Theoretical background:
For more information on the representation of walls/obstacles, please refer to the papers listed in the Hippocampus and Navigation Group homepage.
Representing the presence of walls ...
TAM-WG employs coarse coding in a linear array of cells, in this way affordances are coded as bumps of activity for turns from -180 to +180 degrees.
When in the dais of the 8-arm radial maze, for example, the rat is able to sense eight different visible arms and consequently, eight different affordances (since a rat's visual field covers approximately 320 degrees, we assume it is able to visually sense the turning affordance given by the arm behind it).
When the rat is the junction of the T-maze, 4 affordances are available: 90 and 180 degrees - left and right.
After turning right, but when still in the junction of the T-maze, 4 affordances are available: straight ahead, 90 degrees left, and 180 degrees - left and right.
After turning left, but when still in the junction of the T-maze, 4 affordances are available: straight ahead, 90 degrees right, and 180 degrees - left and right.
When in the middle of a corridor, 3 affordances are available: straight ahead and 180 degrees left and right.
Finally, when the rat reaches the end of an arm, only the affordances to turn backwards are available: 180 degrees left and right.
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All contents copyright (C) 1994-1997. University of Southern California Brain Simulation Lab All rights reserved.Author: Alex Guazzelli <aguazzel@rana.usc.edu>