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Abstract

New, changing, and inherently variable environments force animals to address different sorts of uncertainty. These in turn,
are associated with various aspects of behavioural and neural activity. Hippocampal place cells code in a behaviourallyrelevant
manner for aspects of space and reward. By inducing various forms of uncertainty in these two quantities, we sought
to shed light on the ways that mice experience and accommodate the incompletely known. We designed a novel Uncertain
Reward Task (URTask) in a virtual reality (VR) apparatus (figure1). Mice (six adults) were trained to run along a VR linear
track and lick for a water reward. Different forms of uncertainty were manipulated by varying the distributions of reward
locations and changing the virtual surround. Using two-photon calcium imaging, we recorded activities of place cells in CA1
along with mouse behaviour (licking and velocity) as uncertainty was induced and partially resolved by experience. Given
inherently variable reward locations, animals tend to slow down and lick continuously within the expected reward zone (figure
2), and the place map within the reward zone becomes less spatially precise (figure 3). From limpid changes in reward
locations, the behaviour requires a few trials to adjust to the new task configuration (figure 4), and the place map undergoes a
higher degree of remapping (figure 5). Our data demonstrates that the URTask can engender different forms of uncertainty
that produce different behavioural and neuronal adaptations. The URTask may therefore be used to investigate how the brain
distinguishes and decodes varying forms of
uncertainty.