Serial integration of sensory evidence for perceptual decisions and oculomotor responses

Perceptual decisions often require the integration of noisy sensory evidence over time. This process is formalized with sequential sampling models, where evidence is accumulated up to a decision threshold before a choice is made. Although classical accounts grounded in cognitive psychology tend to consider the process of decision formation and the preparation of the motor response as occurring serially, neurophysiological studies have proposed that decision formation and response preparation occur in parallel and are inseparable (Cisek, 2007; Shadlen et al., 2008). To address this serial vs. parallel debate, we developed a behavioural, reverse correlation protocol, in which the stimuli that influence perceptual decisions can be distinguished from the stimuli that influence motor responses. We show that the temporal integration windows supporting these two processes are distinct and largely non-overlapping, suggesting that they proceed in a serial or cascaded fashion

Structure and dynamics of colloidal depletion gels: coincidence of transitions and heterogeneity

Transitions in structural heterogeneity of colloidal depletion gels formed through short-range attractive interactions are correlated with their dynamical arrest. The system is a density and refractive index matched suspension of 0.20 volume fraction poly(methyl methacyrlate) colloids with the non-adsorbing depletant polystyrene added at a size ratio of depletant to colloid of 0.043. As the strength of the short-range attractive interaction is increased, clusters become increasingly structurally heterogeneous, as characterized by number-density fluctuations, and dynamically immobilized, as characterized by the single-particle mean-squared displacement. The number of free colloids in the suspension also progressively declines. As an immobile cluster to gel transition is traversed, structural heterogeneity abruptly decreases. Simultaneously, the mean single-particle dynamics saturates at a localization length on the order of the short-range attractive potential range. Both immobile cluster and gel regimes show dynamical heterogeneity. Non-Gaussian distributions of single particle displacements reveal enhanced populations of dynamical trajectories localized on two different length scales. Similar dependencies of number density fluctuations, free particle number and dynamical length scales on the order of the range of short-range attraction suggests a collective structural origin of dynamic heterogeneity in colloidal gels.Comment: 14 pages, 10 figure

Proactive and reactive cognitive control and dorsolateral prefrontal cortex dysfunction in first episode schizophrenia.

Cognitive control deficits have been consistently documented in patients with schizophrenia. Recent work in cognitive neuroscience has hypothesized a distinction between two theoretically separable modes of cognitive control-reactive and proactive. However, it remains unclear the extent to which these processes are uniquely associated with dysfunctional neural recruitment in individuals with schizophrenia. This functional magnetic resonance imaging (fMRI) study utilized the color word Stroop task and AX Continuous Performance Task (AX-CPT) to tap reactive and proactive control processes, respectively, in a sample of 54 healthy controls and 43 patients with first episode schizophrenia. Healthy controls demonstrated robust dorsolateral prefrontal, anterior cingulate, and parietal cortex activity on both tasks. In contrast, patients with schizophrenia did not show any significant activation during proactive control, while showing activation similar to control subjects during reactive control. Critically, an interaction analysis showed that the degree to which prefrontal activity was reduced in patients versus controls depended on the type of control process engaged. Controls showed increased dorsolateral prefrontal cortex (DLPFC) and parietal activity in the proactive compared to the reactive control task, whereas patients with schizophrenia did not demonstrate this increase. Additionally, patients' DLPFC activity and performance during proactive control was associated with disorganization symptoms, while no reactive control measures showed this association. Proactive control processes and concomitant dysfunctional recruitment of DLPFC represent robust features of schizophrenia that are also directly associated with symptoms of disorganization

CESR Technical Report 1: The quality and usefulness of the NSW Clinical Cancer Registry Minimum Dataset and Colorectal Dataset Extension for colorectal cancer services research

