Endogenous-like orienting of visual attention in rats

This study investigated the orienting of visual attention in rats using a 3-hole nose-poke task analogous to Posner, Information processing in cognition: the Loyola Symposium, Erlbaum, Hillsdale, (1980) covert attention task for humans. The effects of non-predictive (50% valid and 50% invalid) and predictive (80% valid and 20% invalid) peripheral visual cues on reaction times and response accuracy to a target stimulus, using Stimuli-Onset Asynchronies (SOAs) varying between 200 and 1,200 ms, were investigated. The results showed shorter reaction times in valid trials relative to invalid trials for both subjects trained in the non-predictive and predictive conditions, particularly when the SOAs were 200 and 400 ms. However, the magnitude of this validity effect was significantly greater for subjects exposed to predictive cues, when the SOA was 800 ms. Subjects exposed to invalid predictive cues exhibited an increase in omission errors relative to subjects exposed to invalid non-predictive cues. In contrast, valid cues reduced the proportion of omission errors for subjects trained in the predictive condition relative to subjects trained in the non-predictive condition. These results are congruent with those usually reported for humans and indicate that, in addition to the exogenous capture of attention promoted by both predictive and non-predictive peripheral cues, rats exposed to predictive cues engaged an additional slower process equivalent to human`s endogenous orienting of attention. To our knowledge, this is the first demonstration of an endogenous-like process of covert orienting of visual attention in rats.

Effects of intensity and positional predictability of a visual stimulus on simple reaction time

The influence of visual stimuli intensity on manual reaction time (RT) was investigated under two different attentional settings: high (Experiment 1) and low (Experiment 2) stimulus location predictability. These two experiments were also run under both binocular and monocular viewing conditions. We observed that RT decreased as stimulus intensity increased. It also decreased as the viewing condition was changed from monocular to binocular as well as the location predictability shifted from low to high. A significant interaction was found between stimulus intensity and viewing condition, but no interaction was observed between neither of these factors and location predictability. These findings support the idea that the stimulus intensity effect arises from purely sensory, pre-attentive mechanisms rather than deriving from more efficient attentional capture. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

The effects of target length on the visual control of step length for hard and soft impacts

Adjustments to gait were examined when positioning the foot within a narrow target at the end of an approach for two impact conditions, hard and soft. Participants (6 M, 6 F) ran toward a target of three lengths along a 10-m walkway consisting of two marker strips with alternating black and white 0.5-m markings. Five trials were conducted for each target length and impact task, with trials block randomized between the 6 participants of each gender. A 50-Hz digital video camera panned and filmed each trial from an elevated position adjacent to the walkway. Video footage was digitized to deduce the gait characteristics. A linear speed/accuracy tradeoff between target length and approach time was found for both impact tasks (hard, r = 0.99, p < 0.01; soft, r = 0.96, p < 0.05). For the hard-impact task, visual control time increased linearly (r = 0.99, p < 0.05) when whole-body approach velocity decreased. Visual control time was unaffected by whole-body approach velocity in the soft-impact task. A constant tau-margin of 1.08 describes the onset of visual control when approaching a target while running, with the control of braking during visual control described by a tau-dot of –0.85. Further research is needed to examine the control of braking in different targeting tasks.

Ageing effects on visual reaction time in a single task condition and when treadmill walking

Visual reaction time (RT) was measured in 10 older men (mean age, 71.1 years) and gender-matched controls (mean age, 26.3 years) when standing (single task) and when walking on a motor-driven treadmill (dual task). There were 90 quasirandomly presented trials over 15 min in each condition. Longer mean and median RTs were observed in the dual task compared to the single task. Older males had significantly slower mean and median RTs (315 and 304 ms, respectively) than the younger group (273 and 266 ms, respectively) in both task conditions. There were no age or condition effects on with in-subject variability. Both groups showed a trend of increasing RT over the 90 single task trials but when walking only the younger group slowed. These novel findings demonstrate high but sustained attention by older adults when walking. It is proposed that the motor task's attentional demands might contribute to their slower preferred walking speed.

