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This article comes from the official account of Wechat: SF Chinese (ID:kexuejiaodian), author: SF

Imagine that by turning the knob on the device to affect the neural activity in our brain, we can make the virtual reality more real. This is not entirely a science fiction plot, and researchers have recently figured out how the brain distinguishes imagination from reality, a discovery that will help virtual reality technology become more real.

(by Chen Qiang / tr. by Robert Taylor)

Have you ever fantasized about hanging out with your secret crush, even though they seldom notice you in reality? There is always a gap between fantasy and reality, but several brain scan studies have confirmed that the brain sends out very similar neural signals when it imagines something and when it actually sees something. However, for most people, the subjective experience of the two is quite different. So this leads to a basic question: how does your brain distinguish between imagination and reality?

A new study led by Nadine Dijkstra, a postdoctoral fellow at University College London, was published in the journal Nature Communications. The study gives an interesting answer to this question: the brain compares the visual signal being processed with the "reality threshold". If the signal exceeds the threshold, the brain thinks it is real; if it does not exceed the threshold, the brain thinks it's imaginary.

Did you really see the fruit? When Dijstra started the study, the first thing she noticed was an experiment carried out by American psychologist Mary Cheves Westperky (Mary Cheves West Perky) in 1910. In the experiment, Perky asked participants to stare at the white wall and imagine images of the fruit in their minds. At the same time, she quietly projected faint images of the fruit onto the white wall and asked them if they saw anything. As a result, all the participants thought they didn't see anything, even though they thought they had imagined a particularly sober image of the fruit.

Perky's results show that when perceiving the outside world interferes with the inner imagination, we mistakenly think that perception is also imaginary. This phenomenon is called "Perky effect" in the field of psychology.

Since then, many researchers have tried to reproduce Perky's findings, some of which have been successful, but many have failed. The biggest problem is that once participants know what the test is about, they tend to give what they think is the right answer.

So under the guidance of Steve Fleming (Steve Fleming), a metacognition expert at University College London, Dijstra designed an experiment that could avoid this problem.

Did you really see the diagonal? The researchers recruited 400 participants online and were instructed to look at a series of photos filled with random noise (similar to what happens when a TV has no signal) and imagine several diagonal lines tilting to the right or left. They were also asked to assess the vividness of imagined diagonals on a scale of 1 to 5.

What the participants did not realize was that in the final round of tests, the researchers slightly modified the image to show several blurred diagonals in the same or opposite direction as the participants imagined. They then asked the participants whether the diagonals they saw were real or imaginary.

Dijstra originally thought the experiment would recreate the Perky effect-when the imaginary image matched the actual image, the participants mistook the actual image for their imaginary result. But the results were contrary to expectations, and the participants were more likely to believe that the diagonals in the image were real.

Still, their results confirmed the Perky effect to some extent: participants who believed it was all imaginary saw more vivid images than those who believed it was real.

In the second round of the experiment, Dijstra and her colleagues did not provide any blurry diagonals in the final round of tests. However, the result is the same: those who evaluate the diagonals seen more vividly are also more likely to think they are real.

A certain threshold determines whether imagination or reality, Dijstra and others believe that the imagination in mind is very similar to the visual signals generated by perception in reality. When the signal is strong and vivid enough, we will think that it comes from reality. Whether the brain regards visual signals as reality or imagination, there is likely to be a threshold. But she also suggested that the distinction could also be a more gradual process.

Their research means that the brain must be able to accurately adjust the intensity of mental images to avoid confusing imagination with reality.

They also found that this signal strength can be read or adjusted in the frontal cortex, an area of the brain thought to be the command and control center of the brain.

However, it is not clear which factors will affect the vividness of the psychological image and the gap between the signal intensity and the realistic threshold. The influencing factors may be neurotransmitters, changes in neural connections, or something completely unrelated. There may even be a subset of undiscovered neurons that are responsible for setting realistic thresholds and determining whether the signal should be treated as imaginary or real.

The difference between the research of Dijstra et al and that of Perky may be due to the different design of the experiment. However, the differences in the results also suggest another possibility: we may perceive the world differently from people in the past.

Nowadays, people have become accustomed to computer images, videos and other ways of expressing reality, so people often look forward to seeing extra things. In other words, the reality threshold of people today may be lower than in the past, and if the imaginary images are vivid enough, they will exceed the reality threshold and make the brain think they are real.

The mechanism of making the imagination more real may be applied to other situations. Dijstra, for example, believes that when people become sleepy and reality and dreams begin to blend, their reality threshold may be lowering. The mechanism can also explain why people with diseases such as schizophrenia, high hallucination and post-traumatic stress disorder have hallucinations: one is that their imagination is so vivid that they can exceed the realistic threshold; the other is that their realistic threshold is set too low.

Therefore, the in-depth study of realistic threshold may bring new research ideas for the treatment of some mental or neurological diseases.

Dijstra eventually wanted to find out whether they could manipulate the system to make the imagination more real. If this can be done, it can be applied to virtual reality technology, or nerve implants for medical purposes (such as implants that help blind people regain their eyesight). Maybe in the future, according to your own needs, you can make the virtual reality more real or unreal by turning the knob on the device.

References:

Https://www.nature.com/articles/s41467-023-37322-1

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