Neuroimaging and Reading Research Presented by Mindy Keefer EDSP 765 ©2006 Dyslexia • “a developmental disorder characterized by an unexpected difficulty in reading in children and adults who otherwise possess the intelligence, motivation, and education considered necessary for developing accurate and fluent reading.” (p.419) – 80% of SLD cases – 40% of school-age students read below grade level • Different theories – Phonological-deficit subtype – Naming speed-deficit subtype – Double-deficit subtype (Shaywitz & Shaywitz, 2004; Vukovic & Siegel, 2006) Impact of Phonological Awareness • “phonological awareness measures predict later reading achievement” • “deficits in phonological awareness consistently separate RD and nondisabled children” • “phonological deficits persist into adulthood” • “instruction in phonological awareness promotes the acquisition of reading skills” (Pugh et al., 2000) Phonologic Model of Dyslexia • Higher-order cognitive and linguistic functions intact (intelligence, verbal reasoning, vocabulary, and syntax) • BUT lower-order phonologic processing of small units or phonemes (decoding) block access to higher-order processes (Shaywitz & Shaywitz, 2004) Brain Terms Superior (Dorsal) Posterior (Caudal) Anterior (Rostral) Inferior (Ventral) • Frontal Lobe – Motor – Executive Functions – Broca’s Area • Parietal Lobe – – – – Somatosensory O-P-T crossroads Sound-symbol association Perceptual-motor • Temporal Lobe – Auditory – Wernicke’s Area – Object Recognition • Occipital Lobe – Vision Left vs. Right Hemisphere Left • Leading • Verbal • Analytic • Routinized • Sequential • Local • Microstructural • Fine • Successive • Concordant/convergent Right • Automatic • Nonverbal • Holistic • Novel • Simultaneous • Global • Macrostructural • Coarse • Simultaneous • Discordant/Divergent Reading the Mind 1973 – Computed Tomography (CT) Phrenology Postmortem Studies • Brain Localization – Wernicke’s area – Broca’s area – X-rays; 3-D image Magnetic Resonance Imaging (MRI) **provided info on structure but not function (Collins & Rourke, 2003) Reading the Mind 1980s – functional brain imaging • Baseline activation – Metabolism, signaling • Function-specific activation – Functional connectivity Magnetoencephalography (MEG) – Functional mapping info – Co-registration Positron emission tomography (PET) – Measured blood flow through injected dye Functional magnetic resonance imaging (fMRI) – Noninvasive – Blood oxygen level dependent (BOLD) – Before/during/after images (Papanicolaou et al., 2004) Brain Circuit that Supports Reading • Primary visual cortex • Association visual cortex in the ventral temporo-occipital areas • Posterior portion of the superior temporal gyrus extending posteriorly into the supramarginal gyrus (Wernicke’s area) • Inferior frontal gyrus (Broca’s area) ***except for primary visual cortex, all activity stronger in left hemisphere Major Reading ReadingCircuits Circuits Major Word Analysis Word Form Pathways for Reading Beginning Reading • Parieto-temporal – Step-by-step – Analyzing word, pulling it apart, linking letters to sounds Skilled Reading • Occipito-temporal – – – – Express pathway Hub of sensory info Reacts to whole word Neural model permanently stored (spelling, pronunciation, meaning) (Pugh et al., 2000; Shaywitz, 2003) Circuitry in Dyslexic Readers • Underactivation of left hemisphere and posterior areas • Overactivation in frontal/Broca’s region • Use of right hemisphere – Functional system (accuracy), but not automatic (fluency) (Shaywitz, 2003) In Summary… Two functional-neurobiological hallmarks of dyslexia: – Dysfunction of the perisylvian • Posterior superior temporal gyrus (STG) • Parieto-temporal region (phonological processing) – Dysfunction of the left fusiform regions • Visual word form area (VWFA) • Occipito-temporal region (automaticity/whole word) • Most highly correlated with reading skill Compensatory Shift: – Anterior brain sites – Right hemisphere regions (McCandliss & Noble, 2003) Connection? “We propose that functional and structural abnormalities in the perisylvian regions that subserve phonological processing may have a cascading effect on the development of rapid word recognition processes during the years when the VWFA is becoming increasingly specialized to respond to regularities within the writing system.” (p.201) (McCandliss & Noble, 2003) Is this a global or phonological deficit? • Global-deficit Results – Disruption in functional connectivity? – Structural malformation? • Phonological deficit – Confined to tasks that make explicit demands on phonological assembly – High phono assembly • NI displayed functional connectivity • DYS displayed correlations with the right hemisphere – Low phono assembly • NI & DYS displayed functional connectivity (Pugh et al., 2000b) Implications • No structural dysfunction that would prevent functional connectivity • Weakness in phonological representations – Breakdown occurs when orthographic-tophonological assembly required – Phonological assembly required, DYS readers use right hemisphere • Specific training could prompt cohesive functioning Connecticut Longitudinal Study • Participants followed from age 5 – 18 – Persistently poor