Phenomenological analysis of experimentally induced visual mental imagery associated with shamanic journeying to the lower world

This study explored ostensibly shamanic journeying imagery by (a) assessing visual images across induction techniques (i.e., sonic driving, Ganzfeld, relaxation, and sitting with eyes open); (b) determining combination(s) of induction technique and instructions most associated with religious imagery; and (c) investigating the origins of visual imagery. Six participants were randomly assigned to factorial combinations of a 3 x 4 mixed design (levels of instruction x levels of induction) and were administered the Modified Affect Bridge to explore the origins of mental imagery reported during the experimental conditions. Phenomenological analysis yielded comprehensive constituent themes. Harner’s (1990) shamanic journeying, coupled with religious, instructions were associated with the highest religious imagery, while visual images associated with shamanic journeying were derived primarily from autobiographical memories.

Visual tracking of vehicles using multiresolution analysis and neural network

This paper describes the procedure for detection and tracking of a vehicle from an on-road image sequence taken by a monocular video capturing device in real time. The main objective of such a visual tracking system is to closely follow objects in each frame of a video stream, such that the object position as well as other geometric information are always known. In the tracking system described, the video capturing device is also moving. It is a challenge to detect and track a moving vehicle under a constantly changing environment coupled to real time video processing. The system suggested is robust to implement under different illuminating conditions by using the monocular video capturing device. The vehicle tracking algorithm is one of the most important modules in an autonomous vehicle system, not only it should be very accurate but also must have the safety of other vehicles, pedestrians, and the moving vehicle itself. In order to achieve this an algorithm of multi resolution technique based on Haar basis functions were used for the wavelet transform, where a combination of classification was carried out with the multilayer feed forward neural network. The classification is done in a reduced dimensional space, where principle component analysis (PCA) dimensional reduction technique has been applied to make the classification process much more efficient. The results show the effectiveness of the proposed methodology.

Context-dependent visual preferences in starlings and blue tits: mate choice and light environment

There is considerable interest in the role that ultraviolet (UV) cues play in the foraging and mate choice decisions of birds. However, with the exception of the zebra finch, Taeniopygia guttata, it is not yet clear whether ultraviolet preferences are context specific, or whether birds show a general preference for full-avian-spectrum environments 320-700 nm) irrespective of the activity in which they are engaged. We investigated whether European starlings, Sturnus vulgaris, and blue tits, Parus caeruleus, show general (nonresource based) or context-specific preferences for full-spectrum environments. We found that neither species showed a general preference for UV-present (UV+) over UV-deficient (UV-) environments, when those environments contained no resources (experiment 1). Furthermore, neither species showed a UV+ preference when cages contained food, water and perches (starlings; experiment 2) or food, perches and heterospecifics (blue tits; Hunt et al. 1999. Animal Behaviour, 58, 809-815). However, both species did show highly significant preferences for UV+ conditions when viewing potential mates. Such experiments are necessary before one can conclude that particular wavebands have specific relevance to mate choice. In fact, our results suggest that the importance of particular wavelength compositions do indeed vary with behavioural context. (C) 2002 The Association for the Study of Animal Behaviour.

Study on the visual performance of a vernacular dwelling in Egypt

Vernacular dwelling buildings located in hot arid regions are well known for their sensitive architecture response to the region’s climatic conditions and the socio-cultural norms. The architectural value of these buildings is not only limited to their historical merit, but also to the human conscious adaptation to its context and the optimum utilisation of natural resources creating both a pleasant and a functional environment. The majority of these traditional dwellings are well recognised for their unique perforated fenestration system and courtyard arrangement that evolved to control the harsh solar, climatic conditions without compromising the quality of space and occupants’ wellbeing. However, the successful design of these features and solutions cannot be fully appreciated without understanding the nature of daylight and solar radiation in which these buildings are revealed. This paper investigates the impact of the characteristic of the dense narrow streets of medieval cities on the visual performance of a typical courtyard house in Cairo.The paper examines the daylight  behaviour of one of the well-known historic alleys and of a courtyard house in Cairo. The paper analyzes and measures the variability in the visual perception and comfort for a typical pedestrian street and the occupants of the house using a simulation modelling tool (Integrated Environmental Solutions (IES) software). The paper gives an insight into the overall visual performance of the urban fabric that shapes of the microclimate, which is an important ingredient of the overall identity of the place.

