Assessing visual fields for driving in patients with paracentral scotomata

Background: The binocular Esterman visual field test (EVFT) is the current visual field test for driving in the UK. Merging of monocular field tests (Integrated Visual Field, IVF) has been proposed as an alternative for glaucoma patients. Aims: To examine the level of agreement between the EVFT and IVF for patients with binocular paracentral scotomata, caused by either ophthalmological or neurological conditions, and to compare outcomes with useful field of view (UFOV) performance, a test of visual attention thought to be important in driving. Methods: 60 patients with binocular paracentral scotomata but normal visual acuity (VA) were recruited prospectively. Subjects completed and were classified as “pass” or “fail” for the EVFT, IVF and UFOV. Results: Good agreement occurred between the EVFT and IVF in classifying subjects as “pass” or “fail” (kappa?=?0.84). Classifications disagreed for four subjects with paracentral scotomata of neurological origin (three “passed” IVF yet “failed” EVFT). Mean UFOV scores did not differ between those who “passed” and those who “failed” both visual field tests (p?=?0.11). Agreement between the visual field tests and UFOV was limited (EVFT kappa?=?0.22, IVF kappa 0.32). Conclusions: Although the IVF and EVFT agree well in classifying visual fields with regard to legal fitness to drive in the UK, the IVF “passes” some individuals currently classed as unfit to drive due to paracentral scotomata of non-glaucomatous origin. The suitability of the UFOV for assessing crash risk in those with visual field loss is questionable.

Adults with dyslexia exhibit large effects of crowding, increased dependence on cues, and detrimental effects of distractors in visual search tasks

Difficulties in visual attention are increasingly being linked to dyslexia. To date, the majority of studies have inferred functionality of attention from response times to stimuli presented for an indefinite duration. However, in paradigms that use reaction times to investigate the ability to orient attention, a delayed reaction time could also indicate difficulties in signal enhancement or noise exclusion once oriented. Thus, in order to investigate attention modulation and visual crowding effects in dyslexia, this study measured stimulus discrimination accuracy to rapidly presented displays. Adults with dyslexia (AwD) and controls discriminated the orientation of a target in an array of different numbers of - and differently spaced - vertically orientated distractors. Results showed that AwD: were disproportionately impacted by (i) close spacing and (ii) increased numbers of stimuli, (iii) did use pre-cues to modulate attention, but (iv) used cues less successfully to counter effects of increasing numbers of distractors. A greater dependence on pre-cues, larger effects of crowding and the impact of increased numbers of distractors all correlated significantly with measures of literacy. These findings extend previous studies of visual crowding of letters in dyslexia to non-complex stimuli. Overall, AwD do not use cues less, but they do use cues less successfully. We conclude that visual attention is an important factor to consider in the aetiology of dyslexia. The results challenge existing theoretical accounts of visual attention deficits, which alone are unable to comprehensively explain the pattern of findings demonstrated here.

Adults with dyslexia demonstrate large effects of crowding and detrimental effects of distractors in a visual tilt discrimination task

Previous research has shown that adults with dyslexia (AwD) are disproportionately impacted by close spacing of stimuli and increased numbers of distractors in a visual search task compared to controls [1]. Using an orientation discrimination task, the present study extended these findings to show that even in conditions where target search was not required: (i) AwD had detrimental effects of both crowding and increased numbers of distractors; (ii) AwD had more pronounced difficulty with distractor exclusion in the left visual field and (iii) measures of crowding and distractor exclusion correlated significantly with literacy measures. Furthermore, such difficulties were not accounted for by the presence of covarying symptoms of ADHD in the participant groups. These findings provide further evidence to suggest that the ability to exclude distracting stimuli likely contributes to the reported visual attention difficulties in AwD and to the aetiology of literacy difficulties. The pattern of results is consistent with weaker and asymmetric attention in AwD.

To which extent can attention and/or modulation explains deficits in dyslexia?

