The brain processes receptively and expresssively in the same way with auditory and visual languages. Once does not listen to one's exressive language production in the same way that one listens to another's expressive language production, thus accounting frot the difference in expressive and receptive skills.
But where is the spaitial aspect of the auditory lang?
People who learn ASL from birth or before the age
of 7 process language in the Left Temporal area
AND the Right Temporal area. But Hearing who do
not learn a manual language do not process language
at all in the right area in this way. So there has to
be a difference in processing receptive even if it may be more
"complete" then for hearing people.