Brain regions where a significant correlation between FCD and subjective reports of ego dissolution (LSD minus placebo) was found are colored in red. Brain regions presenting the most selective correlations between FCD increases and ego dissolution scores are colored in green – Tagliazucchi et al., 2016
Disintegration in the DMN and other resting networks was also accompanied by decreased alpha power in regions such as the posterior cingulate cortex (PCC). Regular alpha oscillations are hypothesised to inhibit spontaneous neuronal activity, i.e. that which occurs without exposure to particular stimuli (Tagliazucchi et al., 2016). LSD was found to decrease alpha power and thus trigger spontaneous activity in neurons, an effect that could partially explain the closed-eye imagery associated with the LSD experience.
The mechanisms of closed-eye imagery
Striking results were obtained in the study of closed-eye imagery induced by LSD. The researchers investigated both simple images like geometrical patterns and complex ones including autobiographical scenes occurring under LSD. The study revealed that although there was no visual input, under LSD the visual cortex (VC) behaved as if there was (Carhart-Harris et al., 2016). This observation supports ongoing theories that the appearance of geometrical imagery may be caused by the rendered instability of the VC (Butler et al., 2011).
Apart from the increase in blood flow level, the visual cortex also displayed increased functional connectivity with other brain regions, mainly the parahippocampal cortex (PHC), typically involved in memory retrieval, music-evoked emotion and mental imagery. The researchers used a Dynamic Causal Modelling analysis to reveal increased effective connectivity between the VC and the PHC, where the PHC triggered the activity of the VC. The interconnection of these brain regions can be held responsible for the “colouring” of personal recollections experienced by the subjects under LSD. Apart from the PHC, other brain regions such as those in occipital and inferior frontal lobes also became activated during visuals, leading to the conclusion that a much larger portion of the brain is involved in producing imagery under LSD than in the normal waking state.
The influence of music
The study further revealed the highly important role of music during the psychedelic experience. Mendel Kaelen, a PhD candidate at Imperial College London and board member of the OPEN Foundation, explored the synergistic effects of music during the LSD experience (Kaelen et al., 2016). Three fMRI scans were performed, the first and the third of which were done without the use of music, the second being performed while the subjects listened to music (two excerpts from the album Yearning by the ambient artist Robert Rich and the Indian classical musician Lisa Moscow).
The study showed that the PHC becomes highly activated when subjects are exposed to music and LSD. Furthermore, the increase of interaction between the PHC and the visual cortex corresponded with the intensity of the closed-eye visuals, both simple (geometrical patterns) and complex ones (e.g. based on personal recollections). This certainly underscores the importance of incorporating music into LSD-assisted psychotherapy.
Expanding the knowledge
The findings of the present study with LSD provide firmer ground to the knowledge that has been gathered in experiments using other psychedelics. Psilocybin has been found to have similar effects on brain activity including the disintegration in certain regions such as the default mode network and the emergence of new connections between normally segregated networks. These conclusions emerged from two independent researches, one of which was performed by the authors of the present LSD study (Carhart-Harris et al., 2012, Kometer et al., 2015). Still another research group discovered analogous effects of the Amazonian psychedelic ayahuasca on the human brain (Riba et al., 2002).
The findings of this groundbreaking study have several important implications. First, they hint at a neurological understanding of the therapeutic potential of LSD. Due to its “entropic” effect on the brain – the increase of disintegration within and simultaneous increase of interaction between certain brain regions – LSD may hold the potential for breaking down pathological patterns associated with depression, for instance, and thus increasing the effectiveness of psychotherapy.
The study also demonstrated the potential of LSD in the study of the neurobiology of consciousness, as it seems to put subjects into the so-called primary state of consciousness characteristic of the earlier stages of consciousness development in children, of REM sleep and of early psychosis (Carhart-Harris et al., 2016). This also means that LSD could be applied in psychological research in the study of pathologies (Carhart-Harris et al., 2016).
Apart from the short-term effects of LSD on brain chemistry, more investigation is warranted on the potential of the LSD experience to provoke sustainable changes in personality.
Robin Carhart-Harris and Mendel Kaelen will speak at the OPEN Foundation’s ICPR conference next June.
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