Dissociable Neural Mechanisms Underlie the Effects of Attention on Visual Appearance and Response Bias.

A prominent theoretical framework spanning philosophy, psychology, and neuroscience holds that selective attention penetrates early stages of perceptual processing to alter the subjective visual experience of behaviorally relevant stimuli. For example, searching for a red apple at the grocery store might make the relevant color appear brighter and more saturated compared with seeing the exact same red apple while searching for a yellow banana. In contrast, recent proposals argue that data supporting attention-related changes in appearance reflect decision- and motor-level response biases without concurrent changes in perceptual experience. Here, we tested these accounts by evaluating attentional modulations of EEG responses recorded from male and female human subjects while they compared the perceived contrast of attended and unattended visual stimuli rendered at different levels of physical contrast. We found that attention enhanced the amplitude of the P1 component, an early evoked potential measured over visual cortex. A linking model based on signal detection theory suggests that response gain modulations of the P1 component track attention-induced changes in perceived contrast as measured with behavior. In contrast, attentional cues induced changes in the baseline amplitude of posterior alpha band oscillations (∼9-12 Hz), an effect that best accounts for cue-induced response biases, particularly when no stimuli are presented or when competing stimuli are similar and decisional uncertainty is high. The observation of dissociable neural markers that are linked to changes in subjective appearance and response bias supports a more unified theoretical account and demonstrates an approach to isolate subjective aspects of selective information processing.SIGNIFICANCE STATEMENT Does attention alter visual appearance, or does it simply induce response bias? In the present study, we examined these competing accounts using EEG and linking models based on signal detection theory. We found that response gain modulations of the visually evoked P1 component best accounted for attention-induced changes in visual appearance. In contrast, cue-induced baseline shifts in alpha band activity better explained response biases. Together, these results suggest that attention concurrently impacts visual appearance and response bias, and that these processes can be experimentally isolated.

Stimulus visibility and uncertainty mediate the influence of attention on response bias and visual contrast appearance.

Although attention is known to improve the efficacy of sensory processing, the impact of attention on subjective visual appearance is still a matter of debate. Although recent studies suggest that attention can alter the appearance of stimulus contrast, others argue that these changes reflect response bias induced by attention cues. Here, we provide evidence that attention has effects on both appearance and response bias. In a comparative judgment task in which subjects reported whether the attended or unattended visual stimulus had a higher perceived contrast, attention induced substantial baseline-offset response bias as well as small but significant changes in subjective contrast appearance when subjects viewed near-threshold stimuli. However, when subjects viewed suprathreshold stimuli, baseline-offset response bias decreased and attention primarily changed contrast appearance. To address the possibility that these changes in appearance might be influenced by uncertainty due to the attended and unattended stimuli having similar physical contrasts, subjects performed an equality judgment task in which they reported if the contrast of the two stimuli was the same or different. We found that, although there were still attention-induced changes in contrast appearance at lower contrasts, the robust changes in contrast appearance at higher contrasts observed in the comparative judgment task were diminished in the equality judgment task. Together, these results suggest that attention can impact both response bias and appearance, and these two types of attention effects are differentially mediated by stimulus visibility and uncertainty. Collectively, these findings help constrain arguments about the cognitive penetrability of perception.

GPS sensor-based mobile learning for English: an exploratory study on self-efficacy, self-regulation and student achievement.

This study investigated the effects of self-efficacy and self-regulation on student achievement in a context-aware learning environment. Particularly, an innovative global positioning system (GPS) sensor-based mobile learning system was used to facilitate English learning of different plants on campus. A total of 41 university students participated in the study, divided into high and low groups of self-efficacy and self-regulation. The findings showed that both self-regulation and self-efficacy were significant predictors of learning achievement in the mobile context-aware learning (MCL) context. Moreover, while the GPS-based MCL learning session had positive effects on learning achievement, no significant increase in self-regulation or self-efficacy was found in either the high or the low group, supposedly due to the short duration of the activity. The participants found the system easy to use and useful, but they also raised critical concerns that can inform future improvements. We hope this exploratory study can serve as a starting point from which more interactive, user-friendly GPS sensor-based learning systems will be generated and more areas of application will be further explored to foster self-regulated, self-motivated ubiquitous learning of mobile learners.

Multiscale cross-approximate entropy analysis as a measure of complexity among the aged and diabetic.