Study on the visual performance of a traditional residential neighborhood in old Cairo

Traditional dwellings located in the hot arid zones of the Arabian regions are well known for their sensitive architectural response to the region’s climatic conditions and socio-cultural norms. The majority of these dwellings are well recognized for their courtyard arrangement and perforated fenestration system that evolved to control the harsh solar, climatic conditions without compromising the aesthetic quality of space and occupants’ wellbeing. However, the unique visual characteristics of these structures cannot be fully appreciated by assessing the visual performance of buildings in isolation from their urban context. Given the fact that much of the character of the traditional settlements of this region came from the collective visual perception of their architectural components as well as urban patterns. This paper presents a methodology that can be used to assess daylight behaviour at an architectural level as well as at an urban scale. The work examines the daylight behaviour of a well-known historic alleyway and of a courtyard house in the old city of Cairo. The variability in the visual perception and comfort for a typical pedestrian street and the occupants of the house was predicted using Radiance IES simulation modelling tool and a scaled model under an artificial sky dome. A comparative analysis between simulated results and measured values at target points was conducted and the results reveal a reasonable agreement with the simulation results. Preliminary results from the first phase of modelling were presented that give an insight into the overall visual experience in the traditional settlements in the Old City of Cairo where daylight has contributed to the place unique sense of identity.

Study on the visual performance of a traditional residential neighborhood in Old Cairo

Traditional dwellings located in the hot arid zone in Egypt are well known for their sensitive architectural response to the region's climatic conditions and socio-cultural norms. The majority of these dwellings are well recognized for their courtyard arrangement and perforated fenestration systems that evolved to control the harsh solar, climatic conditions without compromising the aesthetic quality of the space and the occupants' well-being. The unique visual characteristics of these structures cannot be fully appreciated by assessing the visual performance of buildings in isolation from their urban context. Much of the character of the traditional urban fabric of this region came from the collective visual perception of its architectural components as well as urban patterns. This paper examines daylight behavior of a well-known historic alleyway and of a courtyard house in the Old City of Cairo. Using the Radiance IES simulation modeling tool and a scaled model under an artificial sky dome, the paper investigates the visual comfort in a typical pedestrian street and a selected house. A comparative analysis between simulated results and measured values at target points was conducted. The results indicate a reasonable agreement with the simulation results. The paper gives an insight into the overall visual experience in the traditional settlements in the Old City of Cairo in relation to daylight components and hence their contribution to the unique sense of identity of the place.

The importance of sand albedo for the thermal conditions on sea turtle nesting beaches

At Ascension Island and Cyprus, major nesting areas for green turtles (Chelonia mydas) in the Atlantic and Mediterranean, respectively, visual inspection shows some beaches are light in colour while others are darker. We objectively measured the albedo of the sand on different beaches, i.e. the percentage of the incident solar radiation that was reflected from the sand surface. At sites where albedo was recorded, we also measured the temperature of the sand at nest depths. At both rookeries, the sand temperature was markedly higher on darker beaches due to greater absorption of the incident solar radiation over the diurnal cycle. Temperature loggers buried at nest depths revealed seasonal changes in temperature on both islands, but showed that the lowest temperatures found on the darker beaches rarely dropped below the highest temperatures on the lighter beaches. Sea turtles exhibit temperature-dependent sex determination. Since sand albedo is a major avenue for the production of a range of incubation temperatures on both islands, it will also have profound implications for hatchling sex ratios. In comparison with both Ascension Island and Cyprus, for samples collected from sea turtle rookeries around the world there was an even greater range in sand albedo values. This suggests that sand albedo, a factor that has previously received little consideration, will have profound implications for nest temperatures, and hence hatchling sex ratios, for other populations and species.

