A single dose of LSD (75 μg) reduced how often people spontaneously thought about the past, while thoughts about the present or future remained unchanged. In a placebo-controlled crossover study with 20 healthy volunteers, fewer references to past mental spaces appeared in reports collected about 2.5 hours after intravenous administration. This reduction correlated with the drug's subjective intensity and with decreased resting-state functional connectivity within the default-mode network, a brain system involved in autobiographical memory and rumination. The findings suggest LSD may reduce past-focused thinking, which could be relevant for treating conditions like depression where excessive reflection on the past is common.
Mental time travel to the future is reduced during REM and non-REM sleep compared to waking. Three independent judges analyzed 563 mentation reports from sleep onset, REM sleep, non-REM sleep, and waking using a validated linguistic tool based on grammatical and cognitive-semantic theories. The data indicate that both REM and non-REM sleep are characterized by a reduction in future-oriented mental time travel, supporting earlier physiological evidence at the level of brain function.
Mental time travel to the future, but not to the past, decreases during sleep onset hypnagogia. Three independent judges analyzed 150 mentation reports collected before and after sleep onset, using a linguistic tool grounded in grammatical and cognitive-semantic theories. The results indicate that memory for the future diminishes at sleep onset, supporting preliminary physiological evidence at the level of brain function. This state of consciousness may help dissociate between mental time travel to the past and the future, despite recent research emphasizing similarities in their cognitive and physiological processes.