The development of color categories in two languages: a longitudinal study

This study unites investigations into the linguistic relativity of color categories with research on children's category acquisition. Naming, comprehension, and memory for colors were tracked in 2 populations over a 3-year period. Children from a seminomadic equatorial African culture, whose language contains 5 color terms, were compared with a group of English children. Despite differences in visual environment, language, and education, they showed similar patterns of term acquisition. Both groups acquired color vocabulary slowly and with great individual variation. Those knowing no color terms made recognition errors based on perceptual distance, and the influence of naming on memory increased with age. An initial perceptually driven color continuum appears to be progressively organized into sets appropriate to each culture and language. PsycINFO Database Record (c) 2009 APA, all rights reserved

The development of constrained source localisation algorithms for human brain imaging

This work sets out to evaluate the potential benefits and pit-falls in using a priori information to help solve the Magnetoencephalographic (MEG) inverse problem. In chapter one the forward problem in MEG is introduced, together with a scheme that demonstrates how a priori information can be incorporated into the inverse problem. Chapter two contains a literature review of techniques currently used to solve the inverse problem. Emphasis is put on the kind of a priori information that is used by each of these techniques and the ease with which additional constraints can be applied. The formalism of the FOCUSS algorithm is shown to allow for the incorporation of a priori information in an insightful and straightforward manner. In chapter three it is described how anatomical constraints, in the form of a realistically shaped source space, can be extracted from a subject’s Magnetic Resonance Image (MRI). The use of such constraints relies on accurate co-registration of the MEG and MRI co-ordinate systems. Variations of the two main co-registration approaches, based on fiducial markers or on surface matching, are described and the accuracy and robustness of a surface matching algorithm is evaluated. Figures of merit introduced in chapter four are shown to given insight into the limitations of a typical measurement set-up and potential value of a priori information. It is shown in chapter five that constrained dipole fitting and FOCUSS outperform unconstrained dipole fitting when data with low SNR is used. However, the effect of errors in the constraints can reduce this advantage. Finally, it is demonstrated in chapter six that the results of different localisation techniques give corroborative evidence about the location and activation sequence of the human visual cortical areas underlying the first 125ms of the visual magnetic evoked response recorded with a whole head neuromagnetometer.

The investigation of the primary response of the flash visual evoked response

The topographical distribution of the early components of the flash visual evoked response (VER) were investigated using a twenty channel brain mapping system. Thirty subjects, ranging in age from 21 to 84 years, had flash VERs recorded using the standard 10-20 electrode system to a balanced non-cephalic reference. The subjects were divided into three age groups: a young group, a middle group and an older group. The P2 component (positive component around 100-120 msec) of the flash VER was recorded consistently over the occipital region throughout the age range, as was a frontal negative component (N120) of about the same latency. Only the young age group had this single negative component on the frontage channels, whilst the middle age group showed an additional negative component at around 75 msec (N75). Neither group had a recordable P1 component (positive component around 60-75 msec) over the occipital region. The older age group showed both P1 and P2 components over the occipital region with the distribution of the P1 component being more widespread anteriorly. The frontal channels showed both the negative N75 and the later N120 components. The frontal negative components were shown not to be related to the electroretinogram or the balanced non-cephalic reference, but were affected by the type of stimulation. Responses recorded to both pattern reversal and onset/offset stimulation did not show the frontal negative potentials seen with flash stimulation. It was shown that the P1 component is more readily recordable in the elderly and is preceded during middle age by the development of a frontal negative component at around the same latency. The changing morphology of the negative activity in the frontal region across the age range suggests that the use of an Fz reference would produce an artificial P1 component in the middle age group and an enhancement of this component in the elderly, as well as enhance the P2 component in all ages.