Towards person authentication by fusing visual and thermal face biometrics

In this chapter we focus on face appearance-based biometrics. The cheap and readily available hardware used to acquire data, their non-invasiveness and the ease of employing them from a distance and without the awareness of the user, are just some of the reasons why these continue to be of great practical interest. However, a number of research challenges remain. Specifically, face biometrics have traditionally focused on images acquired in the visible light spectrum and these are greatly affected by such extrinsic factors such as the illumination, camera angle (or, equivalently, head pose) and occlusion. In practice, the effects of changing pose are usually least problematic and can oftentimes be overcome by acquiring data over a time period, e.g., by tracking a face in a surveillance video. Consequently, image sequence or image set matching has recently gained a lot of attention in the literature [137–139] and is the paradigm adopted in this chapter as well. In other words, we assume that the training image set for each individual contains some variability in pose, but is not obtained in scripted conditions or in controlled illumination. In contrast, illumination is much more difficult to deal with: the illumination setup is in most cases not practical to control and its physics is difficult to accurately model. Thermal spectrum imagery is useful in this regard as it is virtually insensitive to illumination changes, as illustrated in Fig. 6.1. On the other hand, it lacks much of the individual, discriminating facial detail contained in visual images. In this sense, the two modalities can be seen as complementing each other. The key idea behind the system presented in this chapter is that robustness to extreme illumination changes can be achieved by fusing the two. This paradigm will further prove useful when we consider the difficulty of recognition in the presence of occlusion caused by prescription glasses.

Real-time lane detection on suburban streets using visual cue integration

The detection of lane boundaries on suburban streets using images obtained from video constitutes a challenging task. This is mainly due to the difficulties associated with estimating the complex geometric structure of lane boundaries, the quality of lane markings as a result of wear, occlusions by traffic, and shadows caused by road-side trees and structures. Most of the existing techniques for lane boundary detection employ a single visual cue and will only work under certain conditions and where there are clear lane markings. Also, better results are achieved when there are no other onroad objects present. This paper extends our previous work and discusses a novel lane boundary detection algorithm specifically addressing the abovementioned issues through the integration of two visual cues. The first visual cue is based on stripe-like features found on lane lines extracted using a two-dimensional symmetric Gabor filter. The second visual cue is based on a texture characteristic determined using the entropy measure of the predefined neighbourhood around a lane boundary line. The visual cues are then integrated using a rulebased classifier which incorporates a modified sequential covering algorithm to improve robustness. To separate lane boundary lines from other similar features, a road mask is generated using road chromaticity values estimated from CIE L*a*b* colour transformation. Extraneous points around lane boundary lines are then removed by an outlier removal procedure based on studentized residuals. The lane boundary lines are then modelled with Bezier spline curves. To validate the algorithm, extensive experimental evaluation was carried out on suburban streets and the results are presented. 

Variável colativa por complexidade, seus efeitos no campo visual monocular

Os resultados das análises feitas com estes dados indicaram diferenças significativas no aumento da amplitude do plano meridiano horizontal nasal do campo visual monocular, medidas em unidades angulares. As diferenças foram interpretadas como indicativas da influência dos três diferentes níveis de complexidade dos estímulos visuais. Concluiu-se, portanto, que a variável colativa por complexidade influi no ato perceptual do reconhecimento visual.

Efficacy of herbicides applied to Digitaria horizontalis plants under different water conditions

Este projeto objetivou relacionar a eficiência de controle de herbicidas inibidores da ACCase aplicados em pós-emergência em plantas de Digitaria horizontalis submetidas a diferentes teores de água no solo. Os experimentos foram conduzidos em casa de vegetação, com a aplicação de três diferentes herbicidas (fluazifop-p-butil, haloxyfop-methyl e sethoxydim + óleo mineral Assist). O delineamento experimental utilizado para cada herbicida foi inteiramente casualizado, com quatro repetições, constituído de um fatorial 3 x 4, sendo a combinação de três manejos hídricos (-0,03, 0,07 e -1,5 MPa) e quatro doses desses produtos (100, 50, 25 e 0% da dose recomendada). A aplicação dos herbicidas foi feita em dois estádios vegetativos: 4-6 folhas e 2-3 perfilhos. As avaliações visuais de fitotoxicidade foram realizadas aos 14 dias após a aplicação e avaliou-se a matéria seca das plantas ao final do estudo. A eficiência de controle não foi influenciada pelos manejos hídricos quando se aplicou a dose recomendada de todos os herbicidas na fase inicial de desenvolvimento das plantas (estádio de 4-6 folhas). em aplicações tardias (estádio de 2-3 perfilhos), as plantas mantidas sob estresse hídrico apresentaram menor fitotoxicidade.