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.

Effect of an attentional strategy on movement-related potentials recorded from subjects with Huntington's disease

Huntington's disease patients perform automatic movements in a bradykinetic manner, somewhat similar to patients with Parkinson's disease. Cortical activity relating to the preparation of movement in Parkinson's disease is significantly improved when a cognitive strategy is used. It is unknown whether patients with Huntington's disease can utilise an attentional strategy, and what effect this strategy would have on the premovement cortical activity. Movement-related potentials were recorded from 12 Huntington's disease patients and controls performing externally cued finger tapping movement, allowing an examination of cortical activity related to movement performance and bradykinesia in this disease. All subjects were tested in two conditions, which differed only by the presence or absence of the cognitive strategy. The Huntington's disease group, unlike controls, did not produce a rising premovement potential in the absence of the strategy. The Huntington's disease group did produce a rising premovement potential for the strategy condition, but the early slope of the potential was significantly reduced compared with the control group's early slope. These results are similar to those found previously with Parkinson's disease patients. The strategy may have put the task, which previously might have been under deficient automatic control, under attentional control. (C) 2002 Movement Disorder Society.

Human cortical processing of colour and pattern

The present study investigates 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 we 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. We 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. We 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. (C) 2001 Wiley-Liss, Inc.

Attentionale Modulationen neuronaler Aktivität im primär visuellen Kortex

Visual attention, V1, primary visual cortex, fmri, EEG, MEG, feedback modulation

Les débuts de la communication à trois. Interactions visuelles triadiques entre père, mère et bébé

Plusieurs auteurs ont montré que les échanges visuels entre des mères dépressives ou psychotiques et leur bébé présentent de multiples perturbations : dans cet article, les auteurs proposent une étude exploratoire portant sur les échanges visuels père-mère- bébé (9-18 semaines) dans deux groupes de familles, un groupe suivi pour des difficultés du post-partum et un groupe témoin. Les observations sont réalisées dans le cadre d'un jeu à trois structuré selon diverses modalités d'interaction (un parent joue avec l'enfant en présence de l'autre parent / les deux parents jouent conjointement avec le bébé). Les variables retenues concernent d'une part le niveau d'attention visuelle conjointe des partenaires, d'autre part l'évolution de cette attention visuelle au cours du jeu. Les résultats révèlent que les échanges visuels sont plus intenses dans les familles fonctionnelles, ce qui semble indiquer que l'engagement visuel triadique établi par les partenaires peut être représentatif du fonctionnement de la triade à un moment donné de son développement. D'autre part, l'analyse de l'évolution de l'engagement visuel au travers des différents contextes de jeu amène les auteurs à proposer l'hypothèse d'une « alliance triadique » établie conjointement par les trois partenaires et formant la matrice de leurs échanges dyadiques et triadiques. De façon plus générale, les auteurs supposent que l'établissement de cette alliance joue un rôle déterminant pour le développement et l'autonomisa- tion du bébé au sein de sa famille. Disorders in the visual interaction between depressive or psychotic mothers and their baby have been widely described : in this paper, the authors propose an exploratory study of father-mother-infant visual interaction (infants are 9-18 weeks old) in two groups of families, voluntary families and families in therapy for post-par turn disorders. The observations are gathered during a three-partner play, involving different kinds of triadic interaction (one parent plays with the infant, the other parent being « only present » / both parents play together with the child). The analyses have focused on the amount of visual attention shared by the partners and on the evolution of visual interaction during the game. Results show that triadic interaction is more intense in functional triads, which means that shared visual attention may be representative of the more general functioning of the family at a definite stage of its development. Furthermore, considering the sequential organization of visual interaction throughout the game led the authors to the construct of a « triadic alliance », jointly established by the three partners and providing a matrix for their dyadic and triadic interaction. On a more general level, such an alliance could play an important role for the development and the autonomy of the baby within his j her family.

