Interoception, insula, and agency: a predictive coding account of aphantasia
Silvanto, J. (2025). Interoception, insula, and agency: a predictive coding account of aphantasia. Frontiers in Psychology, 16. doi:10.3389/fpsyg.2025.1564251
Abstract
Researchers have proposed a new explanation for aphantasia—the inability to voluntarily create mental images—suggesting it may result from how our brain processes internal bodily signals (called interoception) through a brain region called the insula. The theory has two key components: individuals with aphantasia may struggle to integrate bodily sensations with mental processes, which normally gives imagery its "embodied" quality, and they may experience reduced "sense of agency" over generating mental images. Using a "predictive coding" framework, researchers suggest our brain normally creates mental imagery through top-down predictions from higher brain regions to sensory areas, but in aphantasia, these predictions don't receive enough amplification due to reduced precision of interoceptive signals, preventing imagery from reaching conscious awareness. Interestingly, many people with aphantasia can still experience visual dreams, suggesting the issue isn't with visual processing itself but with voluntary image creation, and the theory also explains why people with aphantasia often have difficulties integrating information across different senses.
Authors
- Juha Silvanto8
Understanding Why Some People Can't Visualize: A New Theory of Aphantasia
Imagine being asked to picture your childhood home in your mind. For most people, this triggers a vivid mental image—you can "see" the front door, recall the colors, maybe even smell the air. But for about 2-3% of the population, nothing happens. They have aphantasia, a condition where people simply cannot create mental images, no matter how hard they try. It's as if their mind's eye has gone dark.
For decades, this phenomenon puzzled neuroscientists. How could someone's brain fail at something so fundamental to human experience? The leading theories focused on the visual cortex—the brain's image-processing center—suggesting it wasn't communicating properly. But a new theory by psychologist Juha Silvanto offers a surprising twist: perhaps the real problem isn't in the visual system at all, but in a much deeper part of the brain involved in how we sense our own bodies.
Silvanto proposes that aphantasia stems from disrupted processing in the insula, a brain region tucked deep inside the cerebral cortex that acts like an internal monitoring system. This region constantly tracks signals from your heart, stomach, and muscles—what scientists call interoception, essentially your brain's awareness of your internal bodily state. It's background information you rarely notice but constantly rely on. According to this new framework, mental imagery isn't just a visual trick; it's fundamentally tied to your sense of self and your ability to control your own thoughts.
Here's where it gets interesting. Silvanto draws on a theory called predictive coding, which suggests our brains don't passively receive information—they actively predict what should happen next based on past experience. When you voluntarily imagine something, your prefrontal cortex (the decision-making part of your brain) generates predictions that activate visual areas, conjuring up the mental image. But here's the catch: for these predictions to actually reach your conscious awareness, they need something called "gain"—basically, a volume dial that determines how much those predictions matter.
The insula controls that volume dial. It estimates how reliable your internal body signals are and then either turns up or down the gain on the prefrontal cortex's predictions. Think of it like quality control: if your body signals are noisy or unreliable, the insula essentially says, "Don't trust these predictions," and turns down the volume. The predictions fail to activate the visual cortex strongly enough to create a conscious image.
In people with aphantasia, Silvanto argues, this system goes wrong in a specific way. The insula struggles to properly process interoceptive signals, so it misjudges how reliable they are. This affects two things simultaneously. First, it weakens your sense of agency—the feeling that you're in control of your own actions and thoughts. Just like your brain uses internal predictions to anticipate how your arm will move when you reach for a cup, it uses similar predictions to anticipate and control mental imagery. When the insula downregulates these predictions, it becomes harder to feel like you're consciously directing your thoughts. Second, it disrupts embodiment—the sense that mental content is grounded in your physical self and belongs to you personally.
The beauty of this theory is that it explains why aphantasia seems so different from other visual problems. If someone has damage to the visual cortex from a stroke, they might lose the ability to see external images. But with proper rehabilitation and external feedback from the real world, their brain can often adapt and compensate. Mental imagery, however, gets no such external help. It relies entirely on internal predictions. Without the insula properly anchoring these predictions in body signals, they simply never reach consciousness. It's like trying to have a conversation in a room where someone keeps turning down the volume on your voice—the words are there, but nobody can hear them.
This model remains largely theoretical for now. Silvanto openly acknowledges that while the logic is compelling, direct empirical evidence specifically linking disrupted interoception and imagery in aphantasia is still limited. Researchers will need to conduct neuroimaging studies and behavioral tests to verify whether people with aphantasia actually show reduced interoceptive signal processing and weaker connections between the insula and visual regions.
If the theory holds up, it could fundamentally reshape how we think about mental imagery and consciousness itself. It suggests that imagination isn't isolated in the visual cortex but deeply woven into our sense of bodily self—a reminder that our minds don't exist in abstract space but are anchored to the physical reality of our bodies. For the millions of people with aphantasia, this research offers hope for better understanding their condition and potentially developing interventions that help strengthen the signals between brain regions responsible for interoception, agency, and conscious thought.
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