"This is something new to me, not something I've always experienced. And I didn't even realize that it was a thing until I read an article about it. I've recently taken up meditation (about a year ago). It's a Vipassana style meditation practice, but not programatic - I based it on readings and a handful of guided meditations. I found sometimes intense visual artifacts in my "theater of the mind" to be distracting, and tried to eliminate them by not giving them any of my attention. After a couple of months, I succeeded. Now the stage is dark, with only the occasional blip, leakage of light sometimes through my eyelids, and something like a faint afterglow, especially when I first start a meditation.
Later I read an article about aphantasia in a journal, and thought hmm, what do I experience? To my surprise, I found (in the past two or three months) that when I try to visualize anything, I only get a faint ghostlike image, which vanishes almost immediately. This includes faces, places, and physical objects. Just enough to register. It's as if my brain has been trained to minimize the resources involved in the visual channel, serving up the minimal amount of information necessary. I am certain that it wasn't always this way and I never noticed the change until I looked for it. I took the VVIQ online and scored low enough that I could be considered to have at least mild aphantasia.
Naturally I conjectured that there was a link between the meditation practice and aphantasia. I didn't find any clinical evidence of such a linkage in the science literature. So it may be a coincidence, or, it may be confirmation bias on my part. But I have determined over many weeks that I can look at something intensely, and if I close my eyes I can only visualize it faintly and only for a second. I can conjure anything in my memory, but can't hold it for more than a second (literally) before it dissolves into something like an afterglow. I can still describe it, and I have no difficulty recognizing objects or people. It's as if the signal now mainly operates in my subconscious. And it wasn't always this way.
I definitely have an inner voice, which is also being affected by the meditation practice. The effect isn't nearly as noticeable as my visualizations however.
When I was in my 20s I took an weeklong battery of intensive tests of aptitudes and skills and was told that I was a "visual thinker", and would have problems with tasks that involved a lot of words. The testers recommended that I supplement verbal communication with visuals like charts and graphs. This seems like a good benchmark for the changes I've experienced.
There's one more possibly noteworthy development. My work (environmental planning and policy) is spatially oriented, and I often dream within landscapes - in other words, the landscape is a prominent feature of the dream. And lately, I've noticed that I dream in maps! Symbolic representations rather than visual constructions. This is definitely a new experience. Geographic data is sometimes non-Euclidean, drawing on mathematical tools like graph theory, so "maps" aren't always pictorial representations; they can be quite abstract.
I don't have good enough control over dream recollection to know if this is a replacement or an addition. But I have also been dreaming in words a lot. I don't know if that's new, or if I am just looking for confirmation.
So possibly I have aphantasia, or maybe something else is going on. So far, it doesn't affect my daily life (I'm 69, and work from home at a computer most of the time, and slowly losing my hearing). There's no clear benefit or detriment - it's just ... different.
And interestingly, my wife is an artist who has the opposite problem - synesthesia combined with extreme sensitivity to phenomena."