Principal Investigator: Andre Antonio Fenton
Spatial Cognition: Contributions of Place Cells, Hippocampal Pathways, Allocentric and Idiothetic Information
The fact that hippocampal "place cells" only fire in cell-specific locations is the basis of the idea that the hippocampus encodes and stores a cognitive map of space that animals use to solve complex spatial problems. Although this idea has received substantial experimental support, the current understanding of how place cell activity is related to spatial knowledge and behavior is negligible. This is because place cell research has concentrated on discovering the spatial or geometric firing properties of place cells, i.e. what spatial features of the world determine the location-specific activity. Place cells have almost never been recorded in conditions where the individual contributions of exteroception and interoception (allocentric and idiothetic information, respectively) to spatial firing can be assessed although this conceptual distinction is a major issue in the hippocampal place learning literature. A common subject in the modelling and computational literature is the hippocampal spatial representation and navigation system. However, there are almost no physiological data on how different parts of the hippocampus process allocentric and idiothetic information nor how the hippocampal pathways transform and condition the place cell signal.
Experiments are proposed to simultaneously study place cells and the
rat's behavior during three novel tasks in which place cells and the rat's
spatial knowledge can be objectively assessed. Experiments are also proposed
to study the behavioral and place cell effects of dissociating and isolating
the relevance of allocentric and idiothetic information. A third class
of experiment couples unit and EEG recordings with unilateral inactivations
of selected hippocampal pathways to learn how different hippocampal inputs
support 1) spatial cognition and 2) place cell firing when either allocentric
or idiothetic information is relevant. Three key questions that are asked
are: 1. What classes of spatial information contribute to hippocampal
spatial cognition? 2. How do the commissural inputs to Ammon's horn organize
place cell firing? 3. How are place cells related to spatial cognition
in allocentric and idiothetic reference frames during target-directed
navigation, during undirected searching, and during non-locomotor place
recognition?
