Magnocellular mediated visual-spatial attention and reading ability

This study explores the relationship between attentional processing mediated by visual magnocellular (MC) processing and reading ability. Reading ability in a group of primary school children was compared to performance on a visual cued coherent motion detection task. The results showed that a brief spatial cue was more effective in drawing attention either away or towards a visual target in the group of readers ranked in the upper 25% of the sample compared to lower ranked readers. Regression analysis showed a significant relationship between attentional processing and reading when the effects of age and intellectual ability were removed. Results suggested a stronger relationship between visual attentional and non-word reading compared to irregular word reading. (C) 2004 Lippincott Williams & Wilkins, Inc.

Broad direction bandwidths for complex motion mechanisms

Growing evidence from psychophysics and single-unit recordings suggests specialised mechanisms in the primate visual system for the detection of complex motion patterns such as expansion and rotation. Here we used a subthreshold summation technique to determine the direction tuning functions of the detecting mechanisms. We measured thresholds for discriminating noise and signal + noise for pairs of superimposed complex motion patterns (signal A and B) carried by random-dot stimuli in a circular 5° field. For expansion, rotation, deformation and translation we found broad tuning functions approximated by cos(d), where d is the difference in dot directions for signal A and B. These data were well described by models in which either: (a) cardinal mechanisms had direction bandwidths (half-widths) of around 60° or (b) the number of mechanisms was increased and their half-width was reduced to about 40°. When d = 180° we found summation to be greater than probability summation for expansion, rotation and translation, consistent with the idea that mechanisms for these stimuli are constructed from subunits responsive to relative motion. For deformation, however, we found sensitivity declined when d = 180°, suggesting antagonistic input from directional subunits in the deformation mechanism. This is a necessary property for a mechanism whose job is to extract the deformation component from the optic flow field. © 2001 Elsevier Science Ltd.

A comparison between static and kinetic visual attention as a means of detecting age-related deterioration of the visual system and driving performance

A critical review of previous research revealed that visual attention tests, such as the Useful Field of View (UFOV) test, provided the best means of detecting age-related changes to the visual system that could potentially increase crash risk. However, the question was raised as to whether the UFOV, which was regarded as a static visual attention test, could be improved by inclusion of kinetic targets that more closely represent the driving task. A computer program was written to provide more information about the derivation of UFOV test scores. Although this investigation succeeded in providing new information, some of the commercially protected UFOV test procedures still remain unknown. Two kinetic visual attention tests (DRTS1 and 2), developed at Aston University to investigate inclusion of kinetic targets in visual attention tests, were introduced. The UFOV was found to be more repeatable than either of the kinetic visual attention tests and learning effects or age did not influence these findings. Determinants of static and kinetic visual attention were explored. Increasing target eccentricity led to reduced performance on the UFOV and DRTS1 tests. The DRTS2 was not affected by eccentricity but this may have been due to the style of presentation of its targets. This might also have explained why only the DRTS2 showed laterality effects (i.e. better performance to targets presented on the left hand side of the road). Radial location, explored using the UFOV test, showed that subjects responded best to targets positioned to the horizontal meridian. Distraction had opposite effects on static and kinetic visual attention. While UFOV test performance declined with distraction, DRTS1 performance increased. Previous research had shown that this striking difference was to be expected. Whereas the detection of static targets is attenuated in the presence of distracting stimuli, distracting stimuli that move in a structured flow field enhances the detection of moving targets. Subjects reacted more slowly to kinetic compared to static targets, longitudinal motion compared to angular motion and to increased self-motion. However, the effects of longitudinal motion, angular motion, self-motion and even target eccentricity were caused by target edge speed variations arising because of optic flow field effects. The UFOV test was more able to detect age-related changes to the visual system than were either of the kinetic visual attention tests. The driving samples investigated were too limited to draw firm conclusions. Nevertheless, the results presented showed that neither the DRTS2 nor the UFOV tests were powerful tools for the identification of drivers prone to crashes or poor driving performance.

