A variant of the Morris water task for assessing learning and memory processes in mice

Abstract

The Morris water task (MWT) is commonly used to assess rodent spatial learning and memory. Our goal was to develop a 3-phase variant of the hidden goal water task to assess old and new spatial memories acquired in the same context using various measures of spatial learning in C57BL/6 mice. In the first phase, mice were pre-trained to an initially hidden location. The second phase consisted of a massed training session to a new location in the same apparatus and context. The final phase consisted of a competition test between the original and new platform locations. AppNL-G-F/NL-G-F mice, a novel transgenic mouse model for Alzheimers disease (AD), were also used as an independent variable to validate this 3-phase variant of MWT. The results of the present study showed that C57 mice acquired and retained both the old and new location representations; however, AppNL-G-F/NL-G-F mice retained a recently acquired spatial memory but did not remember the old location acquired in the same apparatus and context. The results showed that C57 mice can show precise place learning and memory with the right amount of training and acquire and retain multiple spatial memory locations in the same environment whereas this ability was impaired in AppNL-G-F/NL-G-F mice. In the visible platform test, however, all groups of mice showed normal sensorimotor ability and motivation. These findings indicate that this new version of the MWT provides a robust way for assessment of old and new memories in mice. This paradigm could also be exploited to assess manipulations of neural circuits implicated in learning and memory processes as well as for research investigating human brain diseases.