A Systems-Based Understanding of Visual Processing, Mental Imagery, and Their Absence

Aramis Daniel Munoz-Valverde. Department of Bioethics, School of Global Public Health, New York University. 2025.

The Question

The brain's visual system is one of the most studied systems in all of neuroscience. So why do we still not fully understand what goes wrong in aphantasia? This paper asks whether building a clear map of how visual processing actually works, step by step, can explain why some people cannot generate mental images even though their vision is completely intact.

The Discovery

Think of the brain as having a request system and a display system. The display system is the visual cortex, the part of the brain at the back of your head that processes what you see. It works perfectly in people with aphantasia. The request system lives toward the front of the brain. It is the part that decides what you want to think about or imagine. When a typical imager wants to picture an apple, the front of the brain sends a signal backward through several relay stations until it reaches the visual cortex, which then lights up with a pattern that becomes the mental image. The whole loop constantly checks and corrects itself, like a phone call where both people are confirming they can hear each other.

In aphantasia, the request goes out but does not complete the journey. The front of the brain tries to send the signal. The display system is ready to receive it. But somewhere in the middle, the connection does not come through strongly enough to produce an image.

The paper also makes an important distinction. People who have no imagery in any sense at all, no visual, no sound, no feeling in their mind, appear to have a disruption earlier in the process, closer to the request side. People who only lack visual imagery but can still imagine sounds or other sensations appear to have a disruption further along, closer to the visual display side. Same condition, different location of the problem.

The Insight

A person with aphantasia can see the world perfectly. Their eyes work. Their visual cortex works. What is different is the brain's ability to run that system in reverse, using thought to generate a visual pattern rather than the eyes. That is a completely separate process, and it runs on a separate pathway.

The One Thing to Remember

Aphantasia is not a broken visual system. It is a disruption in the line of communication between the part of the brain that makes requests and the part that would generate the image. The display works. The request is not getting through.

The Connection

The No Picture Needed paper describes aphantasia as a difference in how information is accessed, not a failure of intelligence or effort. This research gives that idea a specific location in the brain. When a student with aphantasia cannot picture something on demand, there is an actual, physical explanation for why. The circuit that would run that process is not completing the loop. That is about as far from laziness as you can get.

You can read the full paper by clicking here.