Absence of snapshot memory of the target view interferes with place navigation learning by rats in the water maze.

Abstract

Contribution of visual and nonvisual mechanisms to spatial behavior of rats in the Morris water maze was studied with a computerized infrared tracking system, which switched off the room lights when the subject entered the inner circular area of the pool with an escape platform. Naive rats trained under light-dark conditions (L-D) found the escape platform more slowly than rats trained in permanent light (L). After group members were swapped, the L-pretrained rats found under L-D conditions the same target faster and eventually approached latencies attained during L navigation. Performance of L-D-trained rats deteriorated in permanent darkness (D) but improved with continued D training. Thus L-D navigation improves gradually by procedural learning (extrapolation of the start-target azimuth into the zero-visibility zone) but remains impaired by lack of immediate visual feedback rather than by absence of the snapshot memory of the target view.

The contribution of visual and inertial mechanisms to navigation in total darkness

“…Devan, Blank, and Petri (1992) also found no effect of suppressing the visual cues when the animal reached and stayed on the platform. These results, however, are contrary to those ofWhishaw (1991) and Arolfo, Nerad, Schenk, and Bures (1994), indicating that access This work was supported by a fellowship from the Programme Cognisciences du Centre National de la Recherche Scientifique (France), by BMFT Grant 01 VG 9200215/26, and by Grant 711401 from IGA of the Czech Academy of Sciences, The author would like to thank 1. Bures, B. Poucet, C. Thinus-Blanc, and two anonymous reviewers for their comments, criticism, and suggestions.…”

“…It could be argued that if we had let the rats swim a little longer in light, they would have reached the platform. Arolfo et als results show that this is not the case, because, although their rats were allowed to swim 50 em before the onset of darkness, they were impaired in place learning (Arolfo et a\., 1994). Our results suggest that the map (which was used in the light condition and in the dark condition) is not precise enough to allow accurate performance in the dark, regardless of the initial amount of information processed in the light (see also Whishaw, 1991, for a similar idea).…”

“…It can be hypothesized, therefore, that the inaccuracy of navigation in darkness could be due to the inability to maintain a trajectory on an inertial basis. Beyond a certain distance, maintaining an accurate trajectory would require viewing the environment (GaIlisteI, 1989;McNaughton, Chen, & Markus, 1991), particularly in the vicinity of the platform (Arolfo et a\., 1994).…”

“…A similar procedure has been used by Arolfo et al (1994), which allowed the animal to update its position in the environment and to make several attempts to reach the platform.…”

Spatial learning by rats across visually disconnected environments

“…A computation based on the integration of several distant visual cues is presumed to allow location of a submerged platform in a circular pool of opaque water (Morris, 1981). Accordingly, place navigation performance is poor in complete darkness (Arolfo, Nerad, Schenk, & Bures, 1994;Schenk et al, 1997;Sutherland & Dyck, 1984). Visual cues do not need to be permanently available to support place learning and may be seen only during part of the escape trajectory in the Morris task (Chapillon, 1999;Sutherland, Chew, Baker, & Linggard, 1987).…”