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

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

• Jennifer Geiss

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Background Information

• Is there actually a region of the brain that is
  activated specifically by written words?

• 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

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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

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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.

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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?

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ROI Question

• VWFA is associated with a readers 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?

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Methods

• Participants
• 30 normal readers
• 30 dyslexic readers
• age range 8 - 18

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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

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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

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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)

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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

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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

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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

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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)

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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

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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

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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

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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

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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

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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?

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Feasibility

• Expensive!
• Time consuming
• Similar studies have been performed before

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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.

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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.

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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.

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Works Cited

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