The role of perceived depth in distance estimation and hippocampal place coding

The hippocampal formation is integral to the construction and maintenance of memories in humans and other animals. Neurons within this network encode spatial components of egocentric self-motion and allocentric environmental features and are theorised to form a representative ‘cognitive map’ necessary for navigation. Vision is an immersive sense rich with spatial information vital for the accurate representation of spatial layout in the brain, however research into the direct relationship between visual perception and the formation of spatial representations is limited. In particular, the susceptibility of the visual cortex to perceptual error may put regions of the cognitive map sensitive to visual input at risk of accumulating bottom-up error, particularly during travel through environments with ambiguous or distorted visual cues to perceived motion and environmental scale. This thesis utilises a novel distance estimation paradigm to assess the effect of distorting purely visual perspective features within the local environment on navigational behaviour and CA1 place cell activity in rats. Animals consistently overestimated the distance travelled to a learned reward zone when projective perspective cues were diverged and showed signs of underestimation of distance when perspective cues converged. This behavioural change coincided with experience-dependent rate remapping and relocation of firing field locations during place cell recording. These findings are further supported by comparative performance in humans using wireless virtual reality, where changes to perspective features elicited altered distance estimates during static viewing and active navigation, implicating projective perspective in the perception of egocentric distance both in anticipation of and during active navigation. Collectively, this research suggests that perceived environmental scale from projective perspective informs the perceived distance during visually guided navigation in both rodents and humans. Through behavioural, electrophysiological and psychophysics research, this thesis provides novel evidence for the role of the visual perception of depth and distance on spatial reasoning across species.