Neural mechanisms of spatial cognition

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The hippocampus is widely believed to be a crucial brain structure for spatial cognition. However, its precise role is still the subject of considerable debate. Our lab has been investigating the role of the hippocampus and related structures in the medial temporal and parietal lobes in spatial memory and mental imagery using a variety of techniques, including computational (neural network) modelling, human memory experiments in virtual reality (VR) environments, neuroimaging using fMRI and EEG, and brain-computer-interfaces. We have developed a computational model that sheds light on the mechanisms underlying spatial memory, mental imagery, and the visual transformation process by which viewer-centred sensory information is transformed into a world-centred representation, commonly known as a “cognitive map”. Our recent work has been aimed at testing several predictions of the model. In virtual reality studies where people incidentally learned the layout of a town by playing a virtual taxi game, we found that people were more likely to encode the spatial locations of objects they saw along routes if the objects were at navigationally relevant locations, and also when attention was particularly focused on spatial cues, suggesting that objects may be flexibly treated as landmarks and incorporated into cognitive maps, according to task demands. We also found that people have a strong tendency to form global, hierarchical representations of large-scale spaces. Moreover, recent neuroimaging (fMRI) studies confirm some of the model’s predictions regarding the specific neural structures that may be involved in the visual transformation from viewer-centric sensory representations to world-centric cognitive maps. The proposed research will further our understanding of these processes. Our computational models of the hippocampal memory system will be extended to account for how we combine geometric, object and path integration cues, and how we learn temporal sequences. Complementing this theoretical work, empirical methods will be used to test predictions of the model and shed further light on the conditions governing the use of cognitive maps and visuospatial transformations. We will investigate the hippocampal mechanisms involved in the formation of distinctive representations for similar spatial contexts, the link between mental imagery and visuospatial transformations, and the effect of lifestyle factors such as stress, alcohol consumption and exercise on hippocampal-dependent spatial strategies. Finally, we will explore an innovative application of our research on mental imagery, using EEG-based brain-computer interfaces and state-of-the-art machine learning methods to decode a person’s internal mental imagery and use it to control a virtual reality display. In the long term, our work could have important implications not only for understanding the basic mechanisms underlying spatial cognition, but for rehabilitating individuals with spatial memory and navigation deficits in ageing, and rehabilitating positive visual imagery deficits in those with mood disorders.