In vitro ability of Staphylococcus aureus isolates from bacteraemic patients with and without metastatic complications to invade vascular endothelial cells

Invasion of vascular endothelial cells is thought to be a critical step in the development of metastatic infections in patients with Staphylococcus aureus bacteraemia. This study was designed to evaluate the association between the ability to invade endothelial cells and metastatic infection by S. aureus. Patients with metastatic infection were identified among those with community-acquired S. aureus bacteraemia in a tertiary referral hospital. Patients with simple bacteraemia caused by S. aureus over the same period served as the control group. The ability of each clinical isolate to invade endothelial cells was evaluated by counting the number of intracellular organisms 1 h after inoculation onto human umbilical vein endothelial cells in vitro. The cytotoxic activity of intracellular S. aureus was determined 24 h after internalization, and expressed as the percentage of cells killed. The clinical isolates varied in invasiveness and cytotoxicity. The median invasiveness, relative to S. aureus reference strain ATCC 29213, was 145 % in the cases (n=10) [interquartile range (IQR) 103-160] and 153 % (IQR 111-173) in the controls (n=11; P=0.44). The median cytotoxicity was 59.4 % (IQR 47-68) in the cases and 65.2 % (IQR 50-74) in the controls (P=0.44). Differences in the ability of S. aureus to invade and destroy vascular endothelial cells in vitro were not associated with the development of metastatic complications in patients with S. aureus bacteraemia. This implies that the invasiveness and toxicity of S. aureus for endothelial cells may not be major determinants of metastatic infection.The work was supported by grant no. 02-05-026 from the research fund of Seoul National University Bundang Hospital

Decomposition of BOLD Activity into Tuned and Untuned Components Reveals Cohabitation of Stimulus and Choice Information in V1

Recent studies on V1 report top-down modulation of input-driven responses of sensory neurons, implying that exogenous sensory drives and endogenous top-down drives jointly determine V1 responses. By measuring fMRI responses in conjunction with a classification task on ambiguous ring stimuli, we sought to understand how V1 carries out its encoding operation on afferent currents while being adaptively modulated by top-down currents associated with perceptual tasks. Population activity of V1, as in its raw eccentricity profiles, failed to resolve the threshold differences between the ring stimuli due to large moment-to-moment fluctuations. The analysis of variance indicated that stimulus-evoked responses explain only one-fifth of the total variance and fMRI responses were highly correlated among eccentricity-bins, implying that a substantial fraction of V1 responses fluctuate as a whole. This led us to decompose the raw fMRI responses into untuned and tuned components: average response across eccentricity-bins and residual responses from the average, respectively, the former varying only in time and the latter varying in both space and time. The tuned responses revealed the veridical encoding operation of V1 by readily distinguishing between the ring stimuli, which was impossible with the raw fMRI responses. In contrast, the untuned were correlated with two major aspects of choice behavior—inter-trial variability in response time and inter-subject variability in response bias. We propose that this cohabitation of stimulus and choice information in V1 indicates the presence of top-down exertion of gain modulation on the early processing stage by the high-tier stage that accumulates evidence for perceptual choices

Introducing Point-of-Interest as an alternative to Area-of-Interest for fixation duration analysis

Many eye-tracking data analyses rely on the Area-of-Interest (AOI) methodology, which utilizes AOIs to analyze metrics such as fixations. However, AOI-based methods have some inherent limitations including variability and subjectivity in shape, size, and location of AOIs. In this article, we propose an alternative approach to the traditional AOI dwell time analysis: Weighted Sum Durations (WSD). This approach decreases the subjectivity of AOI definitions by using Points-of-Interest (POI) while maintaining interpretability. In WSD, the durations of fixations toward each POI is weighted by the distance from the POI and summed together to generate a metric comparable to AOI dwell time. To validate WSD, we reanalyzed data from a previously published eye-tracking study (n=90). The re-analysis replicated the original findings that people gaze less towards faces and more toward points of contact when viewing violent social interactions