Complex fluctuations within physiological signals can be used to evaluate the health of the human body. This study recruited four groups of subjects: young healthy subjects (Group 1, n = 32), healthy upper middle-aged subjects (Group 2, n = 36), subjects with well-controlled type 2 diabetes (Group 3, n = 31), and subjects with poorly controlled type 2 diabetes (Group 4, n = 24). Data acquisition for each participant lasted 30 minutes. We obtained data related to consecutive time series with R-R interval (RRI) and pulse transit time (PTT). Using multiscale cross-approximate entropy (MCE), we quantified the complexity between the two series and thereby differentiated the influence of age and diabetes on the complexity of physiological signals. This study used MCE in the quantification of complexity between RRI and PTT time series. We observed changes in the influences of age and disease on the coupling effects between the heart and blood vessels in the cardiovascular system, which reduced the complexity between RRI and PTT series.

The Arabidopsis hit1-1 mutant has a plasma membrane profile distinct from that of wild-type plants at optimal growing temperature.

High temperatures alter the physical properties of the plasma membrane and cause loss of function in the embedded proteins. Effective membrane and protein recycling through intracellular vesicular traffic is vital to maintain the structural and functional integrity of the plasma membrane under heat stress. However, in this regard, little experimental data is available. Our characterization of the Arabidopsis hit1-1 mutant, linking a subunit of a vesicle tethering complex to plasma membrane thermostability, provided valuable information to this end. We further dissected the effect of the hit1-1 mutation on plasma membrane properties and found that even at optimal growth temperature (23 °C), the hit1-1 mutant exhibited a plasma membrane protein profile distinct from that of wild-type plants. This result implies that the hit1-1 mutation essentially alters vesicle trafficking and results in changes in the plasma membrane components under non-stress conditions. Such changes do not affect normal plant growth and development, but is significant for plant survival under heat stress.

Involvement of the Arabidopsis HIT1/AtVPS53 tethering protein homologue in the acclimation of the plasma membrane to heat stress.

Arabidopsis thaliana hit1-1 is a heat-intolerant mutant. The HIT1 gene encodes a protein that is homologous to yeast Vps53p, which is a subunit of the Golgi-associated retrograde protein (GARP) complex that is involved in retrograde membrane trafficking to the Golgi. To investigate the correlation between the cellular role of HIT1 and its protective function in heat tolerance in plants, it was verified that HIT1 was co-localized with AtVPS52 and AtVPS54, the other putative subunits of GARP, in the Golgi and post-Golgi compartments in Arabidopsis protoplasts. A bimolecular fluorescence complementation assay showed that HIT1 interacted with AtVPS52 and AtVPS54, which indicated their assembly into a protein complex in vivo. Under heat stress conditions, the plasma membrane of hit1-1 was less stable than that of the wild type, as determined by an electrolyte leakage assay, and enhanced leakage occurred before peroxidation injury to the membrane. In addition, the ability of hit1-1 to survive heat stress was not influenced by exposure to light, which suggested that the heat intolerance of hit-1 was a direct outcome of reduced membrane thermostability rather than heat-induced oxidative stress. Furthermore, hit1-1 was sensitive to the duration (sustained high temperature stress at 37 °C for 3 d) but not the intensity (heat shock at 44 °C for 30 min) of exposure to heat. Collectively, these results imply that HIT1 functions in the membrane trafficking that is involved in the thermal adaptation of the plasma membrane for tolerance to long-term heat stress in plants.

Salvia miltiorrhiza bge. f. alba up-regulates Bcl-2 and inhibits apoptosis of human umbilical vein endothelial cells / 第二军医大学学报

Objective To study the influence of Salvia miltiorrhiza bge. f. alba(SMA) on apoptosis and Bcl-2 expression in human umbilical vein endothelial cell (HUVEC) in vitro. Methods HUVECs were isolated using perfusion and enzyme digestion methods, and the obtained cells were identified by morphological observation and VIII = Ag immunoreactivity examination. The cells in the exponential phase of growth were treated with H2O2 and different concentrations of SM A (high dose, 0.10 g/ml, low dose, 0.01 g/ml). The cell apoptosis was determined by flow cytometric analysis and Bcl-2 expression was examined by immunofluorescence mehtod. Results SMA significantly decreased the H2O2-induced apoptosis of HUVECs (P<0.01 in high dose group and P<0.05 in low dose group), and significantly increased the expression of Bcl-2 in high dose group(P<0.01). Conclusion SMA can inhibit H2O2-induced apoptosis of HUVEC, which might be associated with the increase of Bcl-2 expression. Salvia miltiorrhiza bge. f. alba; umbilical veins; endothelial cell; apoptosis; bcl-2 genes.