This thesis investigates the visual deficits associated with developmental dyslexia, particularly that of visual attention. Visual attention has previously been investigated in a wide array of behavioural and psychophysical (amongst others) studies but not many have produced consistent findings. Attention processes are believed to play an integral part in depicting the overall "extent" of reading deficits in dyslexia, so it was of paramount importance to aim at such attention mechanisms in this research. The experiments in this thesis focused on signal enhancement and noise (distractor) exclusion. Given the flexibility of the visual search paradigms employed in this research, factors such as visual crowding and attention distribution was also investigated. The experiments systematically manipulated noise (by increasing distractor count, i.e. set-size), crowding (varying the spacing between distractors), attention allocation (use of peripheral cues to direct attention), and attention distribution (influence of one visual field over the other), all of which were tied to a critical factor, the "location/spatial/decisional uncertainty". Adults with dyslexia were: (i) able to modulate attention appropriately using peripheral pre-cues, (ii) severely affected by crowding, and (iii) unable to counteract increased set-sizes when post or un-cued, the latter signifying poor distractor (noise) suppression. By controlling for location uncertainty, the findings confirmed that adults with dyslexia were yet again affected by crowding and set-size, in addition to an asymmetric attention distribution. Confounding effects of ADHD symptoms did not explain a significant independent variance in performance, suggesting that the difficulty shown by adult dyslexics were not accounted for by co-morbid ADHD. Furthermore, the effects of crowding, set-size and asymmetric attention correlated significantly with literacy, but not ADHD measures. It is believed that a more diffuse and an asymmetric attention system (in dyslexia) to be the limiting factor concerning noise exclusion and attention distribution. The findings from this thesis add to the current understanding of the potential role of deficits in visual attention in dyslexia and in the literacy difficulties experienced by this population.

Bottleneck Problem Solution using Biological Models of Attention in High Resolution Tracking Sensors

Every high resolution imaging system suffers from the bottleneck problem. This problem relates to the huge amount of data transmission from the sensor array to a digital signal processing (DSP) and to bottleneck in performance, caused by the requirement to process a large amount of information in parallel. The same problem exists in biological vision systems, where the information, sensed by many millions of receptors should be transmitted and processed in real time. Models, describing the bottleneck problem solutions in biological systems fall in the field of visual attention. This paper presents the bottleneck problem existing in imagers used for real time salient target tracking and proposes a simple solution by employing models of attention, found in biological systems. The bottleneck problem in imaging systems is presented, the existing models of visual attention are discussed and the architecture of the proposed imager is shown.

Múltiplos fluxos ópticos e o processamento atentivo da informação visual

The environment in which we live in, we constantly deal with a huge amount of dynamic information, thus, attention is an indispensable cognitive resource that allows an effective selection of stimuli for our survival. From this, investigating how we process our encouragement in movements and how the attention spreads into a space to serve more than one stimuli simultanously is something very important. The behavioural urgence hipothesis suggests that the encouragement in a movement of approaching shows a certain priority in the process related to objects which are in a movement away, but there are researches that point out that it might not happen in an attentive phase, but instead as a priorization of motor response. There are also many controversies found in researches about attentive focalization, in which some studies suggest that the focus of attention would work in a similar manner to a zoom lens, while some searches indicate that the focus of attention could be shared to answer some stimuli in non contiguous regions. This study tried to investigate through two experiments the effect of attentive priorization by encouragement in movements and how the attention is spread with distractors stimuli. The first experiment investigated if the amount of moving flows really influenced in the process of information. The results indicate an effect of priorization of the flows guided in relation to aleatory ones and also from the unique flow due to dual flow. The second experiment investigated how the distribution of attention is in a space with the use of flows as an exogenous cue. The results indicate that the focus of attention works as the one suggested in the zoom lens model.

Memory-Based Attentional Guidance: A Window to the Relationship between Working Memory and Attention

Attention, the cognitive means by which we prioritize the processing of a subset of information, is necessary for operating efficiently and effectively in the world. Thus, a critical theoretical question is how information is selected. In the visual domain, working memory (WM)—which refers to the short-term maintenance and manipulation of information that is no longer accessible by the senses—has been highlighted as an important determinant of what is selected by visual attention. Furthermore, although WM and attention have traditionally been conceived as separate cognitive constructs, an abundance of behavioral and neural evidence indicates that these two domains are in fact intertwined and overlapping. The aim of this dissertation is to better understand the nature of WM and attention, primarily through the phenomenon of memory-based attentional guidance, whereby the active maintenance of items in visual WM reliably biases the deployment of attention to memory-matching items in the visual environment. The research presented here employs a combination of behavioral, functional imaging, and computational modeling techniques that address: (1) WM guidance effects with respect to the traditional dichotomy of top-down versus bottom-up attentional control; (2) under what circumstances the contents of WM impact visual attention; and (3) the broader hypothesis of a predictive and competitive interaction between WM and attention. Collectively, these empirical findings reveal the importance of WM as a distinct factor in attentional control and support current models of multiple-state WM, which may have broader implications for how we select and maintain information.

