Visual-spatial learning in the rat: contamination in the eight arm radial maze

Abstract

The purpose of the present study was to: (1) investigate the ability of rats to learn the radial arm maze using only extramaze visual cues while utilizing controls for nonmemorial cues, (2) determine whether rats make use of reference memory cues in the radial maze, and (3) determine the time course for decay of working memory for extramaze visual cues in rats with controls for nonmemorial and reference memory cues. Three month old and twenty-four month old animals were tested in an eight arm radial maze. The maze was in a curtained arena with three visual cues. Odor controls and controls for extramaze visual-spatial cues were instituted. In experiment I, animals were tested for their ability to use intramaze ordor cues and extramaze visual cues. In experiment II, the same and different spatial cues were used. In experiment III, the duration of memory was tested by imposing delay of 10, 60 and 480 seconds between each selection. Both young and aged animals were able to use either odor or visual cues. Young animals performed better than aged animals with both odor and visual cues. No age-related decrement in the use of visual cues was noted. In experiment II, animals using different visual cues each trial performed significantly inferior to those using the same visual cues. Young animals performed better than aged animals in both cue conditions. In experiment III, performance of young and aged animals decreased with increasing delay intervals. Performance appears to reach chance levels with a 480 second delay interval between each selection. Young animals performed significantly better than aged animals. The results were discussed in terms of contamination of the 8-arm radial maze as a test of working memory for spatial cues without the appropriate controls for intramaze odor cues and response strategies.