How the Brain Differentiates Reality and Imagination – A New Study Reveals

By Yashika Sharma

May 26, 2023
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Have you ever imagined your crush hanging out with you, but in reality, she just doesn’t bat an eye on your existence?

Brain scans have shown that the neural signals the brain gives off while imagining and seeing something are highly similar but the subjective experience for both is distinct.

The neural systems for perception and reality are observed to be overlapping each other, so a fundamental question arises, how does your brain distinguish between your wildest dreams and hard reality?

According to a study, fictional experiences are coded in a more shallow layer than real experiences in the brain’s visual cortex, which processes images.

The opposite view, advanced by research led by Joel Pearson at the University of New South Wales, is that the same brain pathways code for both imagination and perception, but that imagination is simply a lesser form of perception.

How Does the New Hypothesis Explain Brain’s Perception of Reality and Imagination?

A new study led by Nadina Dijkrsta published in Nature Communications hypothesized a rather interesting answer to the question of reality and perception, it says that “the brain compares the visuals being processed to a “reality threshold.” If the signal crosses the threshold, the brain believes it is genuine; if it does not, the brain believes it is imaginary”.

Such a system might work well most of the time as the “imagined signals” are pretty weak, but if the imagined signal is strong enough to overcome the threshold our brain might take it for reality.

While allowing for a significant increase in cognitive complexity, the existence of stimulus-independent processing poses a fundamental challenge for the nervous system, because internally and externally triggered signals are frequently similar, and there is a significant risk of confusion between perception and imagery1.

Perceptual Reality Monitoring (PRM) refers to the ability to resolve such uncertainty and discriminate between fantasy and reality.

What if Reality and Imagination Get Overlapped in the Brain?

Researchers took inspiration from anecdotal proof that a similar mechanism might come from the perky effect.

The Perky Effect

The Perky effect explains the relationship between imaginative and perceived reality, it was discovered by Mary Cheves Perky in 1910. Her experiment tends to show that the visualization of the image can depress the sensitivity of perception of real visual targets.

There were quite a lot of studies trying to replicate the perky effect but more or less all of those were a hit or miss.

The research modeled and tested the Perky effect as well as two other competing hypotheses on how the brain distinguishes between truth and imagination.

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Were the Researchers Able to Observe the Perky Effect?

During the pandemic’s lockdown, Dijkstra and Fleming recruited for an online study, 400 participants were instructed to look at a succession of static-filled photos and envision diagonal lines tilting through them to the right or left. 

They were asked to judge how vivid the imagery was on a scale of 1 to 5 between trials.

What the participants didn’t realize was that in the previous trial, the researchers gradually increased the intensity of a faint projected image of diagonal lines — tilted either in the direction the participants were taught to visualize or in the other direction.

The researchers next questioned the subjects if what they saw was real or imagined.

Dijkstra anticipated finding the Perky effect — that when the imagined image matched the projected one, the participants would mistake the projection for the result of their imagination.

Instead, the participants were far more inclined to believe the image was real.

However, there was an echo of the Perky effect in those results, participants who believed the image was there saw it more vividly than people who believed it was all in their heads.

In a subsequent experiment, Dijkstra and her colleagues did not show an image during the previous session.

However, the outcome was the same, those who assessed what they were seeing as more vivid were likewise more likely to rate it as real.

To minimize confusion between fiction and reality, the brain must be able to appropriately modulate the strength of a mental image.

They discovered that the signal strength may be read or adjusted in the frontal cortex, which assesses emotions and memory among other things.

However, it is unclear what factors influence the vividness of a mental image or the discrepancy between the strength of the imagery signal and the reality threshold.

It could be a neurotransmitter, a change in neural connections, or something completely unrelated.

The new findings raise the possibility that changes or abnormalities in this system could result in hallucinations, intrusive thoughts, or even dreaming.

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References

  1. Nadina Dijkrsta, Stephen M. Fleming, ‘Subjective signal strength distinguishes reality from imagination‘, 23 May 2023, Nature, https://www.nature.com/articles/s41467-023-37322-1[]
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