This study visualizes grammar learning. We first understand why words are put into a particular order because we recognize similarities between word locations and meaning in other sentences. We pick up most of our grammar this way...just by immersion, rather than being taught rules. Children with auditory processing difficulties may have difficulty with this approach though, because they may drop out words and miss details frequently in ordinary conversational speech. For them, visual examples (text, sentence diagramming) need to be given, and patterns recognized before the information begins to condense as a 'rule'. The second link below is one of our favorite grammar resources on the web.
Grammar and the Brain
OWL Handouts: Grammar, Punctuation, and Spelling