Highlights d Sleep deprivation improves memory in old mice but worsens it in young ones d Sleep deprivation decreases hippocampal flexibility and spindle counts in young mice d Increased spindle counts are associated with improved memory in old mice d Sleep deprivation improves the quality of hippocampal representations in old mice

Reorientation enables navigators to regain their bearings after becoming lost. Disoriented individuals primarily reorient themselves using the geometry of a layout, even when other informative cues, such as landmarks, are present. Yet the specific strategies that animals use to determine geometry are unclear. Moreover, because vision allows subjects to rapidly form precise representations of objects and background, it is unknown whether it has a deterministic role in the use of geometry. In this study, we tested sighted and congenitally blind mice ( Ns = 8–11) in various settings in which global shape parameters were manipulated. Results indicated that the navigational affordances of the context—the traversable space—promote sampling of boundaries, which determines the effective use of geometric strategies in both sighted and blind mice. However, blind animals can also effectively reorient themselves using 3D edges by extensively patrolling the borders, even when the traversable space is not limited by these boundaries.

Temporal costs influence reward-based decisions. This is commonly studied in temporal discounting tasks that involve choosing between cues signaling an imminent reward option or a delayed reward option. However, it is unclear whether the temporal delay before a reward can alter the value of that option. To address this, we identified the relative preference between different flavored rewards during a free-feeding test using male and female rats. Animals underwent training where either the initial preferred or the initial less preferred reward was delivered noncontingently. By manipulating the intertrial interval during training sessions, we could determine whether temporal delays impact reward preference in a subsequent free-feeding test. Rats maintained their initial preference if the same delays were used across all training sessions. When the initial less preferred option was delivered after short delays (high reward rate) and the initial preferred option was delivered after long delays (low reward rate), rats expectedly increased their preference for the initial less desirable option. However, rats also increased their preference for the initial less desirable option under the opposite training contingencies: delivering the initial less preferred reward after long delays and the initial preferred reward after short delays. These data suggest that sunk temporal costs enhance the preference for a less desirable reward option. Pharmacological and lesion experiments were performed to identify the neural systems responsible for this behavioral phenomenon. Our findings demonstrate the basolateral amygdala and retrosplenial cortex are required for temporal delays to enhance the preference for an initially less desirable reward.

Dexamethasone (DEX), a synthetic glucocorticoid that preferentially binds NR3C1, suppresses endogenous adrenocorticotropic hormone (ACTH) and cortisol production. Dexamethasone suppression tests (DST) are used to evaluate the functioning of the hypothalamicpituitary-adrenal (HPA) axis by assessing the integrity of the glucocorticoid feedback receptor sensitivity 1 and are utilized in basic research involving non-human primate models of stress and neuroendocrine dysfunction. 2-9