The investigation of the sensitivity gradient of the visual field, as a function of stimulus dynamic range, in the normal and abnormal eye

The study utilized the advanced technology provided by automated perimeters to investigate the hypothesis that patients with retinitis pigmentosa behave atypically over the dynamic range and to concurrently determine the influence of extraneous factors on the format of the normal perimetric sensitivity profile. The perimetric processing of some patients with retinitis pigmentosa was considered to be abnormal in either the temporal and/or the spatial domain. The standard size III stimulus saturated the central regions and was thus ineffective in detecting early depressions in sensitivity in these areas. When stimulus size was scaled in inverse proportion to the square root of ganglion cell receptive field density (M-scaled), isosensitive profiles did not result, although cortical representation was theoretically equivalent across the visual field. It was conjectured that this was due to variations in the ganglion cell characteristics with increasing peripheral angle, most notably spatial summation. It was concluded that the development of perimetric routines incorporating stimulus sizes adjusted in proportion to the coverage factor of retinal ganglion cells would enhance the diagnostic capacity of perimetry. Good general and local correspondence was found between perimetric sensitivity and the available retinal cell counts. Intraocular light scatter arising both from simulations and media opacities depressed perimetric sensitivity. Attenuation was greater centrally for the smaller LED stimuli, whereas the reverse was true for the larger projected stimuli. Prior perimetric experience and pupil size also demonstrated eccentricity-dependent effect on sensitivity. Practice improved perimetric sensitivity for projected stimuli at eccentricities greater than or equal to 30o; particularly in the superior region. Increase in pupil size for LED stimuli enhanced sensitivity at eccentricities greater than 10o. Conversely, microfluctuation in the accommodative response during perimetric examination and the correction of peripheral refractive error had no significant influence on perimetric sensitivity.

The neuropathology of the occipital cortex and its significance in the visual problems of patients with variant Creutzfeldt-Jakob disease (vCJD)

The occipital lobe is one of the cortical areas most affected by the pathology of variant Creutzfeldt-Jakob disease (vCJD). To understand the visual problems of vCJD patients, neuropathological changes were studied in striate (B17, V1) and extrastriate (B18, V2) regions of the occipital cortex in eleven cases of vCJD. No differences in the density of vacuoles or surviving neurons were observed in B17 and B18 but densities of glial cell nuclei and deposits of the protease resistant form of prion protein (PrPsc) were greater in B18. The density of PrPsc deposits in B17 was positively correlated with their density in B18. The density of the diffuse PrPsc deposits in B17 was negatively correlated with the density of the surviving neurons in B18. In B17 and B18, the vacuoles either exhibited density peaks in laminae II/III and V/VI or were more uniformly distributed across the laminae. Diffuse PrPsc deposits were most frequent in laminae II/III and florid PrPsc deposits more generally distributed. In B18, the surviving neurons were more consistently bimodally distributed and the glial cell nuclei most abundant in laminae V/VI compared with B17. Hence, both striate and extrastriate areas of the occipital cortex are affected by the pathology of vCJD, the pathological changes being most severe in B18. Neuronal degeneration in B18 may be associated with the development of diffuse PrPsc deposits in B17. These data suggest that the short cortico-cortical connections between B17 and B18 and the pathways to subcortical visual areas are compromised in vCJD. Pathological changes in striate and extrastriate regions of the occipital cortex may contribute to several of the visual problems identified in patients with vCJD including oculomotor and visuo-spatial function.

Impact of senescence and disease on the structural and functional performance of the visual pathway

