Schizophrenia Bulletin vol. 39 no. 6 pp. 1343–1351, 2013
doi:10.1093/schbul/sbs117
Advance Access publication October 6, 2012
Functional Connectivity Measures After Psilocybin Inform a Novel Hypothesis
of Early Psychosis
Robin L. Carhart-Harris*,1,2, Robert Leech3, David Erritzoe1, Tim M. Williams2, James M. Stone1, John Evans4,
David J. Sharp3, Amanda Feilding5, Richard G. Wise4, and David J. Nutt1,2
1
*To whom correspondence should be addressed; Imperial College London, Centre for Neuropsychopharmacology, Burlington Danes
Building, 160 Du Cane Rd, London, UK; e-mail: r.carhart-harris@imperial.ac.uk
Psilocybin is a classic psychedelic and a candidate drug
model of psychosis. This study measured the effects of
psilocybin on resting-state network and thalamocortical
functional connectivity (FC) using functional magnetic
resonance imaging (fMRI). Fifteen healthy volunteers
received intravenous infusions of psilocybin and placebo in
2 task-free resting-state scans. Primary analyses focused
on changes in FC between the default-mode- (DMN) and
task-positive network (TPN). Spontaneous activity in the
DMN is orthogonal to spontaneous activity in the TPN,
and it is well known that these networks support very different functions (ie, the DMN supports introspection, whereas
the TPN supports externally focused attention). Here, independent components and seed-based FC analyses revealed
increased DMN-TPN FC and so decreased DMN-TPN
orthogonality after psilocybin. Increased DMN-TPN FC
has been found in psychosis and meditatory states, which
share some phenomenological similarities with the psychedelic state. Increased DMN-TPN FC has also been
observed in sedation, as has decreased thalamocortical FC,
but here we found preserved thalamocortical FC after psilocybin. Thus, we propose that thalamocortical FC may be
related to arousal, whereas DMN-TPN FC is related to the
separateness of internally and externally focused states.
We suggest that this orthogonality is compromised in early
psychosis, explaining similarities between its phenomenology and that of the psychedelic state and supporting the
utility of psilocybin as a model of early psychosis.
Key words: serotonin/5-HT/resting-state networks/
default-mode network/psychedelics/consciousness/
psychosis/at-risk mental state
Introduction
Background
Psilocybin is a tryptamine psychedelic and the prodrug
of the major psychoactive component of magic mushrooms, psilocin. Psilocybin and psilocin were irst isolated and synthesized by Albert Hofmann1 after which
they were used in psychotherapy before this was curtailed by political pressure.2 Classic psychedelics like
psilocybin produce a range of subjective effects from
supericial perceptual changes to more profound existential-type experiences.3 Much has been written about
the phenomenology of the psychedelic state, but we
have only a limited understanding of how it is produced
in the brain.
Functional MRI Measures of Spontaneous Brain
Activity
There has been an increased interest in measures of
spontaneous brain activity in recent years.4 In humans,
fMRI measures of task-free- or “resting-state” functional
connectivity (FC) have become popular. Measures of
resting-state FC using independent components analysis
(ICA) have identiied a number of spatiotemporally
coherent networks5 that closely resemble stimulus-evoked
activation maps.6 Of particular interest is the defaultmode network (DMN), a network of regions (including
the posterior cingulate cortex; medial prefrontal cortex,
mPFC; and lateral inferior parietal cortex) that show
greater activity during internally oriented cognition
than externally focused attention.7 The DMN receives
© The Author 2012. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved.
For permissions, please email: journals.permissions@oup.com
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Imperial College London, Centre for Neuropsychopharmacology, Division of Experimental Medicine, London, UK; 2University of
Bristol, Academic Unit of Psychiatry, Bristol, UK; 3Imperial College London, the Computational, Cognitive, and Clinical Neuroimaging
Laboratory, Division of Experimental Medicine, London, UK; 4Cardiff University Brain Research Imaging Centre, School of
Psychology, Cardiff University, Cardiff, UK; 5The Beckley Foundation, Beckley Park, Oxford, UK
R. L. Carhart-Harris et al
more blood low8 and consumes more energy7 than other
brain regions, has undergone signiicant evolutionary
expansion,9 and serves as an important convergence zone
or “connector hub” in the cortex.10 The DMN is activated
during high-level cognitions such as predicting the future11;
making personal, social, and moral judgments12,13; and
contemplating the past.14 These properties have led to
speculations that the DMN is the biological system upon
which our psychological notions of self15 or “ego”16 are
based.
