I also struggle to create mental imagery. In this scenario, I do imagine a scene, but it’s not generally composed of imagery. I’m aware that this probably won’t make sense to someone who has a primarily visual imagination, but when I’m imagining a scene like this, it’s more like a network of facts in my head—I piece together the underlying concepts behind what’s being described, rather than a visual representation of them.
For example, if I’m imagining a room full of people, I’ll have a mental model of everyone’s positions in the room, which I’ll then update if the story mentions that someone is stood at the left of the room and I’m imagining them at the right. However, I don’t have a picture of the room in my head while I’m doing this, there’s no image of where the people are stood—it’s just something I ‘know’.
If I’m given a description of a person’s appearance, I incorporate facts about their appearance in my mental model of them, but I still don’t form a mental image representing them. If I was asked to draw someone that was described to me, I could attempt it (despite my poor drawing skills), but I would be converting my mental model into a picture at this stage—I wouldn’t be drawing from a picture in my head. When I try to recall a fictional character, my mental model of them is overwhelmingly based on things like personality traits, and my perception of how their mind might work. I can remember details of appearance, but they take the form of ‘has ~5cm, dark straight hair’, rather than a picture of how said hair might look.
I’m not an expert either, but from what I’ve read on the subject, most of the neocortex does work like this. The architecture used in the visual cortex is largely the same as that used in the rest of the cortex, with some minor variations. This is suggested by the fact that people who lose an area of their neocortex are often able to recover, with another area filling in for it. I’m on a phone, so I can’t go into as much detail as I’d like, but I recommend investigating the work of Mountcastle, and more recently Markram.
Edit: On Intelligence by Jeff Hawkins explains this principle in more depth, it’s an interesting read.