanding the surrounding environment and avoiding collision. Most existing unsupervised methods estimate depth and camera egomotion by minimizing photometric error between adjacent frames. However, the photometric consistency sometimes does not meet the real situation, such as brightness change, moving objects and occlusion. To reduce the influence of brightness change, we propose a feature pyramid matching loss (FPML) which captures the trainable feature error between a current and the adjacent frames and therefore it is more robust than photometric error. In addition, we propose the occlusion-aware mask (OAM) network which can indicate occlusion according to change of masks to improve estimation accuracy of depth and camera pose. The experimental results verify that the proposed unsupervised approach is highly competitive against the state-of-the-art methods, both qualitatively and quantitatively. Specifically, our method reduces absolute relative error (Abs Rel) by 0.017–0.088.

Detection and cataloging of space debris’ small-sized fragment of the 20th stellar magnitude

На обсерватории Терскольского филиала ИНАСАН 24 сентября 2020 г. на комплексе телескопа Цейсс-2000 впервые был обнаружен и наблюдался в течение двух ночей фрагмент космического мусора 20-й звездной величины на геосинхронной орбите, что соответствует размерам менее 10 см. Объект был каталогизирован в динамической базе космических объектов ИПМ им. М.В. Келдыша под номером 71113. Топоцентрическое расстояние до фрагмента во время наблюдений менялось от 36862 км до 37224 км при фазовых углах от 53 ◦ до 68 ◦ , амплитуда изменения блеска объекта - от 19-й до 21-й звездной величины в интегральном свете. Приводятся параметры орбиты и диаграммы изменения блеска. On September 24, 2020, at the Terskol observatory of INASAN, a fragment of space debris’ of the 20th magnitude in geosynchronous orbit was first detected and observed for two nights using the Zeiss-2000 telescope, which corresponds to a size of less than 10 cm. The object was catalogued in the dynamic database of space objects of the Keldysh Institute of the RAS under the number 71113. The topocentric distance to the fragment during observations varied from 36862 km to 37224 km at phase angles from 53 ◦ to 68 ◦ . The object’s brightness ranged from the 19th to the 21st magnitude. The parameters of the orbit and the brightness change diagrams are given.

Navigational strategies underlying temporal phototaxis in Drosophila larvae

Navigating across light gradients is essential for survival for many animals. However, we still have a poor understanding of the algorithms that underlie such behaviors. Here we develop a novel phototaxis assay for Drosophila larvae in which light intensity is always spatially uniform but updates depending on the location of the animal in the arena. Even though larvae can only rely on temporal cues in this closed-loop setup, we find that they are capable of finding preferred areas of low light intensity. Further detailed analysis of their behavior reveals that larvae turn more frequently and that heading angle changes increase when they experience brightness increments over extended periods of time. We suggest that temporal integration of brightness change during runs is an important – and so far largely unexplored – element of phototaxis.Summary statementUsing a novel closed-loop behavioral assay, we show that Drosophila larvae can navigate light gradients exclusively using temporal cues. Analyzing and modeling their behavior in detail, we propose that larvae achieve this by integrating brightness change during runs.

From solar to stellar brightness variations

Context. Comparison studies of Sun-like stars with the Sun suggest an anomalously low photometric variability of the Sun compared to Sun-like stars with similar magnetic activity. Comprehensive understanding of stellar variability is needed to find a physical reason for this observation. Aims. We investigate the effect of metallicity and effective temperature on the photometric brightness change of Sun-like stars seen at different inclinations. The considered range of fundamental stellar parameters is sufficiently small so the stars investigated here still count as Sun-like or even as solar twins. Methods. To model the brightness change of stars with solar magnetic activity, we extended a well-established model of solar brightness variations based on solar spectra, Spectral And Total Irradiance REconstruction (SATIRE), to stars with different fundamental parameters. For this we calculated stellar spectra for different metallicities and effective temperature using the radiative transfer code ATLAS9. Results. We show that even a small change (e.g. within the observational error range) of metallicity or effective temperature significantly affects the photometric brightness change compared to the Sun. We find that for Sun-like stars, the amplitude of the brightness variations obtained for Strömgren (b + y)/2 reaches a local minimum for fundamental stellar parameters close to the solar metallicity and effective temperature. Moreover, our results show that the effect of inclination decreases for metallicity values greater than the solar metallicity. Overall, we find that an exact determination of fundamental stellar parameters is crucially important for understanding stellar brightness changes.

The White Effect

The White effect is an illusion in which gray test patches of identical luminance placed on the black and white bars of a square-wave grating appear different in brightness/lightness. The effect has received much attention because the direction of the brightness change does not correlate with the amount of black or white border in contact with the gray test patch or its general vicinity. The test patch on the black bar appears lighter than the test patch on the white bar despite changes in test patch height or inducing grating spatial frequency. In addition, although the test patch shows a smooth change in brightness/lightness as its spatial position is varied relative to the inducing grating, spatial inhomogeneities in brightness/lightness within the test patch are also visible. A large number of “higher-level” explanations have been offered for the White effect; only the oriented-difference-of-Gaussians model can account for all of these properties.

Adaptation to Brightness Change, Contours, Jogging, and Apparent Motion

Frisby and Stone have dubbed adaptation the “psychophysicist’s electrode” and John Mollon once famously said, “If it adapts, it’s there.” Psychologists piously hope that their many experiments on visual adaptation will tell physiologists where to look inside the brain. This chapter describes visual adaptation to temporal ramps, spatial edges, and apparent motion and touches on kinesthetic aftereffects from jogging. Sawtooth adaptation, a ramp aftereffect that is produced by gazing at a spatially uniform patch whose luminance is temporally modulated by a repetitive sawtooth, either gradually dimming and turning sharply back on (rapid-on) or gradually brightening and turning sharply back off (rapid-off), is discussed. Related concepts that are covered include pattern-specific contrast adaptation, contour adaptation, adaptation to apparent motion, and adapting to flicker, which changes apparent spatial frequency.