Nature communications
October 3, 2022
S Parker Singleton, Andrea I Luppi, Robin L Carhart-Harris et al.
156 citations
Psychedelics like LSD and psilocybin temporarily alter subjective experience by acting on serotonin 2a (5-HT2a) receptors, increasing the diversity (entropy) of brain activity. This increase may arise from a flattening of the brain's control energy landscape. Using fMRI data, the authors show that these compounds reduce the control energy needed for transitions between brain states compared to placebo. Across individuals, lower control energy correlates with more frequent state transitions and higher entropy. Incorporating PET data on 5-HT2a receptor distribution under non-drug conditions, the analysis links these receptors to reduced control energy. The findings demonstrate that receptor-informed network control theory can model how neuropharmacological manipulation affects brain dynamics.
Frontiers in psychiatry
January 1, 2022
S Parker Singleton, Julie B Wang, Michael Mithoefer et al.
36 citations
In nine veterans and first-responders with chronic PTSD, MDMA-assisted therapy (MDMA-AT) did not significantly increase amygdala-hippocampus resting-state functional connectivity as hypothesized, showing only a trend. After treatment, brain activation during trauma memory recall decreased in the cuneus. Recovery from PTSD correlated with changes in four functional connections during autobiographical memory recall: left amygdala with left and right posterior cingulate cortex and left insula, and left isthmus cingulate with left posterior hippocampus. These findings suggest that amygdala, hippocampus, and insula functional connectivity may be a target of MDMA-AT, highlighting regions involved in memory processes.
bioRxiv (Cold Spring Harbor Laboratory)
May 17, 2021
S. Parker Singleton, Andrea I. Luppi, Robin L. Carhart-Harris et al.
30 citations
preprint
LSD and psilocybin reduce the amount of energy the brain needs to transition between different activity states, as measured by functional MRI. This flattening of the brain's control energy landscape allows for more frequent state transitions and more diverse (entropic) brain activity. The effects are linked to the spatial distribution of serotonin 2a receptors, the main target of these psychedelics. The findings suggest that these compounds make brain state transitions more facile and temporally diverse, offering a mechanistic explanation for the altered subjective experience induced by psychedelics.
bioRxiv (Cold Spring Harbor Laboratory)
May 12, 2023
Christopher Timmermann, Emma Eckernäs, Leor Roseman et al.
17 citations
preprint
The serotonergic psychedelic DMT rapidly induces a profoundly immersive altered state lasting less than 20 minutes, allowing the entire drug experience to be captured during a single fMRI scan. Using network control theory, which quantifies the input needed to drive transitions between brain states, brain structure and function were integrated to map energy trajectories of 14 individuals undergoing fMRI during DMT and placebo. Global control energy was reduced following DMT compared to placebo. Longitudinal trajectories of global control energy correlated with EEG signal diversity and subjective drug intensity ratings. Regional effects correlated with serotonin 2a receptor density. Receptor distribution and pharmacokinetic information successfully recapitulated DMT's effects on global control energy trajectories.
medRxiv Preprint Server
May 25, 2022
S. Parker Singleton, Julie B. Wang, Michael Mithoefer et al.
9 citations
preprint
In nine veterans and first-responders with chronic PTSD, MDMA-assisted therapy did not significantly increase amygdala-hippocampus resting-state functional connectivity as hypothesized, only showing a trend. After treatment, activation in the cuneus decreased when recalling traumatic versus neutral memories. The amount of PTSD recovery correlated with changes in four functional connections during autobiographical memory recall: left amygdala with left and right posterior cingulate cortex and left insula, and left isthmus cingulate with left posterior hippocampus. These findings suggest that MDMA-AT may alter functional connectivity in brain regions involved in memory and fear processing, but more research is needed to determine if these effects are specific to MDMA-AT compared to other PTSD treatments.
Communications biology
April 18, 2025
S Parker Singleton, Christopher Timmermann, Andrea I Luppi et al.
7 citations
After DMT injection, the brain requires less control energy to transition between states compared to placebo, indicating a more flexible and less constrained brain dynamic. These energy changes track with EEG signal diversity and subjective intensity of the drug experience. The regional pattern of DMT's effects aligns with serotonin 2a receptor density, and a model using receptor distribution and pharmacokinetics can predict the drug's impact on brain energy trajectories.
bioRxiv (Cold Spring Harbor Laboratory)
July 31, 2025
Rick Zirkel, Matthew Isaacson, Clara Liao et al.
3 citations
preprint
Psilocybin prolongs increases in visual stimulus-evoked capillary blood flow in the mouse visual cortex without altering stimulus-evoked neural activity. This effect was reduced by pretreatment with a 5-HT2A receptor antagonist. Multi-modal widefield imaging confirmed extended vascular responses in surface vessels with no observed effect on population neural response. Computational simulations showed that prolonged neurovascular coupling responses can produce spurious increases in BOLD-based measures of functional connectivity. These findings demonstrate that psilocybin broadens neurovascular responses in the brain, highlighting the need to account for these effects when interpreting human neuroimaging data of psychedelic drug action.