Seeing something that does not exist can be one of the strangest, most terrifying and startling experiences a person can have. However, scientists from the University of Oregon say they've come a bit closer to understanding what happens in the brain when we hallucinate ̵
Because Mice are Unknown You might assume that we could not use them to study hallucinations. Admittedly, according to study author Cristopher Niel, a biologist at the University of Oregon, they may be an imperfect proxy for humans.
For example, we know that a subtype of serotonin is the neurotransmitter that regulates our mood. Memory and appetite among others – called serotonin 2A – is directly affected by hallucinogenic drugs like LSD and has been linked to visual hallucination in humans. And when you administer this kind of drug to mice, there are reliable changes in their behavior, like twitching a strange reaction on the head, indicating that something similar that happens to us is happening to them. Neurologically, these changes also seem to involve their serotonin 2A receptors.
"This is one of the major reservations of this study – we can not know for sure if they hallucinate," said Niel to Gizmodo. "What we are really studying, however, are the effects of activating serotonin 2A receptors on vision."
For their experiment, they administered mice with a drug called 4-iodo-2,5-dimethoxyphenylisopropylamine (DOI)) , In humans, the psychedelic effects of DOI are similar to those of LSD. Unlike LSD, the US is not a controlled substance that makes it easier for scientists to conserve and use animals in animal research (the use of DOI for leisure is not uncommon, but much less common than using LSD). As demonstrated in earlier animal studies on hallucination, they were able to examine the mice while awake thanks to implanted monitors that could track the firing of individual neurons.
Their results, published on Tuesday in Cell Reports, were somewhat surprising. Rather than seeing hectic brain activity in the visual cortex, the area where the eye-tracking information is processed, they discovered that the brains of stumbling mice actually receive less information from the outside world than a control group of mice. 19659003] "This decrease in input to the visual cortex was such that you can imagine a bit like reducing the volume for the vision," said Niel. "We think about seeing as a combination of what is actually out there – the photons that hit your eye – and also the interpretation of what you record. But we believe that the decline in visual input is leading the brain to misinterpret or over-interpret what is actually out there. "
Niel pointed out that this misinterpretation by the brain routinely happens to us when little or no visual information is recorded, eg. B. When we dream or think We can see the faintest shadow of something sinister in the dark.
Tragically, people with mental disorders, such as schizophrenia, treat intrusive distortions of their visual reality. However, serotonin 2A was also closely associated with schizophrenia. Once you understand how exactly hallucinations are occurring in these individuals, one day we can figure out how to short this process. Given that psychedelics are currently being studied for their effects in the treatment of depression and anxiety, this knowledge may also help to gain insight into the interaction of these drugs with the brain.
These are research areas that lie outside of Niel and his team's expertise, however. And he quickly warns that his findings, even if they persist in future studies, reveal only part of the brain circuitry involved in visual hallucinations. For example, in addition to suppression of neuronal activity in the visual cortex, they also found that the time at which neurons were fired was different in DOI-dosed mice. So there is certainly more than one change in the brain when we visually hallucinate, and possibly in areas outside the visual cortex.
"We really want to find out what circuits are involved in the brain," said Niel. "We want to go in and see where different types of neurons and different parts of the brain are put together [while hallucinating]."
The team hopes to leverage genetic manipulation to better investigate and isolate circuits critical to processing and interpret vision.