Evolution and Optimality of Similar Neural Mechanisms for Perception and Action during Search

A prevailing theory proposes that the brain's two visual pathways, the ventral and dorsal, lead to differing visual processing and world representations for conscious perception than those for action. Others have claimed that perception and action share much of their visual processing. But which of these two neural architectures is favored by evolution? Successful visual search is life-critical and here we investigate the evolution and optimality of neural mechanisms mediating perception and eye movement actions for visual search in natural images. We implement an approximation to the ideal Bayesian searcher with two separate processing streams, one controlling the eye movements and the other stream determining the perceptual search decisions. We virtually evolved the neural mechanisms of the searchers' two separate pathways built from linear combinations of primary visual cortex receptive fields (V1) by making the simulated individuals' probability of survival depend on the perceptual accuracy finding targets in cluttered backgrounds. We find that for a variety of targets, backgrounds, and dependence of target detectability on retinal eccentricity, the mechanisms of the searchers' two processing streams converge to similar representations showing that mismatches in the mechanisms for perception and eye movements lead to suboptimal search. Three exceptions which resulted in partial or no convergence were a case of an organism for which the targets are equally detectable across the retina, an organism with sufficient time to foveate all possible target locations, and a strict two-pathway model with no interconnections and differential pre-filtering based on parvocellular and magnocellular lateral geniculate cell properties. Thus, similar neural mechanisms for perception and eye movement actions during search are optimal and should be expected from the effects of natural selection on an organism with limited time to search for food that is not equi-detectable across its retina and interconnected perception and action neural pathways

Perspective taking and theory of mind in hide and seek

Does theory of mind play a significant role in where people choose to hide an item or where they search for an item that has been hidden? Adapting the "Hide-Find Paradigm" of Anderson et al. (2014), participants viewed homogenous or popout visual arrays on a touchscreen table. Their task was to indicate where in the array they would hide an item, or to search for an item that had been hidden, by either a friend or a foe. Critically, participants believed that their sitting location at the touchtable was the same as - or opposite to - their partner's location. Replicating Anderson et al. participants tended to (1) select items nearer to themselves on homogenous displays, and this bias was stronger for a friend than foe; and (2) select popout items, and again, more for a friend than foe. These biases were observed only when participants believed that they shared the same physical perspective as their partner. Collectively the data indicate that theory of mind plays a significant role in hiding and finding, and demonstrate that the hide-find paradigm is a powerful tool for investigating theory of mind in adults

Serum screening with Down's syndrome markers to predict pre-eclampsia and small for gestational age: Systematic review and meta-analysis

<p>Abstract</p> <p>Background</p> <p>Reliable antenatal identification of pre-eclampsia and small for gestational age is crucial to judicious allocation of monitoring resources and use of preventative treatment with the prospect of improving maternal/perinatal outcome. The purpose of this systematic review was to determine the accuracy of five serum analytes used in Down's serum screening for prediction of pre-eclampsia and/or small for gestational age.</p> <p>Methods</p> <p>The data sources included Medline, Embase, Cochrane library, Medion (inception to February 2007), hand searching of relevant journals, reference list checking of included articles, contact with experts. Two reviewers independently selected the articles in which the accuracy of an analyte used in Downs's serum screening before the 25^thgestational week was associated with the occurrence of pre-eclampsia and/or small for gestational age without language restrictions. Two authors independently extracted data on study characteristics, quality and results.</p> <p>Results</p> <p>Five serum screening markers were evaluated. 44 studies, testing 169,637 pregnant women (4376 pre-eclampsia cases) and 86 studies, testing 382,005 women (20,339 fetal growth restriction cases) met the selection criteria. The results showed low predictive accuracy overall. For pre-eclampsia the best predictor was inhibin A>2.79MoM positive likelihood ratio 19.52 (8.33,45.79) and negative likelihood ratio 0.30 (0.13,0.68) (single study). For small for gestational age it was AFP>2.0MoM to predict birth weight < 10^thcentile with birth < 37 weeks positive likelihood ratio 27.96 (8.02,97.48) and negative likelihood ratio 0.78 (0.55,1.11) (single study). A potential clinical application using aspirin as a treatment is given as an example.</p> <p>There were methodological and reporting limitations in the included studies thus studies were heterogeneous giving pooled results with wide confidence intervals.</p> <p>Conclusion</p> <p>Down's serum screening analytes have low predictive accuracy for pre-eclampsia and small for gestational age. They may be a useful means of risk assessment or of use in prediction when combined with other tests.</p

Low-volume-loss tunnelling for London ring main extension

The Thames Water ring main extension is a 4.5 km long tunnel from Stoke Newington, in the London borough of Hackney, to New River Head in Finsbury, in the London borough of Islington. The 2.85 m i.d. tunnel was excavated by an earth pressure balance tunnel-boring machine (TBM) at depths between 40 and 60 m below the surface. Surface settlements along the route were measured by precise levelling, and were found to be small. It was therefore even more important to measure these settlements as accurately as possible, in order to provide informed estimates of subsurface movements induced in third-party underground structures much closer to the tunnel horizon. Because of the relatively large magnitude of the background movements measured, when compared with the small tunnel-induced settlements, it was necessary to adopt a rigorous statistical method to fit a Gaussian curve to the data. This exploited the analogy of the ‘error function' to define the Gaussian curve parameters i and V l. In all, 13 tunnels were underpassed successfully by the TBM, all within the ‘conservative expected value' predictions, and without incident. The predictions and structural monitoring schemes undertaken for the High Speed 1 tunnels near Corsica Street and the Northern line tunnels near Angel station are described in the paper. It was found that the surface and subsurface trough width parameter K did not vary with depth as predicted: therefore a new relationship is proposed

Blood cholesterol and MRI activity in first clinical episode suggestive of multiple sclerosis

OBJECTIVES: The present study was planned to investigate the relationship between the plasma lipid profile and disease activity in patients with a first clinical episode suggestive of multiple sclerosis (MS). MATERIAL AND METHODS: Eighteen consecutive out-patients underwent a monthly brain magnetic resonance imaging (MRI), blood sample and neurological assessment over 6 months. Blood samples were used to evaluate total cholesterol and triglyceride levels as well as their lipoprotein fractions. Plasma total apolipoprotein E concentration was also determined. RESULTS: We found a significant correlation between the mean number of enhancing lesions and the mean plasma level of both total and low density lipoprotein cholesterol. The total plasma cholesterol level increased on average by 4.4 mg/dl for each enhancing lesion. CONCLUSION: Our preliminary data suggest a potential role of plasma cholesterol level as a biological marker of disease activity after a first demyelinating event. Further studies need, however, to be designed to determine whether the plasma cholesterol level is of practical use in monitoring the disease course