readers (PP) – Accuracy-improved readers (AI) – Nonimpaired readers (NI) • Assessments involved pseudoword rhyming and reading real words • Pseduoword rhyming – PP & AI demonstrated underactivation in posterior neural systems • Real word reading – AI demonstrated underactivation of posterior regions – PP demonstrated similar activation patterns as NI (Shaywitz & Shaywitz, 2004) • What are the benefits of sight words? • If students struggle to crack the code, is rote memorization the key? • “With time, effective instruction and the experience of repeatedly reading the same word correctly, the child forms the synaptic connections that result in increasingly accurate neural representations of that word.” (p. 428) – Is repetition all that is needed for synaptic connections? • Repeated readings based on repetition (memorization?)… Direction • Potential for a cohesive system with sufficient training • “Strongly implies that left hemisphere posterior circuits, although poorly developed, are not fundamentally disrupted in readers with RD.” (Papanicolaou et al., 2004, p. 408) (Pugh et al., 2000b) • Compensatory strategies inefficient – Never achieve fluency when utilizing RH – Persistently poor readers rely on rote memorization for recognizing real words • Demonstrates need to incorporate analytic strategies for word identification (Shaywitz & Shaywitz, 2004) Can Dyslexic Readers Develop the FastPaced Word Form Reading System? • Used fMRI to study • End of year images: struggling readers – Right side pathways less prominent before and after a – Further development yearlong experimental of primary neural reading program systems on left side – Observed “brain repair” – Necessary for fluency Neural Effects of Remediation (Temple et al., 2003) • 20 DYS & 12 NI • Fast ForWord Language – Computerized intervention program – Designed to improve auditory and language processing • 100 min per day/ 5 days per week/ 27.9 days Results • Significant improvement in reading ability – Word id, pseudoword, passage comp, rapid naming, oral language • Increased activity in brain regions – LH temporo-parietal cortex, inferior frontal gyrus – RH structures and attentional structures Neural Effects of Remediation (Simos et al., 2002) • 8 DYS & 8 NI • 80 hours of 1:1 instruction – 1-2 hr/day; 8 wks Results • Significant gains in reading skills – Basic word reading avg. • Increased brain activation • Phono-Graphix program • Lindamood Phonemic Sequencing program (2) – Posterior portion of left superior temporal gyrus in all 8 children – dev. of phonologic processing and decoding skills • http://www.brookespublis hing.com/mccardlemris/ Future Directions • • • • • Replication/ Large-scale studies Follow-up studies of brain activation Use untreated dyslexics as control Use more experimental treatments Direct measurement of reading ability Nature vs. Nurture • Are there differences in the structure of the brain when comparing the genetically RD group images and the environmentally influenced RD groups? Do their brains compensate in the same manner if they are different? (Carrie) • Examined relation of leftward planar asymmetry (PTa) and SES to phonological performance • 39 sixth graders Results • Individual variability in brain asymmetry and SES factors account for individual differences in phonological skill (Eckert, Lombardino, & Leonard, 2001) Future imaging studies Classic Dyslexic • Glitch in posterior reading system • High verbal ability used for compensation • Accurate but slow readers Poor Readers as a result of Experience • Inaccurate AND slow readers • Posterior reading system wired yet never activated • Evidence-based reading instruction should improve skills Nature vs. Nurture Summary • Not real clear • “Children may fail to develop adequate reading skills because of their environment, abnormal brain structure, or both…a child with normal leftward PTa from a low-SES family may benefit more than would a child with reversed PTa” (p. 998) • No genetic linkage to PTa • Study did not look at combination of SES and abnormal PTa • Sample size too small • Shaywitz suggests differences but more research needed Limitations to Neuroimaging • Lack of consensus in how to define regions of interest • Lack of consensus in how to measure regions • Lack of consensus on what part to measure Implications • Dyslexia has a neurological basis BUT it is not a disease • “Instruction seems to play a significant role in the development of neural systems that are specialized for reading.” (Simos et al., 2002, p.1212) • Test other hypotheses • Define at-risk and intervene early on Discussion • This chapter presents a wide range of evidence that children who have reading difficulties (they call them “disabilities”) have difficulty with phonological processing, and good readers rely more on the left side of the brain. Given what we can tell about a student based on their early skills such as DIBELS and oral reading fluency, do we really need this information? (Nicole) • does the medical model create a self-fulfilling prophecy, further “disabling” students and making schools less accountable for educating “disabled” students? (Nicole) Discussion • I think confirming evidence from