Scientists Induces Visual Hallucinations In Healthy People Without Using Drugs, Here's How
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Visual hallucination is oftentimes associated with drug use or a mental disorder. However, researchers have recently discovered that there is a new method to induce the same visual hallucination in healthy people, without the use of drugs. Researchers said that these complex experiences share a common underlying mechanism with normal visual perception.
According to Live Science, hallucinations can range from simple geometric shapes, such as blobs, lines, and hexagons, to seeing animals, people or insects. These involuntary experiences are usually thought to happen when spontaneous changes in the brain temporarily take control of the visual function. However, how or why it happens and its underlying mechanisms aren't completely understood.
"We have known for more than 100 years that flickering light can cause almost anyone to experience a hallucination," says UNSW Associate Professor Joel Pearson from the School of Psychology. "However, the unpredictability, complexity and personal nature of these hallucinations make them difficult to measure scientifically," he says.
These visions have colors and forms that appear and how they move around are constantly changing over time and are naturally subjective. "Previous studies have typically relied on drawings and verbal descriptions, but these don't provide us with a way to precisely identify the mechanisms in our brain that cause hallucinations," says Pearson.
Medical Xpress reported that the study's subjects were 100 healthy university students. To induce hallucinations, they were made to watch the image of a plain white ring flicker on and off around 10 times per second against a black backdrop. After looking at the screen, you should be able to see pale gray blobs appear in the ring and rotate around it, first in one direction and then the other. However, it's also worth mentioning that even though this has worked in all students who participated in the study, there is still no assurance that the experiment will work for everyone.
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"With our technique, we get rid of the unpredictability," said Pearson. "People don't see windmills, lines, or different colors, they just hallucinate gray blobs. Once the hallucination is stable like this, with just the blobs, we can start to objectively investigate the underlying mechanisms."
The team was able to objectively measure the strength of people's hallucinations just by placing a second ring marked with permanent gray blobs inside the white ring. Science Alert reported that the researchers then asked the participants if the ones they hallucinated were darker or lighter than the real ones. Using behavioral science techniques, the team was able to demonstrate that the hallucinations were arising inside the visual cortex, without the need for MRI scans. They did this by showing volunteers two flickering lights, one for each eye, displayed randomly.
These lights were flashing about 2.5 times per second - a relatively slow rate, which normally doesn't induce strong hallucinations, explains Pearson. But the volunteers were experiencing hallucinations consistent with lights flashing about 5 times per second. "They were combining the signals from the two eyes. This really only happens in the visual cortex, not in the eye, or other initial processing areas of the brain," says Pearson.
With the help of mathematicians from the University of Pittsburgh, the team developed neural models of the visual cortex to understand what was happening. Pearson compared these models to the vibrational phenomena dubbed as cymatics, where sound frequencies can be seen pushing sand grains into geometric patterns.
"Rather than a metal plate and sand, we're talking about the visual cortex, where we see these reverberating, self-organizing patterns of activity. We think this could be how the brain is creating the hallucination, and it might also help to explain normal consciousness and our experience of what's happening around us every day."