Abstract
Determining one's current location and facing direction is essential for successful navigation. How are these two types of information represented in the brain? Electrophysiological recordings in rodents have identified place cells and head direction cells whose firing properties code for location and facing direction respectively. However, complementary research in humans has been lacking. We addressed this issue by scanning University of Pennsylvania students with fMRI while they viewed photographs taken by cameras facing 4 different compass directions (North, South, East, West) at 8 intersections from the Penn campus. Images (17 of each direction at each intersection; 544 total) were presented every 4 s without repetition in a continuous-carryover design (Aguirre, 2007). fMRI adaptation (fMRIa) and multi-voxel pattern analysis (MVPA) were used to identify regions that code: (1) the intersection at which the image was taken, (2) the compass direction faced by the camera, (3) the specific view depicted in the image. Preliminary MVPA results from 4 subjects suggest that both locations and facing directions can be discriminated in the hippocampus, and that these two kinds of information are localized to different hippocampal regions. Scene-selective regions including parahippocampal place area and retrosplenial complex may also contain information about locations and facing directions. Our findings are consistent with the rodent neurophysiology literature and suggest that navigationally relevant information in humans is present in distributed patterns of activity across both neocortical and hippocampal regions.
This research was funded by NIH grant EY-016464 to R.A.E.