Scientists gave a mouse a psychedelic drug to understand how we hallucinate

Seeing something that is not there can be one of the strangest, scary and confusing experiences that a person can live. Scientists at the University of Oregon say they are a little closer to understanding what happens in the brain when we hallucinate – and that they just had to get out poor mice.

Since mice are not known for their glittering conversation, you can infer that we could not use them to study hallucinations. However, according to study writer Cristopher Niel, a biologist at the University of Oregon, it may be an imperfect proxy for people.

We know, for example, that one subtype of serotonin – the neurotransmitter that regulates our mood, memory and appetite – called serotonin 2A, is directly affected by hallucinogenic drugs like LSD and has been associated with a visual hallucination in humans. . And when you administer this type of drug to mice, their behavior changes reliably, like a strange head reaction that indicates something similar to what happens to them. Neurologically, these changes also appear to involve their serotonin 2A receptors.

"This is one of the great reservations of this study: we can not be sure that they hallucinate," Niel told Gizmodo. "But what we are really studying, ultimately, are the effects of serotonin 2A receptor activation on vision."

For their experience, they administered to mice a drug called 4-iodo-2,5-dimethoxyphenylisopropylamine (DOI). In humans, the psychedelic effects of DOI are similar to those of LSD. Unlike LSD, it is not a controlled substance registered in the United States, which makes it easier for scientists to obtain and use animal research (the human recreational use of DOI is not unknown, but it is much rarer than that of LSD). Demonstrating previous studies on animal hallucinations, they were also able to study awake mice, using implanted monitors capable of tracking the onset of individual neurons.

Their findings, released Tuesday in Cell Reports, were somewhat surprising. Rather than seeing frantic cerebral activity in the visual cortex, the area that processes the information captured by the eyes, they found that the brains of triggering mice actually received less information from the outside world as compared to a group of control mice.

"There has been a decrease in entries into the visual cortex. So you can imagine it a bit like lowering the volume of your vision, "said Niel. "Our vision of vision is a combination of what actually exists – the photons striking your eye – and the interpretation of what you absorb. But we think what is happening here is that this decrease in visual input leads to the brain misinterpreting or overinterpreting what is actually out there. "

Niel pointed out that this misunderstanding of the brain is common when there is little or no visual information being absorbed, such as when we dream or think we can see the slightest shadow of something that is scared in the dark.

More tragically, of course, people with mental disorders such as schizophrenia face intrusive distortions of their visual reality. But serotonin 2A has also been closely linked to schizophrenia, and understanding exactly how hallucinations occur in these people will perhaps one day help us know how to bypass this process. Since the effects of psychedelic drugs on the treatment of depression and anxiety are being explored, this same knowledge could also help us better understand how these drugs interact with the brain.

However, these are areas of research outside the direct expertise of Niel and his team. And he is quick to warn that his discoveries, even if they stick to future studies, only bring to light an element of the cerebral circuit involved in visual hallucinations. In addition to suppressing neuronal activity in the visual cortex, for example, they also found that the timing of neuron activation was different in DOI-dose mice. So, there is almost certainly more than one change in the brain when we hallucinate visually, and perhaps even in areas outside the visual cortex.

"In reality, we want to determine what brain circuits are affected," said Niel. "We want to get in and see where different types of neurons and different parts of the brain are assembled. [while hallucinating]. "

The team then hopes to use genetic manipulation to better study and isolate the circuits considered essential to the treatment and interpretation of the vision.