bioRxiv (Cold Spring Harbor Laboratory)
July 16, 2019
Lionel Barnett, Suresh Muthukumaraswamy, Robin Carhart‐Harris et al.
10 citations
preprint
Psychedelic drugs such as LSD, psilocybin, and low-dose ketamine reduce directed functional connectivity—the flow of information—across the brain, as measured by Granger causality in source-localised MEG recordings. This breakdown in organised information flow supports the idea that the psychedelic state disrupts normal patterns of neural communication. With LSD specifically, directed connectivity decreased while undirected connectivity (measured by correlation and coherence) increased, an opposite movement that highlights the importance of using multiple connectivity measures when analyzing time-resolved neuroimaging data. The non-psychedelic anticonvulsant tiagabine was included for comparison.
Pedro A.M. Mediano, Fernando E. Rosas, Andrea I. Luppi et al.
10 citations
A new method called Complexity via State-space Entropy Rate (CSER) estimates neural signal complexity with better temporal resolution and spectral decomposition than the standard Lempel-Ziv complexity (LZ) approach. CSER matches LZ in distinguishing conscious states but offers two key advantages: it can break complexity down by frequency bands, and it provides temporal resolution about 100 times finer. Using MEG, EEG, and ECoG data from humans and monkeys, CSER revealed that gamma-band activity primarily drives complexity changes across states of consciousness. In an auditory mismatch negativity experiment, CSER detected early entropy increases roughly 20 milliseconds before the standard event-related potential. This method enables finer-grained study of how signal complexity relates to cognitive processes and conscious states.
Human brain mapping
April 1, 2025
Clayton R Coleman, Kenneth Shinozuka, Robert Tromm et al.
4 citations
LSD alters consciousness by changing connectivity between the dorsolateral prefrontal cortex (DLPFC), thalamus, and visual areas. In healthy participants, stronger functional connectivity between the left and right DLPFC, thalamus, and fusiform face area correlated with greater ego dissolution. Emotional arousal was linked to increased connectivity between the right DLPFC, intraparietal sulcus, and salience network. A confirmatory reverse analysis supported these findings. Magnetoencephalography data showed that LSD increased theta-band information flow from the thalamus to the DLPFC, supporting the idea that disrupted thalamic gating underlies ego dissolution. The results clarify the DLPFC's role in LSD-induced altered states.
bioRxiv Preprint Server
July 16, 2025
Borjan Milinkovic, Anil K. Seth, Lionel Barnett et al.
2 citations
preprint
Consciousness depends on neural activity across many scales. A new measure, dynamical independence (DI), quantifies these multi-scale relationships. Applying DI to EEG data from people under three anaesthetics, the authors found that propofol and xenon—which abolish conscious report—produce more emergent but highly variable dynamic structure, indicating fragmented macroscopic organisation. Ketamine, which preserves dream-like states, shows reduced overall emergence but partial preservation of macroscopic structure similar to wakefulness. Regional brain contributions varied. The results reveal drug-specific reconfigurations of emergent dynamics, dissociate the amount of emergence from its organisation, and caution against equating emergence with consciousness level.
bioRxiv Preprint Server
December 9, 2024
Clayton R. Coleman, Kenneth Shinozuka, Robert Tromm et al.
1 citation
preprint
Lysergic acid diethylamide (LSD) alters consciousness by affecting brain connectivity, particularly in the dorsolateral prefrontal cortex (DLPFC). Using fMRI and MEG data from healthy participants, the study found that ego dissolution—a hallmark of the psychedelic experience—was positively correlated with increased functional connectivity between the left and right DLPFC, thalamus, and fusiform face area. Emotional arousal was linked to stronger connectivity between the right DLPFC, intraparietal sulcus, and salience network. A confirmatory analysis supported these findings. MEG data showed that LSD increased directed information flow from the thalamus to the DLPFC in the theta band, suggesting disrupted thalamic gating contributes to ego dissolution. These results indicate a key role for the DLPFC in LSD-induced states of consciousness.