A variety of factors combine to determine the outcome of a navigational scenario. Age, sex, and strategy preference, for example, have quantitative and qualitative influences on how an individual is able to find their way in the environment. However, the structure of the environment itself also plays a critical role. Some environments are easier to understand and navigate than others, but it is not always clear why this is the case. The complexity of the environment appears to be an important determinant of navigational success, bur it is notoriously difficult to define and systematically assess its behavioural consequences. In a series of studies, I provide evidence showing that the complexity of the environment not only affects behaviour and cognition, but also activity in several brain regions that are important for navigation. Chapter 2 describes a behavioural study in which participants performed a navigation task in one simple and one complex virtual environment. Navigation in the complex environment was slower and more error prone, and maps drawn of the complex environment were less accurate, suggesting that complexity makes it difficult to form an accurate cognitive map. Chapter 3 describes an experiment in which participants performed the same task while their brain activity was being assessed using functional magnetic resonance imaging. Navigation in the simple environment was associated with increased brain activity in a number of regions, including the precuneus, retrosplenial cortex, hippocampus, and dorsolateral prefrontal cortex. Chapter 4 describes a series of functional connectivity analyses that characterized how the different regions of the brain identified in Chapter 3 altered their dynamic functional properties measured during the task and at rest. Together, these studies suggest that complexity exerts a powerful influence over
cognition, behaviour, and brain activity during navigation.