The effects of linguistic experience on cerebral lateralization for speech production in normal hearing and deaf adolescents

The cerebral lateralization patterns for speech production in 57 normal hearing and deaf adolescents were studied using the dual-task paradigm. Normal hearing subjects showed left hemispheric dominance for speech production, whereas both the congenitally deaf and those with early acquired deafness showed atypical cerebral representation for speech production. Deaf subjects whose hearing loss occurred after 2 years of age displayed a pattern of mixed cerebral dominance related to complexity of speech production or task difficulty. These results are interpreted as evidence for a relationship between linguistic/cognitive stage of development and the ontogenesis of cerebral lateralization. A parallel lateralization hypothesis of left cerebral dominance for speech production is offered.