Nootropic effects of LSD: Behavioral, molecular and computational evidence

Four complementary experimental approaches were used. First, human induced pluripotent stem cell-derived brain organoids (day 45) were treated with 10 nM LSD or vehicle for 24 hours, and proteomic changes were characterised by liquid-chromatography mass spectrometry. Second, Wistar male rats across three age groups (young, adult, old; total n = 76) received a single dose of LSD (0.13 mg/kg) or saline and were assessed on the novel object preference task 24 hours after dosing to measure hippocampus-dependent memory. Third, 25 healthy adult human volunteers (9 female, 16 male; mean age 35.1 years) participated in a randomised double-blind placebo-controlled crossover study, receiving 50 µg oral LSD or placebo separated by two weeks, with visuospatial memory tasks administered the morning after dosing to assess consolidation and recall. Fourth, a computational model of the cortico-hippocampal circuit was implemented to test whether LSD-induced changes in synaptic plasticity strength could account for the observed behavioural outcomes.

Proteomic analysis of LSD-treated brain organoids revealed upregulation of multiple processes associated with neural plasticity, including synaptic vesicle cycle, neurotransmitter release, DNA replication, axon guidance, and long-term potentiation — consistent with a broad plasticity-promoting molecular signature. In rats, LSD pre-treatment significantly increased novelty preference in young, adult, and old animals relative to saline, with a significant single-dose main effect across age groups, suggesting that LSD-induced plasticity enhanced either novelty-seeking or the consolidation of familiar-object memories. In humans, LSD (versus placebo) improved visual memory on several dimensions the morning after dosing, including overnight consolidation (increased percentage of recalled card locations), spontaneous encoding (improved immediate recall accuracy of Complex Figure elements), and overall recall performance. The computational model closely replicated the critical rat and human behavioural observations, providing a mechanistic causal pathway from plasticity changes to age-dependent memory improvements within a single framework.

Taken together, the convergent findings across organoids, rats, humans, and a computational model provide a multilevel account of LSD's nootropic effects. The molecular data implicate mTOR-dependent synaptic plasticity pathways as the mechanistic substrate, consistent with prior rodent psychedelic literature and with the neuroplasticity-promoting properties reported for psilocybin and 5-MeO-DMT. The age-dependent pattern in rats — and the broad cognitive improvements in adult humans — suggest that LSD-induced plasticity may be particularly beneficial in contexts where baseline plasticity is reduced, such as ageing. The authors interpret the improvement in memory consolidation specifically as consistent with enhanced hippocampal function: the overnight consolidation window during which LSD's subacute plasticity effects are active may create a more favourable synaptic environment for memory trace stabilisation. The study's limitations include the small human sample size and the reliance on a single LSD dose and a single memory domain; broader cognitive outcomes and dose-response relationships warrant future investigation.

This multi-level investigation provides convergent evidence — from molecular changes in human brain organoids to behavioural improvements in rodents and humans — that LSD promotes neural plasticity and exerts measurable nootropic effects on memory consolidation and recall. A computational model of the cortico-hippocampal circuit links plasticity-level changes to cognitive outcomes, extending to humans the notion that psychedelic-induced structural plasticity may have functional cognitive consequences with potential relevance to therapeutic applications in ageing and memory-related disorders.