Neuromagnetic investigations of functional organisation within human visual cortex

This thesis describes a series of experimental investigations into the functional organisation of human visual cortex using neuromagnetometry.This technique combines good spatial and temporal resolution enabling identification of the location and temporal response characteristics of cortical neurones within alert humans. To activate different neuronal populations and cortical areas a range of stimuli were used, the parameters of which were selected to match the known physiological properties of primate cortical neurones. In one series of experiments the evoked magnetic response was recorded to isoluminant red/green gratings. Co-registration of signal and magnetic resonance image data indicated a contribution to the response from visual areas V1, V2 and V4. To investigate the spatio-temporal characteristics of neurones within area V1 the evoked response was recorded for a range of stimulus spatial and temporal frequencies. The response to isoluminant red/green gratings was dominated by a major component which was found to have bandpass spatial frequency tuning with a peak at 1-2 cycles/degree, falling to the level of the noise at 6-8 cycles/degree. The temporal frequency tuning characteristics of the response showed bimodal sensitivity with peaks at 0-1Hz and 4Hz. In a further series of experiments the luminance evoked response was recorded to red/black, yellow/black and achromatic gratings and in all cases was found to be more complex than the isoluminant chromatic response, comprising up to three distinct components. The major response peak showed bandpass spatial frequency tuning characteristics, peaking at 6-8 cycles/degree, falling to the level of the noise at 12-16 cycles/degree. The results provide evidence to suggest that within area V1 the same neuronal population encodes both chromatic and luminance information and has spatial frequency tuning properties consistent with single-opponent cells. Furthermore, the results indicate that cells within area V1 encode chromatic motion information over a wide range of temporal frequencies with temporal response characteristics suggestive of the existence of a sub-population of cells sensitive to high temporal frequencies.

The investigation of oscillatory changes in the visual cortex using synthetic aperture magnetometry

This thesis is an exploration of the oscillatory changes occurring in the visual cortex as measured by a functional imaging technique known as Synthetic Aperture Magnetometry (SAM), and how these compare to the BOLD response, across a number of different experimental paradigms. In chapter one the anatomy and physiology of the visual pathways and cortex are outlined, introducing the reader to structures and terms used throughout the thesis whilst chapter two introduces both the technology and analysis techniques required to record MEG and fMRI and also outlines the theory behind SAM. In chapter three the temporal frequency tuning of both striate and extrastriate cortex is investigated, showing fundamental differences in both tuning characteristics and oscillatory power changes between the two areas. Chapter four introduces the concept of implied-motion and investigates the role of area V5 / MT in the perception of such stimuli and shows, for the first time, the temporal evolution of the response in this area. Similarly a close link is shown between the early evoked potential, produced by the stimulus, and previous BOLD responses. Chapter five investigates the modulation of cortical oscillations to both shifts in attention and varying stimulus contrast. It shows that there are both induced and evoked modulation changes with attention, consistent with areas previously known to show BOLD responses. Chapter six involves a direct comparison of cortical oscillatory changes with those of the BOLD response in relation to the parametric variation of a motion coherence stimulus. It is shown that various cortical areas show a linear BOLD response to motion coherence and, for the first time, that both induced oscillatory and evoked activity also vary linearly in areas coincidental with the BOLD response. The final chapter is a summary of the main conclusions and suggests further work.

Visual symptoms in Parkinson's disease

Parkinson’s disease (PD) is a common disorder of middle-aged and elderly people in which degeneration of the extrapyramidal motor system causes significant movement problems. In some patients, however, there are additional disturbances in sensory systems including loss of the sense of smell and auditory and/or visual problems. This article is a general overview of the visual problems likely to be encountered in PD. Changes in vision in PD may result from alterations in visual acuity, contrast sensitivity, colour discrimination, pupil reactivity, eye movements, motion perception, visual field sensitivity and visual processing speeds. Slower visual processing speeds can also lead to a decline in visual perception especially for rapidly changing visual stimuli. In addition, there may be disturbances of visuo-spatial orientation, facial recognition problems, and chronic visual hallucinations. Some of the treatments used in PD may also have adverse ocular reactions. The pattern electroretinogram (PERG) is useful in evaluating retinal dopamine mechanisms and in monitoring dopamine therapies in PD. If visual problems are present, they can have an important effect on the quality of life of the patient, which can be improved by accurate diagnosis and where possible, correction of such defects.