Materials and Methods
Between-Network FC and Cognitive Function
Participants
The DMN is known to deactivate during cognitive tasks,
while a generic task-positive network (TPN) is activated;
and the TPN deactivates during introspection, while
the DMN becomes more active. Importantly, this competitive relationship between DMN and TPN activity
may be preserved under task-free conditions,17 potentially implying that DMN-TPN competition, or at least
orthogonality, is a fundamental property of global brain
function.18
Spontaneous luctuations in resting-state network
(RSN) activity inluence stimulus-evoked activity and
predict behavioral variability.19 Task performance is more
consistent or less variable if inverse coupling between the
DMN and TPN is greater.20 Moreover, increased spontaneous DMN activity has been associated with increased
mind wandering.21 Thus, a picture emerges of a fundamental orthogonality between the DMN and TPN, with
the DMN serving explorative inner thought, and the
TPN serving focused attention. Crucially, during normal waking consciousness, explorative inner thought and
focused attention do not occur simultaneously, presumably because the systems that support these states are
kept apart. If, however, activity in the DMN and TPN
was to become less orthogonal, then this might cause a
confusion of states and a disturbance of cognition such
as is seen in early psychosis.
Pharmacological fMRI studies have discovered relationships between changes in DMN-TPN FC and changes
in subjective experience. For example, abstinent smokers
with improved cognition following nicotine replacement
therapy showed increased inverse coupling between the
DMN and TPN.22 Changes in DMN-TPN and thalamocortical coupling have also been measured after propofol
infusion. Reduced conscious awareness correlated with
reduced inverse coupling between the DMN and TPN
and decreased thalamocortical FC.23
The present study sought to test the effect of psilocybin on DMN-TPN and thalamocortical FC. We hypothesized that thalamocortical FC would be preserved after
psilocybin but DMN-TPN FC would be increased—consistent with reduced orthogonality between these networks in the psychedelic state.
This is a new analysis on a previously published data set.24
Fifteen healthy subjects took part: 13 males and 2 females
(mean age = 32, SD = 8.9). Recruitment was via word of
mouth. All subjects were required to give informed consent and undergo health screens prior to enrolment. Entry
criteria were the following: at least 21 years of age, no personal or immediate family history of a major psychiatric
disorder, substance dependence, cardiovascular disease,
and no history of a signiicant adverse response to a hallucinogenic drug. All of the subjects had used psilocybin at
least once before (mean number of uses per subject = 16.4,
SD = 27.2) but not within 6 weeks of the study.
This was a within-subjects placebo-controlled study. The
study was approved by a local NHS Research Ethics
Committee and Research and Development department,
and conducted in accordance with Good Clinical Practice
guidelines. A Home Ofice Licence was obtained for storage and handling of a Schedule 1 drug. The University of
Bristol sponsored the research.
Anatomical Scans
Imaging was performed on a 3T GE HDx system.
Anatomical scans were performed before each functional
scan. These were 3D fast spoiled gradient echo scans in an
axial orientation, with ield of view = 256 × 256 × 192 and
matrix = 256 × 256 × 192 to yield 1-mm isotropic voxel resolution (repetition time/echo time [TR/TE] = 7.9/3.0 ms;
inversion time = 450 ms; lip angle = 20°).
Drug and Scanning Parameters
All subjects underwent two 12-min eyes-closed restingstate blood oxygen–level dependent (BOLD) fMRI scans
on 2 separate occasions at least 7 days apart: placebo
(10 ml saline, 60-s intravenous injection) was given on 1
occasion and psilocybin (2 mg dissolved in 10 ml saline)
on the other. Seven of the subjects received psilocybin in
scan 1, and 8 received it in scan 2. Injections were given
manually by a study doctor situated within the scanning
suite. The 60-s infusions began exactly 6 min after the
start of the 12-min scans. Subjective ratings were given
postscan using visual analog scales. The subjective effects
of psilocybin were felt almost immediately after injection
and were sustained for the duration of the scan.25
fMRI Data Acquisition
BOLD-weighted fMRI data were acquired using a gradient echo planar imaging sequence, TR/TE 3000/35 ms,
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Design
Functional Connectivity Measures
ield-of-view = 192 mm, 64 × 64 acquisition matrix, parallel acceleration factor = 2, 90° lip angle. Fifty-three
oblique axial slices were acquired in an interleaved fashion, each 3 mm thick with zero slice gap (3 × 3 × 3 mm
voxels).
