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The neural networks recruited during visual feature binding

Cheetham, Emma 2014. The neural networks recruited during visual feature binding. PhD Thesis, Cardiff University.
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The binding problem presents one of the most challenging questions in psychology and cognitive neuroscience, despite its seemingly effortless resolution in daily life. Binding of visual features begins with stimulation of peripheral receptors and ends with the emergence of a perceived object, yet many questions remain unanswered about the nature of the intervening mechanisms. The primary focus of this thesis was to elucidate neurocognitive processes that support binding of features into a coherent object. Experiment 1 sought to dissociate neural correlates of feature binding from spatial and temporal attention, which are frequently conflated in previous studies. Results showed a widespread network engaged during both forms of attention, without any significant clusters of activity in response to an explicit feature-binding task. One explanation for these results may lie in evidence that feature binding is a spontaneous process that happens implicitly upon observing an object. Therefore, in order to measure the network associated with implicit visual feature binding the established reviewing paradigm was employed in the subsequent studies. Experiments 2 and 3 sought to replicate key aspects of the reviewing paradigm. The reviewing paradigm exploits the finding that when an object is shown in close spatial and temporal succession to another object it is perceived as a continuation of the same object. Therefore, if a feature changes between the initial object and the second presentation of this object then a rebinding of features occurs and a behavioural cost termed a partial repetition cost is often incurred. In order to observe the impact of a relevant feature change compared with an irrelevant feature change, the reviewing paradigm was modified. Results indicated that an irrelevant feature change carried with it a reaction time (RT) cost almost as large as a RT cost observed following a relevant feature change. Experiment 4 aimed to observe the neural network recruited during the completion of the reviewing task experiment using fMRI and a whole brain analysis. Results showed a widespread network encompassing bilateral frontal and occipital areas. Furthermore, the network that was recruited during the irrelevant feature change condition was different from that engaged during the relevant feature change condition. In order to probe the causality of these actions, 3 experiment 5 exploited the offline transcranial magnetic stimulation (TMS) to three key cortical areas: right lateral occipital complex, left superior frontal gyrus and left post-central gyrus. The overarching conclusion of this thesis is that feature binding is an implicit and spontaneous process that is coordinated by a wider cortical network than expected from previous research. The parietal cortex has often been observed as the key area in which object representations become bound, however the results of this thesis do not support a unique or privileged role of this area in binding. The latter experiments show that feature binding is an interaction between the memory trace, action-based implications and perceptual demands of an object. How the brain co-ordinates this widespread cortical network during feature binding is a key question for future research involving TMS and brain imaging techniques.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Psychology
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:50

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