The central processing mechanism for visual and tactile language demonstrated by functional brain imaging technique a review of literature

We reviewed the literature related to the processing of visual and tactile language in the central nervous system as demonstrated by functional brain imaging techniques. Written word recognition activates not only the visual association areas but also the temporal region, especially in lexicsemantic processing. In lip reading and sign language recognition, the auditory association areas may play an important role in addition to the visual association areas both in the case of normal subjects and congenitally deaf subjects. In the case of congenitally blind subjects, visual association areas may play an important role in the processing of speech and Braille reading. In the case of congenitally deaf subjects, the auditory cortex may be involved in the processing of vibratile stimuli. These findings suggests the cross-modal plasticity of the brain in the processing of language. This paper also discusses problems to be resolved in the future.