The neural signature of reading in deaf individuals
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The Neural Signature of Reading in Deaf Individuals. Daniel Koo, Joe Maisog, Carol LaSasso, Kelly Crain, Guinevere Eden. Center for the Study of Learning Department of Pediatrics, Georgetown University Department of Hearing, Speech and Language Sciences, Gallaudet University. Outline.

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The Neural Signature of Reading in Deaf Individuals

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The neural signature of reading in deaf individuals

The Neural Signature of Reading in Deaf Individuals

Daniel Koo, Joe Maisog, Carol LaSasso, Kelly Crain, Guinevere Eden

Center for the Study of Learning

Department of Pediatrics, Georgetown University

Department of Hearing, Speech and Language Sciences, Gallaudet University


Outline

Outline

Introduction

  • Deaf populations

  • Communication systems

  • Reading in Deaf populations

    Functional neuroanatomy of reading in deaf and hearing populations

  • ASL

  • English


Introduction to deaf populations

Introduction to Deaf Populations

  • Approximately 28 million Americans have some degree of hearing loss

    • Approximately 600,000 to 1 million are “functionally deaf”

  • Acquired or congenital deafness before the age of 2 has significant implications for language development

  • Communication options:

    • American Sign Language

    • Cued Speech

    • Oral communication

Sources: National Institute on Deafness and Other Communication Disorders, Gallaudet Research Institute, National Center for Health Statistics


American sign language asl

American Sign Language (ASL)

  • Complete and Independent Language

    • Distinct Phonology, Morphology, Syntax

    • No relationship to English

  • Visuo-spatial Language

    • No writing system

    • Fingerspelling as sign-to-orthography correspondence?


Cued speech

Cued Speech

  • A visual/manual system based on the phonemic units of spoken language

  • Developed at Gallaudet College in 1966 by Dr. R. Orin Cornett

  • Designed to disambiguate and supplement information seen through lip-reading alone

  • Uses handshapes and hand placements near the face to visually represent phonemes


Cued speech1

Cued Speech


Asl and cued speech

ASL and Cued Speech


Reading in deaf populations

Reading in Deaf Populations

3rd to 4th grade reading achievement levels (Trybus & Karchmer, 1977; Allen, 1986; Traxler, 2000)

Deaf Signers

Variable reading proficiency but good readers show evidence of phonological influence in rhymed words (Hanson & Fowler, 1987; Hanson & McGarr, 1989)

Deaf Cuers

Skilled readers who show strong phonological awareness (Leybaert et al. 1996; Alegria et al., 1999; Charlier & Leybaert, 2000)

Problem

Parallel studies using different paradigms make comparisons difficult (LaSasso et al., 2003; Koo et al, in press)


Behavioral data

Behavioral Data

Phoneme Detection Test

cent

cat

Koo et al. (in press)


Behavioral data1

*

*

Behavioral Data

Phoneme Detection Test

* p < .05 (2-tailed)

Koo et al. (in press)


Outline1

Outline

Introduction

  • Deaf populations

  • Communication systems

  • Reading in Deaf populations

    Functional neuroanatomy of reading in deaf and hearing populations

  • ASL

  • English


Functional anatomy of word reading

Functional Anatomy of Word Reading

Left Inferior Frontal Gyrus

Sequencing and control of fine-grained articulatory recoding

Phonological Mapping

Left Temporo-Parietal Region

(Inferior Parietal Lobule/Posterior Superior Temporal Gyrus)

Rule-based grapheme-to-phoneme analysis

Left Occipito-Temporal Region

(Fusiform Gyrus)

Linguistically structured memory-based word identification system

Pugh et al. (2000)


Previous neuroanatomical work in deaf populations

Previous Neuroanatomical work in Deaf Populations

Neville et al. (1998)

  • When reading English sentences, hearing subjects showed strong left lateralization in language processing areas (Left IFG and STS). But deaf subjects did not, instead showing robust right STS activity.

  • Interpretation: Deaf individuals rely on the right hemisphere for visual-form information when reading and encoding written English.

From Neville et al. (1998)


Previous neuroanatomical work in deaf populations1

Previous Neuroanatomical work in Deaf Populations

Deaf > Hearing

Aparicio et al. (2007)

  • During a lexical decision task, French deaf subjects activated the same left IFG, left occipito-temporal and inferior parietal regions as hearing subjects

  • Deaf subjects showed significantly higher activation in right IFG, left STG, and posterior medial frontal gyrus

  • Interpretation: Increased use of right IFG and left STG serves as a compensatory mechanism for limited use of the indirect route (assembled phonology)

Adapted from Aparicio et al. (2007)


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