Visualizing

I am a sighted person.  If I had not ever known sight, I wonder how I would imagine things. How would I “visualize”?  How did Helen Keller, without sight OR hearing, form pictures in her head — and did she?  In the movie “Mask” I remember that the main character handed fluffy cotton balls to someone without sight, to describe clouds — and it seemed effective, at least in the film.  I recently heard of a woman who had been unsighted for her entire life and had undergone an operation that enabled her to have vision.  She previously used Braille for reading and now expressed desire to learn a visual alphabet.  I got to thinking about what sort of change her brain will enact, to go from a tactile to a visual form of reading.  What an amazing challenge.