Visual signs and symptoms of dementia with Lewy bodies

Dementia with Lewy bodies ('Lewy body dementia' or 'diffuse Lewy body disease') (DLB) is the second most common form of dementia to affect elderly people, after Alzheimer's disease. A combination of the clinical symptoms of Alzheimer's disease and Parkinson's disease is present in DLB and the disorder is classified as a 'parkinsonian syndrome', a group of diseases which also includes Parkinson's disease, progressive supranuclear palsy, corticobasal degeneration and multiple system atrophy. Characteristics of DLB are fluctuating cognitive ability with pronounced variations in attention and alertness, recurrent visual hallucinations and spontaneous motor features, including akinesia, rigidity and tremor. In addition, DLB patients may exhibit visual signs and symptoms, including defects in eye movement, pupillary function and complex visual functions. Visual symptoms may aid the differential diagnoses of parkinsonian syndromes. Hence, the presence of visual hallucinations supports a diagnosis of Parkinson's disease or DLB rather than progressive supranuclear palsy. DLB and Parkinson's disease may exhibit similar impairments on a variety of saccadic and visual perception tasks (visual discrimination, space-motion and object-form recognition). Nevertheless, deficits in orientation, trail-making and reading the names of colours are often significantly greater in DLB than in Parkinson's disease. As primary eye-care practitioners, optometrists should be able to work with patients with DLB and their carers to manage their visual welfare.

Oculo-visual dysfunction in Parkinson's disease

This review describes the oculo-visual problems likely to be encountered in Parkinson's disease (PD) with special reference to three questions: (1) are there visual symptoms characteristic of the prodromal phase of PD, (2) is PD dementia associated with specific visual changes, and (3) can visual symptoms help in the differential diagnosis of the parkinsonian syndromes, viz. PD, progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and corticobasal degeneration (CBD)? Oculo-visual dysfunction in PD can involve visual acuity, dynamic contrast sensitivity, colour discrimination, pupil reactivity, eye movement, motion perception, and visual processing speeds. In addition, disturbance of visuo-spatial orientation, facial recognition problems, and chronic visual hallucinations may be present. Prodromal features of PD may include autonomic system dysfunction potentially affecting pupil reactivity, abnormal colour vision, abnormal stereopsis associated with postural instability, defects in smooth pursuit eye movements, and deficits in visuo-motor adaptation, especially when accompanied by idiopathic rapid eye movement (REM) sleep behaviour disorder. PD dementia is associated with the exacerbation of many oculo-visual problems but those involving eye movements, visuo-spatial function, and visual hallucinations are most characteristic. Useful diagnostic features in differentiating the parkinsonian symptoms are the presence of visual hallucinations, visuo-spatial problems, and variation in saccadic eye movement dysfunction.

Characteristics of motor resonance predict the pattern of flash-lag effects for biological motion