The diagnosis and monitoring of ocular disease presents considerable clinical difficulties for two main reasons i) the substantial physiological variation of anatomical structure of the visual pathway and ii) constraints due to technical limitations of diagnostic hardware. These are further confounded by difficulties in detecting early loss or change in visual function due to the masking of disease effects, for example, due to a high degree of redundancy in terms of nerve fibre number along the visual pathway. This thesis addresses these issues across three areas of study: 1. Factors influencing retinal thickness measures and their clinical interpretation As the retina is the principal anatomical site for damage associated with visual loss, objective measures of retinal thickness and retinal nerve fibre layer thickness are key to the detection of pathology. In this thesis the ability of optical coherence tomography (OCT) to provide repeatable and reproducible measures of retinal structure at the macula and optic nerve head is investigated. In addition, the normal physiological variations in retinal thickness and retinal nerve fibre layer thickness are explored. Principal findings were: • Macular retinal thickness and optic nerve head measurements are repeatable and reproducible for normal subjects and diseased eyes • Macular and retinal nerve fibre layer thickness around the optic nerve correlate negatively with axial length, suggesting that larger eyes have thinner retinae, potentially making them more susceptible to damage or disease • Foveola retinal thickness increases with age while retinal nerve fibre layer thickness around the optic nerve head decreases with age. Such findings should be considered during examination of the eye with suspect pathology or in long-term disease monitoring 2. Impact of glucose control on retinal anatomy and function in diabetes Diabetes is a major health concern in the UK and worldwide and diabetic retinopathy is a major cause of blindness in the working population. Objective, quantitative measurements of retinal thickness. particularly at the macula provide essential information regarding disease progression and the efficacy of treatment. Functional vision loss in diabetic patients is commonly observed in clinical and experimental studies and is thought to be affected by blood glucose levels. In the first study of its kind, the short term impact of fluctuations in blood glucose levels on retinal structure and function over a 12 hour period in patients with diabetes are investigated. Principal findings were: • Acute fluctuations in blood glucose levels are greater in diabetic patients than normal subjects • The fluctuations in blood glucose levels impact contrast sensitivity scores. SWAP visual fields, intraocular pressure and diastolic pressure. This effect is similar for type 1 and type 2 diabetic patients despite the differences in their physiological status. • Long-term metabolic control in the diabetic patient is a useful predictor in the fluctuation of contrast sensitivity scores. • Large fluctuations in blood glucose levels and/or visual function and structure may be indicative of an increased risk of development or progression of retinopathy 3. Structural and functional damage of the visual pathway in glaucomatous optic neuropathy The glaucomatous eye undergoes a number of well documented pathological changes including retinal nerve fibre loss and optic nerve head damage which is correlated with loss of functional vision. In experimental glaucoma there is evidence that glaucomatous damage extends from retinal ganglion cells in the eye, along the visual pathway, to vision centres in the brain. This thesis explores the effects of glaucoma on retinal nerve fibre layer thickness, ocular anterior anatomy and cortical structure, and its correlates with visual function in humans. Principal findings were: • In the retina, glaucomatous retinal nerve fibre layer loss is less marked with increasing distance from the optic nerve head, suggesting that RNFL examination at a greater distance than traditionally employed may provide invaluable early indicators of glaucomatous damage • Neuroretinal rim area and retrobulbar optic nerve diameter are strong indicators of visual field loss • Grey matter density decreases at a rate of 3.85% per decade. There was no clear evidence of a disease effect • Cortical activation as measured by fMRI was a strong indicator of functional damage in patients with significant neuroretinal rim loss despite relatively modest visual field defects These investigations have shown that the effects of senescence are evident in both the anterior and posterior visual pathway. A variety of anatomical and functional diagnostic protocols for the investigation of damage to the visual pathway in ocular disease are required to maximise understanding of the disease processes and thereby optimising patient care.

The neuropathology of the occipital cortex and its significance in the visual problems of patients with variant Creutzfeldt-Jakob Disease (vCJD)

