Attention Increases the Temporal Precision of Conscious Perception: Verifying the Neural-ST2 Model

What role does attention play in ensuring the temporal precision of visual perception? Behavioural studies have investigated feature selection and binding in time using fleeting sequences of stimuli in the Rapid Serial Visual Presentation (RSVP) paradigm, and found that temporal accuracy is reduced when attentional control is diminished. To reduce the efficacy of attentional deployment, these studies have employed the Attentional Blink (AB) phenomenon. In this article, we use electroencephalography (EEG) to directly investigate the temporal dynamics of conscious perception. Specifically, employing a combination of experimental analysis and neural network modelling, we test the hypothesis that the availability of attention reduces temporal jitter in the latency between a target''s visual onset and its consolidation into working memory. We perform time-frequency analysis on data from an AB study to compare the EEG trials underlying the P3 ERPs (Event-related Potential) evoked by targets seen outside vs. inside the AB time window. We find visual differences in phase-sorted ERPimages and statistical differences in the variance of the P3 phase distributions. These results argue for increased variation in the latency of conscious perception during the AB. This experimental analysis is complemented by a theoretical exploration of temporal attention and target processing. Using activation traces from the Neural-ST² model, we generate virtual ERPs and virtual ERPimages. These are compared to their human counterparts to propose an explanation of how target consolidation in the context of the AB influences the temporal variability of selective attention. The AB provides us with a suitable phenomenon with which to investigate the interplay between attention and perception. The combination of experimental and theoretical elucidation in this article contributes to converging evidence for the notion that the AB reflects a reduction in the temporal acuity of selective attention and the timeliness of perception.     

Metallic nickel nano- and fine particles induce JB6 cell apoptosis through a caspase-8/AIF mediated cytochrome c-independent pathway

Background  

Carcinogenicity of nickel compounds has been well documented. However, the carcinogenic effect of metallic nickel is still unclear. The present study investigates metallic nickel nano- and fine particle-induced apoptosis and the signal pathways involved in this process in JB6 cells. The data obtained from this study will be of benefit for elucidating the pathological and carcinogenic potential of metallic nickel particles.     

Heparin binding induces conformational changes in Adeno-associated virus serotype 2

Adeno-associated virus serotype 2 (AAV2) uses heparan sulfate proteoglycan as a cell surface-attachment receptor. In this study the structures of AAV2 alone and complexed with heparin were determined to 18 Å resolution using cryo-electron microscopy and three-dimensional image reconstruction. A difference map showed positive density, modeled as heparin, close to the icosahedral twofold axes and between the protrusions that surround the threefold axes of the capsid. Regions of the model near the threefold place the receptor in close proximity to basic residues previously identified as part of the heparin binding site. The region of the model near the twofold axes identifies a second contact site, not previously characterized but which is also possibly configured by heparin binding. The difference map also revealed two significant conformational changes: (I) at the tops of the threefold protrusions, which have become flattened in the complex, and (II) at the fivefold axes where the top of the channel is widened possibly in response to movement of the HI loops in the capsid proteins. Ordered density in the interior of the capsid in the AAV2–heparin complex was interpreted as nucleic acid, consistent with the presence of non-viral DNA in the expressed capsids.     

Using Real-Time PCR to Assess Changes in the Hydrocarbon-Degrading Microbial Community in Antarctic Soil During Bioremediation

A real-time polymerase chain reaction (PCR) method to quantify the proportion of microorganisms containing alkane monooxygenase was developed and used to follow changes in the microbial community in hydrocarbon-contaminated Antarctic soil during a bioremediation field trial. Assays for the alkB and rpoB genes were validated and found to be both sensitive and reproducible (less than 2% intrarun variation and 25–38% interrun variation). Results from the real-time PCR analysis were compared to analysis of the microbial population by a culture-based technique [most probable number (MPN) counts]. Both types of analysis indicated that fertilizer addition to hydrocarbon-contaminated soil stimulated the indigenous bacterial population within 1 year. The proportion of alkB containing microorganisms was positively correlated to the concentration of n-alkanes in the soil. After the concentration of n-alkanes in the soil decreased, the proportion of alkane-degrading microorganisms decreased, but the proportion of total hydrocarbon-degrading microorganisms increased, indicating another shift in the microbial community structure and ongoing biodegradation.     

Pattern of maternal serum corticotropin-releasing hormone concentration during pregnancy in the common marmoset (Callithrix jacchus)

Corticotropin-releasing hormone (CRH), a potent neuropeptide, is produced by the placenta of anthropoid primates. No other mammals, including prosimian primates, are known to produce placental CRH. In humans, placental CRH appears to play an important role in the progression of pregnancy to parturition. Maternal circulating CRH begins to rise early in pregnancy and increases until parturition. Gorillas and chimpanzees share this pattern of increasing maternal CRH during pregnancy with humans. In humans, chimpanzees, and gorillas, maternal CRH and estradiol concentrations are correlated, consistent with the hypothesis that CRH is involved in the biosynthetic pathway for placental estrogen production. In contrast, in baboons, maternal circulating CRH rises precipitously early in pregnancy and then declines, though CRH is detectable until birth. This research was designed to investigate the pattern of maternal circulating CRH in the common marmoset during pregnancy. Blood samples were taken across gestation from nine subjects over 11 pregnancies, and the plasma was assayed for CRH. The pattern of maternal circulating CRH in the common marmoset was similar to that of the baboon, with a rapid rise starting at about 50 days postconception and a peak at approximately 70 days postconception. By 110 days postconception, CRH concentration had plateaued at a significantly lower value. The peak and mean values for CRH were associated with fetal number (e.g., females gestating triplets had higher values than females gestating twins). Urinary estradiol showed no association with plasma CRH concentration. Marmosets appear to differ from the great apes in this regard, and to share a pattern of maternal CRH during pregnancy with the baboon, indicating that the baboon and marmoset pattern may be ancestral. The function of the early rapid rise of CRH in baboons and marmosets, and the significance of this difference between monkeys and apes, are not known.