The psychedelic state induced by LSD appears to weaken the association between anatomical brain structure and functional connectivity, according to new research published in the journal NeuroImage. The study also provides evidence that LSD increases the complexity of segregated brain states.

The findings provide new insights into the relationship between brain function and consciousness.

“My main interest and the focus of my research is on understanding the neuroscience of human consciousness,” said study author Andrea I. Luppi (@loopyluppi), a Gates Scholar at the University of Cambridge in the Cognition and Consciousness Imaging Group.

“Most studies of consciousness focus on its loss: sleep, anesthesia, or coma. But we think that a complementary way to obtain insights is to study states of altered consciousness, such as the psychedelic state induced by LSD.”

Consciousness is believed to involve the integration of multiple segregated brain networks and their subnetworks, and the researchers sought to better understand how these patterns of brain connectivity varied over time under the influence of LSD.

Luppi and his colleagues used functional magnetic resonance imaging (fMRI) to examine the structural and functional brain connectivity of 15 healthy volunteers during two separate sessions. During one session, the participants were given a placebo. During the other, they were given an active dose of LSD.

Typically, “neurons that fire together, wire together.” But the researchers found that LSD decoupled the relationship between structural and functionally connectivity, indicating that brain activity is “less constrained than usual by the presence or absence of an underlying anatomical connection” under the influence of the substance.

“We know that brain structure has a large influence on brain function under normal conditions. Our research shows that under the effects of LSD, this relationship becomes weaker: function is less constrained by structure. This is largely the opposite of what happens during anesthesia,” Luppi explained.

As the researchers wrote in their study, under the influence of LSD, it appears that “the brain is free to explore a variety of functional connectivity patterns that go beyond those dictated by anatomy – presumably resulting in the unusual beliefs and experiences reported during the psychedelic state, and reflected by increased functional complexity.”

“Integration and segregation of information are fundamental properties of brain function: We found that LSD does not affect them equally, but rather it has specific effects on each,” Luppi told PsyPost. In addition, these changes in brain integration and segregation fluctuated over time, and these fluctuations were associated with subjective experiences.

For example, the experience of losing one’s sense of self during a psychedelic experience, a phenomenon known as “ego dissolution” or “ego death,” was associated with a state of high global integration.

“This is a relatively new area of neuroscience, and research on larger cohorts will be needed to fully understand the effects of LSD and other psychedelics on brain function,” Luppi said. “A more thorough characterization may also shed light on potential clinical applications such as the ongoing research at the new Centre for Psychedelic Research in London.”

“Studying psychoactive substances offers a unique opportunity for neuroscience: we can study their effects in terms of brain chemistry, but also at the level of brain function and subjective experience,” he added. “In particular, the mind is never static, and neither is the brain: we are increasingly discovering that when it comes to brain function and its evolution over time, the journey matters just as much as the destination.”

The study, “LSD alters dynamic integration and segregation in the human brain“, was authored by Andrea I. Luppi, Robin L. Carhart-Harris, Leor Roseman, Ioannis Pappas, David K. Menon, and Emmanuel A. Stamatakis.