The occipital lobe is one of the cortical areas most affected by the pathology of variant Creutzfeldt-Jakob disease (vCJD). To understand the visual problems of vCJD patients, neuropathological changes were studied in striate (B17, V1) and extrastriate (B18, V2) regions of the occipital cortex in eleven cases of vCJD. No differences in the density of vacuoles or surviving neurons were observed in B17 and B18 but densities of glial cell nuclei and deposits of the protease resistant form of prion protein (PrPsc) were greater in B18. The density of PrPsc deposits in B17 was positively correlated with their density in B18. The density of the diffuse PrPsc deposits in B17 was negatively correlated with the density of the surviving neurons in B18. In B17 and B18, the vacuoles either exhibited density peaks in laminae II/III and V/VI or were more uniformly distributed across the laminae. Diffuse PrPsc deposits were most frequent in laminae II/III and florid PrPsc deposits more generally distributed. In B18, the surviving neurons were more consistently bimodally distributed and the glial cell nuclei most abundant in laminae V/VI compared with B17. Hence, both striate and extrastriate areas of the occipital cortex are affected by the pathology of vCJD, the pathological changes being most severe in B18. Neuronal degeneration in B18 may be associated with the development of diffuse PrPsc deposits in B17. These data suggest that the short cortico-cortical connections between B17 and B18 and the pathways to subcortical visual areas are compromised in vCJD. Pathological changes in striate and extrastriate regions of the occipital cortex may contribute to several of the visual problems identified in patients with vCJD including oculomotor and visuo-spatial function. © 2012 Nova Science Publishers, Inc. All rights reserved.

Teallach - a flexible user - interface development environment for object database applications

The Teallach project has adapted model-based user-interface development techniques to the systematic creation of user-interfaces for object-oriented database applications. Model-based approaches aim to provide designers with a more principled approach to user-interface development using a variety of underlying models, and tools which manipulate these models. Here we present the results of the Teallach project, describing the tools developed and the flexible design method supported. Distinctive features of the Teallach system include provision of database-specific constructs, comprehensive facilities for relating the different models, and support for a flexible design method in which models can be constructed and related by designers in different orders and in different ways, to suit their particular design rationales. The system then creates the desired user-interface as an independent, fully functional Java application, with automatically generated help facilities.

A randomised controlled trial investigating the effect of nutritional supplementation on visual function in normal, and age-related macular disease affected eyes:design and methodology [ISRCTN78467674]

Background: Age-related macular disease is the leading cause of blind registration in the developed world. One aetiological hypothesis involves oxidation, and the intrinsic vulnerability of the retina to damage via this process. This has prompted interest in the role of antioxidants, particularly the carotenoids lutein and zeaxanthin, in the prevention and treatment of this eye disease. Methods: The aim of this randomised controlled trial is to determine the effect of a nutritional supplement containing lutein, vitamins A, C and E, zinc, and copper on measures of visual function in people with and without age-related macular disease. Outcome measures are distance and near visual acuity, contrast sensitivity, colour vision, macular visual field, glare recovery, and fundus photography. Randomisation is achieved via a random number generator, and masking achieved by third party coding of the active and placebo containers. Data collection will take place at nine and 18 months, and statistical analysis will employ Student's t test. Discussion: A paucity of treatment modalities for age-related macular disease has prompted research into the development of prevention strategies. A positive effect on normals may be indicative of a role of nutritional supplementation in preventing or delaying onset of the condition. An observed benefit in the age-related macular disease group may indicate a potential role of supplementation in prevention of progression, or even a degree reversal of the visual effects caused by this condition.

Multi-frequency segmental bio-impedance device:design, development and applications

Bio-impedance analysis (BIA) provides a rapid, non-invasive technique for body composition estimation. BIA offers a convenient alternative to standard techniques such as MRI, CT scan or DEXA scan for selected types of body composition analysis. The accuracy of BIA is limited because it is an indirect method of composition analysis. It relies on linear relationships between measured impedance and morphological parameters such as height and weight to derive estimates. To overcome these underlying limitations of BIA, a multi-frequency segmental bio-impedance device was constructed through a series of iterative enhancements and improvements of existing BIA instrumentation. Key features of the design included an easy to construct current-source and compact PCB design. The final device was trialled with 22 human volunteers and measured impedance was compared against body composition estimates obtained by DEXA scan. This enabled the development of newer techniques to make BIA predictions. To add a ‘visual aspect’ to BIA, volunteers were scanned in 3D using an inexpensive scattered light gadget (Xbox Kinect controller) and 3D volumes of their limbs were compared with BIA measurements to further improve BIA predictions. A three-stage digital filtering scheme was also implemented to enable extraction of heart-rate data from recorded bio-electrical signals. Additionally modifications have been introduced to measure change in bio-impedance with motion, this could be adapted to further improve accuracy and veracity for limb composition analysis. The findings in this thesis aim to give new direction to the prediction of body composition using BIA. The design development and refinement applied to BIA in this research programme suggest new opportunities to enhance the accuracy and clinical utility of BIA for the prediction of body composition analysis. In particular, the use of bio-impedance to predict limb volumes which would provide an additional metric for body composition measurement and help distinguish between fat and muscle content.

