Poster E109, Monday, March 26, 2:30-4:30 pm, Exhibit Hall C
How Does the Brain Compose Mental Images?
Dillon Plunkett1, Joshua D. Greene1; 1Harvard University
Imagine a penguin riding on a giraffe. This example highlights a critical feature of human cognition: It is compositional. We routinely combine familiar conceptual components (e.g., giraffes, penguins, riding) in order to construct novel thoughts, and do so in a structured way—distinguishing, for example, between the notions “penguin riding giraffe” and “giraffe riding penguin.” Not only can we understand the idea of a penguin riding a giraffe, we can picture this spectacle despite never having seen it before, composing a novel mental image from these familiar elements. In this study, we use functional magnetic resonance imaging to investigate how spatially structured, composite mental images are represented in the brain. Following a written cue on each trial, 24 participants imagined two shapes in a vertical configuration (e.g., “circle above square”), then held their mental image in mind for a brief delay before matching that image to one of two objects (e.g., “snow shovel” versus “snow globe”). Using multivoxel pattern analysis performed on imaging data collected during the delay, we identify a bilateral region in posterior parietal cortex which encodes information about the identity of the top shape in the configuration, as well as an adjacent bilateral region which encodes information about the identity of the bottom shape. These findings suggest that spatially structured mental imagery is supported by a spatiotopic map in parietal cortex and, to our knowledge, they are the first direct evidence for the spatiotopic representation of components of mental images in parietal cortex.
Topic Area: THINKING: Other