Thread by @SMortaheb

🎉 Our work "Dynamic Functional Hyperconnectivity after Psilocybin Intake is Primarily Associated with Oceanic Boundlessness" is out in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging! 🧠🍄Have a look here .
A thread below:hdl.handle.net/2268/312426

1/20 🍄 Psilocybin is a psychedelic substance whose administration leads to an altered state of consciousness. Changes in phenomenology, such as ego dissolution, experience of unity, and visual pseudo-hallucinations, are common after its administration.

2/20 After psilocybin intake, the brain’s functional organization is also shown to change, generally becoming more connected and less modular.
❓How changes between neural and phenomenological domains are associated?

3/20 We used previous fMRI data acquired at @PIMaastricht (). Participants were divided into two groups: one received psilocybin (n=22) and the other placebo (bitter lemon; n=27).go.nature.com/3PM8j2I

4/20 🧠❓At the drug’s peak effect time, 7T resting-state fMRI data were acquired. The drug-related subjective experiences were retrospectively evaluated using the 5 Dimensions of Altered State of Consciousness (5D-ASC) questionnaire.

5/20 🧐Phenomenological analyses revealed significant differences in all dimensions of 5D-ASC and its 11 factors (11-ASC) with large effect sizes, such that the psilocybin group had more substantial phenomenological changes.

6/20 🧠Neuroimaging analysis revealed overall increases of averaged functional connectivity (FC) in all 100 ROIs (Schaefer atlas) in the psilocybin group, in line with previous studies. The increase in FC was more significant in transmodal regions.

7/20 🧠 We further observed decreases in the BOLD signal amplitude: by calculating the Euclidean norm of the BOLD time series related to each region, we found a cortex-wide decrease in the BOLD signal amplitude after psilocybin administration.

8/20 To investigate the effect of psilocybin on the dynamics of the whole-brain functional connectome, we estimated phase-based coherence matrices at each scan volume, which were summarized into four connectivity patterns using k-means clustering.

9/20 The patterns concerned both correlations and anti-correlations (P1), anti-correlations of the DMN with other networks (P2), global hyperconnectivity (P3), and low inter-areal connectivity (P4). The hyperconnected Pattern 3 showed the highest occurrence rate after psilocybin.

10/20 Also, the psilocybin group showed significantly higher transition probabilities toward this hyperconnected Pattern 3 (Markov modeling).

11/20 Changing the number of clusters from 3 to 7 yielded consistent results. Across all conditions, the hyperconnected pattern was notably prevalent in the psilocybin group.

12/20 Motion did not affect the results. Mean framewise displacement (FD) remained consistent across groups and connectivity patterns, showing no significant differences. Moreover, it did not correlate with mean functional connectivity or BOLD amplitude.

13/20 Also, regressing out the global signal (GS) eliminated the hyperconnectivity pattern in dynamic connectivity states, yielding no significant difference between the Placebo and Psilocybin groups. Therefore, GS is crucial for a more comprehensive analysis.

14/20 To bridge neural and behavioral data, we performed canonical correlation analysis, by considering between-state transition probabilities as the neural features, and the 11-ASC factors as phenomenological features.

15/20 We found that the transition probabilities to the hyperconnected Pattern 3 and the phenomenological factors related to Oceanic Boundlessness and Visionary Restructuralization showed the highest correlations with the first canonical vector of their associated spaces.

16/20 In conclusion, we illuminate the intricate interplay between brain dynamics and subjective experience under psilocybin, providing new insights into the neurophenomenology and neurophysiology of the psychedelic state.

17/20 The decreases in BOLD signal amplitude in the psychedelic state could imply that increased cortical arousal mediates this hyperconnected pattern (e.g. ).bit.ly/4594U2s

18/20 Therefore, we suggest considering GS amplitude as a complementary measure to the extracted connectivity profiles as they illuminate their physiological substrate, as we recently showed for the case of mind-blanking bit.ly/3yg2st5

19/20 This was a highly collaborative work between the @PhysioCognGIGA , and @PIMaastricht , with @LarryDFort , #Jan_Ramaekers, @NL_Mason , @PMallaroni , and @ADemertzi !

20/20 And big thanks for the support of @Giga_CRCivi , @GIGA_ULiege , @UniversiteLiege , and @frsFNRS .