Funded Grants

Navigational guidance systems in the human brain

Finding our way through the world is crucial for survival. When this ability is lost, as occurs in the early stages of Alzheimer’s dementia, the result is devastating. While over half a century of research has provided us with a detailed understanding of how the brain determines current location and orientation, we know surprisingly little about how the brain represents our spatial relationship to distant goals or guides navigation to them. A recent neuroimaging study of London taxi drivers suggests a network of brain regions may act as a navigational guidance system. These regions include the medial temporal lobe, posterior parietal cortex and prefrontal cortex. However, the precise role played by each brain region and how they interact during navigation remains unclear.

Our hypothesis, based on computational models, is that during navigation the medial temporal lobe computes a vector to the goal and estimates future paths at decision points. The posterior parietal cortex computes the direction to the goal relative to the body’s axis and the environment. While these brain regions help select efficient routes and find shortcuts, another system in the striatum is thought to guide navigation through learned associations (e.g. the habit of turning left at the pub). The prefrontal cortex may help switch between these systems, and cooperate with them to learn goal locations. Emerging evidence highlights the importance of theta band oscillations (4-12Hz), which may allow neural activity to be synchronized between different brain areas, creating time-windows for information transfer or modulation of processing.

To test this model, we have developed a new approach to studying navigation in the real world. Volunteers initially learn an environment using the method London taxi drivers use to learn ‘The Knowledge’ of London. Subsequently, volunteers undergo neuroimaging while watching first-person-view movies and choosing their direction to the goal at each street junction. By conducting this research in parallel with experiments recording neuronal ensembles in rodents, we aim to understand how brain networks support navigation at different levels of anatomical specificity and cross-fertilize analytical approaches to neural and behavioural data.

We expect this research to lead to major advances in our understanding of the neural bases of navigation and goal-directed behavior. The research is important because we know little about how our brain updates and tracks dynamic information in real-world environments. Characterising the interactions between regions such as the hippocampus and prefrontal cortex is highly relevant to memory in general as well as to diseases such as schizophrenia where disrupted connectivity may be critical. Therefore, the results obtained will likely have far reaching implications which extend well beyond navigation.