Motion-Induced Position Shifts Activate Early Visual Cortex

The ability to correctly determine the position of objects in space is a fundamental task of the visual system. The perceived position of briefly presented static objects can be influenced by nearby moving contours, as demonstrated by various illusions collectively known as motion-induced position shifts. Here we use a stimulus that produces a particularly strong effect of motion on perceived position. We test whether several regions-of-interest (ROIs), at different stages of visual processing, encode the perceived rather than retinotopically veridical position. Specifically, we collect functional MRI data while participants experience motion-induced position shifts and use a multivariate pattern analysis approach to compare the activation patterns evoked by illusory position shifts with those evoked by matched physical shifts. We find that the illusory perceived position is represented at the earliest stages of the visual processing stream, including primary visual cortex. Surprisingly, we found no evidence of percept-based encoding of position in visual areas beyond area V3. This result suggests that while it is likely that higher-level visual areas are involved in position encoding, early visual cortex also plays an important role

Nonadiabatic electron heat pump

We investigate a mechanism for extracting heat from metallic conductors based on the energy-selective transmission of electrons through a spatially asymmetric resonant structure subject to ac driving. This quantum refrigerator can operate at zero net electronic current as it replaces hot by cold electrons through two energetically symmetric inelastic channels. We present numerical results for a specific heterostructure and discuss general trends. We also explore the conditions under which the cooling rate may approach the ultimate limit given by the quantum of cooling power.Comment: 4 pages, 3 figures; published version, typos correcte

Adherence to Nutrition and Physical Activity Cancer Prevention Guidelines and Development of Colorectal Adenoma.

Adherence to the American Cancer Society's (ACS) Nutrition and Physical Activity Cancer Prevention Guidelines is associated with reductions in overall cancer incidence and mortality, including site-specific cancers such as colorectal cancer. We examined the relationship between baseline adherence to the ACS guidelines and (1) baseline adenoma characteristics and (2) odds of recurrent colorectal adenomas over 3 years of follow-up. Cross-sectional and prospective analyses with a pooled sample of participants from the Wheat Bran Fiber (n = 503) and Ursodeoxycholic Acid (n = 854) trials were performed. A cumulative adherence score was constructed using baseline self-reported data regarding body size, diet, physical activity and alcohol consumption. Multivariable logistic regression demonstrated significantly reduced odds of having three or more adenomas at baseline for moderately adherent (odds ratio [OR] = 0.67, 95% confidence intervals [CI]: 0.46⁻0.99) and highly adherent (OR = 0.50, 95% CI: 0.31⁻0.81) participants compared to low adherers (p-trend = 0.005). Conversely, guideline adherence was not associated with development of recurrent colorectal adenoma (moderate adherence OR = 1.16, 95% CI: 0.85⁻1.59, high adherence OR = 1.23, 95% CI: 0.85⁻1.79)

Unconscious Neural Processing Differs with Method Used to Render Stimuli Invisible

Visual stimuli can be kept from awareness using various methods. The extent of processing that a given stimulus receives in the absence of awareness is typically used to make claims about the role of consciousness more generally. The neural processing elicited by a stimulus, however, may also depend on the method used to keep it from awareness, and not only on whether the stimulus reaches awareness. Here we report that the method used to render an image invisible has a dramatic effect on how category information about the unseen stimulus is encoded across the human brain. We collected fMRI data while subjects viewed images of faces and tools, that were rendered invisible using either continuous flash suppression (CFS) or chromatic flicker fusion (CFF). In a third condition, we presented the same images under normal fully visible viewing conditions. We found that category information about visible images could be extracted from patterns of fMRI responses throughout areas of neocortex known to be involved in face or tool processing. However, category information about stimuli kept from awareness using CFS could be recovered exclusively within occipital cortex, whereas information about stimuli kept from awareness using CFF was also decodable within temporal and frontal regions. We conclude that unconsciously presented objects are processed differently depending on how they are rendered subjectively invisible. Caution should therefore be used in making generalizations on the basis of any one method about the neural basis of consciousness or the extent of information processing without consciousness

Evaluating Health and Disease in Sub-Saharan Africa: Minimally Invasive Collection of Plasma in the Malawi Longitudinal Study of Families and Health (MLSFH)

Background: The collection of biomarker-based indicators of adult health and fitness is an important addition to socioeconomic surveys since these indicators provide valuable insights into the biological functions, and the complex causal pathways between socioeconomic environments and health of adult individuals. Other than select Demographic and Health Surveys (DHS), there are almost no population-based sources of biomarker-based indicators of adult health in sub-Saharan Africa (SSA), where most population-based biologic data are focused on HIV, other STDs, malaria, or nutritional status. While infectious diseases---such as HIV and malaria---attract the majority of research and NGOs attention in sub-Saharan Africa, there is an important need to understand the general determinants of adult health in SSA since the region will rapidly age in the next decades in ways that are significantly different from the aging patterns in other developing regions due to the AIDS epidemic, and chronic diseases will increasingly become relevant for understanding the health of sub-Saharan populations. Methods and Design: We document our protocol for the collection of biomarker-based health indicators as a pilot project within the Malawi Longitudinal Study of Families and Health (MLSFH), and we provide basic descriptive information about the study population and the collected biomarker-based indicators of adult health obtained from respondents in rural Malawi. LabAnywhere kits were used to obtain blood plasma from 980 adult men and women living in Balaka, the southern-most region in rural Malawi. The procedure allows for the non-invasive collection of blood plasma, but has not been been previously used in the context of a developing country. We collected biomarkers for inflammation and immunity, lipids, organ function, and metabolic processes. We specifically collected wide-range CRP, total cholesterol, LDL, HDL, total protein, urea, albumin, blood urea nitrogen, creatinine, random blood glucose and HbA1c assays. Overall, the mean values of the biomarkers are below the lower limits of clinical guidelines for adult populations in the U.S. and other developed countries, and only small proportions of the sample are above the upper limits of the normal clinical ranges as defined by U.S. standards. The correlationional patterns of the collected biomarkers are consistent with observations from developed countries, and the comparison with other low-income populations such as the Tsimane in Bolivia or the Yakuts in Siberia show remarkably similar age-specific patterns of the biomarkers despite differences in the mode of blood sampling. Discussion: The MLSFH biomarker sample makes a potentially important contribution to understanding the health of the adult populations in low income environments. The present study confirms that the collection of such biomarkers using the LabAnywhere system is feasible in rural sub-Saharan contexts: the refusal rate was very low in the MLSFH and following the procedures described above, only a small fraction of the biomarker samples could not be analyzed by LabAnywhere. The system therefore provides an attractive alternative to the collection of dried blood spots (DBS) and venous blood samples, providing a broader range of potential biomarkers than DBS and being logistically easier than the collection of venous blood