How different are the visual representations used for object recognition in middle childhood and adulthood?

Recent experimental studies have shown that development towards adult performance levels in configural processing in object recognition is delayed through middle childhood. Whilst partchanges to animal and artefact stimuli are processed with similar to adult levels of accuracy from 7 years of age, relative size changes to stimuli result in a significant decrease in relative performance for participants aged between 7 and 10. Two sets of computational experiments were run using the JIM3 artificial neural network with adult and 'immature' versions to simulate these results. One set progressively decreased the number of neurons involved in the representation of view-independent metric relations within multi-geon objects. A second set of computational experiments involved decreasing the number of neurons that represent view-dependent (nonrelational) object attributes in JIM3's Surface Map. The simulation results which show the best qualitative match to empirical data occurred when artificial neurons representing metric-precision relations were entirely eliminated. These results therefore provide further evidence for the late development of relational processing in object recognition and suggest that children in middle childhood may recognise objects without forming structural description representations.

Evaluating techniques to improve visual performance with and assessment of premium intraocular lenses

Premium Intraocular Lenses (IOLs) such as toric IOLs, multifocal IOLs (MIOLs) and accommodating IOLs (AIOLs) can provide better refractive and visual outcomes compared to standard monofocal designs, leading to greater levels of post-operative spectacle independence. The principal theme of this thesis relates to the development of new assessment techniques that can help to improve future premium IOL design. IOLs designed to correct astigmatism form the focus of the first part of the thesis. A novel toric IOL design was devised to decrease the effect of toric rotation on patient visual acuity, but found to have neither a beneficial or detrimental impact on visual acuity retention. IOL tilt, like rotation, may curtail visual performance; however current IOL tilt measurement techniques require the use of specialist equipment not readily available in most ophthalmological clinics. Thus a new idea that applied Pythagoras’s theory to digital images of IOL optic symmetricality in order to calculate tilt was proposed, and shown to be both accurate and highly repeatable. A literature review revealed little information on the relationship between IOL tilt, decentration and rotation and so this was examined. A poor correlation between these factors was found, indicating they occur independently of each other. Next, presbyopia correcting IOLs were investigated. The light distribution of different MIOLs and an AIOL was assessed using perimetry, to establish whether this could be used to inform optimal IOL design. Anticipated differences in threshold sensitivity between IOLs were not however found, thus perimetry was concluded to be ineffective in mapping retinal projection of blur. The observed difference between subjective and objective measures of accommodation, arising from the influence of pseudoaccommodative factors, was explored next to establish how much additional objective power would be required to restore the eye’s focus with AIOLs. Blur tolerance was found to be the key contributor to the ocular depth of focus, with an approximate dioptric influence of 0.60D. Our understanding of MIOLs may be limited by the need for subjective defocus curves, which are lengthy and do not permit important additional measures to be undertaken. The use of aberrometry to provide faster objective defocus curves was examined. Although subjective and objective measures related well, the peaks of the MIOL defocus curve profile were not evident with objective prediction of acuity, indicating a need for further refinement of visual quality metrics based on ocular aberrations. The experiments detailed in the thesis evaluate methods to improve visual performance with toric IOLs. They also investigate new techniques to allow more rapid post-operative assessment of premium IOLs, which could allow greater insights to be obtained into several aspects of visual quality, in order to optimise future IOL design and ultimately enhance patient satisfaction.

