BEHAVIORAL AND NEURAL MECHANISMS UNDERLYING SPATIAL EXPLORATION AND DECISION

Abstract

The ability to explore novel environments and make decisions is a fundamental component of human and animal behavior. Even though significant progress has been made in recent years in understanding the mechanisms of exploration and decision-making, little is known on how the brain extracts, encodes and processes information from the environment to make decisions. The primary goal of this thesis is to understand the behavioral and neural mechanisms underlying the processing of spatial information, acquired during exploration of realistic environments to make spatial decisions. We designed a novel task, in which subjects had to explore maps from various U.S. cities to decide where to build a City Hall, while neuromagnetic fluxes were recorded from their heads using a whole-head MEG device. We found that ongoing neuronal activity in a network of cortical regions was associated with particular spatial parameters of the city maps. This network involved predominantly the right frontal and prefrontal areas of the brain, suggesting that these areas have an important role in processing spatial information for making decisions. Additionally, we found other brain areas that were also involved in the processing of spatial information, such as right temporal areas and the cerebellum. These results indicate that processing spatial information for making a decision is a complex process that requires the involvement of more than one regions. Finally, we found that the associations between changes in the ongoing neural activity and spatial parameters were modulated by the street network type. This suggests that, depending on the type of street network, people may use different spatial information to explore the map and make a spatial decision.We also studied how people make spatial decisions in realistic environments when they were forced to select between a limited set of choices. In this experiment, individuals had to explore maps from various U.S. cities, but now to select between two locations to build a hypothetical Post Office. We recorded subjects' eye positions and analyzed the gaze behavior to characterize how people explored maps to select between these options. We found that subjects were continuously exploring the areas around the two options and the center of the map, by looking back and forth between them before making a decision. Unlike economic choices, in which people follow similar strategies by looking repeatedly at the available options, in our experiment individuals were also exploring the area around the center of the map. These findings suggest that the subjects might have mentally placed themselves at the center of the map and evaluated the alternative options with respect to their current location. We also found other similarities with economic choice paradigms, such as people spent more time exploring the area around the option ultimately chosen. Finally, subjects showed a strong bias to select the option they initially explored.