Complex sentence: Dyslexia is "a cluster of language-related conditions in which reading problems reflect impairment in the representation and manipulation of phonemes" that is thought to have two kinds of causes, one related to language processing, and the other, to visual processing.
Split into simpler sentences: Dyslexia is "a cluster of language-related conditions in which reading problems reflect impairment in the representation and manipulation of phonemes". It is thought to have two kinds of causes, one related to language processing, and the other, to visual processing.