A Feedback Neural Network for Small Target Motion Detection in Cluttered Backgrounds

Small target motion detection is critical for insects to search for and track mates or prey which always appear as small dim speckles in the visual field. A class of specific neurons, called small target motion detectors (STMDs), has been characterized by exquisite sensitivity for small target motion. Understanding and analyzing visual pathway of STMD neurons are beneficial to design artificial visual systems for small target motion detection. Feedback loops have been widely identified in visual neural circuits and play an important role in target detection. However, if there exists a feedback loop in the STMD visual pathway or if a feedback loop could significantly improve the detection performance of STMD neurons, is unclear. In this paper, we propose a feedback neural network for small target motion detection against naturally cluttered backgrounds. In order to form a feedback loop, model output is temporally delayed and relayed to previous neural layer as feedback signal. Extensive experiments showed that the significant improvement of the proposed feedback neural network over the existing STMD-based models for small target motion detection

Modelling Drosophila motion vision pathways for decoding the direction of translating objects against cluttered moving backgrounds

Decoding the direction of translating objects in front of cluttered moving backgrounds, accurately and efficiently, is still a challenging problem. In nature, lightweight and low-powered flying insects apply motion vision to detect a moving target in highly variable environments during flight, which are excellent paradigms to learn motion perception strategies. This paper investigates the fruit fly Drosophila motion vision pathways and presents computational modelling based on cuttingedge physiological researches. The proposed visual system model features bio-plausible ON and OFF pathways, wide-field horizontal-sensitive (HS) and vertical-sensitive (VS) systems. The main contributions of this research are on two aspects: (1) the proposed model articulates the forming of both direction-selective and direction-opponent responses, revealed as principalfeaturesofmotionperceptionneuralcircuits,inafeed-forwardmanner;(2)italsoshowsrobustdirectionselectivity to translating objects in front of cluttered moving backgrounds, via the modelling of spatiotemporal dynamics including combination of motion pre-filtering mechanisms and ensembles of local correlators inside both the ON and OFF pathways, which works effectively to suppress irrelevant background motion or distractors, and to improve the dynamic response. Accordingly, the direction of translating objects is decoded as global responses of both the HS and VS systems with positive ornegativeoutputindicatingpreferred-direction or null-direction translation.The experiments have verified the effectiveness of the proposed neural system model, and demonstrated its responsive preference to faster-moving, higher-contrast and larger-size targets embedded in cluttered moving backgrounds

Alcohol use and extramarital sex among men in Cameroon

<p>Abstract</p> <p>Background</p> <p>The spread of HIV in sub-Saharan Africa is believed to be driven by unsafe sex, and identification of modifiable risk factors of the latter is needed for comprehensive HIV prevention programming in the region. Some previous studies suggest an association between alcohol abuse and unsafe sexual behaviour, such as multiple concurrent sexual partnerships and inconsistent condom use in sex with non-spousal non-cohabiting partners. However, most of these studies were conducted in developed countries and the few studies in Africa were conducted among well-defined social groups such as men attending beer halls or sexually transmitted infection clinics. We therefore examined the association between alcohol and extramarital sex (a sign of multiple concurrent sexual partnerships) among men in a population-based survey in Cameroon; a low-income country in sub-Saharan Africa with a high rate of alcohol abuse and a generalised HIV epidemic.</p> <p>Methods</p> <p>We analyzed data from 2678 formally married or cohabiting men aged 15 to 59 years, who participated in the 2004 Cameroon Demographic and Health Survey, using a multivariate regression model.</p> <p>Results</p> <p>A quarter of the men (25.8%) declared having taken alcohol before their last sexual intercourse and 21% indicated that the last sex was with a woman other than their wife or cohabiting partner. After controlling for possible confounding by other socio-demographic characteristics, alcohol use was significantly associated with having extramarital sex: adjusted odds ratio (OR) 1.70, 95% confidence intervals (CI) 1.40 to 2.05. Older age (30–44 years: OR 3.06, 95%CI 2.16–4.27 and 45–59 years: OR 4.10, 95%CI 2.16–4.27), higher education (OR 1.25, 95%CI 1.10–1.45), and wealth (OR 1.71, 95%CI 1.50–1.98) were also significantly associated with higher odds of having extramarital sex. The men were more likely to have used a condom in their last sex if it was extramarital (OR 10.50, 95%CI 8.10–13.66). Older age at first sex (16–19 years: OR 0.81, 95%CI 0.72–0.90 and > 19 years: OR 0.74, 95% CI 0.65–0.87) and being the head of a household (OR 0.17, 95%CI 0.14–0.22) significantly decreased the odds of having sex outside of marriage. Religion and place of residence (whether urban or rural) were not significantly associated with extramarital sex.</p> <p>Conclusion</p> <p>Alcohol use is associated with having multiple concurrent non-spousal sexual partnerships among married men in Cameroon. We cannot infer a causal relationship between alcohol abuse and unsafe sex from this cross-sectional study, as both alcohol use and unsafe sexual behaviour may have a common set of causal personal and social factors. However, given the consistency with results of studies in other settings and the biologic plausibility of the link between alcohol intake and unsafe sex, our findings underscore the need for integrating alcohol abuse and HIV prevention efforts in Cameroon and other African countries with similar social profiles.</p

