Calcium-Mediated Actin Reset (Caar) Mediates Acute Cell Adaptations

Actin has well established functions in cellular morphogenesis. However, it is not well understood how the various actin assemblies in a cell are kept in a dynamic equilibrium, in particular when cells have to respond to acute signals. Here, we characterize a rapid and transient actin reset in response to increased intracellular calcium levels. Within seconds of calcium influx, the formin INF2 stimulates filament polymerization at the endoplasmic reticulum (ER), while cortical actin is disassembled. The reaction is then reversed within a few minutes. This Calcium-mediated actin reset (CaAR) occurs in a wide range of mammalian cell types and in response to many physiological cues. CaAR leads to transient immobilization of organelles, drives reorganization of actin during cell cortex repair, cell spreading and wound healing, and induces long-lasting changes in gene expression. Our findings suggest that CaAR acts as fundamental facilitator of cellular adaptations in response to acute signals and stress

Isotropic actomyosin dynamics promote organization of the apical cell cortex in epithelial cells

Although cortical actin plays an important role in cellular mechanics and morphogenesis, there is surprisingly little information on cortex organization at the apical surface of cells. In this paper, we characterize organization and dynamics of microvilli (MV) and a previously unappreciated actomyosin network at the apical surface of Madin–Darby canine kidney cells. In contrast to short and static MV in confluent cells, the apical surfaces of nonconfluent epithelial cells (ECs) form highly dynamic protrusions, which are often oriented along the plane of the membrane. These dynamic MV exhibit complex and spatially correlated reorganization, which is dependent on myosin II activity. Surprisingly, myosin II is organized into an extensive network of filaments spanning the entire apical membrane in nonconfluent ECs. Dynamic MV, myosin filaments, and their associated actin filaments form an interconnected, prestressed network. Interestingly, this network regulates lateral mobility of apical membrane probes such as integrins or epidermal growth factor receptors, suggesting that coordinated actomyosin dynamics contributes to apical cell membrane organization

Only Time will Tell the Future : Anticipatory saccades reveal the temporal dynamics of time-based location and task expectancy

Humans form associations between time intervals and subsequent events and thus develop time-based expectancies that enable time-based action preparation. For instance, when each of two foreperiods (short vs. long) is frequently paired with one specific task (e.g., number magnitude judgment vs. number parity judgment) and infrequently with the alternative task, participants are faster to respond to frequent rather than infrequent foreperiod–task combinations. Here, we investigated the time course of time based task expectancy by measuring eye movements toward a left and right target location. Foreperiods predicted target locations with 100% validity and tasks with 90% validity. In 2 experiments, without having any explicit knowledge about the foreperiod–location or foreperiod–task contingencies, participants first moved their eyes to the location associated with the short foreperiod and then looked toward the location of the long foreperiod (if no stimulus had been presented after the short foreperiod had passed). That is, they proactively moved their eyes to optimize perception in line with the specific time and location they expected an event to occur at. Importantly, these eye movements reflected not only time-based location expectations, but also time-based task expectations. We discuss new insights in time-based expectancy and its temporal dynamics obtained from anticipatory eye movements and highlight spontaneous eye movements as a window into cognitive processes that cannot be assessed via behavioral response measures

Time-based expectancy in temporally structured task switching

In many situations, people have to switch between different tasks. Previous research has shown that task switching leads to relatively slow responses and high error rates. In many real-life task-switching contexts, tasks are not randomly distributed over time, but the temporal distribution of tasks carries information. Often the delay before a task predicts to some degree which task it will be, like when a longer browser loading time for a website makes the search for an alternative more likely. The present study investigated whether and how humans adapt to such temporal regularities. In a series of five experiments, intertask delays predicted with different probabilities the task in the upcoming trial, or whether the task switches in the upcoming trial. Participants adapted their response behavior to the predictability of the task, for all tested degrees of predictability (70%, 80%, 90%), but only for the degree of 90% predictability when the task transition was temporally predictable. The adaptation was implicit and task repetitions as well as switches, both benefitted from this adaptation. Likewise, performance after 500 ms and 1,500 ms delays was facilitated by time-based predictability. The results are discussed in the context of previous findings on nontemporal task predictability. (PsycINFO Database Record. (c) 2018 APA, all rights reserved)

Quality ratings of wine Bottles in E-commerce : The influence of time delays and spatial arrangement

The present study, for the first time, investigated the influence of time delays and the spatial arrangement of products on the quality rating of wine bottles in an online wine shop. For this purpose, an online shop was simulated in which participants selected various wine bottles from an overview page. After participants had selected a wine bottle, an enlarged version was presented after a system response time of either 200 or 1400 ms. Participants then viewed and rated wine bottles from various locations on the website overview page. Results showed that the average quality ratings after the short and the long system response time did not differ. However, products presented on the left or the right side of the overview page received worse ratings than wine bottles presented in the centre. By explicitly comparing the influence of temporal delays and spatial arrangement of products on quality ratings in an online shop, we derived best practice suggestions for the interface design in online shopping environments