A cross-cultural study of the representation of shape: Sensitivity to generalized cone dimensions

Many of the phenomena underlying shape recognition can be derived from an assumption that the representation of simple parts can be understood in terms of independent dimensions of generalized cones, e.g., whether the axis of a cylinder is straight or curved or whether the sides are parallel or nonparallel. What enables this sensitivity? One explanation is that the representations derive from our immersion in a manufactured world of simple objects, e.g., a cylinder and a funnel, where these dimensions can be readily discerned independent of other stimulus variations. An alternative explanation is that genetic coding and/or early experience with extended contours - a characteristic of all naturally varying visual worlds - would be sufficient to develop the appropriate representations. The Himba, a seminomadic people in a remote region of Northwestern Namibia with little exposure to regular, simple artifacts, were virtually identical to western observers in representing generalized-cone dimensions of simple shapes independently. Thus immersion in a world of simple, manufactured shapes is not required for the development of a representation that specifies these dimensions independently

The `Parahippocampal Place Area' Responds Selectively to High Spatial Frequencies

Defining the exact mechanisms by which the brain processes visual objects and scenes remains an unresolved challenge. Valuable clues to this process have emerged from the demonstration that clusters of neurons (“modules”) in inferior temporal cortex apparently respond selectively to specific categories of visual stimuli, such as places/scenes. However, the higher-order “category-selective” response could also reflect specific lower-level spatial factors. Here we tested this idea in multiple functional MRI experiments, in humans and macaque monkeys, by systematically manipulating the spatial content of geometrical shapes and natural images. These tests revealed that visual spatial discontinuities (as reflected by an increased response to high spatial frequencies) selectively activate a well-known place-selective region of visual cortex (the “parahippocampal place area”) in humans. In macaques, we demonstrate a homologous cortical area, and show that it also responds selectively to higher spatial frequencies. The parahippocampal place area may use such information for detecting object borders and scene details during spatial perception and navigation.National Institutes of Health (U.S.) (NIH Grant R01 MH6752)National Institutes of Health (U.S.) (grant R01 EY017081)Athinoula A. Martinos Center for Biomedical ImagingNational Center for Research Resources (U.S.)Mind Research Institut

Incremental grouping of image elements in vision

One important task for the visual system is to group image elements that belong to an object and to segregate them from other objects and the background. We here present an incremental grouping theory (IGT) that addresses the role of object-based attention in perceptual grouping at a psychological level and, at the same time, outlines the mechanisms for grouping at the neurophysiological level. The IGT proposes that there are two processes for perceptual grouping. The first process is base grouping and relies on neurons that are tuned to feature conjunctions. Base grouping is fast and occurs in parallel across the visual scene, but not all possible feature conjunctions can be coded as base groupings. If there are no neurons tuned to the relevant feature conjunctions, a second process called incremental grouping comes into play. Incremental grouping is a time-consuming and capacity-limited process that requires the gradual spread of enhanced neuronal activity across the representation of an object in the visual cortex. The spread of enhanced neuronal activity corresponds to the labeling of image elements with object-based attention

Preference for facial averageness: evidence for a common mechanism in human and macaque infants

Human adults and infants show a preference for average faces, which could stem from a general processing mechanism and may be shared among primates. However, little is known about preference for facial averageness in monkeys. We used a comparative developmental approach and eye-tracking methodology to assess visual attention in human and macaque infants to faces naturally varying in their distance from a prototypical face. In Experiment 1, we examined the preference for faces relatively close to or far from the prototype in 12-month-old human infants with human adult female faces. Infants preferred faces closer to the average than faces farther from it. In Experiment 2, we measured the looking time of 3-month-old rhesus macaques (Macaca mulatta) viewing macaque faces varying in their distance from the prototype. Like human infants, macaque infants looked longer to faces closer to the average. In Experiments 3 and 4, both species were presented with unfamiliar categories of faces (i.e., macaque infants tested with adult macaque faces; human infants and adults tested with infant macaque faces) and showed no prototype preferences, suggesting that the prototypicality effect is experience-dependent. Overall, the findings suggest a common processing mechanism across species, leading to averageness preferences in primates

Automatic segmentation of in-vivo intra-coronary optical coherence tomography images to assess stent strut apposition and coverage

