Activation of the Visual Activation of the Visual Word Form Area in Word Form Area in Dyslexic Readers: Dyslexic Readers: A Research ProposalA Research Proposal
Jennifer Geiss
Background Information
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
Is there actually a region of the brain that is activated specifically by written words?
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
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.
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?
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?
Methods
Participants 30 normal readers 30 dyslexic readers age range 8 - 18
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
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
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)
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
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
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
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)
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
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
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
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
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
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?
Feasibility
Expensive! Time consuming Similar studies have been performed before
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.
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.
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.
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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