It is entirely possible I'm still using my visual cortex. I was once sighted. When I'm in flow my wife tells me that my eyes spasm as though they're following some kind of pattern in space. I'm not aware I was doing this until she mentioned it. I can say, however, that I'm not visualizing the way I once did. In fact, because I don't have a visual input, conjuring up some kind of imaginary visualization would actually slow me down and be a cognitive burden.