An FMRI Study Of Chinese Sign Language In Cerebral Functional Cortex Of Prelingual Deaf Signers

Objective: observe the changes of cerebral functional cortex in prelingual deafsingers for Chinese sign language(CSL) so as to identify the difference between suchpatients and normal individuals [hearing non-signers(HnS), hearing native signers(HNS) and hearing later signers(HLS)].Materials and methods: 14 prelingual deaf singers (groupⅠ), 13 HnS (groupⅡ), 11 HNS (groupⅢ) and 12 HLS (groupⅣ) were examined. The prelingual deafsingers are all lost hearing before 2 years old, and are all severe or profoundlysensorineural hearing loss which were examined by pure tone test, the patients in thisgroup are aged from 18～26 with the average age is 21.9, of whom 4 are male and 10are female. HnS who never contact with CSL are aged from 19～25 with the averageage is 23.2, of whom 5 are male and 8 are female. HNS were born to deaf parents andwho acquired both CSL and Chinese as native languages. The subjects in this groupare aged from 18～24 with the average age is 22.9, of whom 8 are male and 3 arefemale. HLS are the teachers of school for deafmutes or memenbers of deafassociation. All of them never study CSL before the age of 18. The duration of usingCSL is 2 to 4 years with average duration is 2.5 years. The subjects in this group areaged from 20～26 with the average age is 22.5, of whom 5 are male and 7 are female.The pure tone test results of hearing individuals are all less than 25dB. All of thesubjects were right-hand dominant and none of them had serious impairments of theheart, liver, kidney, etc. or history of cerebral tumors and other cranial or cerebraldiseases or psychopharmaca-taking history. The tasks for each group were to observeand imitate CSL. The occurrence of stimulus turned up in way of visual presentation. Results: There were no statistical differences about the age and gender in thesefour groups (ANOVA and chi-square test for the age and gender respectively, P＞0.05).The activated areas in all groups include bilateral frontal lobe, temporal lobe, parietallobe, occipital lobe and bilateral cerebellar hemisphere. The activation of bilateralsuperior temporal gyrus and inferior parietal lobule were found in groupⅠand groupⅢin both observing and imitating CSL, but no activation in others. The activation ofbilateral inferior frontal gyrus were found in groupⅠ, groupⅢand groupⅣ, butno activation in groupⅡ. During observing CSL, there were statistical differences(p＞0.05) about the activated voxel in bilateral inferior frontal gyrus, superior temporalgyrus, superior parietal lobule, cuneate lobe and lingual gums. The activation of groupⅠwas greater than that of groupⅢandⅣin bilateral inferior frontal gyrus. Theactivation of groupⅠwas greater than that of groupⅢin superior temporal gyrus.The activation of groupⅠwas greater than that of groupⅡ,ⅢandⅣin bilateralsuperior parietal lobule, cuneate lobe and lingual gurus. The activation of groupⅢwas greater than that of groupⅣin left superior lobule. There were no statisticaldifferences about the activated voxel in other activated areas. There were no statisticaldifferences about the intensity change in the functional cortex among all groupsexcept for groupⅠwas greater than that of groupⅢin left superior temporal gyrus(p＜0.05). During imitating CSL, there were statistical differences (p＞0.05) about theactivated voxel in bilateral inferior frontal gyrus, superior temporal gyrus, superiorparietal lobule, cuneate lobe and lingual gurus. The activation of groupⅠwas greaterthan that of groupⅢandⅣin bilateral inferior frontal gyrus. The activation ofgroupⅠwas greater than that of groupⅢin superior temporal gyrus. The activationof groupⅠwas greater than that of groupⅡ,ⅢandⅣin bilateral superior parietallobule, cuneate lobe and lingual gurus. The activation of groupⅡwas greater than thatof groupⅢand groupⅣin left cuneate lobule. There were no statisticaldifferences about the activated voxel in other activated areas and intensity change inthe functional cortex among all groups (p＜0.05). In groupⅠ, the activation of bilateral inferior frontal gyrus, superior parietal lobule and left middle temporal gyrusin imitating task were greater than that of in observing task (p＜0.05). In groupⅢ, theactivation of bilateral inferior frontal gyrus in imitating task were greater than that ofin observing task (p＜0.05). In groupⅣ, the activation of bilateral inferior frontalgyrus in imitating task were greater than that of in observing task (p＜0.05). Therewere no statistical differences about the intensity change in the functional cortexbetween observing and imitating tasks (p＞0.05). There were no statistical differencesabout the activation and intensity change in the symmetrical functional cortex in allgroups during observing and imitating tasks (p＞0.05).Conclusion: The functional cortex in prelingual deaf singers has occurredcrossing-model reorganization, after losing their auditory and learning the CSL.Bilateral inferior frontal gyrus (Broca's area), superior temporal gyrus (Wernicke'sarea) and superior parietal lobule activation can be found during oberserving andimitating CSL. It is bilateral-equilibrium and no linguistic hemisphere's predominanceexits. The extent of activation in bilateral inferior frontal gyrus (Broca's area) andsuperior parietal lobule are greater during imitating task, it suggests Broca's areaproducing CSL, whereas the activation of bilateral superior temporal gyrus(Wernicke's area) was similar between oberserving and imitating CSL, which takeresponsibility of receptiving and understanding of CSL. During observing andimitating CSL, the secondary auditory cortex (BA42) and association area (BA22) ofdeaf singers can be activated, illustrating that it turns to take part in the processing ofvisual language when no auditory afference, whereas the primary auditory cortex(BA41) do not participate the reorganization. Addtionally, the visual cortex of deafsingers is more sensitive than those of heaing individuals. The reorganization offunctional cortex in deaf singers is related to the expericence of CSL, but is mainlycaused by the effect of hearing loss.