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Abstract:
The way animals respond to a stimulus depends largely on an internal comparison between
the current sensation and the memory of previous stimuli and outcomes. We know little about
the accuracy with which the physical properties of the stimuli influence this type of memory-
based discriminative decisions. Research has focused largely on discriminations between sti-
muli presented in quick succession, where animals can make relative inferences (same or dif-
ferent; higher or lower) from trial to trial. In the current study we used a memory-based task to
explore how the stimulus’ physical properties, in this case tone frequency, affect auditory dis-
crimination and generalization in mice. Mice performed ad libitum while living in groups in
their home quarters. We found that the frequency distance between safe and conditioned
sounds had a constraining effect on discrimination. As the safe-to-conditioned distance
decreased across groups, performance deteriorated rapidly, even for frequency differences
significantly larger than reported discrimination thresholds. Generalization width was influ-
enced both by the physical distance and the previous experience of the mice, and was not
accompanied by a decrease in sensory acuity. In conclusion, memory-based discriminations
along a single stimulus dimension are inherently hard, reflecting a high overlap between the
memory traces of the relevant stimuli. Memory-based discriminations rely therefore on wide
sensory filters.
