Behavioural and neural correlates of object-location representation in human spatial navigation

Chan, Edgar (2012). Behavioural and neural correlates of object-location representation in human spatial navigation PhD Thesis, School of Psychology, The University of Queensland.

       
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Author Chan, Edgar
Thesis Title Behavioural and neural correlates of object-location representation in human spatial navigation
School, Centre or Institute School of Psychology
Institution The University of Queensland
Publication date 2012
Thesis type PhD Thesis
Supervisor Mattingley, J.B.
Bellgrove, M.A.
Total pages 139
Total colour pages 16
Total black and white pages 123
Language eng
Subjects 1701 Psychology
1109 Neurosciences
Abstract/Summary Spatial navigation is a complex and dynamic process that is crucial for survival. An important aspect of successful navigation is the ability to form an accurate representation of the surrounding spatial environment and retrieve that information when necessary. The experiments described in this thesis used behavioural and neuroimaging techniques in human participants to investigate some of the factors that influence object location representations during spatial navigation. During navigation, relevant objects in the environment act as landmarks to aid orientation and way-finding behaviour, and provide a framework for internal spatial representations of the external world. The thesis begins with a review of the relevant literature in Chapter 2 in which I explore the different ways in which environmental objects can be used as landmarks for spatial navigation. A novel taxonomy for categorizing landmarks is proposed focussing on the navigational functions of objects and their related neural substrates. Chapter 3 sought to identify the neural circuits involved in the distinct processes of encoding and retrieval of object locations during landmark-based navigation. Previous studies have highlighted possible cortical and subcortical circuits involved in navigation, but none has explicitly determined whether encoding and retrieval processes are subserved by distinct neural networks. Functional magnetic resonance imaging (fMRI) was used to measure neural responses while participants undertook an object-location encoding and retrieval task within a sparse virtual environment. Results revealed that during encoding, greater activity within the right hippocampus and bilateral parahippocampal gyri predicted more accurate navigation performance. In contrast, during the retrieval phase, greater activity in left hippocampus and bilateral striatum predicted better performance. Differences in neural activity were further modulated by individual differences in navigational ability. Chapters 4 and 5 investigated the influence of reference systems on the organization of allocentric spatial representations. The reference systems account of spatial memory proposes that relationships between objects in the environment are encoded with respect to salient axes provided by surrounding environmental landmarks. Behavioural evidence for this account is derived in part from alignment effects. Judgements of relative direction are faster and more accurate when an imagined orientation is aligned, as opposed to misaligned, with the axes defined by salient landmarks. Chapter 4 reports the results of a series of behavioural experiments, in which I used a novel virtual environment to examine the reference systems account of spatial memory. Findings demonstrated that reference systems are a stable property of allocentric representations and are invariant across time and encoding viewpoint. Chapter 5 presents fMRI data showing that retrieval of spatial information from aligned orientations resulted in greater activity in inferior occipital and temporal cortical areas, whereas retrieval from misaligned orientations resulted in greater activity in the prefrontal cortex and anterior cingulate. These findings are consistent with the notion that object location representations are organized and stored with respect to salient axes. Not all landmarks have equal salience. For example, priority may be given to locations at which negative events are encountered during exploration, thus helping the individual avoid potential threats in the future. In Chapter 6 I examined whether affective stimuli encountered during navigation influence object-location memory and associated neural responses. In an active object-location memory task, positive, negative or neutral stimuli were paired with different locations within a virtual indoor environment. Post-learning performance and neural responses measured using fMRI revealed that place representations in the parahippocampal gyrus were enhanced for locations at which negative emotional events had previously been encountered. Furthermore, emotional arousal during learning significantly improved object-location memory. The research presented in the thesis highlights the complexity of navigation-related spatial memory processes. Individual differences, the spatial positioning of environmental objects, and the valence of emotional experiences were all found to significantly affect behavioural performance and the neural substrates involved in object-location representations. Some of these new findings may help to better understand and diagnose navigation-related disorders arising from brain injury or disease.
Keyword Spatial Memory
Navigation
Object-Location
Fmri
landmark
emotion
Arousal
virtual environments
Additional Notes Printed in colour 25,29,33,51,54,55,56,68,74,88,91,94,95,108,110,114

 
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Created: Mon, 21 May 2012, 22:57:15 EST by Edgar Chan on behalf of Library - Information Access Service