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Title: The human executive system : modularity and coordination
Author: Hampshire, A. D. G.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2005
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It was the aim of this thesis, to develop a more unitary model of the executive functions, by tying together some of the diverse strands of research on the role of the human prefrontal cortex. In the first section of this thesis, event-related functional magnetic resonance imaging was utilised to investigate the neural correlates of working memory and attentional switching in a series of 3 experiments. The findings of this series of studies suggest that the ventrolateral prefrontal cortex is involved in working memory at the level of stimulus type. Further, transient peaks of activation were observed in this region only when the attentional focus moved between stimulus dimensions. From the findings it was proposed that the ventrolateral prefrontal cortex forms a specific module, which adapts to code for the currently relevant task dimensions, and that on reconfiguring its focus between those task dimensions, displays a transient peak of activity. This model therefore, potentially ties together findings from both the working memory and attentional switching literature. A task was then developed, which behaviourally dissociated the effects on difficulty of between-dimension and reward-based attentional switching, in a paradigm suitable for fMRI analyses. Subsequently multiple brain regions involved in the executive functions were fractionated using an fMRI version of this task according to their specific contributions to attentional control. The findings of this study again suggested that the ventrolateral prefrontal cortex was involved in focusing the locus of attention according to stimulus dimension. The orbitolateral prefrontal cortex was demonstrated to be involved in implementing switches when response suppression was required based on negative feedback, whereas the orbitomedial prefrontal cortex was involved in processing positive feedback. Further, the posterior parietal cortex appeared to play a role in changes to stimulus-response mapping.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available