a variety of fields is extremely important. Neuropsych research further confirms what we have been reading about reading! THIS IS A GOOD THING! How can we discount what we have learned from a variety of fields- does a behavioral approach tell us everything-nope, does a neuropsych approach tell us everything-no again. THe reason all of these fields exist is because they all have something important to offer. (Tara) • why use indirect measures to study the brain and cognitive functioning when direct measures are available? (Jodi) Discussion • Since there is involvement in the visual cortex and the fast-acting recognition circuit is in the complex visual processing of the brain, I'm wondering if the visual training programs that are being offered might actually have some benefit? (Sue) Discussion • if parts of the brain that are implicated in fluency are impaired, how will interventions in this area be very effective? (Christy) • However, is there a point at which the brain is no longer able to form new circuitry for phonlogical skills? I guess until we know, we continue to intervene? What else is there to do? (Kristi) Discussion • My biggest question regarding this chapter is that if we know that real differences exist in the brains of individuals with specific reading disability as compared to those with no disability, and there are major questions regarding accurate SLD diagnoses, then why can’t we use functional imaging to provide confirming data? Why is data gathered through neuroimaging so elusive to us in this profession? If it could really help us in our diagnoses, why can’t we do more to cooperate with the medical community to get this type of information? (Tom) Discussion • Although we know that differences exist between the neural pathways of students with disabilities and those without (so to speak), how can schools best utilize this information in a practical manner without increasing budgets? (Julie) • when one reviews a study in which a fMRI was used, it is important for the researcher to mention the same MRI machine was used for all subjects. Otherwise, dfferences in machines may impact obtained results. (Rick) Discussion • What does brain imaging really tell us anyway? Does it tell us there are damaged areas in the brain of individuals with RD or maybe there brains developed preferred neuropathways that can be retrained? (Erin) References • Collins, D.W., & Rourke, B.P. (2003). Learning-disabled brains: A review of literature. Journal of Clinical and Experimental Neuropsychology, 25(7), 1011-1034. • Demonet, J.F., Taylor, M.J., & Chaix, Y. (2004). Developmental dyslexia. The Lancet, 363, 1451-1460. • Eckert, M.A., Lombardino, L.J., & Leonard, C.M. (2001). Planar asymmetry tips the phonological playground and environment raises the bar. Child Development, 72(4), 988-1002. • Hale, J.B., & Fiorello, C.A. (2004). School Neuropsychology: A Practitioner’s Handbook. New York, NY: The Guilford Press. • Krasuski, J., Horwitz, B., & Rumsey, J.M. (1996). A survey of functional and anatomical neuroimaging techniques. In R. Lyon & J. Ramsey (Eds)., Neuroimaging: A Window to the Neurological Foundations of Learning and Behavior in Children (pp. 25-52). Baltimore, MD: Paul H. Brooks Publishing Co. References • Lyon, G.R. (1996). Foundations of neuroanatomy and neuropsychology. In R. Lyon & J. Ramsey (Eds)., Neuroimaging: A Window to the Neurological Foundations of Learning and Behavior in Children (pp. 3-23). Baltimore, MD: Paul H. Brooks Publishing Co. • McCandliss, B.D., & Noble, K.G. (2003). The development of reading impairment: A cognitive neuroscience model. Mental Retardation and Developmental Disabilities Research Reviews, 9, 196-205. • Papanicolaou, A.C., Pugh, K.R., Simos, P.G., & Mencl, W.E. (2004). Functional brain imaging: An introduction to concepts and applications. In P. McCardle & V. Chhabra (Eds.), The Voice of Evidence in Reading Research (pp. 385-416). Baltimore, MD: Paul H. Brooks Publishing Co. • Pugh, K.R., Mencl, W.E., Jenner, A.R., Katz, L., Frost, S.J., Lee, J.R., Shaywitz, S.E., & Shaywitz, B.A. (2000a). Functional neuroimaging studies of reading and reading disability (developmental dyslexia). Mental Retardation and Developmental Disabilities Research Reviews, 6, 207-213. 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Chhabra (Eds.), The Voice of Evidence in Reading Research (pp. 417-442). Baltimore, MD: Paul H. Brooks Publishing Co. References • Simos, P.G., Fletcher, J.M., Bergman, E., Breier, J.I., Foorman, B.R., Castillo, E.M., Davis, R.N., Fitzgerald, M., & Papanicolaou, A.C. (2002). Dyslexia-specific brain activation profile becomes normal following successful remedial training. Neurology, 58(8), 1203-1213. • Temple, E., Deutsch, G.K., Poldrack, R.A., Miller, S.L., Tallal, P., Marzenich, M.M., & Gabrieli, J.D.E. (2002). Neural deficits in children with dyslexia ameliorated by behavioral remediation: Evidence from functional MRI. Proceedings of the National Academy of Sciences of the United States of America, 100(5), 28602865. • Vukovic, R.K., & Siegel, L.S. (2006). The double-deficit hypothesis: A comprehensive analysis of the evidence. Journal of Learning Disabilities, 39(1), 25-47.