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

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 S entered the inner circular area of the pool with an escape platform. 10 naive male rats trained under light–dark (LD) conditions found the escape platform more slowly than 10 male rats trained in permanent light (LT). After group members were swapped, the LT-pretrained rats found under LD conditions the same target faster and eventually approached latencies attained during LT navigation. Performance of LD-trained rats deteriorated in permanent darkness (PD) but improved with continued PD training. Thus LD 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)