Sci Rep
October 13, 2017
Robin L Carhart-Harris, Leor Roseman, Mark Bolstridge et al.
590 citations
In patients with treatment-resistant depression, a single dose of psilocybin combined with psychological support reduced depressive symptoms and altered brain activity and connectivity. Functional MRI scans before and after treatment showed decreased blood flow in the temporal cortex, including the amygdala, and increased resting-state functional connectivity within the default-mode network. Reduced amygdala blood flow correlated with fewer depressive symptoms. Changes in connectivity between the ventromedial prefrontal cortex and inferior lateral parietal cortex, as well as between the parahippocampus and prefrontal cortex, predicted treatment response at five weeks. These brain changes differ from the drug's acute effects and suggest a 'reset' of neural circuits.
Molecular psychiatry
September 1, 2023
Matthew B Wall, Rebecca Harding, Rayyan Zafar et al.
39 citations
Psychedelic therapy shows promise for treating depression, addiction, PTSD, and other psychiatric disorders. Classic serotonergic psychedelics like psilocybin and LSD act primarily at the 5-HT2A receptor, while ketamine, MDMA, and ibogaine also show potential. Modern neuroimaging techniques, especially PET and MRI, now allow precise measurement of brain effects. Key knowledge gaps remain: the link between acute drug effects and long-term clinical outcomes, detailed characterization of 5-HT2A receptor effects, and the role of neuroplasticity. Future studies combining PET with 5-HT2A-selective ligands like [11C]Cimbi-36 and MRI could bridge molecular, functional, and clinical understanding.
J Psychopharmacol
June 15, 2020
Anna Borissova, Bart Ferguson, Matthew B Wall et al.
37 citations
MDMA did not increase prosocial behavior in a controlled laboratory setting, despite raising blood levels of the drug and self-reported feelings of closeness and euphoria. In a double-blind, placebo-controlled experiment with 20 healthy volunteers, MDMA (100 mg) failed to significantly change task-based measures of empathy, trust, or cooperative behavior compared to placebo. Bayesian analyses supported the conclusion that MDMA and placebo had equivalent effects on empathy and cooperation. The drug also did not alter mood three days after administration. These findings suggest that the acute prosocial effects of MDMA observed in naturalistic or therapeutic contexts may not replicate under controlled experimental conditions.
Journal of affective disorders
July 15, 2023
Matthew B Wall, Cynthia Lam, Natalie Ertl et al.
36 citations
Psilocybin-assisted therapy for depression alters the brain's response to music, suggesting an elevated responsiveness to music after treatment that is related to subjective drug effects during dosing. Nineteen patients with treatment-resistant depression underwent two psilocybin dosing sessions. Brain scans before and after treatment showed increased activity in the superior temporal cortex when listening to music, and decreased activity in the medial frontal lobes during rest. These changes in music-related brain activity correlated with the intensity of subjective effects felt during the psilocybin sessions. The findings imply that psychedelic therapy may enhance emotional responsiveness to music, which could be relevant for treating depression.
American Journal of Psychiatry
May 7, 2025
Matthew B Wall, Lysia Demetriou, Bruna Giribaldi et al.
16 citations
Psilocybin therapy greatly improved depressive symptoms but had only a small effect on how the brain responds to emotional stimuli. This contrasts with SSRIs, which often reduce emotional responsiveness alongside their antidepressant action. The findings suggest that psychedelic therapy may work through different neural mechanisms than conventional antidepressants.
Neurosci Insights
October 8, 2024
Matthew B Wall, Rebecca Harding, Natalie Ertl et al.
3 citations
Psychedelic therapies are new psychiatric treatments that may need to be combined with existing medications, but little is known about their interactions with common psychiatric drugs. This commentary reviews key findings on such drug-drug interactions and proposes that multimodal neuroimaging, combining PET and fMRI with other measures, offers the most thorough way to study these interactions across molecular, functional, and clinical levels.
bioRxiv
February 8, 2025
Natalie Ertl, Imran Ashraf, Lisa Azizi et al.
1 citation
preprint
LSD and MDMA, two psychoactive drugs being explored for psychiatric use, alter how the striatum—a brain region central to reward and motivation—communicates with other areas. In a resting-state fMRI study, neither drug changed connectivity within the striatum's own networks. However, MDMA reduced connectivity between the limbic striatum and the amygdala, while LSD increased connectivity between the associative striatum and frontal, sensorimotor, and visual cortices. These changes occurred mostly outside standard striatal networks, suggesting the drugs reduce the brain's usual network segregation, which may help explain their therapeutic potential for conditions like addiction, mood disorders, and PTSD.
bioRxiv Preprint Server
May 1, 2025
Claudio Agnorelli, Joseph Peill, Gabriela Sawicka et al.
preprint
A single psychedelic dose of ketamine (1 mg/kg, intravenous) alters brain chemistry and connectivity in healthy people for at least one to eight days. After the dose, glutamate levels in the anterior cingulate cortex rose significantly. Functional connectivity decreased within high-order networks such as the default mode network, while integration between low- and high-order networks increased. Increases in a PET marker of synaptic plasticity correlated with reduced intrinsic activity in default mode network regions and a diminished influence of the posterior cingulate cortex on global network dynamics. The posterior cingulate cortex appears to be a central hub through which ketamine may reshape brain hierarchies over the long term.
International review of neurobiology
January 1, 2025
Matthew B Wall, Robin L Carhart-Harris
Functional MRI has been central to recent psychedelic research in healthy and clinical populations. Classic psychedelics such as psilocybin, LSD, and DMT acutely and profoundly disrupt normal resting-state brain connectivity, an effect likely linked to their subjective experiences and longer-term positive emotional impacts. This chapter outlines fMRI methodology and reviews current knowledge from task and resting-state studies in both non-clinical and clinical groups. Current limitations include small datasets and lack of standardization; future work should provide more data, standardize acquisition and analysis, conduct multi-modal imaging, and share data openly. fMRI remains a key tool for understanding psychedelic mechanisms and developing psychedelic-based treatments.
Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism
March 21, 2026
Claudio Agnorelli, Joseph Peill, Gabriela Sawicka et al.
A single intravenous dose of ketamine (1 mg/kg) in eleven healthy men altered brain chemistry and connectivity days later. Glutamate levels rose in the anterior cingulate cortex (ACC). Functional coupling between the ACC and the dorsolateral prefrontal cortex decreased, while coupling between the ACC and the amygdala increased. Participants whose PET scans indicated increased synaptic plasticity showed reduced intrinsic activity in default mode network (DMN) regions. The findings suggest the DMN is a central hub where ketamine may reshape brain hierarchies, offering clues to its therapeutic mechanisms.