Clinical techniques to assess the visual and optical performance of intraocular lenses:a review

A number of clinical techniques are available to assess the visual and optical performance of the eye. This report aims to review the advantages and limitations of techniques used in previous studies of patients implanted with intraocular lenses (IOLs), whose designs are ever increasing in optical complexity. Although useful, in-vitro measurements of IOL optical quality cannot account for the wide range of biological variation in ocular anatomy and corneal optics, which will impact on the visual outcome achieved. This further highlights the need for a standardised series of visual performance tests that can be applied to a wide range of IOL designs. The conclusions of this report intend to assistresearchers in developing a comprehensive series of investigations to evaluate IOL performance. Repeatable and reproducible in-vivo assessments of visual and optical performance are desirable to further develop IOL concepts and designs, in the hope of improving current postoperative visual satisfaction. © 2013 Nova Science Publishers, Inc.

B2B service brand identity:scale development and validation

Several brand identity frameworks have been published in the B2C and the B2B brand marketing literature. A reliable, valid and parsimonious service brand identity scale that empirically establishes the construct's dimensionality in a B2B market has yet to be developed. This paper reports the findings of a study conducted amongst 421 senior executives working in the UK IT Service sector to develop and validate a B2B Service Brand Identity Scale. Following established scale development procedures support is provided for a B2B Service Brand Identity Scale comprising five dimensions; employee and client focus, visual identity, brand personality, consistent communications and human resource initiatives. Concluding remarks discuss theoretical and managerial implications with limitations and directions for future research. © 2011 Elsevier Inc.

The association between glycated haemoglobin levels and P100 visual evoked potentials in diabetes mellitus

Diabetes mellitus (DM) is a metabolic disorder which is characterised by hyperglycaemia resulting from defects in insulin secretion, insulin action or both. The long-term specific effects of DM include the development of retinopathy, nephropathy and neuropathy. Cardiac disease, peripheral arterial and cerebrovascular disease are also known to be linked with DM. Type 1 diabetes mellitus (T1DM) accounts for approximately 10% of all individuals with DM, and insulin therapy is the only available treatment. Type 2 diabetes mellitus (T2DM) accounts for 90% of all individuals with DM. Diet, exercise, oral hypoglycaemic agents and occasionally exogenous insulin are used to manage T2DM. The diagnosis of DM is made where the glycated haemoglobin (HbA1c) percentage is greater than 6.5%. Pattern-reversal visual evoked potential (PVEP) testing is an objective means of evaluating impulse conduction along the central nervous pathways. Increased peak time of the visual P100 waveform is an expression of structural damage at the level of myelinated optic nerve fibres. This was an observational cross sectional study. The participants were grouped into two phases. Phase 1, the control group, consisted of 30 healthy non-diabetic participants. Phase 2 comprised of 104 diabetic participants of whom 52 had an HbA1c greater than 10% (poorly controlled DM) and 52 whose HbA1c was 10% and less (moderately controlled DM). The aim of this study was to firstly observe the possible association between glycated haemoglobin levels and P100 peak time of pattern-reversal visual evoked potentials (PVEPs) in DM. Secondly, to assess whether the central nervous system (CNS) and in particular visual function is affected by type and/or duration of DM. The cut-off values to define P100 peak time delay was calculated as the mean P100 peak time plus 2.5 X standard deviations as measured for the non-diabetic control group, and were 110.64 ms for the right eye. The proportion of delayed P100 peak time amounted to 38.5% for both diabetic groups, thus the poorly controlled group (HbA1c > 10%) did not pose an increased risk for delayed P100 peak time, relative to the moderately controlled group (HbA1c ≤ 10%). The P100 PVEP results for this study, do however, reflect significant delay (p < 0.001) of the DM group as compared to the non-diabetic group; thus, subclincal neuropathy of the CNS occurs in 38.5% of cases. The duration of DM and type of DM had no influence on the P100 peak time measurements.