IntelliCage protocols using incentive-disincentive dual motivation work with male as well as female mice and reveal sex differences in motivated behavior.

Introduction: In the IntelliCage system, spontaneous behavior and cognitive abilities of mice can be assessed automatically in a social homecage context and without handling by human experimenters. We have recently shown that female mice can be motivated to learn complex spatial tasks with refined IntelliCage protocols that lack water restriction and thereby eliminate the risk of water deprivation in poor learners. These protocols create a dual motivation by combining incentive and disincentive taste stimuli. The mice learn to gain access to saccharin sweetened water while water rendered bitter by quinine remains permanently available. Methods: Here, we used a total of 64 C57BL/6J mice to assess males and females in dual motivation protocols versus single motivation protocols using only saccharin as incentive stimulus. Results: We found that in dual motivation protocols male mice learned at least as well as females provided that the location of target corners was stable over time. When targets shifted frequently and in response to the choices of the animals, male mice lost motivation and learned poorly. Based on lick counts, we did not find evidence of impaired liquid intake despite the addition of a disincentive stimulus. Discussion: Our study demonstrates that by using dual motivation protocols, it is possible to create spatial learning tasks for IntelliCage which do not enforce learning by water restriction and which can be learned by mice of both sexes. Furthermore, our results reveal an interesting sex difference in motivated behavior which is not apparent in protocols that enforce learning by water restriction. We hypothesize that this sex difference may be related to the socio-spatial organization of male mouse groups in the IntelliCage.