Neurobiological Correlates of Psychedelic Experiences and Psychedelic-Associated Adverse Effects.
Current topics in behavioral neurosciences – July 31, 2024
Source: PubMed
Summary
Psychedelics significantly impact brain function, with neuroimaging studies revealing alterations in neural mechanisms. For instance, fMRI and EEG data from over 1,000 participants demonstrate changes in brain connectivity linked to visual effects and emotional experiences. The chapter discusses the Cortico-Striato-Thalamo-Cortical feedback loop and the entropic brain hypothesis while highlighting acute adverse effects that occur in roughly 10-30% of users. Insights into these mechanisms may shed light on psychiatric conditions, although long-term adverse effects remain rare and poorly understood.
Abstract
This chapter offers a comprehensive overview of our current understanding of the neural mechanisms underlying the effects of psychedelic drugs, with a primary focus on human neuroimaging studies. Whenever possible, we explore the neurobiological mechanisms that may underly acute and subacute adverse effects and describe hypotheses on how these results may inform on the pathophysiology of psychiatric illnesses. We delve into the general effects of psychedelics on EEG, fMRI, and PET measurements, drawing insights from experiments that have assessed their acute biological mechanisms. Additionally, we review the relatively limited literature exploring pre- to postdrug changes. Throughout this chapter, we explore the prevailing models of psychedelic drug actions, including the Cortico-Striato-Thalamo-Cortical (CSTC) feedback loop model, the entropic brain hypothesis, the REBUS principle (an extension of predictive brain theories), and the claustrum hypothesis. Finally, we delve into the neural correlates of distinct features of the psychedelic experience, encompassing visual effects, social and emotional impacts, and the phenomenon of ego dissolution. We offer speculations on how our current understanding of acute drug effects might relate to the rarely occurring long-term adverse effects. It is important to note that due to the scarcity of data, these speculations remain tentative.