Summary: For decades, scientists believed that imagining an apple was simply the brain “replaying” the sensory data of seeing one—a process called sensory reinstatement. However, a precision fMRI study reveals that imagination is far more sophisticated.
The team found that imagination doesn’t just mimic raw sight or sound; it emerges in high-level association networks where the brain transforms sensations into holistic concepts, scenes, and language. This suggests that our ability to “see” with our mind’s eye is hardwired into the very brain regions that make humans uniquely advanced at planning and speculation.
Key Facts
- Beyond Raw Sensation: Imagination activity overlapped with actual perception primarily in “transmodal” association areas—the parts of the brain that handle abstract meaning—rather than the primary visual or auditory cortices.
- The Network Split: What you imagine determines which “highway” the brain uses. Imagining scenes (like a castle) taps into the Default Network and hippocampus, while inner speech activates the Language Network.
- The Vividness Link: The study found that the more “vivid” a participant reported their imagination to be, the more active these higher-order association regions became.
- Evolutionary Edge: These association areas are significantly more expanded in humans than in our primate ancestors, suggesting that our rich “inner life” is a key part of what makes us human.
Source: Northwestern University
Imagination is one of the most powerful things our brains can do. We can relive past events while taking a walk, rehearse future conversations through inner speech or sense the heat of a fire without touching it — allowing us to learn, plan and avoid danger without direct experience.
Why imagination is often accompanied by mental imagery remains a longstanding question. When one thinks of an apple, for example, many “see” an image of an apple in their mind.
When one thinks of their favorite song, many “hear” that song playing in their mind, including vocals and specific lyrics. Mental imagery has often been thought to rely mainly on reactivating the brain’s sensory regions in the absence of input — a process known as sensory reinstatement.
But a new Northwestern University study suggests that higher‑level brain systems that interpret and organize perception may also play a central role in imagination.
The scientists asked study participants to imagine different scenarios, such as a child’s birthday party or a castle on a hill, while undergoing individual‑level precision fMRI scanning. The findings suggest that imagination is not simply a copy of sensation. Instead, it appears to emerge at later stages of processing, when the brain represents information holistically as scenes, words, events or ideas rather than raw sensory input.
“When you ask someone to imagine the sound of a kid’s birthday party, they don’t just hear it — they also automatically picture the scene,” said senior author Rodrigo Braga, assistant professor of neurology at Northwestern University Feinberg School of Medicine.
“It makes sense that imagination operates in this holistic, higher‑level space, given that we use it to plan, understand and speculate.”
The study will publish March 31 in Neuron.
The findings suggest mental imagery is closely tied to higher-level cognitive functions, as opposed to being a strictly sensory phenomenon.
“Our study doesn’t refute sensory reinstatement theory, but it does suggest we need to refine it,” Braga said. “It’s not just the sensory parts of the brain that are involved. When people imagine rich scenes or an internal dialogue, the strongest overlap with perception appears in later stages, where sensation has already been transformed into meaning.”
How the study worked
Eight study participants imagined different scenarios during eight separate MRI sessions, as part of a study that resulted in more than 60 hours of fMRI data. The scientists mapped each participant’s sensory and association networks and compared brain activity during imagination with activity during actual perception. They found brain activity related to imagining and perception overlapped in the higher-level association areas, not the early sensory areas.
“These association areas are particularly interesting because they are greatly expanded in the human brain compared to our close evolutionary ancestors,” Braga said.
“They also allow humans to do things we are particularly advanced at, such as communicating using language. This suggests that the generation of mental imagery relies on brain networks that are particularly prominent in the human brain and suggests that these association areas likely work with earlier sensory parts of the brain to institute mental experiences.”
After exiting the scanner, participants self-reported what they had imagined in the scanner, which allowed the scientists to relate each participant’s subjective reports about each imagined item with their own brain activity patterns. The participants reported that they experienced vivid visual imagery when imagining scenes and vivid sound imagery when imagining speech.
The data supported two insights into mental imagery: First, different types of imagining activated different networks, Braga said. When people thought about scenes, they were tapping into parts of a brain network called the “default network” — which works with the hippocampus (a key memory structure) to support internally generated thought such as when we think about the past or future. But when they used inner speech or thought about speech, they activated a different network called the “language network.”
Despite these differences, in both cases, imagination overlapped with perception primarily in high-level, transmodal brain regions rather than sensory-specific regions.
“The default network has sometimes been implicated as the brain’s ‘hub’ for mental imagery,” said first author Nathan Anderson, a former postdoctoral fellow at Northwestern.
“Our results do show that the default network is generally engaged during imagining, but we also see different large-scale brain networks activated depending on what you are imagining.”
Activity in these association regions also tracked how vivid participants reported their imagery to be, suggesting that naturalistic imagination relies especially strongly on higher‑order interpretive systems, Braga said. The results advance our understanding of how the brain supports self-generated and sensory-independent forms of thought, Braga said.
The findings do not mean the brain’s sensory cortex is irrelevant, Braga emphasized, but they suggest a more nuanced understanding of how the brain generates mental imagery.
The study is titled, “Mental imagery and perception overlap within transmodal association networks.”
Key Questions Answered:
A: Your brain makes you feel like you are, but this study shows that the most intense activity isn’t in the “hearing” part of your brain. Instead, it’s in higher-level areas that interpret the song’s meaning, structure, and lyrics. Your brain is essentially “assembling” the concept of the song rather than just hitting “play” on a recording.
A: While this study didn’t focus on aphantasia specifically, it found that the vividness of imagery directly tracks with activity in these high-level association regions. This suggests that a “vivid” imagination depends on how strongly these “meaning centers” can communicate with the rest of the brain.
A: Exactly. The study showed a clear split: Daydreaming about places or the future (mental time travel) uses the Default Network. But that “inner voice” you use to rehearse a conversation uses the Language Network. They are two different systems for two different types of imagination.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neuroscience and imagination research news
Author: Kristin Samuelson
Source: Northwestern University
Contact: SfN Media – Northwestern University
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Mental imagery and perception overlap within transmodal association networks” by Nathan L. Anderson, Joseph J. Salvo, Jonathan Smallwood, and Rodrigo M. Braga. Neuron
DOI:10.1016/j.neuron.2026.03.013
Abstract
Mental imagery and perception overlap within transmodal association networks
Human cognition relies on two modes: a perceptually coupled mode where mental states are driven by sensory input and a perceptually decoupled mode featuring self-generated mental content.
Imagined states that evoke mental imagery are thought to be supported primarily by reinstated activity in sensory cortex, but transmodal systems are also implicated in imagery-related processes like mind-wandering, recollection, and imagining the future.
During a precision fMRI experiment, participants imagined different scenarios in the scanner, then rated their mental states using multi-dimensional experience sampling.
Thinking involving scenes evoked activity within parts of the canonical default network, while imagining speech evoked activity within the language network.
In each domain, imagining-related activity overlapped with activity evoked by viewing scenes or listening to speech, respectively; however, this overlap was predominantly within transmodal association networks, rather than adjacent unimodal sensory networks.
We conclude that the engagement of transmodal networks supports self-generated mental states involving different forms of mental imagery.
