The effect of auditory experience on hemispheric asymmetry in a post-lingually deaf child: a case study.

We have previously shown that cerebral asymmetry in congenitally deaf children differs from that observed in normal hearing children. The effect of early auditory experiences on this process was investigated in a 14 year-old boy who had completely lost his hearing at the age of 5 due to meningitis. His recognition of laterally projected words and faces was compared with that of 18 congenitally deaf and 18 normal hearing children. In the word recognition test, a right hemisphere advantage was found in the patient and in congenitally deaf subjects and a left hemisphere advantage in normal hearing subjects. In the face recognition test, the left hemisphere was more proficient in the patient and the right hemisphere in normal hearing subjects. There was no hemispheric difference in the congenitally deaf. While hemispheric asymmetry has an ontogenetic base, these findings suggest that the degree and nature of such asymmetries can be influenced by environmental factors during development.