Descriptive analysis of the test of everyday attention for children in a Spanish normative sample

Introduction. Test of Everyday Attention for Children (TEA-Ch) has been validated in different countries demonstrating that it is an instrument with a correct balance between reliability and duration. Given the shortage of trustworthy instruments of evaluation in our language for infantile population we decide to explore the Spanish version of the TEA-Ch. Methods. We administered TEA-Ch (version A) to a sample control of 133 Spanish children from 6 to 11 years enrolled in school in the Community of Madrid. Four children were selected at random by course of Primary Education, distributing the sex of equivalent form. Descriptive analysis and comparison by ages and sex in each of the TEA-Ch's subtests were conducted to establish a profile of the sample. In order to analyze the effect of the age, subjects were grouped in six sub-samples: 6, 7, 8, 9, 10 and 11 years-old. Results. This first descriptive analysis demonstrates age exerted a significant effect on each measure, due to an important "jump" in children's performance between 6 and 7 years-old. The effect of sex was significant only in two visual attention measures (Sky Search & Map) and interaction age and sex exerted a significant effect only in the dual task (Score DT). Conclusions. The results suggest that the Spanish version of the TEA-Ch (A) might be a useful instrument to evaluate attentional processes in Spanish child population.

Human cortical processing of colour and pattern

Investigated human visual processing of simple two-colour patterns using a delayed match to sample paradigm with positron emission tomography (PET). This study is unique in that the authors specifically designed the visual stimuli to be the same for both pattern and colour recognition with all patterns being abstract shapes not easily verbally coded composed of two-colour combinations. The authors did this to explore those brain regions required for both colour and pattern processing and to separate those areas of activation required for one or the other. 10 right-handed male volunteers aged 18–35 yrs were recruited. The authors found that both tasks activated similar occipital regions, the major difference being more extensive activation in pattern recognition. A right-sided network that involved the inferior parietal lobule, the head of the caudate nucleus, and the pulvinar nucleus of the thalamus was common to both paradigms. Pattern recognition also activated the left temporal pole and right lateral orbital gyrus, whereas colour recognition activated the left fusiform gyrus and several right frontal regions.

Different cognitive profiles for single compared with recurrent fallers without Dementia

Relationships between self-reported retrospective falls and cognitive measures (executive function, reaction time, processing speed, working memory, visual attention) were examined in a population based sample of older adults (n = 658). Two of the choice reaction time tests involved inhibiting responses to either targets of a specific color or location with hand and foot responses. Potentially confounding demographic variables, medical conditions and postural sway were controlled for in logistic regression models, excluding participants with possible cognitive impairment. A factor analysis of cognitive measures extracted factors measuring reaction time, accuracy and inhibition, and visual search. Single fallers did not differ from non-fallers in terms of health, sway or cognitive function, except that they performed worse on accuracy and inhibition. In contrast, recurrent fallers performed worse than non-fallers on all measures. Results suggest that occasional falls in late life may be associated with subtle age-related changes in the pre-frontal cortex leading to failures of executive control, whereas recurrent falling may result from more advanced brain ageing that is associated with generalized cognitive decline.

Image synthesis based on a model of human vision

Modern computer graphics systems are able to construct renderings of such high quality that viewers are deceived into regarding the images as coming from a photographic source. Large amounts of computing resources are expended in this rendering process, using complex mathematical models of lighting and shading. However, psychophysical experiments have revealed that viewers only regard certain informative regions within a presented image. Furthermore, it has been shown that these visually important regions contain low-level visual feature differences that attract the attention of the viewer. This thesis will present a new approach to image synthesis that exploits these experimental findings by modulating the spatial quality of image regions by their visual importance. Efficiency gains are therefore reaped, without sacrificing much of the perceived quality of the image. Two tasks must be undertaken to achieve this goal. Firstly, the design of an appropriate region-based model of visual importance, and secondly, the modification of progressive rendering techniques to effect an importance-based rendering approach. A rule-based fuzzy logic model is presented that computes, using spatial feature differences, the relative visual importance of regions in an image. This model improves upon previous work by incorporating threshold effects induced by global feature difference distributions and by using texture concentration measures. A modified approach to progressive ray-tracing is also presented. This new approach uses the visual importance model to guide the progressive refinement of an image. In addition, this concept of visual importance has been incorporated into supersampling, texture mapping and computer animation techniques. Experimental results are presented, illustrating the efficiency gains reaped from using this method of progressive rendering. This visual importance-based rendering approach is expected to have applications in the entertainment industry, where image fidelity may be sacrificed for efficiency purposes, as long as the overall visual impression of the scene is maintained. Different aspects of the approach should find many other applications in image compression, image retrieval, progressive data transmission and active robotic vision.

