Navigation is a complex behavior that involves integrating information about multiple spatial constructs such as location and facing direction. To date, the neural underpinnings of this behavior have been most commonly studied by making electrophysiological recordings in rats. Such studies have contributed to our understanding of spatial cognition by revealing neurons (e.g., place cells) whose firing patterns code for one or more of these spatial constructs. Although these important discoveries have advanced our understanding of the neural correlates of rodent spatial cognition, it remains unclear whether similar processes occur in the human brain. Therefore, this proposal will use advanced functional magnetic resonance imaging (fMRI) techniques to 1) identify the neural representations of location and facing direction and 2) elucidate the properties of map-like coding of location. In Experiment 1, multivoxel pattern analysis (MVPA) and fMRI adaptation (fMRIa) will be used to look for distributed representations of location and facing direction and test whether these two constructs are coded independently or conjointly. Next, I will expand on my early work, which provided the first evidence for a metric representation of space in the hippocampus that preserves distance relationships between locations, one of the key features of a cognitive map (Morgan et al., In Press). Specifically, when subjects viewed photographs of landmarks from their campus, BOLD signal in the left anterior hippocampus scaled with the real-world distance between landmarks shown on successive trials. I will further characterize this map-like coding by probing the distance signal in two fMRI experiments. In Experiment 2, I will test whether the map represents space at one scale or multiple scales by comparing the distance signal when subjects view landmarks drawn from a large environment (the city of Philadelphia) to the distance signal when subjects view landmarks drawn from a smaller environment (the University of Pennsylvania campus). In Experiment 3, I will test whether the map represents locations based on their position in Euclidean space or the route length and angles between different places. To distinguish between these two possibilities, I will train subjects on a virtual environment where the route length is much longer than the Euclidean distance for some landmark pairs. This proposal aims to elucidate the neural representations that allow successful wayfinding behavior in humans. Difficulties with this behavior can arise from a variety of neurological insults including cerebrovascular accidents and Alzheimer's Disease. By probing the neural locus of spatial representations, this research can improve the assessment and diagnosis of patients that present with wayfinding difficulties and may inform patient treatments by suggesting coping strategies that utilize the intact brain areas. )
This proposal uses neuroimaging methods to understand how the human brain represents information about location and facing direction to navigate. By probing these spatial representations, this research can improve the assessment and diagnosis of patients that present with wayfinding difficulties (e.g., stroke victims and patients with Alzheimer's Disease) and may inform patient treatments by suggesting coping strategies that utilize the intact brain areas.
|Epstein, Russell A; Vass, Lindsay K (2014) Neural systems for landmark-based wayfinding in humans. Philos Trans R Soc Lond B Biol Sci 369:20120533|
|Vass, Lindsay K; Epstein, Russell A (2013) Abstract representations of location and facing direction in the human brain. J Neurosci 33:6133-42|