Reading in the Deaf: Neuroanatomical Underpinnings of Fluent Reading

Daphne Bavelier, Ph.D.

University of Rochester

Funded in December, 2004: $100000 for 3 years
LAY SUMMARY . ABSTRACT . HYPOTHESIS . SELECTED PUBLICATIONS .

LAY SUMMARY

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How Do Some People Who are Deaf Develop Fluent Reading Abilities?

Rochester investigators will combine behavioral tests with brain imaging to understand how people who are deaf acquire reading skills.  Their research could lead to improvements in methods for helping deaf people increase their capacity to read. 

While research shows an association between greater residual hearing and better reading skills, some profoundly deaf people acquire above-average reading skills. The investigators will identify the factors involved.  They will use MRI to show standard left-brain language areas and the corresponding right-brain areas used, and relate these observations to reading ability. Their first hypothesis: learning American Sign Language (ASL) early correlates with reading ability and use of working memory.  Do participants show on fMRI that they rely on visual strategies usually absent in normally hearing adults?

Their second hypothesis: oral speech training promotes higher reading skills compared to ASL signers.  On imaging, do deaf people develop a model of the sound structure of English that promotes involvement of the language (left-brain) hemisphere during reading?  Their third hypothesis: exposure to natural language facilitates reading acquisition.  Orally-trained and ASL signers will be expected to read better than users of “Signed English” (a manual communication system that violates language structure rules).

Significance:  This project could advance understanding of how factors, other than residual hearing, affect the ability of deaf individuals to learn to read at higher levels.  The results could be used to devise improved instruction methods.  

ABSTRACT

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Reading in the Deaf: Neuroanatomical Underpinnings of Fluent Reading

The central goal of this project is to understand how deaf individuals acquire reading skills. It is well known that the greater the residual hearing, the better the reading skills. This relationship explains, for the most part, the lower reading skills observed in the deaf community. However, above average reading skills have been noted in some profoundly deaf individuals, indicating that literacy can be achieved even in the absence of hearing. In this proposal, we focus on individuals who have had little-or-no access to the speech sounds of English through the auditory modality in order to determine those factors that facilitate reading above and beyond residual hearing. We propose to use the recruitment of standard left hemisphere language areas and their homologous areas on the right, as measured by fMRI, in conjunction with behavioral markers to characterize the reading strategies used by profoundly deaf readers.

Our first aim is to test the hypothesis that early acquisition of a sign language can promote reading by providing foundations necessary to develop literacy, such as a general understanding of the world and language use early on during development. We will test the hypothesis that sign language proficiency and working memory abilities are positively correlated with better reading skills. Using fMRI, we will ask whether this increase may rely on visual strategies usually not observed in hearing individuals.

Our second aim is to determine the impact of training in speech reception and production on reading by studying deaf readers who have had minimal access to signed communication, but have been orally trained. We will test the hypothesis that deaf individuals can develop a model of the sound structure of English, even in the absence of remaining hearing, and that this skill promotes the recruitment of the left hemisphere during reading. Finally, we will test the extent to which exposure to a natural language facilitates reading acquisition by comparing the two previous groups with deaf people who use a manual communication system (Signed English) that violates some of the regularities found in natural languages, such as English or American Sign Language.

HYPOTHESIS

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Hypothesis:
We will first test the hypothesis that early acquisition of a natural language, such as American Sign Language (ASL), fosters skilled reading as it allows the individual to develop fully-fledged linguistic skills (Mayberry et al., 2002). We will also test the hypothesis that oral training promotes reading abilities as it provides the learner with an opportunity to better understand the phonology of English. Finally, we will contrast the effects of natural language exposure such as ASL or English with the use of communication devices such as Signed English, which have been devised by hearing committees to promote reading but which violate basic principles of natural language.

Goals:
We will characterize the factors that promote proficient reading in deaf individuals. Whereas the amount of residual hearing is one of the best predictors of reading ability in the deaf population, our work focuses on factors above and beyond residual hearing. By studying factors that can facilitate English proficiency, other than residual hearing, our work aims at providing an adequate safety net for all deaf children—the most commonly cited functional disability in deaf persons is a problem acquiring literacy levels equivalent to that of their hearing peers.

Methods:
Comprehensive and reliable assessment of language skill in English and in ASL will be combined with brain imaging to assess reading proficiency in the deaf population as a function of ASL and English skills, and to characterize the neuroanatomical regions that mediate reading as a function of  language background and reading proficiency.

SELECTED PUBLICATIONS

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Bavelier D., Newport E., Hall M., Supalla T., and Boutla, M.  Persistent difference in short-term memory span between sign and speech: Implications for cross-linguistic comparisons.  Psychol Sci. 2006 Dec;17(12):1090-2.

Mohammed T., Campbell R., MacSweeney M., Milne E., Hansen P., and Coleman M.  Speechreading skill and visual movement sensitivity are related in deaf speechreaders.  Perception. 2005;34(2):205-16.

Cohen L., Lehéricy S., Chochon F., Lemer C., Rivaud S., and Dehaene S.  Language-specific tuning of visual cortex? Functional properties of the Visual Word Form Area.  Brain. 2002 May;125(Pt 5):1054-69.