How does the brain build mental scenes step-by-step?
Creating a mental image of a scene step-by-step activates different parts of the brain at different times, rather than using one single, continuous process.
Source
Differential engagement of brain regions within a 'core' network during scene construction
What they did
The researchers scanned nineteen healthy participants using a 1.5 tesla MRI machine while they built mental scenes. Participants listened to auditory descriptions and imagined indoor scenes step-by-step by adding 3, 4, 5, or 6 sequential elements. They also performed matched control trials to control for memory load and attention, rating their imagination after each run.
What they found
They discovered that imagining the first element activated both the object-processing network and parts of the core scene network. Adding the second element temporarily deactivated these core areas, but adding a third element reactivated them, marking the point where participants achieved a coherent scene. Beyond 3 elements, adding more details did not further increase activation in the core network.
The limits
What it doesn't show
The study did not establish a causal relationship because functional imaging is correlational. Furthermore, the small sample of nineteen young, healthy individuals might not represent how older adults or individuals with clinical brain damage construct scenes.
Key terms
- scene construction
- The mental process of gathering and combining various sensory, semantic, and contextual details into a cohesive, three-dimensional representation of a space or event.
- core network
- A set of interconnected brain regions—including the hippocampus and default mode network—that consistently activates when people recall memories, imagine the future, or navigate spaces.
- acontextual
- Describing an imagined object that is visualized entirely on its own, without any surrounding background, environment, or associated setting.
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Quiz yourself
What was the key methodological novelty of this study's scene construction task?
Common questions
Why did the hippocampus deactivate when the second element was added?
The researchers suggest that the core network is not continuously active. It is active at the start to set the scene, temporarily quietens as the second element is held in working memory, and reactivates once a third element is added.
Does adding more than 3 elements make a mental scene more vivid?
No, participants reported that vividness actually decreased as they had to maintain 4, 5, or 6 elements, suggesting that after 3 elements, the cognitive load of holding the details in working memory offsets the richness of the scene.
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