Colorectal cancer is one of the most common cancers worldwide. Population-based studies of care and outcomes are essential to monitor the uptake of evidence-based treatment guidelines and identify groups most at risk of receiving suboptimal care or experiencing poor outcomes. With the development of locally-managed Clinical Cancer Registries (ClinCR) in public facilities in NSW since 2006, ‘patterns of care’ studies which previously relied on the collection of clinical information through time- and resource-intensive surveys or medical record audits now have the potential to be conducted through linkage of routinely collected data. However there is little experience with the use of ClinCR data for research. The purpose of this report is to assess the quality, coverage and completeness of ClinCR data for use in colorectal cancer services research, and to assess the feasibility of developing surgical process and outcomes indicators that rely on ClinCR data items.Cancer Institute NS

Atmospheric oxidation chemistry and ozone production: Results from SHARP 2009 in Houston, Texas

This study considers whether spikes in nitrate in snow sampled at Summit, Greenland, from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, solar proton event (SPE)-enhanced NOy calculated within the atmospheric column is too small to account for the observed nitrate peaks in surface snow. Instead, our WACCM results suggest that nitrate spikes not readily accounted for by measurement correlations are likely of anthropogenic origin. These results, consistent with other recent studies, imply that nitrate spikes in ice cores are not suitable proxies for individual SPEs and motivate the need to identify alternative proxies

The effects of more realistic forms of lead heterogeneity in soil on uptake, biomass and root response of two brassica species

The spatial heterogeneity of soil constituents is known to have significant impacts on plant growth and plant uptake of nutrients and contaminants, yet studies have rarely used patterns of heterogeneity based on those found in the field. Heterogeneity refers to how lumpy materials are distributed in the soil, whilst homogeneity is the uniformity in the distribution of such materials. We identified patterns of lead contamination at historically polluted field sites and conducted pot trials using field–based parameters to determine the pattern of distribution of lead within the pots. We examined plant Pb uptake and growth in simulated low, medium and high heterogeneity environments as well as a control homogeneous treatment. We found a significant effect of Pb spatial heterogeneity on uptake and biomass of two Brassica species (Brassica napus and Brassica juncea), both candidate species for phytoremediation projects. Biomass was 4 to 5 fold lower in the high heterogeneity treatment and total plant Pb uptake as Pb mass in (µg) was 40 to 80% lower, compared to the homogeneous treatment. Plant lead concentration (mg/kg) increased by a factor of 2 with increasing heterogeneity. Peak uptake was observed in low and medium heterogeneity treatments of B. napus and B. juncea respectively. We also explored roots behaviour in the high heterogeneity treatment and found variation in root mass by 20 to 80% between concentric patches with significant (P < 0.05) differences between patches and species. High proportion of roots (40 to 50%) were proliferated in patches of lower Pb concentration. The tap root was a greater proportion of root in B. napus, which was absent in B. juncea. Results suggest that root morphology of this plant species might be a factor influencing the placement of roots in concentric patches and consequently the overall root response to Pb spatial heterogeneity. This is an indication that the root response could be realistic of that experienced by plants in field conditions. Generally result showed that spatial heterogeneity of Pb has a significant effect on plant growth and biomass. This study also demonstrated that the presence and extent of in situ heterogeneity of Pb in soil plays an important role in Pb uptake by plants. This work has implications for improving the phytoremediation of Pb contaminated land, phytomining, the reliability of risk assessment/models of human exposure to Pb and the quality of trace mineral content of agricultural produce

Nitrate deposition to surface snow at Summit, Greenland, following the 9 November 2000 solar proton event

Abstract This study considers whether spikes in nitrate in snow sampled at Summit, Greenland, from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, solar proton event (SPE)-enhanced NOy calculated within the atmospheric column is too small to account for the observed nitrate peaks in surface snow. Instead, our WACCM results suggest that nitrate spikes not readily accounted for by measurement correlations are likely of anthropogenic origin. These results, consistent with other recent studies, imply that nitrate spikes in ice cores are not suitable proxies for individual SPEs and motivate the need to identify alternative proxies. Key Points A global model simulates nitrate deposition from solar proton events Soluble ion correlations in Summit snow identify tropospheric sources of nitrate Nitrate ions in snow are found not to be a good proxy for solar proton events

Two‐step continuous production of monodisperse colloidal ellipsoids at rates of one gram per day

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141576/1/aic16009_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141576/2/aic16009.pd