Network Structure and Dynamics of the Mental Workspace

The conscious manipulation of mental representations is central to many creative and uniquely human abilities. How does the human brain mediate such flexible mental operations? Here, multivariate pattern analysis of functional MRI data reveals a widespread neural network that performs specific mental manipulations on the contents of visual imagery. Evolving patterns of neural activity within this mental workspace track the sequence of informational transformations carried out by these manipulations. The network switches between distinct connectivity profiles as representations are maintained or manipulated

Coherent charge transport through molecular wires: influence of strong Coulomb repulsion

We derive a master equation for the electron transport through molecular wires in the limit of strong Coulomb repulsion. This approach is applied to two typical situations: First, we study transport through an open conduction channel for which we find that the current exhibits an ohmic-like behaviour. Second, we explore the transport properties of a bridged molecular wire, where the current decays exponentially as a function of the wire length. For both situations, we discuss the differences to the case of non-interacting electrons.Comment: 15 pages, 4 figures, elsart style, accepted at Chem Phy

Representation of Maximally Regular Textures in Human Visual Cortex

This research was supported by National Science Foundation INSPIRE Grant 1248076, which was awarded to Y.L. and A.M.N.Peer reviewedPublisher PD

The human visual system preserves the hierarchy of 2-dimensional pattern regularity

Symmetries are present at many scales in images of natural scenes. A large body of literature has demonstrated contributions of symmetry to numerous domains of visual perception. The four fundamental symmetries, reflection, rotation, translation and glide reflection, can be combined in exactly 17 distinct ways. These wallpaper groups represent the complete set of symmetries in 2D images and have recently found use in the vision science community as an ideal stimulus set for studying the perception of symmetries in textures. The goal of the current study is to provide a more comprehensive description of responses to symmetry in the human visual system, by collecting both brain imaging (Steady-State Visual Evoked Potentials measured using high-density EEG) and behavioral (symmetry detection thresholds) data using the entire set of wallpaper groups. This allows us to probe the hierarchy of complexity among wallpaper groups, in which simpler groups are subgroups of more complex ones. We find that this hierarchy is preserved almost perfectly in both behavior and brain activity: A multi-level Bayesian GLM indicates that for most of the 63 subgroup relationships, subgroups produce lower amplitude responses in visual cortex (posterior probability: > 0.95 for 56 of 63) and require longer presentation durations to be reliably detected (posterior probability: > 0.95 for 49 of 63). This systematic pattern is seen only in visual cortex and only in components of the brain response known to be symmetric-specific. Our results show that representations of symmetries in the human brain are precise and rich in detail, and that this precision is reflected in behavior. These findings expand our understanding of symmetry perception, and open up new avenues for research on how fine-grained representations of regular textures contribute to natural vision

The global variation of medical student engagement in teaching: Implications for medical electives.

INTRODUCTION: International medical electives, whereby undergraduates visit an institution in a country other than their own, are a common part of medical training. Visiting students are often asked to provide local teaching, which may be acceptable where the visitor is acting within the bounds of their own competency and the normal practices of both their home and host institutions. However, the extent to which teaching is an accepted student activity globally has not previously been described. This study aims to address this using an international survey approach. METHODS: A voluntary electronic survey, created using the Checklist for Reporting Results of Internet E-Surveys (CHERRIES) framework, was distributed across established international medical student networks. This assessed the involvement of medical students in teaching and the educator training they receive, with the intention of comparing experiences between high-income countries (HICs) and low/middle-income countries (LMICs) to gauge the engagement of both "host" and "visiting" students. RESULTS: 443 students from 61 countries completed the survey, with an equal proportion of respondents from LMICs (49.4%, 219/443) and HICs (50.6%, 224/443). Around two thirds of students reported providing teaching whilst at medical school, with most reporting teaching numerous times a year, mainly to more junior medical students. There was with no significant difference between LMICs and HICs. Around 30 per cent of all medical students reported having received no teacher training, including 40 per cent of those already providing teaching. CONCLUSION: This study suggests that students are engaged in teaching globally, with no difference between HIC and LMIC contexts. However, students are underprepared to act as educators in both settings. Providing teaching as part of an elective experience may be ethically acceptable to both host and home institutions, but needs to be supported by formal training in delivering teaching.NIHR Global Health Research Group on Neurotraum