What happens when psychedelics meet your brain?

Last update: May 15, 2023
Reading time: 5 minutes
By Brain Matters

You have probably noticed that your mental state and the conscious experience of the world surrounding you feels different depending on the activity you are engaged in. For instance, being deeply focused on a task, about to fall asleep, dreaming, or running a 100-meter sprint go together with different “modes of consciousness”. Even if there is no clear and universally accepted definition for the word consciousness, it can simply be put as a term to describe the awareness or perception of your physical and mental experience. Those different “modes” mentioned hereinabove depict a few examples of normal, healthy states of consciousness. Nonetheless, other sorts of conscious experiences defined as altered states of consciousness can arise through meditation, somatic and mental illnesses, or drug consumption. In this article, I will focus on the particular altered state of consciousness induced by a specific class of drugs, referred to as hallucinogens or psychedelics. You have probably already heard of LSD or psilocybin, however, I will show you how they affect the human brain and how they can reshape our internal and external perceptions.

Psychedelics and the brain

Psychedelics drugs represent a class of psychoactive compounds producing significant changes in perception, mood, and cognitive processes. This umbrella term includes a few main substances, all found or derived from naturally occurring organisms. Among them LSD may be the most famous one, and is derived from a fungus that grows on rye. Then, psilocybin is a compound found in multiple so-called magic mushrooms. Finally, DMT, considered the most potent drug by many, is found in plants, but also in humans, in the pineal gland. The unifying characteristic of these various molecules is that they are all serotonin 2A receptor (also written 5-HT2A receptors) agonists. Are we going too fast? Let’s step back and have a look at how the brain communicates.

Our brain contains many neurons that secrete signaling molecules that affect other neurons across a kind of chemical bridge that we refer to as synapses. These molecules are called neurotransmitters, and you may be familiar with some of them, like dopamine, glutamate, GABA, noradrenaline, or serotonin. Each of these neurotransmitters are secreted and can bind to specific neurons of the same family through customized receptors placed on the surface of the second neuron of the “bridge”, called the postsynaptic neuron. Specifically, the serotonin system, which is of interest in psychedelics, includes 15 subtypes of receptors. Because the classic psychedelics mentioned before have a very similar chemical structure to that of the neurotransmitter serotonin, they are also able to bind to these same serotonin receptors, particularly to the 5-HT2A. Thus, when one ingests for instance a dose of LSD, the drug mimics the serotonin and binds to these various serotonin receptors, leading to a very complex and not yet fully comprehended restructuration of the brain function.

The work of different researchers including Dr. Carhart-Harris show that psychedelics induce a decreased activation in different structures of the brain, which are part of the “default mode network”, including the thalamus, the cingulate cortex, and the medial prefrontal cortex. These regions are not restricted to specific functions, but rather, act as important centers of information integration. Therefore, they can be compared to disciplinarians or important institutions holding and monitoring the system together in a balanced way. As a result, when such structures are inhibited, a subsequent sort of chaos emerges in the brain. This happens through increased functional connectivity, an indicator of the intensity in which brain regions interact with each other, between areas of the brain that do not often communicate, or at least not in the same manner. Eventually, this unique kind of interplay among brain structures gives rise to a myriad of psychological and subjective changes altering the normal state of consciousness, which will be discussed in the following section. That being said, this neurobiological explanation is conspicuously oversimplified, and much is still to be discovered about the precise operation of the brain in a psychedelic state.

Psychedelics and the mind

As we saw in the first section, consciousness refers to the perception of internal and external stimuli. As you can imagine after reading section two, when the disciplinarians of the brain are inhibited, and therefore many other brain areas start communicating differently, the subsequent perception and interpretation of one’s thoughts, feelings, or surroundings might change radically. The primary tool used to assess one’s conscious experience is the 5-Dimensional Altered States of Consciousness Questionnaire (5D-ASC). Unsurprisingly, it contains five overarching dimensions: oceanic boundlessness, visionary restructuralization, anxious ego dissolution, auditory alterations, and reduction of vigilance. Here I will discuss only the first three dimensions.

The first one, oceanic boundlessness, includes lower-order scales such as feelings of unity (with the world or other living organisms), spiritual or religious experiences, or a blissful state. Many tribes in Latin America for instance embedded psychedelic experiences into their cultures for many centuries. Some of them also organized religious rituals around the consumption of these compounds, and the experiences described in this dimension are presumably at the root of such practices.

Then, the most famous one, visionary restructuralization, basically refers to the visual hallucinations that can occur during a trip, but this is not everything. As described previously, the thalamus is one of the brain structures inhibited by psychedelic consumption. It can be simply defined as a sensory hub, and therefore all the input coming from the external world (visuals, smells, sounds, etc.) are processed differently by the psychedelic brain. Thus, it can result in the linking of different senses together. As a matter of fact, some people report hearing a color, or seeing a song. Such experiences are called audio-visual synesthesia.

Last but not least, feelings of anxious ego-dissolution can appear in the form of impaired control and cognition, disembodiment, or anxiety, and can hence provoke a “bad trip”. Indeed, a psychedelic adventure involves important contingencies, and two critical variables to control in order to diminish the risk of acute adverse psychological effects to classic hallucinogens are the set and setting. The set is defined as the mindset or the preparation of the individual toward the psychedelic experience, including personality and the current mood. The setting encompasses the atmosphere as well as the physical, social, and cultural environment in which the user lives his experience.

Future perspectives

Even if psychedelic drugs bear a contentious history and are still controversial today, their future seems brighter than ever. Indeed, many scientists have investigated their potential for treating psychopathologies characterized by reduced communication between different parts of the brain. Among them, LSD and psilocybin show encouraging evidence for reducing symptoms in obsessive-compulsive disorder (OCD), addictions, depression, and anxiety. At the same time, MDMA is already approved to treat PTSD in the USA and has demonstrated to be highly effective. Furthermore, Australia recently allowed the use of psilocybin for treatment-resistant depression, and of MDMA for treating PTSD. More research is being done but the future of treatments for mental disorders will presumably incorporate psychedelic compounds.

If this subject got you interested, you should definitely check this article; https://www.brainmatters.nl/en/tripping-terror-psychedelics-and-fear/

Author: Pablo de Chambrier


  • Carhart-Harris, R., Leech, R., & Tagliazucchi, E. (2014). How do hallucinogens work on the brain. Journal of Psychophysiology, 71(1), 2-8.
Related Posts
Check onze database
Alles wat je wilt weten over het brein op één plek. 
Related posts:
Here you will write about your company, a tittle description with a maximum of 2 sentences
Copyright © 2022 Brainmatters