Integration of Sensory Systems
No single sensory system functions in isolation. Visual and auditory systems, which are activated during reading, have been explained separately in order to clarify their unique functions during communication. Sensory input must be integrated in the central nervous system to generate perceptual ideation and to initiate the appropriate motor responses. Learning to read the first language is superimposed on a linguistic system already in place as speech. Auditory functions in reading are well documented and widely accepted. Less understood is the integration of somatic, or bodily, senses in learning to read and in comprehending print. Some typologies distinguish between "language disorders" and "articulatory/graphomotor" disorders. Olson, Kliegel, Davidson, and Foltz analyzed the coding skills, regularity effects, and spelling errors of large groups of poor readers versus superior readers. Vision-based reading disabilities have been described as visuoperceptual disorder syndrome; a dyseidetic form of dyslexia; surface dyslexia; and primarily visuospatial dyslexia.