Independent Components Analysis
Between-Network FC Using ICA
Of the 20 components derived from the group ICA, 11
were identiied as “functionally meaningful” RSNs;
explicitly, we excluded 9 components where the majority
of the voxels were in white matter, ventricular space, or
outside of the brain. Henceforth, we will refer to these
as “noise” components because their signal was most
likely nonneuronal. The remaining 11 RSNs included an
anteriorly loaded DMN (aDMN), a posteriorly loaded
DMN (pDMN), right- and left-lateralized frontoparietal
networks (rFPN & lFPN), an auditory network (AUD),
salience network (SAL), visual network, precuneus network, dorsal attention network (DAN), cerebellar network, and sensorimotor network. These 11 networks are
shown in igure 1 with the aDMN in every image.
Time series for the last 100 volumes (postinjection) for
all 20 components were extracted using multiple regression. Our analyses focused on the relationship between the
DMN and other RSN in the psychedelic state. Thus, the
aDMN was chosen as the dependent variable in regression
analyses run in SPSS. One RSN at a time plus the 9 noise
components were entered as independent variables. The
noise components were included to remove nonneuronal
variance. This process was repeated for each of the RSNs,
with the aDMN as the dependent variable in every case.
The unstandardized regression coeficient for the RSN of
interest were plotted and compared across the 2 conditions
(psilocybin vs placebo) in paired t tests. All t tests were 2
Between-Network FC Using Seed-Based FC
In addition to the ICA approach, we assessed DMN-TPN
FC using seed-based FC. The results of a ventromedial
PFC (vmPFC) seed-based resting-state FC analysis were
used to deine the DMN (vmPFC-positive network) and
TPN (vmPFC-negative network).24 Activity in these networks is sometimes referred to as being “anticorrelated,”
but this can be misleading because “anticorrelations” can
be introduced by regressing out the global grey matter
signal.18 For this reason, we chose not to include global
grey matter regression in any of the analyses presented
in this article. The DMN and TPN (cluster threshold
Z > 2.3, P < .05 whole brain corrected) were converted
into spatial masks from which time series were extracted
for each functional scan. We also extracted times series
from white matter and cerebrospinal luid (CSF) masks
to serve as nonneuronal “noise regressors.”
Linear regression was performed to calculate the FC
strengths between the DMN and TPN for all of the scanning sessions. Times series were separated into the irst 100
volumes (preinjection) and the last 100 volumes (postinjection), with the 40 volumes surrounding the injection
period excluded from the analysis. The DMN time series
served as the dependent variable and the TPN, white matter, and CSF time series, plus motion parameters served
as independent variables. The unstandardized regression
coeficients for the DMN vs TPN were compared before
vs after psilocybin injection, plus after placebo vs after
psilocybin injection, using t tests.
Thalamic FC
To test for an effect of psilocybin on FC between the thalamus and high-level cortical networks, a bilateral thalamic
mask was generated based on an anatomical template in
FSL. This mask was thresholded and transformed into single-subject functional space, and time series were extracted
for each subject. Linear regression was used to measure
changes in thalamocortical connectivity after psilocybin.
The thalamic time series served as the dependent variable,
and the DMN and TPN time series served as independent
variables. Thalamus-DMN and thalamus-TPN FC were
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All analyses were performed using the Functional
Magnetic Resonance Imaging of the Brain (FMRIB)
Software Library (FSL, www.fmrib.ox.ac.uk/fsl). FSLs
MELODIC was used to derive 20 spatiotemporally coherent components from 30 concatenated data sets. Twenty
preinjection “baseline” components were derived so that
the effect of psilocybin on FC between these components
could then be examined. Thus, the data sets from which
the components were derived included the irst 6 min of
each subjects’ placebo and psilocybin resting-state scans
(ie, the 100 volumes that were acquired prior to the injection of saline or psilocybin). These data were motion corrected using FSLs MCFLIRT function and a high-pass
ilter of 100 s was applied. The 20 components were registered to the subjects’ T1-weighted high-resolution (1 ×
1 × 1 mm) anatomical scans that were themselves registered to the Montreal Neurological Institute standard
brain (1 × 1 × 1 mm).
tailed. Pearson’s correlational analyses were used to test
for relationships between aDMN-RSN FC and subjective ratings. Based on their relevance to the hypothesis that
decreased orthogonality between the DMN and TPNs
would predict experiences of disturbed ego boundaries
and cognition, we chose the following 5 questionnaire
items for correlational analyses: “I felt a sense of merging
with my environment,” “I experienced a loss of separation
from my surroundings,” “my thinking was muddled,” “I
lost all sense of ego,” and the item that required subjects
to rate the “intensity” of the drug effects. Results were corrected for multiple comparisons (Bonferonni).
