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Activation of the Visual Word Form Area in Dyslexic Readers: A Research Proposal

Activation of the Visual Word Form Area in Dyslexic Readers: A Research Proposal. Jennifer Geiss. Yes! Lesion studies & pure alexia There are specialized regions for stimuli such as faces, places, and body parts, why not words as well. No! Lesion studies & pure alexia

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Activation of the Visual Word Form Area in Dyslexic Readers: A Research Proposal

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  1. Activation of the Visual Word Form Area in Dyslexic Readers: A Research Proposal Jennifer Geiss

  2. Yes! Lesion studies & pure alexia There are specialized regions for stimuli such as faces, places, and body parts, why not words as well No! Lesion studies & pure alexia Evolution: written language has not been around long enough for our brains to develop a VWFA Background Information Is there actually a region of the brain that is activated specifically by written words?

  3. Background Information • Evolution of VWFA? • Writing was invented about 5400 years ago which is not enough time for the brain to engineer a specialized module for visual word recognition • Reading experience may drive progressive specialization of a pre-existing inferotemporal pathway for visual object recognition

  4. Background Information • Assuming there is a VWFA… • Activation begins after approximately 150-200 ms of presentation • It is specific to visual and not to auditory words • Relatively insensitive to retinal position • Relatively insensitive to surface features of the presented words such as letter case, font, or size.

  5. Rationale for Current Study • Can we infer from evidence that suggests people with lesions in VWFA/split brain patients have reading difficulties that people with reading difficulties (i.e. dyslexia) have abnormal VWFA functioning?

  6. ROI Question • VWFA is associated with a reader’s ability to recognize words by sight • What does the VWFA care about with respect to reading in dyslexics? • Will VWFA show reduced or no activation in dyslexics as compared to normal readers? • Will VWFA activation be affected more, less, or equally by real words than pseudo-words?

  7. Methods • Participants • 30 normal readers • 30 dyslexic readers • age range 8 - 18

  8. Methods • Materials • 400 words in 5 frequency levels (0 [lowest] – 4 [highest] ) • 80 items in levels 1 – 4 = 320 words • 20 pseudo-words created by exchanging vowel letter(s) for 20 items of each of the 4 word-frequency categories = 80 words

  9. Methods • Blocked Design Procedure • 10 items of a specific frequency category constituting a single reading epoch of 16 s • Each reading epoch followed by a baseline epoch of 16 s with a fixation cross • Ten reading and 10 baseline epochs will be grouped into a run (= 4 runs) • Runs are separated by pauses of 20 s • Word presentation is pseudorandom

  10. Methods • Parameters • Slice • Orientation: axial • Thickness: 4.5 mm • n = 24 • Voxel • Whole head image voxel size: 3.44 × 3.44 × 4.50 mm (including the whole cerebrum and upper half of the cerebellum)

  11. Methods • Parameters • Images • During each of the four runs 160 whole head images will be acquired (640 whole head images) • Hardware • 1.5 Tesla scanner • Video Projector for stimulus presentation • Headphones for ear protection • Panic button

  12. Methods • Parameters • T2* weighted gradient echo EPI (echo planar imaging) sequence • TR (scan repeat) = 3 s • TE (echo time) = 40 ms • Matrix = 64 × 64 • FOV (field of view) = 220 mm • FA (flip angle) = 90º

  13. Methods • Data Analysis • Preprocessing • To compensate for T1 equilibration effects, 6 dummy scans will be acquired at the beginning of each functional run before stimulus presentation starts

  14. Methods • Data Analysis • Preprocessing • After functional scanning, a high resolution structural scan will be acquired to facilitate normalization and localization of functional activations • Structural image will use a T1 weighted Turbo Field Echo sequence (matrix 256 × 256 mm, FOV 220 mm, 130 slices, 1mm thick)

  15. Methods • Data Analysis • SPM 99 in MATLAB • Motion correction • Done by realigning all functional images to first functional image • Functional images and structural image coregistered and normalized to template brain

  16. Methods • Anticipated difficulties • Getting 60 kids to participate • Usable images from such young children (they may move a lot) • Understanding which/what kinds of words activate VWFA and using the wrong kind which may result in 0 activation in normal and dyslexic readers

  17. Methods • Money • 30 minutes for 60 people = 1800 minutes (30 hours) • $537 × 30 hours = $16,110 just for experiment time. Prep time, data analysis extra! • $1500 for 30 subjects’ participation at $50/hr • $600 publication costs

  18. Methods • Time • 4 hours/subject (120 hours) for basic data analysis • 10 hours/subject (300 hours) for advanced data analysis • 10 hours/subject (300 hours) backups, preprocessing, etc. • Scanner setup • Data collection

  19. Results and Discussion • Expected Activation • In normal readers: • VWFA (left mid-fusiform gyrus-- behind the left ear, near the hairline) • Peak at approximately x = -43, y = -54, z = -12 • In dyslexic readers: • Reduced or no activation in VWFA

  20. Results and Discussion • Alternate possible outcomes? • No VWFA activation in normal readers • Normal VWFA activation in dyslexic readers • Implications of the possible outcome? • Reconfigure methods protocol • Data analysis • Existence of VWFA? • VWFA connection in dyslexics?

  21. Feasibility • Expensive! • Time consuming • Similar studies have been performed before

  22. Works Cited Cohen, L., et al. (2000). The visual word form area: Spatial and temporal characterization of an initial stage of reading in normal subjects and posterior split-brain patients. Brain, 123,291-307. Cohen, L. & Dehaene, S. (2004). Specialization within the ventral stream: the case for the visual word form area. NeuroImage, 22, 466-476.

  23. Works Cited Dehaene, S., et al. (2002). The visual word form area: A prelexical representation of visual words in the fusiform gyrus. NeuroReport, 13, 3, 321-325. Dehaene, S., et al. (2005). The neural code for written words: A proposal. TRENDS in Cognitive Science, 9, 7, 335-341.

  24. Works Cited Kronbichler, M., et al. (2004). The visual word form area and the frequency with which words are encountered: evidence from a parametric fMRI study. NeuroImage, 21, 946-953. McCandliss, B.D., Cohen, L. & Dehaene, S. (2003). The visual word form area: expertise for reading in the fusiform gyrus. TRENDS in Cognitive Science, 7, 7, 293-299.

  25. Works Cited Price, C.J. & Devlin, J.T. (2003). The myth of the visual word form area. NeuroImage, 19, 473-481.

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