Pseudoneglect and visual attention networks

Pseudoneglect represents the tendency for healthy individuals to show a slight but consistent bias in favour of stimuli appearing in the left visual field. The bias is often measured using variants of the line bisection task. An accurate model of the functional architecture of the visuospatial attention system must account for this widely observed phenomenon, as well as for modulation of the direction and magnitude of the bias within individuals by a variety of factors relating to the state of the participant and/or stimulus characteristics. To date, the neural correlates of pseudoneglect remain relatively unmapped. In the current thesis, I employed a combination of psychophysical measurements, electroencephalography (EEG) recording and transcranial direct current stimulation (tDCS) in an attempt to probe the neural generator(s) of pseudoneglect. In particular, I wished to utilise and investigate some of the factors known to modulate the bias (including age, time-on-task and the length of the to-be-bisected line) in order to identify neural processes and activity that are necessary and sufficient for the lateralized bias to arise. Across four experiments utilising a computerized version of a perceptual line bisection task, pseudoneglect was consistently observed at baseline in healthy young participants. However, decreased line length (experiments 1, 2 and 3), time-on-task (experiment 1) and healthy aging (experiment 3) were all found to modulate the bias. Specifically, all three modulations induced a rightward shift in subjective midpoint estimation. Additionally, the line length and time-on-task effects (experiment 1) and the line length and aging effects (experiment 3) were found to have additive relationships. In experiment 2, EEG measurements revealed the line length effect to be reflected in neural activity 100 – 200ms post-stimulus onset over source estimated posterior regions of the right hemisphere (RH: temporo-parietal junction (TPJ)). Long lines induced a hemispheric asymmetry in processing (in favour of the RH) during this period that was absent in short lines. In experiment 4, bi-parietal tDCS (Left Anodal/Right Cathodal) induced a polarity-specific rightward shift in bias, highlighting the crucial role played by parietal cortex in the genesis of pseudoneglect. The opposite polarity (Left Cathodal/Right Anodal) did not induce a change in bias. The combined results from the four experiments of the current thesis provide converging evidence as to the crucial role played by the RH in the genesis of pseudoneglect and in the processing of visual input more generally. The reduction in pseudoneglect with decreased line length, increased time-on-task and healthy aging may be explained by a reduction in RH function, and hence contribution to task processing, induced by each of these modulations. I discuss how behavioural and neuroimaging studies of pseudoneglect (and its various modulators) can provide empirical data upon which accurate formal models of visuospatial attention networks may be based and further tested.

Clydebank in the inter-war years: a study in economic and social change

The main theme of this thesis is the social, economic and political response of a single community to economic dislocation in the interwar years. The community under consideration is Clydebank., The thesis is divided into several parts. Part I establishes the development of the burgh and considers the physical framework of the community, mainly in the years before 1919. The town's characteristics are examined in terms of population structure and development between the world wars. In the last part of this section there is a review of the economic structure of the burgh and changes occurring in it between 1919 and 1939. In Part II consideration is given to the actual extent and form of the unemployment affecting Clydebank at this time, and comparison is made with other communities and geographic/economic areas. Attention is then focussed more narrowly on the actual individuals suffering unemployment in the burgh during the 1930s, in an attempt to personalise the experience of the unemployed. Part III reviews central and local government responses to the situation in which Clydebank found itself oetween 1919 and 1939. Central government policies discussed include unemployment insurance, public works, the Special Areas legislation, assistance in the construction of the 534 "Queen Mary" and the direction of financial support to areas of particular need. Amongst local authority actions described are additional local support for the poor, public works, efforts to attract new industry to the town, attempts to deal with the housing problem which was particularly acute at times of high unemployment and measures to maintain health standards in the community. In Part IV the responses of the community to unemployment and government policies are detailed. The burgh's commercial sector is surveyed as are developments in leisure provision, religion, temperance and crime, and local politics. A number of individual responses are also given consideration such as migration, commuting, changes in birth and marriage rates and suicide.