Major depressive disorder's high heterogeneity makes broad treatments difficult. Focusing on single, biologically understood core symptoms may be more viable. The Research Domain Criteria framework offers a trans-diagnostic dimensional approach. Psychedelics show potential antidepressant activity, possibly explained through multi-level analysis of cognitive systems. Cognitive deficits like negative emotional processing and negativity bias lead to depressive rumination. Psychedelics increase long-term cognitive flexibility, normalizing negativity bias and reducing rumination.
Psilocybin alters how rats suppress actions when facing a conflict between seeking reward and avoiding punishment, but the effect depends on timing. During learning, psilocybin increased behavioral suppression in female rats as they learned that a risky action could lead to punishment. After the reward-punishment associations were already learned, psilocybin decreased behavioral suppression in both male and female rats. These divergent effects suggest that psilocybin's influence on approach-avoidance conflict changes depending on whether the conflict is being learned or has already been learned, which may relate to its therapeutic action in mood disorders.
Applying targeted memory reactivation (TMR) during REM sleep improves learning of a whole-body procedural task more than TMR applied during slow-wave sleep, wake, or no reactivation. Dreams that incorporate kinesthetic elements of the task, such as flying or accelerating, are associated with greater performance gains than dreams with visual elements or no task-related content. TMR does not directly alter dream content, but its performance benefits are larger when task-related dream reactivations also occur in REM sleep. These results suggest that dream imagery may reflect memory reactivation processes that support skill consolidation during sleep.
Incorporation of waking-life events into REM sleep dreams is highest on the night after and then 5-7 nights after the events, known as the day-residue and dream-lag effects. In experiment 1 with 44 participants, the dream-lag effect appeared for personally significant events incorporated into REM dreams recalled at home, but not for major daily activities or major concerns. No dream-lag effect was found for slow wave sleep dreams or for REM dreams collected in the lab after earlier SWS awakenings. In experiment 2, the dream-lag effect appeared for references to the sleep lab experience in home dreams only among participants who had prior concerns about being in the lab.
Overnight improvement on two memory tasks was linked to different sleep stages, challenging existing models of sleep-dependent learning. Participants who improved on the Corsi Block Tapping task had more REM sleep, while those who improved on the Tower of Hanoi task had more N2 sleep. Sleep spindle density was associated with Tower of Hanoi improvement, and spindle amplitude with Corsi Block improvement. The number of REM awakenings for dream reporting was linked to Corsi Block improvement but was confounded with total REM sleep time. The findings suggest capacity limitations on REM sleep and indicate that experimental awakenings for dream sampling may not disrupt—and might even enhance—sleep-dependent learning.