ok, thanks .

Isn't the visual cortex of birth-blind people mostly remodeled by neurplasticity into a different task specific area (e.g. auditory processing)?

Most of the researchers agree that, as Karlo said, chidren that lose vision early in life aren't capable of dreaming and visualization because their cortex didn't have enough time to learn how to see. 

"Just as the somatosensory cortex must respond in the appropriate sensory mode, so must the visual cortex during both perception and dreaming. What evidence is there that in the visual cortex there are neurons that respond to a neural stimulus from the retina in a verisimilar manner to that of photoreceptors? This evidence comes from dreams of the blind8. Persons who are congenitally blind or who become blind in early childhood do not have visual dreams. However, if blindness due to ocular disease supervenes after early childhood that person continues to experience visual dreams. This tells us that, in those people with ocular blindness, the visual cortex involved in reproducing the dream action can respond in the visual mode provided it has been given the opportunity to learn. Some five to seven years of ongoing vision are required for the visual cortex to gain this ability to respond in the visual mode. Moreover, the visual cortex retains this function even in the absence of continuing retinal connectivity because individuals who undergo bilateral eye enucleation after childhood likewise have visual dreams. This situation is similar to that of a post-amputation phantom limb in which the somatosensory cortex requires a period of time to permanently acquire the ability to respond to afferent impulses in the appropriate sensory mode." 

from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC539396/

However, I suggest you read attached file by Helder Bertolo et al.: Visual dream content, graphical representation and EEG alpha activity in congenitally blind subjects.

"The observation of alpha attenuation/visual content correlation along with no differences in the graphical representations leads us to hypothesize that blind subjects can produce virtual images, that is, that their dreams correspond to the activation of visual cortical regions. It has in fact been established by several authors that congenitally blind subjects use the visual cortex to process different kinds of information, namely auditory [42,43], tactile [55], somatosensitive [53], and during the encoding and transformation of haptic images [52]. Behind such controversy lies the fact that experience is considered essential both for visual imagery and for visualisation. Visualisation without previous experience, as is the case for congenitally blind, would indicate the existence of visual imagery independent of visual perception. This implies that the born-blind subjects are capable of using other sensory modalities to integrate these inputs via the visual system to produce concepts capable of graphical representation."

Another suggested read: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2814941/

Best regards,

Jan

thanks a lot!