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.