Physical activity and enhanced fitness to improve cognitive function in older people without known cognitive impairment

Physical activity is beneficial for healthy ageing. It may also help maintain good cognitive function in older age. Aerobic activity improves cardiovascular fitness, but it is not known whether this sort of fitness is necessary for improved cognitive function.��Eleven studies of aerobic physical activity programmes for healthy people over the age of 55 years have been included in this review. Eight of these 11 studies reported that aerobic exercise interventions resulted in increased fitness of the trained group and an improvement in at least one aspect of cognitive function. The largest effects were on cognitive speed, auditory and visual attention. However, the cognitive functions which improved were not the same in each study and the majority of comparisons yielded no significant results.��The data are insufficient to show that the improvements in cognitive function which can be attributed to physical exercise are due to improvements in cardiovascular fitness.

Role of the superior parietal lobules in letter-identity processing within strings: FMRI evidence from skilled and dyslexic readers.

Traditionally, the ventral occipito-temporal (vOT) area, but not the superior parietal lobules (SPLs), is thought as belonging to the neural system of visual word recognition. However, some dyslexic children who exhibit a visual attention span disorder - i.e. poor multi-element parallel processing - further show reduced SPLs activation when engaged in visual multi-element categorization tasks. We investigated whether these parietal regions further contribute to letter-identity processing within strings. Adult skilled readers and dyslexic participants with a visual attention span disorder were administered a letter-string comparison task under fMRI. Dyslexic adults were less accurate than skilled readers to detect letter identity substitutions within strings. In skilled readers, letter identity differs related to enhanced activation of the left vOT. However, specific neural responses were further found in the superior and inferior parietal regions, including the SPLs bilaterally. Two brain regions that are specifically related to substituted letter detection, the left SPL and the left vOT, were less activated in dyslexic participants. These findings suggest that the left SPL, like the left vOT, may contribute to letter string processing.

Suivi neurodéveloppemental à 5ans des extrêmes prématurés et détection des difficultés sur le plan des fonctions exécutives [Detection of executive function disorders with a standard neurodevelopmental follow-up of premature children].

INTRODUCTION: A significant proportion of prematurely born children encounter behavioral difficulties, such as attention deficit or hyperactivity, which could be due to executive function disorders. AIMS: To examine whether the standard neurodevelopmental assessment offered to premature children in Switzerland recognizes executive function disorders. METHODS: The study population consisted of 49 children born before 29 weeks of gestation who were examined between 5 and 6 years of age with a standard assessment, with additional items to assess executive functioning. Children with severe neurodevelopmental impairment were excluded (mental retardation, cerebral palsy, autism). Standard assessment consisted in the Kaufman Assessment Battery for Children (K-ABC), which comprises three subscales: sequential processes (analysis of sequential information), simultaneous processes (global analysis of visual information), and composite mental processes (CMP) (result of the other two scales), as well as a behavioral evaluation using the standardized Strengths and Difficulties Questionnaire (SDQ). Executive functioning was assessed with tasks evaluating visual attention, divided attention, and digit memory as well as with a specialized questionnaire, the Behavior Rating Index of Executive Functions (BRIEF), which evaluates several aspects of executive function (regulation, attention, flexibility, working memory, etc). RESULTS: Children were divided according to their results on the three K-ABC scales (< or>85), and the different neuropsychological tasks assessing executive function were compared between the groups. The CMP did not differentiate children with executive difficulties, whereas a score<85 on the sequential processes was significantly associated with worse visual and divided attention. There was a strong correlation between the SDQ and the BRIEF questionnaires. For both questionnaires, children receiving psychotherapy had significantly higher results. Children who presented behavioral problems assessed with the SDQ presented significantly higher scores on the BRIEF. CONCLUSION: A detailed analysis of the standard neurodevelopmental assessment allows the identification of executive function disorders in premature children. Children who performed below 85 on the sequential processes of the K-ABC had significantly more attentional difficulties on the neuropsychological tasks and therefore have to be recognized and carefully followed. Emotional regulation had a strong correlation with behavioral difficulties, which were suitably assessed with the SDQ, recognized by the families, and treated.

Dynamique cérébrale et réserve cognitive en situation d’attention sélective dans le vieillissement normal et les troubles de la cognition : approche neurofonctionnelle

Réalisée en cotutelle avec l'Unité de Formation à la Recherche Lettres Arts et Sciences Humaines - Université Nice-Sophia Antipolis.