Background - When a moving stimulus and a briefly flashed static stimulus are physically aligned in space the static stimulus is perceived as lagging behind the moving stimulus. This vastly replicated phenomenon is known as the Flash-Lag Effect (FLE). For the first time we employed biological motion as the moving stimulus, which is important for two reasons. Firstly, biological motion is processed by visual as well as somatosensory brain areas, which makes it a prime candidate for elucidating the interplay between the two systems with respect to the FLE. Secondly, discussions about the mechanisms of the FLE tend to recur to evolutionary arguments, while most studies employ highly artificial stimuli with constant velocities. Methodology/Principal Finding - Since biological motion is ecologically valid it follows complex patterns with changing velocity. We therefore compared biological to symbolic motion with the same acceleration profile. Our results with 16 observers revealed a qualitatively different pattern for biological compared to symbolic motion and this pattern was predicted by the characteristics of motor resonance: The amount of anticipatory processing of perceived actions based on the induced perspective and agency modulated the FLE. Conclusions/Significance - Our study provides first evidence for an FLE with non-linear motion in general and with biological motion in particular. Our results suggest that predictive coding within the sensorimotor system alone cannot explain the FLE. Our findings are compatible with visual prediction (Nijhawan, 2008) which assumes that extrapolated motion representations within the visual system generate the FLE. These representations are modulated by sudden visual input (e.g. offset signals) or by input from other systems (e.g. sensorimotor) that can boost or attenuate overshooting representations in accordance with biased neural competition (Desimone & Duncan, 1995).

Are dyslexics' visual deficits limited to measures of dorsal stream function?

We tested the hypothesis that the differences in performance between developmental dyslexics and controls on visual tasks are specific for the detection of dynamic stimuli. We found that dyslexics were less sensitive than controls to coherent motion in dynamic random dot displays. However, their sensitivity to control measures of static visual form coherence was not significantly different from that of controls. This dissociation of dyslexics' performance on measures that are suggested to tap the sensitivity of different extrastriate visual areas provides evidence for an impairment specific to the detection of dynamic properties of global stimuli, perhaps resulting from selective deficits in dorsal stream functions. © 2001 Lippincott Williams & Wilkins.

A mozgókép reneszánsza: nagytotál a videográfia módszertanáról = The renaissance of the motion pictures: wide shot of the videography

A posztmodern fogyasztó hiperreális környezetébe csöppenő pozitivista kutató gyakran megtántorodik attól a forgószélszerű pörgéstől és vizuális dinamikától, amelyet a posztmodern világ ont rá. A szupersztrádán teknős módjára kullogó kutató ezért inkább visszahúzódik páncélja mögé, és előhúz valamit a szokásos módszerek közül, függetlenül attól, hogy azok relevánsak-e a probléma vizsgálatára vagy sem. A mozgóképek újjászületése a megváltozott fogyasztói látásmódhoz kapcsolható. Dziga Vertov mechanisztikus szemével egyre inkább a fogyasztók kacsintgatnak, és a curlingben látható módon csúsztatják tovább a magáról megfeledkező és kőnek látszó teknőst. A videográfia a videó és az etnográfia szavak összekapcsolásából keletkezett, vagyis etnográfiai kutatás a mozgókép segítségével. Egyre több nyugati cég arra kéri fel a kutatókat, hogy a fogyasztói magatartásról csupán videó prezentációt készítsenek, mindenféle szöveges magyarázat nélkül. A cikk nagytotálból mutatja be a Belk és Kozinets (2005, 2006) által életre keltett módszertan sajátosságait. / === / The positivist researcher in the middle of the hyperreal context seems to lurch due to the tornado-like whirl and a visual dynamism caused by the postmodern world. This researcher is just like a paddling tortoise on the superhighway draws back in the tortoiseshell and shows one of the classic research methods, no matter the type of the research problem. The rebirth of the motion pictures is linked to the altered consumer perspective. Dziga Vertov’s mechanical eye is used more and more by the consumers, and the tortoise-like researcher is considered to be a curling stone. The consumer researchers tend to ignore the lived visual and auditory aspects of the consumer culture and the appropriate research methods of this field. The aim of this article is to present the types and the main features of the videography vivified by Belk and Kozinets (2005, 2006).

