Seeing things that aren't really there can be a terrifying experience. New research suggests that hallucinations are not produced by the visual cortex.
It is rather a result of a brain taking less information from the outside world, at least, according to the new study done in mice.
The findings of the study were published on Tuesday in Cell Reports.
Hallucinogenic Drug On Mice
For the study, neuroscientist Cristopher Niell at the University of Oregon and his colleagues dosed mice with a hallucinogenic drug known as 4-iodo-2,5-dimethoxyphenylisopropylamine or DOI. Then, they looked at their brains.
In humans, the hallucinogenic effects of DOIs are similar to those of Lysergic acid diethylamide or LSD.
After dosing, scientists showed images on a screen to the mice and measured the responses in their brains. With the use of fine imaging techniques, the study found that the primary visual region of the mice was put by the drug into a weak and disorganized state.
DOI Effects On Visual Cortex
They compare the results with mice that were not dosed with DOI and the primary visual cortex of the drugged mice showed a weakness in the strength of neural signaling. The visual cortex is the region in the brain that processes visual information.
"The responses were dialed down," Niell said, "but the information being conveyed was the same."
The information that is going into the visual cortex is decreasing and Niell says it is like turning down a bit the volume on the person's vision. He said that the decrease in visual input makes the brain misinterpret or over-interpret what is actually out there.
He pointed out that this misinterpretation or over-interpretation by the brain routinely happens to humans when there is little or no visual input. An example of this is when one is dreaming, or when one thinks he has seen a faint shadow of a frightening creature in the dark.
However, the study has one a big caveat.
"We can't know for sure that they're hallucinating," he told Gizmodo.
Niell is careful to say that their study is primarily meant to encourage further research, according to Inverse.