Learning, remembering and applying an arbitrary non-matching to position rule in mice

We describe maze-based behavioural methodologies to assay aspects of arbitrary rule learning in mice. The methods allow for rapid acquisition of a non-matching to position (NMTP) rule that is relatively uninfluenced by innate behavioural strategies, and which give rise to stable baseline performance. Use of the NMTP rule under baseline conditions did not appear to be influenced by extra-maze cues nor intra-maze cues based on olfactory information. Hence the information used to guide performance at test was probably a visual and/or a kinaesthetic representation of the sample. Whatever the precise nature of the trace, its availability to guide behaviour was degraded by introducing delays between sample and test run components of the task. The characteristics of the so-called "forgetting curve" produced did not seem to be influenced by mediating strategies, whereby performance could be maintained following a delay by use of persistent olfactory cues or rehearsal of the correct response using body position, suggesting that, to some degree the degraded performance following delays was indexing effects on short term memory processes. We then went on to obtain behavioural indices that may be of use in dissociating, within-subjects, between learning the basic NMTP rule and being able to apply it in a choice situation, using single and simultaneous discrimination conditions, respectively. The data are discussed in terms of the utility of the behavioural methods to assay different psychological functions underlying the ability to learn, remember and apply non-matching to position rules in mice and their particular use in examining age-related deficits in cognitive functioning.