Do you See That Tree...I Do: Drug induced Hallucinations
The body is a well-oiled machine, generally not faltering in its steps. The ability to always breathe on time, and make the heart beat at the right moment, is due largely to the nervous system and the brain. The nervous system is comprised of neurons that send and receive signals, resulting in an output, or some sort of response to the stimuli. What happens if the stimulus being sent is interrupted or altered, due to an exterior influence? The use of drugs such as LSD is an example of such a case, in which the body responds to an altered stimulus, resulting in an altered perception. These altered perceptions are better referred to as hallucinations.
A hallucination is a response in the absence of a stimulus, an output without a corresponding input. A person may have a hallucination however there is no stimulus for the person to see, hear, or smell what is being falsely visualized. A hallucination is different from an illusion, because an illusion is a perception that is due to an incorrect stimulus. An illusion is similar to a mirage, something is seen not because of an incorrect stimulus, but due to the tricks of the light and the way it bends and refracts as it moves from an area of denser cold air to warmer air(1). While the general connotation of a hallucination is that it is something that is experienced visually, there are actually a variety of hallucinations that one can experience like auditory, olfactory, tactile, and many more. Auditory hallucinations are most generally associated with schizophrenic patients. The hallucinations that are generally experienced when under the influence of toxins, such as LSD are visual hallucinations.
Visual hallucinations are not solely drug induced. A hypnagogic hallucination is felt just before one goes to sleep. It is generally a result of an abnormality in the brainstem. A peduncular hallucination occurs in the evenings but not when a person is sleepy or drowsy in any manner. This is generally a result of something occurring in the neural tract to and from the pons. The pons is an area of the brain located on the brain stem and commonly thought to be associated with dreams(2). When hallucinations were first being studied, it was postulated that they were a portrayal of a person’s unconscious desires; this was considered the Freudian view (3), which was mainly accepted by psychologists. With time, hallucinations were further studied, and it was learnt that they were in response to an abnormal chemical reaction in the brain.
Normally without other influences, the process for visualization is rather straight forward. The eye is struck by a ray of light and this induces a signal to be transmitted via neurons to the occipital lobe of the brain. This lobe is located towards the back of the brain and is the visual processing center in human and most mammal brains (4). The signal is transmitted through the neurons as an action potential, the neuron is depolarized and the signal is sent through as an action potential. As the action potential progresses through the neurons, it repolarizes the portion of the cell behind it. This repolarization ensures that the action potential does not move backwards, because this would be quite confusing for the body to coordinate. Between the neurons there are small gaps referred to as synaptic gaps. At the synaptic gaps, the electrical signal is translated into a chemical neurotransmitter, which travels across the synaptic gap and binds to the occipital lobe, in turn activating the lobe. Once activated by the signals it processes the information and a response is given in the form of a visual perception. This seemingly simple process takes a lot of coordination in the nervous system, and can be easily fooled due to outside chemicals.
When a person uses drugs the foreign chemical travels through the blood stream and can be found in the synaptic gaps. If these foreign chemicals are appropriately matched it can falsely activate the occipital lobe and cause a visual experience or hallucination. This visual experience would be falsely induced, and while there is no obvious signal or input that causes the hallucination, the abnormal chemical reaction in the brain acts as an internal stimulus. This would then cause an output or create a false vision or a hallucination.
Hallucinogens are a group of drugs that result in altered perceptions or hallucinations as one of the major side-effects. Hallucinogens are a varied group of drugs with little in common on the surface, for example they have a wide range of chemical formulas. Despite all their differences they share the symptom of causing hallucinations. Some of these drugs are PCP, ecstasy, THC, LSD, and many more. LSD, in particular, is an interesting drug in its ability to fool the nervous system and cause hallucinations.
Lysergic acid diethylamide, more colloquially known as LSD was one of the first hallucinogens to be discovered. Albert Hofmann, a Swiss chemist discovered the drug in 1938, however the use of the drug as a hallucinogenic was only discovered in 1943. Albert Hofmann accidentally ingested the drug, and the effects of LSD were discovered. LSD is the most potent member of the hallucinogenic drugs, and has an impact on the body after about 30-90 minutes of ingestion. The effects can last up to 12 hours after use. LSD is a white, odorless, and tasteless drug, that can be administered either orally or intranasal (5).
Experiments have been done to test the sensory response of animals on LSD. Electrical measurements along the optic nerve show an intensified impulse is received from the retina after use of LSD. The impulse intensity increases under the influence of LSD and the signal traveling from the optic nerve to the brain, also becomes more distorted (3). This is a demonstration of the general effects LSD has on the signal sent to the brain.
LSD has an impact on the brain, mainly in the areas in which serotonin are dominant. It affects areas of the brain that detect external stimuli, making it more responsive to the environmental inputs or signals. This area of impact is mainly the Locus Coeruleus (LC) and the Raphe Nuclei. The LC is on the brain stem and regulates a person’s stress and panic response. The Raphe Nuclei are found in the middle portion of the brain stem and function to release serotonin to the rest of the brain. Serotonin, occasionally referred to as 5-HT, is a chemical neurotransmitter that is derived from tryptophan. Serotonin regulates the behavior and mood of a person, and plays a vital role in the language portion of the brain, in terms of hearing and reading. An appropriate question would be to consider, why LSD would target areas of the brain with high serotonin levels. LSD and serotonin share a common structure in their chemical structures. The molecular formula of LSD is C20H25N3O and the molecular formula for Serotonin is C10H12N2O. While the number of atoms in each formula may seem completely different, it is the way in which the atoms are arranged that give the two the similarity in structure. Both of these chemicals contain an indole ring in their structure. This similarity allows LSD to readily bind at serotonin receptors and alter the response of the nervous system.
There are two main receptors for serotonin, the 5-HT1 receptor and the 5-HT2 receptor. The 5-HT1 receptor is located on the pre-synaptic neuron, or the neuron that is before the synaptic gap. When LSD attaches to this receptor the production of serotonin is decreased and stopped. The 5-HT2 receptor is on the post-synaptic neuron and if LSD attaches to it, the receptor is inhibited making it difficult to generate an action potential. It has not been scientifically proven but it is hypothesized that LSD prefers to attach to the 5-HT1 receptor (6). It is also believed that the 5-HT2 receptors cause hallucinogenic effects when bound to LSD, which acts as an agonist to the 5-HT2 receptor (3). An agonist is a substance that binds to a specific receptor which triggers a response in a cell, the agonist mimics the action of a hormone etc. that may bind to the same receptor (7). After LSD binds to a receptor the decrease in serotonin levels, will affect the Raphe Nuclei, which is meant to protect the brain from overstimulation. The Raphe Nuclei is connected to many other areas of the brain as well. The intake of LSD results in a lower Serotonin level, which in turn affects the Raphe Nuclei. If the Raphe Nuclei is affected, then the other areas of the brain that are connected to the Raphe Nuclei are also affected. This explains how LSD can have such a large range of side-effects on a user (6).
It is amazing how a person’s senses can be altered and manipulated by tiny molecules such as LSD and serotonin. The false binding of a molecule to a receptor can be paralleled to the effect it has on the body as a hallucination or a false interpretation of the world around. Further research on the ability of LSD to bind at a serotonin receptor would lead to remarkable discoveries and help us understand how the complexities of the nervous system, which controls movement, thoughts, and subconscious actions, is able to miss out on the incorrect binding of a molecule to a receptor neuron.