EXCEED THE SPACE PROVIDED. This project will investigate the structure of hippocampal spatial representations, focusing on the phe- nomenon of remapping in place cells. Remapping refers to an abrupt or gradual change in a map in response to a change in the environment or task. The modeling component of the project will investigate two al- ternative hypotheses about the cause of remapping. The attractor diversion hypothesis is that a mismatch between local view and path integrator representations diverts the animal from settling into the basin of attraction for the previously-learned map. The attractor suppression hypothesis is that remapping is caused by a learned difference representation in dentate gyms suppressing the original map. The two hypotheses make differing predictions about the effects on remapping of disorientation, overtraining in the original envi- ronment, and accumulated experience in the new environment. Computer simulations will be used to verify the viability of both proposals, and to generate additional predictions that will be tested experimentally. A model of gradual remapping based on a competitive synaptic learning rule (the BCM rule) will also be investigated. Complementing the modeling work, remapping will be studied by multielectroderecording in the rat, using technology that permits recording from up to 100 place cells simultaneously. In Experiments 1-3, rats will forage in a cylinder with white and/or black cue cards along the wall. Experiment 1 will investigate differen- tiation of maps over time, and whether it is possible to create mixures of maps by combining landmarks from two familiar environments. Experiment 2 will investigate whether disorienting the rat prior to exposing it to an environment similar to the first increases the probability of remapping. Experiment 3 will investigate the effects of prior experience on remapping. Experiment 4 will test the stability of the partially remapped state. Rats will forage in two visually identical boxes connected by a corridor, which previous experiments indicate should produce highly similar maps. A cue card will then be added to one box to see if it causes the maps to diverge. These combined modeling and empirical studies are expected to yield a substantially improved understanding of how the hippocampus forms its representations of the world. PERFORMANCE SITE ========================================Section End===========================================
| Fuhs, Mark C; Touretzky, David S (2007) Context learning in the rodent hippocampus. Neural Comput 19:3173-215 |
| Fuhs, Mark C; Touretzky, David S (2006) A spin glass model of path integration in rat medial entorhinal cortex. J Neurosci 26:4266-76 |
| Touretzky, David S; Weisman, Wendy E; Fuhs, Mark C et al. (2005) Deforming the hippocampal map. Hippocampus 15:41-55 |
| Fuhs, Mark C; Vanrhoads, Shea R; Casale, Amanda E et al. (2005) Influence of path integration versus environmental orientation on place cell remapping between visually identical environments. J Neurophysiol 94:2603-16 |