Introducing Point-of-Interest as an alternative to Area-of-Interest for fixation duration analysis

Many eye-tracking data analyses rely on the Area-of-Interest (AOI) methodology, which utilizes AOIs to analyze metrics such as fixations. However, AOI-based methods have some inherent limitations including variability and subjectivity in shape, size, and location of AOIs. In this article, we propose an alternative approach to the traditional AOI dwell time analysis: Weighted Sum Durations (WSD). This approach decreases the subjectivity of AOI definitions by using Points-of-Interest (POI) while maintaining interpretability. In WSD, the durations of fixations toward each POI is weighted by the distance from the POI and summed together to generate a metric comparable to AOI dwell time. To validate WSD, we reanalyzed data from a previously published eye-tracking study (n = 90). The re-analysis replicated the original findings that people gaze less towards faces and more toward points of contact when viewing violent social interactions.</p

Introducing Point-of-Interest as an alternative to Area-of-Interest for fixation duration analysis.

Many eye-tracking data analyses rely on the Area-of-Interest (AOI) methodology, which utilizes AOIs to analyze metrics such as fixations. However, AOI-based methods have some inherent limitations including variability and subjectivity in shape, size, and location of AOIs. In this article, we propose an alternative approach to the traditional AOI dwell time analysis: Weighted Sum Durations (WSD). This approach decreases the subjectivity of AOI definitions by using Points-of-Interest (POI) while maintaining interpretability. In WSD, the durations of fixations toward each POI is weighted by the distance from the POI and summed together to generate a metric comparable to AOI dwell time. To validate WSD, we reanalyzed data from a previously published eye-tracking study (n = 90). The re-analysis replicated the original findings that people gaze less towards faces and more toward points of contact when viewing violent social interactions

Overt attentional correlates of scene memorability and their relationships to scene semantics

Studying factors that contribute to scene memorability is important for understanding human vision and memory. Here we demonstrated in two different eye-tracking datasets that the higher the fixation map consistency (also called inter-observer congruency of fixation maps) of a scene, the higher its memorability is. Fixation map consistency and, more importantly, its correlation to scene memorability were the highest in the first 2 s of viewing, suggesting that scene features (other than center bias) that contribute to producing more consistent fixation maps early in viewing may also be important for scene encoding. We also found that although fixation count was positively correlated with scene memorability, it was not significantly correlated with fixation map consistency, suggesting that these eye-tracking measures reflect different attentional mechanisms. Using the proxies of scene semantics and mediation analyses, we found that the relationship between scene semantics and scene memorability was partially (but not fully) mediated by attentional mechanisms. Finally, we found that fixation map consistency, fixation count, and scene semantics all significantly and differently contributed to scene memorability. Together, these results suggest 2 s of eye-tracking can complement computer vision-based algorithms in better predicting scene memorability

Characterizing the role of impulsivity in costly, reactive aggression using a novel paradigm

Lack of self-control has long been theorized to predict an individual’s likelihood to engage in antisocial behaviors. However, existing definitions of self-control encompass multiple psychological constructs and lab-based measures of aggression have not allowed for the examination of aggression upon provocation where self-control is needed most. We introduce two versions of a novel paradigm, the Retaliate or Carry-on: Reactive AGgression Experiment (RC-RAGE) to fill this methodological gap. Using large online samples of US adults (N = 354 and N = 366), we test to what extent dispositional impulsivity, self-control, aggression, and state anger contribute to aggression upon provocation when there is a financial cost involved. Results showed that costly retaliation on this task was related to trait aggression and being in an angry emotional state, but not related to social desirability. Importantly, we show that the tendency to act impulsively is a better predictor of costly retaliation than other forms of self-control, such as the ability to delay gratification, resist temptation, or plan ahead. As a browser-based task, the RC-RAGE provides a tool for the future investigation of reactive aggression in a variety of experimental settings