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Seeing speech and seeing sign: insights from a fMRI study
1Division of psychology and Language Sciences, Deafness, Cognition, and Language Research Centre, University College London, UK. r.campbell@ucl.ac.uk
International Journal of Audiology
|November 26, 2008
Summary
Deaf individuals show strong activation in auditory brain regions when speechreading. Speechlike mouth movements in sign language also activate these same auditory areas, suggesting preferential access for oral speech information.
Area of Science:
- Neuroscience
- Auditory Processing
- Sign Language Linguistics
Background:
- Deaf individuals often rely on visual cues for language processing.
- The role of auditory cortex in processing visual speech information is not fully understood.
Purpose of the Study:
- To investigate brain activation patterns in deaf signers during silent speechreading and sign language processing.
- To explore the neural basis of how speechlike mouth movements influence language processing in the deaf.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used to study deaf native signers of British Sign Language (BSL).
- Participants processed silently spoken English words (speechread) and British Sign Language (BSL) signs.
Main Results:
- Deaf participants showed significant activation in the left superior temporal cortex, including auditory regions, during speechreading compared to hearing individuals.
- Cortical activation patterns in BSL processing varied with the presence and type of mouth actions accompanying manual signs.
- Speechlike oral actions in BSL differentiated activation patterns from signs using only manual actions.
Conclusions:
- Speechlike mouth actions, whether in speechreading or sign language, preferentially activate 'auditory speech' regions in the left superior temporal cortex of deaf individuals.
- This suggests a potential neural pathway for visual speech information to access auditory processing areas.
- Findings have implications for spoken language acquisition in deaf children and interventions like cochlear implantation.