R. L. Carhart-Harris et al
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Fig. 1. Default-mode network-resting-state network (DMN-RSN) connectivity after psilocybin vs after placebo. (A) anteriorly loaded
DMN (aDMN)-left frontoparietal network connectivity, (B) aDMN-right frontoparietal connectivity, (C) aDMN-dorsal attention
network connectivity, (D) aDMN-salience network connectivity, (E) aDMN-visual network connectivity, (F) aDMN-auditory network
connectivity, (G) aDMN-motor network connectivity, (H) aDMN-cerebellar network connectivity, (I) aDMN-precuneus network
connectivity, (J) aDMN-posterior DMN connectivity. Images show the aDMN in orange and the relevant RSN in blue with the adjacent
chart displaying the regression coeficient or “functional connectivity (FC) strength” after placebo (gray) and psilocybin (blue). The
betas on the y-axis refer to regression coeficients. Contrasts B, C, D and F were all statistically signiicant when corrected for multiple
comparisons (corrected α = 0.005).
1346
Functional Connectivity Measures
calculated in 2 separate regression analyses. As before,
white matter and CSF time series and motion variance
were entered as regressors of no interest. Again, global
grey matter signal regression was not included in this analysis. Regression coeficients for thalamus-DMN and thalamus-TPN FC were compared before and after psilocybin
and placebo, and after psilocybin vs after placebo.
positive correlations between DMN-TPN FC and ratings
of psychedelic effects. The item “my thinking was muddled” showed suggestions of a relationship with increased
DMN-rFPN FC, but this did not survive correction for
multiple comparison (P = .02, revised α = 0.002); ratings
of drug effects intensity showed suggestions of a relationship with increased DMN-TPN FC, but this was also not
signiicant (P = .16).
Results
DMN and TPN Connectivity With the Thalamus
The subjective effects of psilocybin have been documented elsewhere.24,25 Briely, the subjective effects of
2 mg psilocybin given as an intravenous injection over 60 s
begin at the end of the injection period, reach a sustained
peak after 4 min, and subside completely after 45–60 min.
Primary subjective effects include altered visual perception (eg, hallucinated motion and geometric patterns), an
altered sense of space and time, and viviied imagination.
Previous work found a positive correlation between
increases in DMN-TPN FC and propofol-induced reductions in consciousness23; however, none of our subjects
reported reduced consciousness after psilocybin. The
same study also reported reduced thalamocortical connectivity that correlated with reduced consciousness;
thus, we tested to see if psilocybin caused similar reductions in thalamocortical connectivity. Thalamic-DMN
FC showed a nonsigniicant increase after psilocybin
(igure 4D,E), and there was a signiicant increase in thalamic-TPN FC (igure 4G). The increases in thalamocortical FC after psilocybin did not correlate with ratings of
the intensity of the subjective effects of psilocybin.
ICA and Between-Network FC
Eleven RSNs were identiied from the preinjection time
series. These RSNs are listed in the Materials and Methods
section and shown in igure 1. Of these 11 networks, there
were 2 DMNs, an anteriorly loaded DMN (aDMN, igure 1, orange in all images) with all of the major DMN
nodes present, and a posteriorly loaded DMN (pDMN,
blue in igure 1J). FC between the aDMN and each of
the 10 remaining networks was compared in turn. Charts
in igure 1 show the strength of the FC between aDMN
and the other RSNs after placebo and after psilocybin.
Signiicant increases in FC between the aDMN and the
SAL were evident after psilocybin (P = .0002), as well as
the right frontoparietal network (P = .0003), the AUD
(P = .0006), and the DAN (P = .0009). There was also
a suggestion of decreased FC between the anterior and
posterior DMNs (P = .02), but this did not survive correction for multiple comparisons (α = 0.005, Bonferonni
corrected). An example of increased aDMN-SAL FC
after psilocybin is shown in Figuer 2C.
Seed-Based FC and Between-Network FC
A vmPFC seed-based FC analysis24 was used to derive
DMN and TPN spatial masks (igure 3A, orange and
blue, respectively). Linear regression revealed signiicantly increased FC between the DMN and TPN after
psilocybin vs placebo (igure 3B, P = .001) and post- vs
prepsilocybin injection (igure 3C, P = 009).
