Improving Image Captioning with Conditional Generative Adversarial Nets

In this paper, we propose a novel conditional-generative-adversarial-nets-based image captioning framework as an extension of traditional reinforcement-learning (RL)-based encoder-decoder architecture. To deal with the inconsistent evaluation problem among different objective language metrics, we are motivated to design some "discriminator" networks to automatically and progressively determine whether generated caption is human described or machine generated. Two kinds of discriminator architectures (CNN and RNN-based structures) are introduced since each has its own advantages. The proposed algorithm is generic so that it can enhance any existing RL-based image captioning framework and we show that the conventional RL training method is just a special case of our approach. Empirically, we show consistent improvements over all language evaluation metrics for different state-of-the-art image captioning models. In addition, the well-trained discriminators can also be viewed as objective image captioning evaluatorsComment: 12 pages; 33 figures; 36 refenences; Accepted by AAAI201

Molecular mechanisms separating two axonal pathways during embryonic development of the avian optic tectum

During embryonic development of the avian optic tectum, retinal and tectobulbar axons form an orthogonal array of nerve processes. Growing axons of both tracts are transiently very closely apposed to each other. Despite this spatial proximity, axons from the two pathways do not intermix, but instead restrict their growth to defined areas, thus forming two separate plexiform layers, the stratum opticum and the stratum album centrale. In this study we present experimental evidence indicating that the following three mechanisms might play a role in segregating both axonal populations: Retinal and tectobulbar axons differ in their ability to use the extracellular matrix protein laminin as a substrate for axonal elongation; the environment in the optic tectum is generally permissive for retinal axons, but is specifically nonpermissive for tectobulbar axons, resulting in a strong fasciculation of the latter; and growth cones of temporal retinal axons are reversibly inhibited in their motility by direct contact with the tectobulbar axon's membrane

Exercise, cognition and Alzheimer’s disease: More is not necessarily better

Regional hypoperfusion, associated with a reduction in cerebral metabolism, is a hallmark of Alzheimer’s disease (AD) and contributes to cognitive decline. Cerebral perfusion and hence cognition can be enhanced by exercise. The present review describes first how the effects of exercise on cerebral perfusion in AD are mediated by nitric oxide (NO) and tissue-type plasminogen activator, the release of which is regulated by NO. A conclusion of clinical relevance is that exercise may not be beneficial for the cognitive functioning of all people with dementia if cardiovascular risk factors are present. The extent to which cardiovascular risk factors play a role in the selection of older people with dementia in clinical studies will be addressed in the second part of the review in which the effects of exercise on cognition are presented. Only eight relevant studies were found in the literature, emphasizing the paucity of studies in this field. Positive effects of exercise on cognition were reported in seven studies, including two that excluded and two that included patients with cardiovascular risk factors. These findings suggest that cardiovascular risk factors do not necessarily undo the beneficial effects of exercise on cognition in cognitively impaired people. Further research is called for, in view of the limitations of the clinical studies reviewed here.

An in vitro spinal cord injury model to screen neuroregenerative materials

Implantable 'structural bridges' based on nanofabricated polymer scaffolds have great promise to aid spinal cord regeneration. Their development (optimal formulations, surface functionalizations, safety, topographical influences and degradation profiles) is heavily reliant on live animal injury models. These have several disadvantages including invasive surgical procedures, ethical issues, high animal usage, technical complexity and expense. In vitro 3-D organotypic slice arrays could offer a solution to overcome these challenges, but their utility for nanomaterials testing is undetermined. We have developed an in vitro model of spinal cord injury that replicates stereotypical cellular responses to neurological injury in vivo, viz. reactive gliosis, microglial infiltration and limited nerve fibre outgrowth. We describe a facile method to safely incorporate aligned, poly-lactic acid nanofibre meshes (±poly-lysine + laminin coating) within injury sites using a lightweight construct. Patterns of nanotopography induced outgrowth/alignment of astrocytes and neurons in the in vitro model were strikingly similar to that induced by comparable materials in related studies in vivo. This highlights the value of our model in providing biologically-relevant readouts of the regeneration-promoting capacity of synthetic bridges within the complex environment of spinal cord lesions. Our approach can serve as a prototype to develop versatile bio-screening systems to identify materials/combinatorial strategies for regenerative medicine, whilst reducing live animal experimentation.EPSRC Doctoral Training Centre in regenerative medicine (EP/F500491/1

A fractal nature for polymerized laminin

Polylaminin (polyLM) is a non-covalent acid-induced nano- and micro-structured polymer of the protein laminin displaying distinguished biological properties. Polylaminin stimulates neuritogenesis beyond the levels achieved by ordinary laminin and has been shown to promote axonal regeneration in animal models of spinal cord injury. Here we used confocal fluorescence microscopy (CFM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize its three-dimensional structure. Renderization of confocal optical slices of immunostained polyLM revealed the aspect of a loose flocculated meshwork, which was homogeneously stained by the antibody. On the other hand, an ordinary matrix obtained upon adsorption of laminin in neutral pH (LM) was constituted of bulky protein aggregates whose interior was not accessible to the same anti-laminin antibody. SEM and AFM analyses revealed that the seed unit of polyLM was a flat polygon formed in solution whereas the seed structure of LM was highly heterogeneous, intercalating rod-like, spherical and thin spread lamellar deposits. As polyLM was visualized at progressively increasing magnifications, we observed that the morphology of the polymer was alike independently of the magnification used for the observation. A search for the Hausdorff dimension in images of the two matrices showed that polyLM, but not LM, presented fractal dimensions of 1.55, 1.62 and 1.70 after 1, 8 and 12 hours of adsorption, respectively. Data in the present work suggest that the intrinsic fractal nature of polymerized laminin can be the structural basis for the fractal-like organization of basement membranes in the neurogenic niches of the central nervous system.This work was supported by a grant from the Brazilian National Research Council (CNPq; 476772/2008-7) to TCS. 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