The implantation of intracoronary stents is currently the standard approach for the treatment of coronary atherosclerotic disease. The widespread adoption of this technology has boosted an intensive research activity in this domain, with continuous improvements in the design of these devices, aiming at reducing problems of restenosis (re-narrowing of the stented segment) and thrombosis (sudden occlusion due to thrombus formation). Recently, a new, light-based intracoronary imaging modality, optical coherence tomography (OCT), was developed and introduced into clinical practice. Due to its very high axial resolution (10-15 mu m), it allows for in vivo evaluation of both stent strut apposition and neointima coverage (a marker of healing of the treated segment). As such, it provides valuable information on proper stent deployment, on the behaviour of different stent types in-vivo and on the effect of new types of stents (e.g. drug-eluting stents) on vessel wall healing. However, the major drawback of the current OCT methodology is that analysis of these images requires a tremendous amount of-currently manual-post-processing. In this manuscript, an algorithm is presented that allows for fully automated analysis of stent strut apposition and coverage in coronary arteries. The vessel lumen and stent struts are automatically detected and segmented through analysis of the intensity profiles of the A-lines. From these data, apposition and coverage can then be measured automatically. The algorithm was validated using manual assessments by two experienced operators as a reference. High Pearson's correlation coefficients were found (R = 0.96-0.97) between the automated and manual measurements while Bland-Altman analysis showed no significant bias with good limits of agreement. As such, it was shown that the presented algorithm provides a robust and fast tool to automatically estimate apposition and coverage of stent struts in in-vivo OCT pullbacks. This will be important for the integration of this technology in clinical routine and for the analysis of datasets of larger clinical trials

The safety and feasibility of live-stream proctoring for CTO procedures

Background/Introduction: Compared with other percutaneous coronary interventions, chronic total occlusions carries a higher risk of complications, has lower success rates, and higher costs. Multiple types of educational programs have been offered (theoretical courses, live demonstrations) and for the moment on-site direct supervision with proctoring seems to be the most effective method to improve the outcome of CTO PCI procedures. In-person proctoring requires a considerable amount of arrangements and planning, which limits the number of proctoring sessions, prolong the training period, and makes the training process less efficient. Purpose: To assess a new method of educational training, based on audio-video communication between a physician and all cath lab members with an expert that are in different locations. Methods: The study group consisted of nine patients who underwent PCI CTO using the Virtual Proctoring approach. The strategy of the CTO PCI procedure and all the decisions through the intervention were taken only by the proctor. Results: All the procedural steps were performed by the operator guided by the remote proctor. No single decision was taken by the operator alone as the proctor was able to notice perfectly all the angiographic details and all the other important parameters recorded by the AV system. No major complications occurred during the index hospitalization. Conclusions: A new method of virtual proctoring based on live video-communication is feasible and safe even in the case of highly complex CTO PCI procedures. This modern approach is easy to organize between physicians regardless of their location. It could potentially increase global interaction between colleagues and facilitate sharing of knowledge which are both major key aspects in the development of the CTO PCI field. This trial could serve as a basis for future large studies to fully analyze the potential role and benefits of virtual proctoring for complex CTO PCI procedures

PLGA nanoparticles and nanosuspensions with Amphotericin B: Potent in vitro and in vivo alternatives to Fungizone and Ambisome

This paper describes the development of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) and nanosuspensions with the polyene antibiotic amphotericin B (AmB). The nanoformulations were prepared using nanoprecipitation and were characterised with respect to size, zeta potential, morphology, drug crystallinity and content. Standard in vitro sensitivity tests were performed on MRC-5 cells, red blood cells, Leishmania infantum promastigotes and intracellular amastigotes and the fungal species Candida albicans, Aspergillus fumigatus and Trichophyton rubrum. The in vivo efficacy was assessed and compared to that of Fungizone and AmBisome in the acute A. fumigatus mouse model at a dose of 2.5 and 5.0mg/kg AmB equivalents. The developed AmB nanoformulations were equivalently or more effective against the different Leishmania stages and axenic fungi in comparison with the free drug. The in vitro biological activity, and especially hemolytic activity, clearly depended on the preparation parameters of the different nanoformulations. Further, we demonstrated that the superior in vitro antifungal activity could be extrapolated to the in vivo situation. At equivalent dose, the optimal AmB-loaded PLGA NP was about two times and the AmB nanosuspension about four times more efficacious in reducing the total burden than AmBisome. The developed AmB nanomedicines could represent potent and cost-effective alternatives to Fungizone and AmBisome.status: publishe