Correlations Between DMN-RSN FC and Psychedelic
Effects
Pearson’s correlational analyses were performed to test
for relationships between altered DMN-RSN FC and
psilocybin’s subjective effects. There were suggestions of
Validity Tests
Between-Condition Differences in Movement. Movement
regressors were included in all of our FC analyses, but
it remains possible that the increases in FC between the
aDMN and other RSNs may have been caused by different levels of movement in the 2 conditions. Thus, we calculated the mean movement per volume for each subject’s
scan and compared the psilocybin and placebo scans in
a paired t test. Signiicantly, greater movement was seen
under psilocybin (mean movement per volume = 0.06 mm
[SD = 0.015] for placebo vs 0.1 mm [SD = 0.05] for psilocybin, P < .01). However, there was considerable variability in movement under psilocybin, with some participants
showing less movement under drug. Therefore, to test
whether the between-condition differences in movement
could explain the regression results shown in igure 1, we
ran correlational analyses on all of the positive results
from this analysis (ie, aDMN-DAN, aDMN-rFPN,
aDMN-SAL, and aDMN-AUD). No relationships were
found between the changes in between-network coupling
under psilocybin and the differences in movement, so the
argument that the observed changes in between-network
coupling were caused by between-condition differences in
movement is not supported by the data.
Discussion
ICA revealed 11 RSNs, including a canonical DMN.
Increased FC was evident between this DMN and 4
RSNs. These 4 RSNs include well-characterized TPNs,
ie, the dorsal attention, salience and right frontoparietal
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Subjective Effects
R. L. Carhart-Harris et al
Fig. 3. Increased functional FC between the default-mode- and task-positive network under psilocybin. (A) vmPFC-positive- (DMN,
orange) and vmPFC-negative regions (TPN, blue). (B) Increased FC between the DMN and TPN after psilocybin vs placebo (P = .001).
(C) Increased FC between the DMN and TPN post vs prepsilocybin (P = .009).
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Fig. 2. The effect of psilocybin on DMN connectivity seen at the single-subject level. (A) The aDMN (orange) and salience network
(blue) derived from Independent Components Analysis. (B) An illustrative single-subject time series for the DMN (red) and salience
network (blue) after placebo injection. (C) The same subject’s time series for the DMN and salience network after psilocybin injection.
Note the increase in FC between the DMN and salience network after psilocybin vs after placebo. (D) Positive (orange) and “negative”
(blue) FC with the ventromedial prefrontal cortex (vmPFC) based on data from ifteen placebo condition 12-min resting-state scans. This
vmPFC-positive network is the DMN, and the vmPFC-negative network is the task-positive network. (E) The complete time series for
the DMN and task-positive network (TPN) for a single subject’s psilocybin scan. Note the increase in DMN-TPN FC after psilocybin.
Subject CR rated the intensity of the effects at 9/10 and JB 10/10.
Functional Connectivity Measures
network, and the auditory network. Importantly, DMN
and TPN activity is normally orthogonal, or even competitive,17 so increased DMN-TPN FC implies that
these networks’ functionality became less distinct under
psilocybin. Conirmatory results were found when we
repeated the analysis with DMN and TPN masks derived
from a seed-based FC analysis; increased DMN-TPN
FC was evident after psilocybin. These results imply
that increased DMN-TPN FC, and so decreased DMNTPN orthogonality, is an important characteristic of the
psychedelic state.
The question now arises, is increased DMN-TPN coupling speciic to the psychedelic state? Boveroux and colleagues found a graded decrease in DMN-TPN inverse
coupling (or increase in DMN-TPN FC) with increasing
levels of propofol-induced sedation. However, none of
our subjects reported sedation after psilocybin; in fact,
psychedelics are often described as “mind expanding.”
This inconsistency in phenomenology but consistency
in physiology is intriguing. Because decreased thalamocortical excitation is closely linked to reduced arousal26
and large decreases in thalamocortical connectivity were
evident in the propofol study, we tested to see if the same
thalamocortical decoupling occurred under psilocybin.
We hypothesized that if thalamocortical connectivity is
preserved in the psychedelic state, then this may explain
the psychological differences between the psychedelic
and sedated state. As shown above, thalamic FC with
the DMN was preserved under psilocybin. Moreover,
while thalamic FC with a right frontoparietal network
was decreased under propofol, thalamic-TPN connectivity was actually increased under psilocybin. In summary, the results of the present study strongly imply that
increased DMN-TPN FC, especially in the presence of
preserved thalamocortical FC, is not an index of reduced
consciousness but rather a change in the speciic mode or
style of consciousness.
