Abstract
BackgroundSign-language comprehension activates the auditory cortex in deaf subjects. It is not known whether this functional plasticity in the temporal cortex is age dependent. We conducted functional magnetic-resonance imaging in six deaf signers who lost their hearing before the age of 2 years, five deaf signers who were >5 years of age at the time of hearing loss and six signers with normal hearing. The task was sentence comprehension in Japanese sign language.ResultsThe sign-comprehension tasks activated the planum temporale of both early- and late-deaf subjects, but not that of hearing signers. In early-deaf subjects, the middle superior temporal sulcus was more prominently activated than in late-deaf subjects.ConclusionsAs the middle superior temporal sulcus is known to respond selectively to human voices, our findings suggest that this subregion of the auditory-association cortex, when deprived of its proper input, might make a functional shift from human voice processing to visual processing in an age-dependent manner.
Highlights
Sign-language comprehension activates the auditory cortex in deaf subjects
Pettito et al [3] observed increased activity in the superior temporal gyrus (STG) in native deaf signers compared with hearing non-signers. These findings suggest that the changes associated with audio-visual cross-modal plasticity occur in the auditory-association cortex
All groups showed activation in the occipito-temporal junction extending to the portion of the STG posterior to the Vpc line
Summary
Sign-language comprehension activates the auditory cortex in deaf subjects It is not known whether this functional plasticity in the temporal cortex is age dependent. Using functional MRI (fMRI), Neville et al [1] observed increased activity in the superior temporal sulcus (STS) during the comprehension of American Sign Language (ASL) in both congenital deaf subjects and hearing native signers. Nishimura et al [2] found that activity was increased in the auditory-association cortex but not the primary auditory cortex of a prelingual-deaf individual during the comprehension of Japanese sign language (JSL). After this patient received a cochlear implant, the primary auditory cortex was activated by the sound of spoken words, but the auditory association cortex was not. The authors suggested that (page number not for citation purposes)
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