Chronological age and age-related cognitive deficits are associated with an increase in multiple types of driving errors in late life

Objective: Older driver research has mostly focused on identifying that small proportion of older drivers who are unsafe. Little is known about how normal cognitive changes in aging affect driving in the wider population of adults who drive regularly. We evaluated the association of cognitive function and age, with driving errors. Method: A sample of 266 drivers aged 70 to 88 years were assessed on abilities that decline in normal aging (visual attention, processing speed, inhibition, reaction time, task switching) and the UFOV® which is a validated screening instrument for older drivers. Participants completed an on-road driving test. Generalized linear models were used to estimate the associations of cognitive factor with specific driving errors and number of errors in self-directed and instructor navigated conditions. Results: All errors types increased with chronological age. Reaction time was not associated with driving errors in multivariate analyses. A cognitive factor measuring Speeded Selective Attention and Switching was uniquely associated with the most errors types. The UFOV predicted blindspot errors and errors on dual carriageways. After adjusting for age, education and gender the cognitive factors explained 7% of variance in the total number of errors in the instructor navigated condition and 4% of variance in the self-navigated condition. Conclusion: We conclude that among older drivers errors increase with age and are associated with speeded selective attention particularly when that requires attending to the stimuli in the periphery of the visual field, task switching, errors inhibiting responses and visual discrimination. These abilities should be the target of cognitive training.

Useful field of view test

A test of the useful field of view was introduced more than two decades ago and was designed to reflect the visual difficulties that older adults experience with everyday tasks. Importantly, the useful field of view is one of the most extensively researched and promising predictor tests for a range of driving outcomes measures, including driving ability and crash risk, as well as other everyday tasks. Currently available commercial versions of the test can be administered using personal computers and measure speed of visual processing speed for rapid detection and localization of targets under conditions of divided visual attention and in the presence and absence of visual clutter. The test is believed to assess higher order cognitive abilities, but performance also relies on visual sensory function since targets must be visible in order to be attended to. The format of the useful field of view test has been modified over the years; the original version estimated the spatial extent of useful field of view, while the latest versions measures visual processing speed. While deficits in the useful field of view are associated with functional impairments in everyday activities in older adults, there is also emerging evidence from several research groups that improvements in visual processing speed can be achieved through training. These improvements have been shown to reduce crash risk, and have a positive impact on health and functional well being, with the potential to increase the mobility and hence independence of older adults.

Linguistic and perceptual processing of communicative cues in Asperger Syndrome

Asperger Syndrome (AS) belongs to autism spectrum disorders where both verbal and non-verbal communication difficulties are at the core of the impairment. Social communication requires a complex use of affective, linguistic-cognitive and perceptual processes. In the four studies included in the current thesis, some of the linguistic and perceptual factors that are important for face-to-face communication were studied using behavioural methods. In all four studies the results obtained from individuals with AS were compared with typically developed age, gender and IQ matched controls. First, the language skills of school-aged children were characterized in detail with standardized tests that measured different aspects of receptive and expressive language (Study I). The children with AS were found to be worse than the controls in following complex verbal instructions. Next, the visual perception of facial expressions of emotion with varying degrees of visual detail was examined (Study II). Adults with AS were found to have impaired recognition of facial expressions on the basis of very low spatial frequencies which are important for processing global information. Following that, multisensory perception was investigated by looking at audiovisual speech perception (Studies III and IV). Adults with AS were found to perceive audiovisual speech qualitatively differently from typically developed adults, although both groups were equally accurate in recognizing auditory and visual speech presented alone. Finally, the effect of attention on audiovisual speech perception was studied by registering eye gaze behaviour (Study III) and by studying the voluntary control of visual attention (Study IV). The groups did not differ in eye gaze behaviour or in the voluntary control of visual attention. The results of the study series demonstrate that many factors underpinning face-to-face social communication are atypical in AS. In contrast with previous assumptions about intact language abilities, the current results show that children with AS have difficulties in understanding complex verbal instructions. Furthermore, the study makes clear that deviations in the perception of global features in faces expressing emotions as well as in the multisensory perception of speech are likely to harm face-to-face social communication.