Increased DMN-TPN coupling (or decreased inverse
coupling) has been observed in patients with schizophrenia27–30; however, it is not known how this relates to symptomatology. Increased DMN-TPN coupling has been
found in people at high risk of psychosis31 and an inability
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Fig. 4. Thalamic connectivity with the DMN and TPN. (A) The thalamic (orange) and DMN (blue) masks from which time series were
extracted. (B) Thalamic-DMN connectivity postplacebo vs postpsilocybin (P = .1). (C) Thalamic-DMN connectivity postpsilocybin vs
prepsilocybin (P = .2). (D) The thalamic (orange) and TPN (blue) networks from which time series were extracted. (E) Thalamic-TPN
connectivity postplacebo vs postpsilocybin (P = .03). (F) Thalamic-TPN connectivity post- vs prepsilocybin (P = .06).
R. L. Carhart-Harris et al
1350
between inner thought and external focus becomes
blurred.
This is the irst time that between-network FC has been
assessed after a psychedelic. The indings make an important contribution to our understanding of the brain
effects of these drugs. The phenomenological and neurobiological association between the psychedelic state, early
psychosis and spiritual-type experiences suggest that psychedelics may serve as models of the prodrome to psychosis, as well as tools to deconstruct abstract concepts
such as “the ego” and scientiically study mystical-type
experiences.
Funding
Beckley Foundation; Neuropsychoanalysis Foundation;
Multidisplinary Association for Psychedelic Studies; and
Heffter Research Institute.
Acknowledgments
We are grateful to the reviewers for improving this manuscript. We are also grateful to Alison Diaper, Ann Rich,
Sue Wilson for help with this research.
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to distinguish between one’s internal world and the external environment, sometimes referred to as “disturbed ego
boundaries,” is a hallmark of early psychoses32 and the
psychedelic state.33,34 For example, one of our volunteers
reported the following after psilocybin: “It was quite dificult at times to know where I ended and where I melted into
everything around me.” And the following account is from
a patient experiencing early psychotic symptoms: “My personality is in danger … my ‘self’ is beginning to disappear.”35
It is intriguing to consider whether increased DMNTPN FC can explain such phenomena. Disturbed ego
boundaries is a key component of spiritual-type experiences.36 It is curious therefore that increased DMN-TPN
coupling has been found in experienced mediators,37
especially those practicing a form of meditation known
as “nondual awareness,” which speciically promotes a
unitary state of awareness in which there is no distinction between the subject and object.38 Supplementing
the mapping between DMN activity and the sense-ofself, decreased DMN activity has also been found in
meditation37,39,40 and the psychedelic state.24 There is
increasing evidence that DMN functioning is related to
the sense-of-self15 or “the ego,”16 and “ego dissolution”
is commonly described in meditation and the psychedelic state. For example, one of our volunteers reported
after psilocybin: “That was real ego death stuff, a total
dissolving of the ego-boundaries ... I only existed as a concept ... as an idea.”
There is a fundamental motivation towards organization in biological systems. However, it is also know that
biological systems retain a degree of stochasticity in
their processes, so to enable lexibility. An imbalance in
the relative inluence of these 2 factors may occur in the
psychedelic and early psychotic states. Characterizing the
psychedelic and early psychotic states as states of relative
disorganization yet heightened plasticity may enable us
to explain a range of phenomena. For example, focusing
on the psychedelic state, it is known that psychedelics can
promote suggestibility, spiritual and religious revelation,
and delusional thoughts; and there is also evidence that
they can be effective treatments for addiction and perhaps
other mental illnesses.2 All of these phenomena presumably rely on heightened plasticity in the brain. Translating
this to psychosis lends emphasis to the importance of
early intervention because it suggests that there is a window of opportunity for changes in associative learning in
the early phase of the disorder.
To conclude, this study found increased DMN-TPN
FC using 2 complementary FC analyses. Secondary
analyses of thalamocortical FC were carried out to
explore differences between the psychedelic and sedated
state. These analyses revealed preserved thalamocortical
FC, which is opposite to the effects of sedation. We propose that increased DMN-TPN coupling in the presence
of preserved thalamocortical connectivity is related to
a state in which arousal is preserved but the distinction
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