The Psychedelic State Induced by Ayahuasca Modulates the Activity and Connectivity of the Default Mode Network

Abstract

The experiences induced by psychedelics share a wide variety of subjective features, related to the complex changes in perception and cognition induced by this class of drugs. A remarkable increase in introspection is at the core of these altered states of consciousness. Self-oriented mental activity has been consistently linked to the Default Mode Network (DMN), a set of brain regions more active during rest than during the execution of a goal-directed task. Here we used fMRI technique to inspect the DMN during the psychedelic state induced by Ayahuasca in ten experienced subjects. Ayahuasca is a potion traditionally used by Amazonian Amerindians composed by a mixture of compounds that increase monoaminergic transmission. In particular, we examined whether Ayahuasca changes the activity and connectivity of the DMN and the connection between the DMN and the task-positive network (TPN). Ayahuasca caused a significant decrease in activity through most parts of the DMN, including its most consistent hubs: the Posterior Cingulate Cortex (PCC)/Precuneus and the medial Prefrontal Cortex (mPFC). Functional connectivity within the PCC/Precuneus decreased after Ayahuasca intake. No significant change was observed in the DMN-TPN orthogonality. Altogether, our results support the notion that the altered state of consciousness induced by Ayahuasca, like those induced by psilocybin (another serotonergic psychedelic), meditation and sleep, is linked to the modulation of the activity and the connectivity of the DMN.

Psychedelics

“…Consequently, postsynaptic activity of pyramidal cells, the most abundant neurons in the CA1, is not directly linked to the measured BOLD response. Palhano-Fontes et al (2015) used fMRI to inspect the DMN after ayahuasca administration to 10 healthy volunteers who were regular users of ayahuasca. Subjects underwent fMRI sessions before and 40 minutes after ayahuasca intake.…”

The Therapeutic Potential of Psychedelic Drugs: Past, Present, and Future

“…There now exists a foundation of human neuroimaging (Carhart-Harris et al, 2012a;Carhart-Harris et al, 2016d;Daumann, Wagner, Heekeren, Neukirch, Thiel & Gouzoulis-Mayfrank, 2010;Muthukumaraswamy et al, 2013;Palhano-Fontes et al, 2015;Preller et al, 2017;Riba, Anderer, Jane, Saletu & Barbanoj, 2004;Riba, Romero, Grasa, Mena, Carrio & Barbanoj, 2006;Vollenweider, Leenders, Scharfetter, Maguire, Stadelmann & Angst, 1997), psychology (Carhart-Harris et al, 2016c;Carhart-Harris, Kaelen, Whalley, Bolstridge, Feilding & Nutt, 2015;Carter, Hasler, Pettigrew, Wallis, Liu & Vollenweider, 2007;Gouzoulis-Mayfrank et al, 2005;Griffiths, Richards, McCann & Jesse, 2006;MacLean, Johnson & Griffiths, 2011;Schmid et al, 2015) and psychopharmacology studies with psychedelics (Kometer, Schmidt, Bachmann, Studerus, Seifritz & Vollenweider, 2012;Preller et al, 2017;Valle et al, 2016;Vollenweider, Vollenweider-Scherpenhuyzen, Babler, Vogel & Hell, 1998).…”

Ayahuasca: what mental health professionals need to know

“…Effects of ayahuasca on the human brain EEG (acute) 14,19,24,[26][27][28][29] Reduced power in the alpha, delta and theta bands Increased power in the beta and gamma bands Neuroimaging (acute) 20,32,33 Increased activation of frontal and limbic areas (parahippocampal gyrus, insula, amygdala, visual and frontal cortices, ACC) (SPECT, fMRI) Increased activation of the primary visual area during an imagery task (fMRI) Decreased activation of key hubs of the DMN (PCC, mPFC, precuneus) (fMRI) Decreased functional connectivity within the PCC/precuneus (fMRI) Neuroimaging (long-term) 34 Cortical thickening in precentral gyrus and ACC (CT) Cortical thinning in the mesotemporal and inferior frontal gyri, precuneus, superior frontal gyrus, PCC, and superior occipital gyrus (CT) ACC: anterior cingulate cortex; CT: cortical thickness; DMN: default mode network; EEG: electroencephalography; fMRI: functional magnetic resonance imaging; mPFC: medial prefrontal cortex; PCC: posterior cingulate cortex; SPECT: single-photon emission computed tomography.…”

“…A resting-state fMRI study showed that ayahuasca decreased activation of key hubs of the default mode network (DMN), including the posterior cingulate (PCC) and the medial prefrontal cortices and the precuneus 33 . Furthermore, ayahuasca decreased functional connectivity within the PCC/precuneus.…”

“…Its important to highlight that individuals with a personal or family history of psychotic illness or nonpsychotic mania are usually not enrolled in these studies, which could explain the absence of reports of prolonged dysphoric or psychotic reaction in the experimental and clinical settings 5,14,[18][19][20][21]23,24,[27][28][29]32,33,36,[41][42][43]60 . These results are in line with experimental and clinical studies with other serotonergic hallucinogens such as LSD and psilocybin 13,15,30,31,36,[44][45][46][47][50][51][52][53] .…”