Robust Models for Optic Flow Coding in Natural Scenes Inspired by Insect Biology

The extraction of accurate self-motion information from the visual world is a difficult problem that has been solved very efficiently by biological organisms utilizing non-linear processing. Previous bio-inspired models for motion detection based on a correlation mechanism have been dogged by issues that arise from their sensitivity to undesired properties of the image, such as contrast, which vary widely between images. Here we present a model with multiple levels of non-linear dynamic adaptive components based directly on the known or suspected responses of neurons within the visual motion pathway of the fly brain. By testing the model under realistic high-dynamic range conditions we show that the addition of these elements makes the motion detection model robust across a large variety of images, velocities and accelerations. Furthermore the performance of the entire system is more than the incremental improvements offered by the individual components, indicating beneficial non-linear interactions between processing stages. The algorithms underlying the model can be implemented in either digital or analog hardware, including neuromorphic analog VLSI, but defy an analytical solution due to their dynamic non-linear operation. The successful application of this algorithm has applications in the development of miniature autonomous systems in defense and civilian roles, including robotics, miniature unmanned aerial vehicles and collision avoidance sensors

Gendered Sexual Uses of Alcohol and Associated Risks: A Qualitative Study of Nigerian University Students

Background: Alcohol misuse among young people is a global phenomenon. In many countries, young people engage in heavy drinking and this exacerbates risky sexual behaviour. In Nigeria, alcohol held multiple roles in the traditional era but was mainly consumed by adult males for pleasure. Adult females and young people were culturally constrained from drinking in most communities. In contemporary Nigeria, young people’s drinking is increasing, and many engage in sexual intercourse under the influence of alcohol. Methods: This study draws on the traditional gender and social sexual scripts to explore the factors that motivate young people to use alcohol for sexual purposes. In-depth interviews were conducted with 19 to 23-year old male and female undergraduate students from a Nigerian university. Thematic analysis was conducted with the aid of NVivo 10 software. Results: Men drink to become confident to initiate sexual relationships, stimulate sexual urges, prolong erection, increase sexual satisfaction and become more aggressive during sexual intercourse. Women also drink to be bold in initiating sexual relationships, for sexual arousal and to increase satisfaction. Relatedly, not every brand of alcohol is used for sexual purposes. For example, while men use ‘herbal’ alcoholic beverages and a mixture of locally-produced gin and marijuana, women use champagne and other flavoured alcoholic beverages. The results also revealed that young people use alcohol or salt in a bid to prevent conception after sexual intercourse. Conclusions: Adherence to the traditional gender (masculinity) and social sexual scripts amongst men and the enactment of what appears to be a new form of femininity script amongst women contribute to a culturally specific understanding of the motivations to use alcohol for sexual purposes. Evidence-based strategies should be employed to distribute information about the consequences of sexual intercourse under the influence of alcohol