The Oddity of Man

• Reading and writing are unique to man
  • It has no evolutionary basis (as far as we can tell).
• It gives us the ability to preserve and transmit knowledge across time and space.
• According to the archeological record, disparate writing systems appeared independently of each other (e.g. cuneiform, Mayan).

https://www.lds.org/

Known reading network

• Ventral (orthographic) system
  • VWFA
• Dorsal (phonologic) system
  • Supramarginal gyrus
  • Angular gyrus
  • Sup. temporal cortex
  • Dorsal premotor cortex

Prerequisites to reading

• Eye(s) with normal or corrected to normal vision
• Oculomotor control
• Language fluency

Types of Eye Movements

• Fixations – when the fovea is stationary on a visual target.

• Saccades – a ballistic movement in which the eye changes orientation between fixations.

Image courtesy of: Müri, R. M., & Nyffeler, T. (2008). Neurophysiology and neuroanatomy of reflexive and volitional saccades as revealed by lesion studies with neurological patients and transcranial magnetic stimulation (TMS). Brain and Cognition, 68(3), 284-292. doi:10.1016/j.bandc.2008.08.018

The Study

• The aim of this analysis is to explore saccadic control during reading and determine ROIs necessary for saccade execution and planning for future investigation.

The Study

How we did it:

• Participants underwent 3 functional scans during which they were presented with 18 paragraphs to read per scan.
• Eye movements were recorded during functional scans.
• Structural scans were also performed.

Methods

Participants

• 43 BYU undergraduates, recruited via SONA.
• Normal or corrected to normal vision.
• No contraindications for an MRI.

Materials

• Text was taken from online news articles and literature.​

Acquisition

Scanner

• Siemens 3T Trio Tim with 12-channel head coil.

Parameters

• 3 consecutive blocks of interleaved T2* weighted echo-planar imaging.
  • Slice number 43
  • Orientation is transverse
  • Phase encoding direction is anterior to posterior
  • Rotation is 0°
  • FOV= 224x224
  • Matrix 64x64
  • Slice thickness 3.0 mm
  • TR 2500 ms, TE 28 ms
  • 134 repetitions
  • Flip angle 90°

Acquisition

Parameters

• T1-weighted imaging
  • Orientation is sagittal
  • Anterior to posterior phase encoding
  • FOV=218x250
  • Matrix 256x256
  • Slice thickness 1.00 mm
  • TR 1900 ms, TE 2.26 ms
  • Flip angle is 9°

Eye Tracking Methods

SR Research Eyelink 1000 Plus

• Spatial resolution 0.01 degrees.
• Sampling rate 1000 Hz.
• Text adjusted to 3.4 letters per degree of visual angle.
• Head movement stabilized with foam pads.

Preprocessing & Analysis

Eye tracking

• Saccades were excluded if they included a blink or if they ended outside predefined interest areas (i.e. did not land on a word).
• Fixations shorter than 50 msec or longer than 1500 msec were also excluded.
• Therefore 75,270 saccade/fixation pairs were included in the analysis.
• These were then temporally registered to the start of each functional scan.

Imaging data were preprocessed and analyzed using:

• Analysis of Functional NeuroImages
• Advanced Normalization Tools

#DICOM files were imported
to3d 
    -time:zt <slice number> <number of TRs per run> <TR in msec> \
    alt+z epi[1,2,3] <epi dicom>

to3d -prefix struct <t1 dicom>

#Co-registration of structural to functional
3dWarp -oblique_parent <epi3> \
       -prefix <warped file prefix> <input t1>

#Slice time correction
3dTshift -verbose -prefix <new prefix> <input epi>

#Motion correction within runs
3dvolreg 
    -base <middle TR of run> 
    -prefix <output epi prefix> 
    -1Dfile <1D output file> <input slice time corrected epi>

#Motion correction across runs
3dvolreg 
    -base <middle TR of reference run> 
    -prefix <aligned epi> <input epi>

#Motion censor creation
cat <1D output file> >> motion.txt
move_censor.pl

Preprocessing

#Mask creation
3dSkullStrip 
    -input <coregistered t1> \
    -o_ply <output name>

3dfractionize 
    -template <reference epi> \
    -input <skullstripped t1> \
    -prefix <output prefix>

3dcalc 
    -a <fractionized t1> \
    -prefix <prefix> 
    -expr "step(a)"

Mask Creation

#Regression
        3dDeconvolve \
            -input <epi run 1> <epi run 2> <epi run 3> \
            -mask <t1 mask> \
            -polort A \
            -num_stimts 7 \
            -stim_file 1 "motion.txt[0]" -stim_label 1 "Roll"  -stim_base   1 \
            -stim_file 2 "motion.txt[1]" -stim_label 2 "Pitch" -stim_base   2 \
            -stim_file 3 "motion.txt[2]" -stim_label 3 "Yaw"   -stim_base   3 \
            -stim_file 4 "motion.txt[3]" -stim_label 4 "dS"    -stim_base   4 \
            -stim_file 5 "motion.txt[4]" -stim_label 5 "dL"    -stim_base   5 \
            -stim_file 6 "motion.txt[5]" -stim_label 6 "dP"    -stim_base   6 \
            -stim_times_AM2 7 <Timing file> 'dmBLOCK' \
	    -stim_label 7 "<label>" \
            -num_glt 1 \
            -gltsym 'SYM: <label>' \
            -glt_label 1 <label> \
            -censor 'motion_censor_vector.txt[0]' \
            -nocout -tout \
            -bucket <output prefix> \
            -xjpeg <design JPEG> \
            -jobs 2 \
            -GOFORIT 12

#Output blurring
3dmerge 
    -prefix <output prefix> \
    -1blur_fwhm 5.0 \
    -doall <input file>

Individual Subject Regression

#T1 transformation
ants.sh <transformation dimensions> <model template> <subject t1>

#EPI transformation
ANTifyFunctional <input structural> <model template> <blurred epi> 

ANTs Transformation

3dttest++ -prefix <output prefix> \
    -mask <model template mask> \
    -setA \
        <Subject 1 transformed regression input> \
        <Subject 2 transformed regression input> \
        ...
        <Subject 43 transformed regression input> \

Group t-test

Results

Significant ROIs

Where is this going?

Where is this going?

• Individual differences in reading measures are highly consistent over time in adults.
  • Functional and structural comparisons.
• Begin to untangle language in the brain.
  • Influence of word frequency, predictability and other lexical variables on HDR.
  • ​Influence of linguistic factors on saccade-control related HDR as well as subcortical regions.
• Contrast healthy readers with unhealthy populations to determine diagnostic potential of reading.

Why Study This?