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Different Mechanisms for Supporting Mental Imagery and Perceptual Representations: Modulation Versus Excitation

DOI: 10.1177/09567976231198435
Pace, T., Koenig-Robert, R., & Pearson, J. (2023). Different mechanisms for supporting mental imagery and perceptual representations: modulation versus excitation. Psychological Science, 34(11), 1229–1243. doi:10.1177/09567976231198435

Abstract

Recent research suggests imagery is functionally equivalent to a weak form of visual perception. Here we report evidence across five independent experiments on adults that perception and imagery are supported by fundamentally different mechanisms: Whereas perceptual representations are largely formed via increases in excitatory activity, imagery representations are largely supported by modulating nonimagined content. We developed two behavioral techniques that allowed us to first put the visual system into a state of adaptation and then probe the additivity of perception and imagery. If imagery drives similar excitatory visual activity to perception, pairing imagery with perceptual adapters should increase the state of adaptation. Whereas pairing weak perception with adapters increased measures of adaptation, pairing imagery reversed their effects. Further experiments demonstrated that these nonadditive effects were due to imagery weakening representations of nonimagined content. Together these data provide empirical evidence that the brain uses categorically different mechanisms to represent imagery and perception.

Authors

  • Thomas Pace2
  • Roger Koenig-Robert3
  • Joel Pearson33

What This Study Is About

Researchers wanted to know if imagining an object is just a "weak" version of actually seeing it, or if the brain uses a totally different trick to create mental images. They explored whether the brain "drives" neurons to fire when we see things but "tunes" existing activity when we imagine them.

How They Studied It

The team ran five experiments with small groups of adults (about 15 to 23 people per test). They used a technique called adaptation, which is like "tiring out" specific brain cells by making them look at a pattern for a long time. Once the cells were tired, participants were asked to either look at a very faint real pattern or use mental imagery (the ability to picture things in your mind) to imagine that same pattern.

What They Found

The study discovered that seeing and imagining are fundamentally different. When participants saw a faint real image, it added to the "tiredness" of their brain cells. However, when they *imagined* the image, it actually reversed the effect!
Think of it like a bucket of water:
  • Perception (Seeing): Like pouring more water into the bucket.
  • Imagery (Imagining): Like stirring the water that’s already there.
The researchers also found that people with more "vivid" (clear and lifelike) mental images had a much stronger reversal effect than those with fuzzy imagery.

What This Might Mean

This suggests that mental imagery isn't just "weak seeing." Instead of creating a new signal from scratch, the brain might be "turning down the background noise" of other neurons to let a mental picture emerge.
This helps explain why mental images usually feel less "solid" than real sight. While this study didn't focus specifically on people with aphantasia (the inability to visualize or "see" things in the mind's eye), it provides a roadmap for understanding why their brains might process information differently. Because the study groups were small, we can't be 100% certain yet, but it suggests a "hard limit" on how strong a mental image can ever be.

One Interesting Detail

The researchers found that bright light can actually "disrupt" your mental images. If you’ve ever found it easier to imagine something in a dark room, this study explains why: bright light creates too much "noise" for the brain to tune out!
This summary was generated by AI and may contain errors. Always refer to the original paper for accuracy.