Development of an open architecture motion control system

A multipurpose open architecture motion control system was developed with three platforms for control and monitoring. The Visual Basic user interface communicated with the operator and gave instructions to the electronic components. The first platform had a BASIC Stamp based controller and three stepping motors. The second platform had a controller, amplifiers and two DC servomotors. The third platform had a DSP module. In this study, each platform was used on machine tools either to move the table or to evaluate the incoming signal. The study indicated that by using advanced microcontrollers, which use high-level languages, motor controllers, DSPs (Digital Signal Processor) and microcomputers, the motion control of different systems could be realized in a short time. Although, the proposed systems had some limitations, their jobs were performed effectively. ^

EFFECTS OF A VISUAL HORIZON ON DROSOPHILA MELANOGASTER OBJECT-TRACKING RESPONSES

To navigate effectively in three-dimensional space, flying insects must approximate distances to nearby objects. Humans are able to use an array of cues to guide depth perception in the visual world. However, some of these cues are not available to insects that are constrained by their rigid eyes and relatively small body size. Flying fruit flies can use motion parallax to gauge the distance of nearby objects, but using this cue becomes a less effective strategy as objects become more remote. Humans are able to infer depth across far distances by comparing the angular distance of an object to the horizon. This study tested if flying fruit flies, like humans, use the relative position of the horizon as a depth cue. Fruit flies in tethered flight were stimulated with a virtual environment that displayed vertical bars of varying elevation relative to a horizon, and their tracking responses were recorded. This study showed that tracking responses of the flies were strongly increased by reducing the apparent elevation of the bar against the horizon, indicating that fruit flies may be able to assess the distance of far off objects in the natural world by comparing them against a visual horizon.

The functional subdivision of the visual brain : Is there a real illusion effect on action? A multi-lab replication study

Acknowledgements We thank Brian Roberts and Mike Harris for responding to our questions regarding their paper; Zoltan Dienes for advice on Bayes factors; Denise Fischer, Melanie Römer, Ioana Stanciu, Aleksandra Romanczuk, Stefano Uccelli, Nuria Martos Sánchez, and Rosa María Beño Ruiz de la Sierra for help collecting data; Eva Viviani for managing data collection in Parma. We thank Maurizio Gentilucci for letting us use his lab, and the Centro Intradipartimentale Mente e Cervello (CIMeC), University of Trento, and especially Francesco Pavani for lending us his motion tracking equipment. We thank Rachel Foster for proofreading. KKK was supported by a Ph.D. scholarship as part of a grant to VHF within the International Graduate Research Training Group on Cross-Modal Interaction in Natural and Artificial Cognitive Systems (CINACS; DFG IKG-1247) and TS by a grant (DFG – SCHE 735/3-1); both from the German Research Council.

3D considerations for motion perception and visuomotor transformations

Moving through a stable, three-dimensional world is a hallmark of our motor and perceptual experience. This stability is constantly being challenged by movements of the eyes and head, inducing retinal blur and retino-spatial misalignments for which the brain must compensate. To do so, the brain must account for eye and head kinematics to transform two-dimensional retinal input into the reference frame necessary for movement or perception. The four studies in this thesis used both computational and psychophysical approaches to investigate several aspects of this reference frame transformation. In the first study, we examined the neural mechanism underlying the visuomotor transformation for smooth pursuit using a feedforward neural network model. After training, the model performed the general, three-dimensional transformation using gain modulation. This gave mechanistic significance to gain modulation observed in cortical pursuit areas while also providing several testable hypotheses for future electrophysiological work. In the second study, we asked how anticipatory pursuit, which is driven by memorized signals, accounts for eye and head geometry using a novel head-roll updating paradigm. We showed that the velocity memory driving anticipatory smooth pursuit relies on retinal signals, but is updated for the current head orientation. In the third study, we asked how forcing retinal motion to undergo a reference frame transformation influences perceptual decision making. We found that simply rolling one's head impairs perceptual decision making in a way captured by stochastic reference frame transformations. In the final study, we asked how torsional shifts of the retinal projection occurring with almost every eye movement influence orientation perception across saccades. We found a pre-saccadic, predictive remapping consistent with maintaining a purely retinal (but spatially inaccurate) orientation perception throughout the movement. Together these studies suggest that, despite their spatial inaccuracy, retinal signals play a surprisingly large role in our seamless visual experience. This work therefore represents a significant advance in our understanding of how the brain performs one of its most fundamental functions.